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Patent Searching and Data


Title:
MULTIPOLAR MACHINES
Document Type and Number:
WIPO Patent Application WO/2004/006304
Kind Code:
A2
Abstract:
A homopolar machine with a current channeling rotor (2) rotating between the cylindrical aligned parallel permanet magnets (5 and 6). Currents are conducted by brushes (27) and slip rings (34) at both axial ends of the rotor.

More Like This:
JPS56153672CONDUCTIVE BRUSH
Inventors:
KUHLMANN-WILSDORF DORIS (US)
Application Number:
PCT/US2003/022248
Publication Date:
January 15, 2004
Filing Date:
July 08, 2003
Export Citation:
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Assignee:
KUHLMANN-WILSDORF DORIS (US)
International Classes:
H01R39/24; H02K31/02; (IPC1-7): H01L/
Foreign References:
US5049771A1991-09-17
US6051905A2000-04-18
US5434462A1995-07-18
US3886385A1975-05-27
Other References:
See also references of EP 1573886A2
Attorney, Agent or Firm:
Wright, Bryan D. (401 East Market Street Suite 10, Charlottesville VA, US)
Download PDF:
Claims:
WHAT IS CLAIMED AS NEW AND DESIRED TO BE SECURED BY LETTERS PATENT OF THE UNITED STATES IS:
1. A homopolar machine capable of operating as an electric motor, an electric generator, an electric transformer and/or an electric heater comprising: at least one electrically conductive rotatable rotor configured to flow currents in a plurality of current paths when power is applied; a plurality of magnetic field sources disposed to apply a magnetic field penetrating the rotor in a plurality of zones and intersecting the plurality of current paths when the rotor is rotated by means of said applied power; and current channeling means in said rotor provided so as to be parallel to said plurality of current paths during rotation of said rotor;.
2. A homopolar motor configured to be driven by at least one current source comprising: at least one electrically conductive rotatable rotor configured to flow current in at least one current path when the motor is driven by the at least one current source; a plurality of magnetic field sources disposed to apply a magnetic field penetrating the rotor in at least one zone and intersecting the at least one current path when the motor is driven by the current source; and current channeling in said rotor provided so as to be parallel to said at least one current path during rotation of said rotor;.
3. A homopolar generator configured to generate a current when rotated by a mechanical torque comprising: at least one electrically conductive rotatable rotor configured to flow current in at least one current path when the generator is rotated by a mechanical torque; a plurality of magnetic field sources disposed to apply a magnetic field penetrating the rotor in at least one zone and intersecting the at least one current path when the generator is rotated by a mechanical torque; and current channeling means in said rotor provided so as to be parallel to said at least one current path during rotation of said rotor;.
4. A homopolar transformer comprising: at least one electrically conductive rotatable rotor configured to flow at least one primary current and at least one secondary current in at least one primary and at least one secondary current path when said rotor is rotated through power supplied to said at least one primary current path from at least one primary current source; a plurality of magnetic field sources disposed to apply a magnetic field penetrating the rotor in a plurality of zones and intersecting the at least one primary current path and the at least one secondary current path; and current channeling means in said rotor provided so as to be parallel to said at least one primary current path and said at least one secondary current path;.
5. A homopolar machine according to claims 1,2, 3, or 4 wherein a plurality of said magnetic field sources is disposed outside of said rotor and a plurality of said magnetic field sources is disposed inside said rotatable rotor.
6. A homopolar machine according to claim 5 wherein a plurality of said magnetic field sources are configured into at least one of an outer and an inner magnet tube.
7. A homopolar machine according to claim 6 operating as a motor.
8. A homopolar machine according to claim 6 operating as a generator.
9. A homopolar machine according to claim 6 operating as a transformer.
10. A homopolar machine according to claim 6 simultaneously operating as a selection of a motor, a generator, a transformer and a heater.
11. A homopolar machine according to claim 6 wherein said magnetic field sources are a selection of at least one permanent magnet, at least one electromagnet or at least one superconducting magnet.
12. A homopolar machine according to claim 6 wherein said magnetic field sources are magnets that pairwise face each other across the wall of said at least one rotatable rotor.
13. A homopolar machine according to claim 6 wherein said magnetic field sources are horseshoetype magnets that pairwise face each other across the wall of said at least one rotatable rotor.
14. A homopolar machine according to claim 6 wherein said at least one rotatable rotor comprises at least one slip ring for electrical brushes at either end where said rotor projects beyond said at least one outer and one inner magnetic tube.
15. A homopolar machine according to claim 14 wherein said electrical brushes are a selection of monolithic brushes, metal fiber brushes and metal foil brushes.
16. A homopolar machine according to claim 14 wherein said electrical brushes are monolithic brushes.
17. A homopolar machine according to claim 14 wherein said electrical brushes are metal foil brushes.
18. A homopolar machine according to claim 14 wherein said electrical brushes are metal fiber brushes.
19. A homopolar machine according to claim 11. wherein a selection of said permanent magnets is assembled from modules.
20. A homopolar machine according to claim 6 wherein said at least one outer magnetic tube is made as a plurality of lengthwise aligned sections.
21. A homopolar machine according to claim 6 wherein said at least one inner magnet tube is made as a plurality of lengthwise aligned sections.
22. A homopolar machine according to claim 6 wherein at least one of said inner magnet tubes is constrained from lateral movements relative to said rotatable rotor by means of at least one bearing that centers the rotation axis of said at least one inner magnet tube on the rotation axis of said rotatable rotor.
23. A homopolar machine according to claim 21 wherein at least one of said plurality of lengthwise aligned sections of an inner magnet tube is constrained from lateral movements relative to said rotatable rotor by means of at least one bearing that centers the rotation axis of said at least one lengthwise aligned section of an inner magnet tube on the rotation axis of said rotatable rotor.
24. A homopolar machine according to claim 6 wherein said inner magnet tube is constrained from rotation relative to said outer magnet tube by means of gravity.
25. A homopolar machine according to claim 21 wherein at least one of said plurality of lengthwise aligned sections is constrained from rotation relative to said outer magnet tube by means of at least one gyroscope.
26. A homopolar machine according to claim 6 comprising a mechanical constraint that inhibits lateral movements of the machine axle relative to the major surrounding structure such as the floor of a machine room, the hull of a ship or the body of a tank.
27. A homopolar machine according to claim 6 wherein said outer magnet tube is constrained from lateral and rotational movements relative to the major surrounding structure such as the floor of a machine room, the hull of a ship or the body of a tank by means of a mechanical structure.
28. A homopolar machine according to claim 20 wherein at least one of said plurality of lengthwise aligned sections is constrained from lateral and rotational movements relative to the major surrounding structure such as the floor of a machine room, the hull of a ship or the body of a tank by means of a mechanical structure.
29. A homopolar machine according to claims 1,2, 3,4, 5, or 6 comprising cooling means.
30. A homopolar machine according to claim 29 wherein the cooling means medium is water.
31. A homopolar machine according to claim 28 wherein the cooling means medium is fluid other than water such as atmospheric air or an organic liquid.
32. A homopolar machine according to claim 29 wherein the cooling means medium is circulating in a closed system and is driven by pumping means.
33. A homopolar machine according to claim 29 that wherein said cooling means is by direct immersion into water.
34. A homopolar machine according to claims 13,19 and 29 wherein a cooling means medium circulates through the channels formed by the arms of said horseshoetype magnets.
35. A homopolar machine according to claims 1,2, 3 and 4 wherein said at least one rotatable rotor is at least partly made of inherently current channeling material.
36. A homopolar machine according to claims 1,2, 3 and 4 wherein said current channeling means in said at least one rotatable rotor comprise at least two elongated metallurgical phases of widely different electrical conductivities in a microstructure.
37. A homopolar machine according to claims 1,2, 3 and 4 wherein said current channeling means in said rotor consist of a least one manmade composite comprising elongated electrical conductors in an insulating matrix.
38. A homopolar machine according to claims 1,2, 3 and 4 wherein said current channeling means in said at least one rotatable rotor consist of an assembly of macroscopic, elongated electrical conductors joined by means of at least one electrically insulating material such as a lacquer, a commercial insulating adhesive, an epoxy, a ceramic, or a polymer.
39. A homopolar machine according to claims 1,2, 3 and 4 wherein said current channeling means in said at least one rotatable rotor comprise continuous elongated electrical conductors that are embedded in an electrically insulating matrix material.
40. A homopolar machine according to claim 39 wherein the cross sectional shape of said continuous elongated electrical conductors is circular, ringshaped (as in tubing), rectangular (as in strips of foils sheet or plates), irregular, starshaped or elliptical.
41. A homopolar machine according to claims 37, 38, 39, and 40 wherein said elongated electrical conductors consist of a selection of copper, silver, aluminum, lithium, beryllium, gold, copper alloys, silver alloys, aluminum alloys, lithium alloys, beryllium alloys and gold alloys.
42. A homopolar machine according to claim 41, wherein said elongated electrical conductors are at least partly mutually electrical insulated through surface films gained through oxidation, e. g. as in anodizing aluminum and aluminum alloys.
43. A homopolar machine according to claims 1,2, 3 or 4 wherein said channeling means are weaves or meshes in which one set of parallel fibers or strands is metallic and the other is nonmetallic.
44. A homopolar machine according to claim 43 wherein said rotor is made by winding said weaves or meshes onto a spindle and fixing their shape by infiltrating with an electrically nonconductive hardenable material such as a polymer or an epoxy.
45. A homopolar machine according to claims 35,36, 37,38, 39 and 40 further comprising at least one layer of an electrically insulating material between two adjoining individual rotors in a set of rotors, such as a layer or sheet of an electrically insulating polymer, an electrically insulating elastomer, a textile, paper, Teflon or other.
46. A homopolar machine according to claim 35, 36, 37, 38,39 and 40 wherein said rotor is made by extrusion.
47. A homopolar machine according to claims 1,2, 3 and 4 wherein said rotor is made by layering or rolling up current channeling material in the form of foils or sheet.
48. A homopolar machine according to claims 1,2, 3 and 4 wherein said rotor is made by assembling macroscopic elongated electrical conductors in arcs of cylindrical molds.
49. A homopolar machine according to claims 1,2, 3 and 4 wherein said rotor is made from modules in the shape of cylindrical arcs.
50. A homopolar machine according to claim 6 wherein a plurality of said magnetic field sources are horseshoetype permanent magnets.
51. A homopolar machine according to claim 6 wherein at least one of said outer magnet tube and inner magnet tube comprises a matrix material comprising a selection of at least one of a polymer, a rosin, a phenol, an epoxy, Teflon, any other commercial polymeric material, a reinforced composite, aluminum, an aluminum alloy, lithium, a lithium alloy, beryllium, a beryllium alloy, tin, a tin alloy, zinc, a zinc alloy, cadmium, a cadmium alloy, titanium, a titanium alloy, copper, a copper alloy favorably among these a bronze, steel, stainless steel, a noble metal, a noble metal alloy, a commercially proven casting metal, a metallic sintering powder, a polymorphic sintering powder, a ceramic sintering powder, a glassy sintering powder, a polymeric material suitable for casting, a glassy material suitable for casting, a ceramic material suitable for casting, as metal suitable for casting as a slurry, an experimental casting metal and an experimental sintering powder.
52. A homopolar machine according to claim 6 wherein at least one of said outer magnet tube and inner magnet tube comprises a matrix material shaped by means of at least one of casting, molding, machining, spark cutting, extruding, slurry casting and sintering.
53. A homopolar machine according to claims 51 or 52 wherein said matrix material is provided with shaped channels for filling with magnets or modules of magnets.
54. A homopolar machine according to claim 53 wherein at least one of said shaped channels is shaped to provide retention, in the sense of dental fillings, for at least one of said magnets or a plurality of said modules of magnets.
55. A homopolar machine according to claim 53 wherein said filling of said channels with magnets or modules of magnets is accomplished by means of sliding, mechanical pressing, casting, molding or sintering.
56. A homopolar machine according to claim 53 wherein said magnets or modules of magnets are joined together by means of gluing with an adhesive, soldering, or a lubricant that hardens into an adhesive on drying.
57. A homopolar machine according to claims 1,2, 3 and 4, wherein said magnetic field sources comprise at least one precision manufactured magnet or magnet module.
58. A homopolar machine according to claim 6 wherein one of said inner magnet tube and outer magnet tube is replaced by a flux return.
59. A homopolar machine according to claims 1, 2,3 and 4 wherein at least one of said magnetic field sources is replaced by a keeper that acts as a flux return.
60. A homopolar machine according to claim 14 wherein the at least one slip ring is manufactured through a selection of mechanical shaping, electrochemical means and spark cutting.
61. A homopolar machine according to claims 14 and 60 wherein the at least one slip ring is manufactured separate from said rotor.
62. A homopolar machine according to claim 14 comprising slip rings and boundaries between them that are generated through shaping at least one end of said rotor.
63. A homopolar machine according to claim 6 wherein said at least one outer magnetic tube is assembled from modules.
64. A homopolar machine according to claim 6 wherein said at least one inner magnetic tube is assembled from modules.
65. A homopolar machine according to claim 29 comprising vanes affixed to the at least one rotor.
66. A homopolar machine according to claim 29 comprising at least one cooling ring.
67. A homopolar machine according to claim 29 comprising pumping means for circulating a coolant.
68. A homopolar machine according to claim 29 comprising a closed system wherein a coolant is circulated by pumping means.
69. A homopolar machine according to claim 68 comprising at least one seal for preventing the escape of a coolant out of the machine.
70. A homopolar machine according to claim 69 wherein said at least one seal is a seal pair enclosing a leak space from which leaked coolant is drained via a drain hole.
71. A homopolar machine according to claim 29 wherein coolant circulates through at least part of the space between the rotor and at least one outer magnet tube.
72. A homopolar machine according to claim 29 wherein coolant circulates through at least part of the space between at least one rotor and at least one inner magnet tube.
73. A homopolar machine according to claim 29 wherein coolant circulates through at least part of the space between at least one rotor and at least one inner magnet tube.
74. A homopolar machine according to claim 29 that is cooled by a gaseous coolant that is blown over it from the outside.
75. A homopolar machine according to claim 6 wherein sliding friction between at least one rotor and at least one inner magnet tube or between at least one rotor and at least one outer magnet tube is reduced by means of a lowfriction coating.
76. A homopolar machine according to claim 6 wherein sliding friction between at least one rotor and at least one inner magnet tube or between at least one rotor and at least one outer magnet tube is reduced by means of lubrication.
77. A homopolar machine according to claim 6 wherein sliding friction between at least one rotor and at least one inner magnet tube or between at least one rotor and at least one outer magnet tube is reduced by means of a lowfriction coating and lubrication.
78. A homopolar machine according to claim 21 wherein the weight of at least one lengthwise section of said inner magnet tube is at least partially supported by means of at least one mechanical member that includes a bearing that encircles the axle.
79. A homopolar machine according to claim 6 wherein the weight of the rotatable rotor is at least partly supported by at least one inner magnet tube or at least one section of an inner magnet tube.
80. A homopolar machine according to claim 6 wherein the weight of the rotatable rotor is at least partly supported by at least one outer magnet tube or at least one section of an outer magnet tube.
81. A homopolar machine according to claims 20 or 21 wherein the weight of the rotatable rotor is at least partly supported by at least one lengthwise section of a magnet tube.
82. A homopolar machine according to claims 1,2, 3,4, 5, or 6 comprising at least one brush holder for mechanically loading and guiding a plurality of electrical brushes in their respective axial directions by means of a plurality of mutually electrically insulated brush holder channels that each are correlated with a zone.
83. A homopolar machine according to claim 82 wherein said at least one brush holder comprises at least two arcshaped brush holder sections, wherein each of said at least two brush holder sections comprises mutually insulated brush holder channels for mechanically loading and guiding a plurality of electrical brushes in their respective axial directions.
84. A homopolar machine according to claims 82 or 83 wherein at least two of said plurality of electrical brushes are joined into a brush pair by means of a rigid, electrically conductive connection.
85. A homopolar machine according to claims 82 or 83 wherein at least one of said plurality of electrical brushes is a split brush composed of a plurality of electrically parallel, independently electrically connected and independently mechanically loaded brushes positioned in close axial proximity to each other on the same slip ring in the same radial position.
86. A homopolar machine according to claims 82 or 83 wherein at least one of said plurality of electrical brushes is a split brush composed of a plurality of electrically parallel, independently electrically connected and independently mechanically loaded brushes that slide in the same brush holder channel.
87. A homopolar machine according to claims 82 or 83 wherein at least two of said plurality of electrical brushes form a split brush pair composed of a plurality of electrically parallel, independently electrically connected and independently mechanically loaded brush pairs positioned in close axial proximity to each other on the same slip ring in the same radial position.
88. A homopolar machine according to claims 82 or 83 wherein at least two of said plurality of electrical brushes form a split brush pair composed of a plurality of electrically parallel, independently electrically connected and independently mechanically loaded brushes that slide in the same brush holder channel.
89. A homopolar machine according to claims 82 or 83 wherein said at least one brush holder or said at least one arcshaped brush holder section is mechanically attached to a wall of a cooling ring.
90. A homopolar machine according to claims 82 or 83 wherein said at least one brush holder or at least one of said at least two arcshaped brush holder sections is mechanically attached to an outer magnet tube.
91. A homopolar machine according to claims 82 or 83 wherein said at least one brush holder or at least one of said at least two arcshaped brush holder sections is mechanically attached to an inner magnet tube.
92. A homopolar machine according to claims 82 or 83 wherein said at least one brush holder or at least one of said at least two arcshaped brush holder sections is mechanically attached to a machine base plate or housing.
93. A homopolar machine according to claims 82 or 83 wherein said at least one brush holder or at least one of said at least two arcshaped brush holder section comprises at least one terminal for making at least one electrical connection to the outside.
94. A homopolar machine according to claims 82 or 83 wherein said at least one brush holder or at least one of said at least two arcshaped brush holder sections comprises at least one switch for switching from and to at least one outside circuit.
95. A homopolar machine according to claims 1,2, 3 and 4 wherein said zones are parallel to the rotation axis of said rotatable rotor and said magnetic fields have alternating orientation in neighboring zones.
96. A homopolar machine according to claim 95 wherein current is conducted between neighboring zones by means of electric brush pairs.
97. A homopolar machine according to claim 95 wherein current is conducted between neighboring zones by means of split electric brush pairs.
98. A homopolar motor according to claim 2 wherein said current source is at least partially at least one DC source.
99. A homopolar motor according to claim 2 wherein said current source is at least partly at least two different and independently controllable DC power sources.
100. A homopolar motor according to claim 2 wherein said current source is at least partially the rectified current of at least one AC source.
101. A homopolar motor according to claim 2 wherein said current source is at least partially the rectified current of at least one threephase current source.
102. A homopolar motor according to claim 2 wherein said current source is at least partially at least two of the selection of a DC current source, an AC current source and a threephase current source.
103. A homopolar generator according to claim 3 wherein a current is generated when said rotatable rotor is rotated by means of an externally applied torque.
104. A homopolar generator according to claim 3 wherein at least two different currents are generated at different voltages when said rotatable rotor is rotated by means of an externally applied torque.
105. A homopolar transformer according to claim 4 wherein said primary current is supplied to at least one primary current path by at least one primary DC current source and power is delivered to at least one outside secondary circuit.
106. A homopolar transformer according to claim 4 wherein said primary current is supplied by a plurality of primary DC power sources to a plurality of primary circuits.
107. A homopolar transformer according to claim 4 wherein part of said primary current is supplied to at least one primary circuit by the rectified currents of at least one of an AC and a threephase power source.
108. A homopolar transformer according to claim 4 wherein said primary current is supplied to a plurality of primary circuits by the rectified currents of a plurality of AC or threephase power sources.
109. A homopolar transformer according to claim 4 wherein said primary current is supplied to a plurality of primary circuits by the rectified currents of a plurality of AC and threephase power sources.
110. A transformer according to claims 107,108 and 109 supplying a single secondary circuit.
111. A transformer according to claims 107,108 and 109 further comprising a plurality of secondary current circuits.
112. A homopolar machine according to claim 1 operating alternatively as at least two of a multipolar motor, a multipolar generator, a multipolar transformer and an electric heater.
113. A homopolar machine according to claim 1 operating simultaneously as at least two of a multipolar motor, a multipolar generator, a multipolar transformer and an electric heater.
114. A homopolar machine according to claim 93 comprising a multiplicity of said terminals for making electrical connections to the outside.
115. A homopolar machine according to claim 114 wherein all of said terminals are located at the same end of said homopolar machine.
116. A homopolar machine according to claim 115 wherein at least one of said terminals is located on each end of said homopolar machine.
117. A homopolar machine according to claim 115 wherein at least one of said terminals are provided with a switch for switching a current.
118. A homopolar machine according to claims 1,2, 3,4, 5, and 6 with claim 61 wherein said at least one slip ring is comprised in an end piece of said rotatable rotor.
119. A homopolar machine according to claims 1,2, 3,4, 5 and 6 wherein said end piece of said rotatable rotor is joined to said rotatable rotor by means of a joint that provides sufficient torsional strength and lengthwise electrical conductivity for the satisfactory operation of said homopolar machine.
120. A homopolar machine according to claim 119 wherein said joint is slanted against the axis of said rotatable rotor.
121. A homopolar machine according to claim 119 wherein said joint is slotted.
122. A homopolar machine according to claim 119 wherein said joint is conical.
123. A homopolar machine according to claim 119 wherein said joint is stepped.
124. A homopolar machine according to claim 119 wherein said joint is interlocking.
125. A homopolar machine according to claims 120,121, 122,123, and 124 wherein adhesion in said joint so as to provide requisite mechanical shearing strength between said rotatable rotor and the end piece of said rotatable rotor is provided by soldering or brazing.
126. A homopolar machine according to claims 120,121, 122,123, and 124 wherein adhesion in said joint so as to provide requisite mechanical shearing strength between said rotatable rotor and the end piece of said rotatable rotor is provided by an electrically conducting adhesive.
127. A homopolar machine according to claims 120,121, 122,123, and 124 wherein adhesion in said joint so as to provide requisite mechanical shearing strength between said rotatable rotor and the end piece of said rotatable rotor is provided by a induction heating.
128. A homopolar machine according to claims 1,2, 3,4, 5, and 6 wherein said rotatable rotor is made out of at least two lengthwise sections that are joined together by means of a joint that provides sufficient torsional strength and lengthwise electrical conductivity for the satisfactory operation of said homopolar machine.
129. A homopolar machine according to claim 128 wherein said joint between said at least two lengthwise sections is slanted against the axis of said rotatable rotor.
130. A homopolar machine according to claim 128 wherein said joint between said at least two lengthwise sections is slotted.
131. A homopolar machine according to claim 128 wherein said joint between said at least two lengthwise sections is conical.
132. A homopolar machine according to claim 128 wherein said joint between said at least two lengthwise sections is stepped.
133. A homopolar machine according to claim 128 wherein said joint between said at least two lengthwise sections is interlocking.
134. A homopolar machine according to claims 129,130, 131,132, and 133 wherein bonding in said joint between said at least two lengthwise sections is provided by soldering or brazing.
135. A homopolar machine according to claims 129,130, 131,132 and 133 wherein bonding in said joint between said at least two lengthwise sections is provided by an electrically conducting adhesive.
136. A homopolar machine according to claims 129,130, 131,132 and 133 wherein bonding in said joint between said at least two adjoining lengthwise sections is provided by induction heating.
137. A homopolar machine according to claims 14 wherein, for the purpose of achieving a reduced brush sliding velocity, the diameter of the ends of said rotor that project beyond the at least one outer and one inner magnet, is smaller than the diameter of the midsection of said rotor.
138. A homopolar machine according to claims 96 and 97 further comprising a dielectric barrier interposed between two neighboring brush pairs on the same slip ring wherein said dielectric barrier is designed for electrical breakdown and thereby to short circuit the current path across two adjoining zones when the voltage across them rises above some predetermined value.
139. A homopolar machine according to claims 82 or 83 wherein at least one of said brush holder or at least two of said arc shaped brush holder sections are configured to leave a gap between opposing ends of said brush holder or said at least two arc shaped brush holder sections.
140. A homopolar machine according to claims 82 or 83 wherein at least one of said brush holder or at least two of said arc shaped brush holder sections are configured to leave a gap between opposing ends of said brush holder or said at least two arc shaped brush holder sections for the purpose of decreasing the electric field between said opposing ends.
141. A homopolar machine according to claims 82 or 83 wherein at least one of said brush holder or at least two of said arc shaped brush holder sections are configured to leave a gap between opposing ends of said brush holder or said at least two arc shaped brush holder sections for the purpose of increasing the space for accommodating electrical terminals.
142. A homopolar machine according to claims 82 or 83 wherein at least one of said brush holder or at least two of said arc shaped brush holder sections are configured to leave a gap between opposing ends of said brush holder or said at least two arc shaped brush holder sections for the purpose of providing geometrical barriers against leak current flow.
143. A homopolar machine according to claims 82 or 83 wherein at least one of said brush holder or at least two of said arc shaped brush holder sections are configured to leave a gap between opposing ends of said brush holder or said at least two arc shaped brush holder sections for the purpose of providing means for the switching of currents among brushes and/or terminals within the said homopolar machine.
144. A homopolar machine according to claims 1,2, 3, or 4 wherein said at least one rotatable rotor is made at least partly from axially extended conductors whose radial dimension spans the wall width of said at the least one rotatable rotor.
145. A homopolar machine according to claims 1,2, 3, or 4 wherein said at least one rotatable rotor comprises currentchanneling, mechanically fused, electrically isolated concentric individual rotors.
146. A homopolar machine according to claim 145 wherein at least one of said individual rotors is at least partly made from axially extended conductors whose radial dimension spans the wall width of said at least one individual rotor.
147. A homopolar machine according to claims 144 and 146 wherein the circumferential dimension of said axially extended conductors compares to or is larger than the wall width of said at least one individual rotor.
148. A homopolar machine according to claims 1, 2,3 or 4 wherein the manufacture of said at least one rotatable rotor includes assembling of said axially extended conductors in the annular gap between two concentric cylinders.
149. A homopolar machine according to claim 148 wherein said axially extended conductors are made of at least one of the selection of copper, silver, aluminum, lithium, beryllium, gold, copper alloys, silver alloys, aluminum alloys, lithium alloys, beryllium alloys and gold alloys.
150. A homopolar machine according to claims 1, 2,3 or 4 wherein the manufacture of said at least one rotatable rotor includes applying an electrically insulating surface layer to said axially extended conductors.
151. A homopolar machine according to claims 1,2, 3 or 4 wherein the manufacture of said at least one rotatable rotor includes assembling of said axially extended conductors into modules.
152. A homopolar machine according to claims 1, 2,3, 4 and 151 wherein the manufacture of said at least one rotatable rotor includes assembling of said axially extended modules by means of an insulating surface layer and curing it to stick said modules together.
Description:
MULTIPOLAR MACHINES -OPTIMIZED HOMOPOLAR MOTORS/GENERATORS/TRANSFORMERS RELATED U. S. APPLICATION DATA [0001] A related U. S. patent application is: 1. "Bipolar Machines-A New Class of Homopolar Motor Generator", D. Kuhlmann- Wilsdorf, Patent Application, filed May 6,2002. Serial Number 10/139, 533, Pub. No.

2003/0052564A1, Pub. Date March 20,2003.

Applicant claims priority for this application to the following: 2."Multipolar Machines-Optimized Homopolar Motor/Generators", D. Kuhlmann- Wilsdorf, Provisional Patent Application, filed July 9, 2002 ; Serial Number 60/394,639.

3."Multipolar Machines-Transformer Applications", D. Kuhlmann-Wilsdorf, Provisional Patent Application, filed July 30,2002 ; Serial Number 60/399, 546.

FIELD OF THE INVENTION [0002] The present invention relates to"multipolar machines", an optimized, and believed to be the ultimate, class of homopolar machine, including motors, generators and transformers, comprising at least one"current-channeling"rotor of Nr> 1 concentric, mechanically rigidly joined but electrically insulated rotors that are electrically highly conductive only in the desired current direction or current directions (normally but not necessarily parallel to the rotation axis). For this reason a rotor with NT > 1 may also be referred to as a"rotor set"and its components as"individual"rotors.

[0003] Multipolar machines according to the present invention may have No » 1 electrical current"turns"even for NT = 1, i. e. per individual rotor, whereas ordinary homopolar and "bipolar" (patent application of May 6,2002, Serial Number 10/139,533, reference zu above) machines have ND = 1 and ND = 2 current"turns"per individual rotor, respectively.

Thus the number of turns in multipolar machines is NDNT with ND ranging from ND = 1 up to

ND = 100 or even more, whereas the number of turns in ordinary homopolar machines equals NT and in bipolar machines equals 2NT.

[0004] The typically sizeable value of ND of multipolar machines is valuable because at same rotor dimensions, rotor surface speed (vR) and machine current (iM), the machine voltage (VM) is proportional to NTND if all"turns"are electrically connected in-series. Therefore, for ND 2 3, multipolar machines exhibit a correspondingly increased machine voltage compared to ordinary and bipolar homopolar machines. For example, with all turns in series, for same machine power (WM), value of NT, machine dimensions and rotation speed, the machine voltage (VM) of multipolar motors is larger by the factor No and ND/2 compared to ordinary homopolar and to bipolar motors, respectively, while their machine current is correspondingly decreased by the factors of 1/ND and/ND, respectively. This last feature is beneficial for at least two reasons 1. increased adaptability of machine design to specific needs or circumstances 2. greater suitability for low rotation speeds, e. g. as for ship drives with typical propeller rotation speeds of v S 180RPM = 3/sec which might otherwise require prohibitively large input currents with the corresponding massive bus bars for current supply.

[0005] Reversal of the current direction reverses the rotation direction of multipolar motors.

This provides a simple method for stopping a large machine. Next, the application of currents in opposite directions to two selections of in-series connected turns will provide a net mechanical torque equal to the difference of the two opposing torques produced by the two opposing currents, thus slowing or stalling a motor, for example. The difference between the electrical power input and the mechanical power output will be converted into heat in the machine or, by the use of electronic controls, may be extracted as heat in external heating coils; i. e. a multipolar machine may simultaneously be used as a motor and a heater

[0006] Further, reversing the direction of conversion between electrical and mechanical energy by supplying mechanical energy to a multipolar machine through rotating the machine axle, causes it to act as a generator, as is equivalently the case for the majority of electrical motors. The output voltage of multipolar generators is correspondingly proportional to NDNT and thus is increased relative to ordinary homopolar and bipolar generators of otherwise similar dimensions by the factor of ND and ND/2, respectively.

[0007] Another important feature of multipolar machines according to the present invention is the fact that, electrically, each"turn"is independent of any other. Therefore the NDNT turns of a multipolar machine may be connected in-parallel and/or in-series, as may be desired. Also, any combination or selection of"turns"may be used in the motor mode, by passing externally supplied current to them, optionally with different input voltages and current strengths, while other combinations or selections of"turns"may be used in the generator mode, again with different input and output voltages, namely proportional to the number of turns that are connected in-series in the different primary and secondary transformer circuits.

[0008] Differences in the overall consumption of mechanical and electrical power supplied externally as compared to the mechanical and electrical power and heat provided to the outside through motor, generator and heater function determine whether any particular multipolar machine requires a net input of electrical or mechanical energy. Moreover, that balance of power may be changed at will from time to time. The only basic limitation of versatility in the indicated use of the"turns"of a multipolar machine is that all"turns"are situated on the same rotor, i. e. are mechanically rigidly connected and therefore move with substantially the same surface speed.

[0009] The outlined electrical mutual independence of the turns permit, also, the use of a multipolar machine as a transformer by supplying a primary voltage to a predetermined

selection of turns connected in-series, and extracting current at a secondary voltage from another prede-termined selection of turns connected in-series. In a multipolar machine of a sufficiently large number of turns, two or more such primary and/or secondary transformer circuits may be operated simultaneously, and by the use of rectifiers, direct, alternating and three-phase currents may be used for inputs, singly or in any combination, although the output current will only be DC.

[0010] Finally, any and all of the indicated functions may be operated simultaneously in any desired combination.

I. GENERAL DESCRIPTION OF THE INVENTION 1. Basic Design [0011] The relevant background regarding homopolar and bipolar machines has been presented in published application, "Bipolar Machines-A New Class of Homopolar Motor Generator", D. Kuhlmann-Wilsdorf, Patent Application, filed May 6,2002, Pub. No.

2003/005264A1, reference [1], above. In bipolar machines [1], at least one NT 1 axially current-channeling rotor encloses an axially elongated bar-type magnet centered on the rotation axis, whose magnetic axis is normal to the rotation axis and whose two poles extend almost to the opposite sides of the inner rotor surface. This magnet, together with a cylindrical flux return about the rotor, provides two similar, diametrically opposed axially extended zones within the rotor that are penetrated by a radial magnetic field in the same direction and whose circumferential widths compare to the thickness of the magnet normal to its magnetic axis. An electrical current flowing from one end of these zones to the other end and back along the other zone in the opposite direction, is acted on by the corresponding opposite Lorentz forces so as to generate a torque about the machine axis in the same sense.

Conversely, when the machine is mechanically rotated, it acts as an electrical generator wherein the corresponding axial currents are induced in the two zones.

[0012] According to the present invention, the at least one rotor of a multipolar machine, by contrast, comprises a plurality of typically narrower, axially extended zones each of which is penetrated by a radial magnetic field due to radially aligned magnetic field sources of opposite polarity that are elongated parallel to the rotation axis and are disposed inside and outside of the rotor along at least one mid-section of the rotor. The magnetic field sources are geometrically arranged such that the rotor is free to rotate in the gaps between their magnetic poles. Thus the opposing magnetic field sources establish at least two axially extended zones that are penetrated by a radial magnetic field wherein the widths of the zones compare to the width normal to the magnetic axis of the aligned magnetic field sources.

[0013] A current flowing along any one such zone will experience a Lorentz force that generates a torque about the rotation axis. The sense of that torque depends on the direction of the current relative to the orientation of the radial magnetic field. The torque will be in the same sense of rotation when both the direction of the magnetic field and the direction of the current flow are reversed, as is the case when a current flows, say, from left to right in a zone with a magnetic vector pointing radially outwards, and returns from right to left in a zone with a magnetic vector pointing inwards.

[0014] Physically, the magnetic field sources may for example be the axially extended poles of individual bar-type permanent magnets or of electromagnets, or in sufficiently large machines even of super-conducting magnets, whose magnetic axis is radially oriented and whose extent in circumferential direction is typically small compared to the rotor circumference. Advantageously, radially aligned pairs of opposed similar magnetic field sources generate strip-shaped zones which are radially penetrated by magnetic fields. These correlated pairs of magnetic field sources may differ from each other from zone to zone; the

arbitrary number of zones may be even or uneven; the widths of the sources of magnetization and thus the circumferential width of the zones may differ arbitrarily and need not to be uniform; the sense of direction of the radial magnetic fields in the zones may arbitrarily change from zone to zone; the zones may be arbitrarily disposed about the set of rotors; the zones need not be straight nor be parallel to the rotation axis; and the length of the zones in axial direction may be arbitrary. Further, there may be more than one rotor on the same axle and a rotor may have a plurality of midsections along which zones are arranged.

[0015] In preferred embodiments, a plurality and up to all of said strip-shaped zones in any one mid-section of a rotor are similar to each other, are parallel to the rotation axis, are evenly disposed about the rotor circumference, and/or the sense of direction of the magnetic field in them alternates. Further, advantageously said magnetic field sources are the poles of horseshoe-type permanent magnets that are elongated in and parallel to the rotation axis direction so that geometrically they resemble tunnels such that each magnet pair generates two parallel zones exhibiting opposite directions of the radial magnetic field.

[0016] Independent of specifics as to numbers and kinds of magnetic field sources, when operated as a motor, a multipolar machine is driven by at least one current source, and the current is constrained to flow along the indicated zones by"current channeling means"of which various forms have been disclosed in [1] and which are further discussed below.

[0017] Each current passage along the length of a zone constitutes a current"turn". On account of the current channeling feature, each turn is electrically insulated from its neighbors, except as it may be passed to or from the outside and among zones by means of electrical brushes that slide on slip rings on the at least one rotor and electrical connections to such brushes. Correspondingly, in principle each current turn is independent of all of the others and may be used independently of all the others, except (i) that mechanically each zone has its fixed location determined by the magnetic field sources that produce the zone

and (ii) that each zone experiences the same surface speed of the rotor, and the induced voltage or the mechanical torque due to the zone, as the case may be, is proportional to that surface speed. Therefore, singly or in any combination, current turns may be driven by a single current source or by a plurality of current sources as guided by suitably positioned electrical brushes and circuit connections to these.

[0018] If the current is made to flow in one direction, e. g. from left to right, in zones in which the magnetic vector points, say, radially outwards from the axis, and returns from right to left in zones with the opposite magnetic polarity, the Lorentz forces in the different zones act in the same sense of rotation and are additive, and reversal of the polarity of the current source reverses the sense of rotation.

[0019] If rotated by an externally applied mechanical force, a multipolar machine will act as a generator. In that case currents are induced in the zones and will be channeled to and fro by the same current channeling means, arrangement of brushes and electrical connections to these, to generate the corresponding current and voltage. In that case the voltages induced in zones connected in-series are additive.

[0020] Advantageously, for zones connected in series, the radial magnetic field alternates from zone to zone and the current is led from at least one electrical brush on a slip ring adjacent to the end of one zone, through the zone, to at least one other brush on a slip ring adjacent to the other end of the zone, from there to neighboring brush on the same slip ring and back along the neighboring zone etc, wherein each brush is individually aligned with the zone. Thus by means of electrical connections between them, said electrical brushes electrically connect consecutive current turns, as already indicated, advantageously but not necessarily, among geometrically neighboring zones so as to reduce the length of current connections between brushes.

[0021] In a motor with all zones connected in series and driven by a single DC current source, consecutive concentric rotors may be electrically connected in any desired order. However, so as to minimize the length of electrical leads among brushes, preferably the electrical brush at the exit end of the last zone of one of the concentric rotors will be electrically connected to the brush at the entry end of the first zone of the next rotor, and so on, until all of the magnetic zones have been traversed by current. Advantageously, independent of the particular use of a multipolar machine, neighboring zones will be connected by means of"brush pairs"being brushes that are rigidly, electrically conductively joined and whose foot prints straddle the interval between the zones.

[0022] According to the present invention, commonly but not necessarily, there will be an even number of similar zones per rotor and each rotor will ordinarily comprise one slip ring at each end. Except for the described interconnection between electrical brushes on the same slip ring for guiding the current from one zone to the next, brushes on the same slip ring are electrically insulated through the indicated current channeling means. Further, according to the present invention as well as [1], adjoining rotors in a set of rotors and their slip rings are mutually electrically insulated either by means of electrically insulating cylindrical layers between them, or the rotors may in fact not the physically separate but a rotor set of concentric, mechanically joined but electrically insulated rotors may consist of a material with inherent current channeling structures such as polymer matrix/metal fiber composites without particular boundaries between the concentric rotors. In that case the requisite insulation between adjacent concentric rotors is provided by suitably constructed boundary zones between slip rings, as for example discussed in conjunction with Figure 22E and 22F in [1] and will be discussed in conjunction with Figures 11 and 12 below. In such a case it is necessary as well as sufficient (i) that the electrical insulation among adjoining electrical conductors in the rotor withstand the voltage difference between them, (ii) that the slip rings are constructed such that the electrical

insulation between them withstands the voltage difference between them, and (3) that adjoining electrical brushes are electrically insulated from each other.

[0023] The voltage difference between most adjoining conductors in a current-channeling rotor is minor, in fact it is near zero within any one zone and among zones on the same'track", i. e. the same individual rotor, the voltage difference is that between two current turns over a separation distance that is comparable to the zone width. With suitable machine construction, the resulting electrical field will rarely exceed 100 V/cm of current channeling structure.

Considering that within any rotor the channeling structure is static, i. e. does not have to withstand relative rubbing motions, already thin insulating layers in the channeling structure such as of lacquer or adhesive, of provide adequate insulation. However, across the first and last"turn"in any one individual rotor as well as between neighboring rotors and adjoining slip rings, the voltage difference is NDVI which may amount to thousands of volts and may require the corresponding more elaborate electrical insulation.

2. Electrical Brushes [0024] Electrical brushes in multipolar machines according to the present invention may be of any type.. While, the friction and joule heat losses of conventional monolithic carbon-based brushes are too high and their capacity for both current density and sliding speed is too low for successful use in previous types of homopolar machines, the performance and reliability of metal fiber brushes [2] has been increasingly proven to be satisfactory for even high demands.

For this reason the brushes and brush pairs considered in the present invention disclosure are assumed to be of metal fiber brush type, meaning that the current is transferred to and from the slip rings via thin metal fibers as described in [2], albeit employing a novel morphology and construction for brush pairs in accordance with a separately submitted patent application.

Even so, the present invention does not depend on the use of metal fiber or any other particular

type of electrical brushes, including for example also metal foil brushes [3]. This is so on account of the typically greatly increased machine voltages and correspondingly decreased machine currents of the multipolar machines of the present invention, as compared to other types of homopolar machines. This makes the use of conventional carbon or any other type of successful brushes a viable possibility.

[0025] On account of the gradual development of the metal fiber brush technology, the performance limits of metal fiber brushes in continuous operation at low wear rates, i. e. less than Nlx10-1° dimensionless wear, are historically rising. At this point metal fiber brushes are believed to be capable of a sustained maximum current density of at least jma = 2000 A/in = 3. 1 x 106 A/m2 and maximum sustained sliding speeds of at least 50m/sec. Possible speed bursts of up to at least 150m/sec and current peaks well above 4000 A/in2 have been proven but may involve substantially increased wear rates [2].

[0026] Friction and joule losses of metal fiber brushes on slip rings in controlled atmospheres may be predicted based on a simple theory. They depend on brush pressure, speed and current as discussed in [2], and typically are an order of magnitude smaller than for carbon brushes. At the time of writing, metal fiber brushes have been developed also for operation in the open atmosphere and for commutation. Practical experience amounts to cumulatively well above ten thousand hours of operation outside of the laboratory and includes several weeks of operation in a 15hp pump with commutating motor in regular service in a US Navy submarine.

Laboratory tests and practical experience have consistently supported the underlying theory (unchanged since 1979!) as well as numerical estimates presented in [2], including also the estimates of dimensionless wear rates in the mid 10'11 range for typical applications.

[0027] To-date, practical experience is restricted to metal fiber brushes that depend on adsorbed moisture for low wear rate, at a friction coefficient of between about 0.3 and 0.4 in a moisturized controlled atmosphere, and somewhat higher, e. g. about 0.6, in the open air.

Accordingly, for metal fiber brushes of the kind so far in use, adequate access of moisture, meaning humidities of about 30% or more, is required. For this reason it is believed, albeit so far without experimental proof, that the foot prints of currently available individual brushes should not be longer than about 3cm in sliding direction, that intervals between consecutive brushes on the same sliding track should equal to or exceed the brush length in sliding direction, and that no more than one half of slip ring area should be covered with brush foot prints. Similarly, currently available metal fiber brushes that slide on suitable (typically electroplated) surfaces, may be operated in the open atmosphere at ambient temperatures of up to about 80°C (limited apparently by desorption of moisture), while their lower temperature limit is not yet known but believed to be higher than freezing temperature.

[0028] Recent developments in metal fiber brush technology suggest that advanced metal fiber brushes will soon become available that are not limited by the above restrictions but may be operated at any arbitrary areal density of brush foot print on slip rings, at any humidity, even in space, and at any realistic temperature, i. e. from well below freezing to well above boiling.

3. Significance of the Various Parameters [0029] In a machine connected to a single current supply in the case of a motor, or to a single "customer"in case of a generator, in which all zones are similar and are connected in-series, the machine voltage is VM = NDNTV1. Here ND is the number of zones about the circumference of the set of rotors, NT is the number of rotors per set of rotors as before, and V1 is the voltage per current"turn". For good machine efficiency, the magnetic flux should not be unnecessarily constrained within the bodies of too narrow magnetic field sources, meaning that in the case of permanent magnets their cross sectional area anywhere should preferably not be smaller than the area of their poles. Therefore wide zones require proportionally wide magnets also in radial direction. Consequently, assuming a fixed

proportion of the rotor circumference to be covered by zones, for otherwise constant dimensions the total weight of the magnets is proportional to the zone width. As a result, increasing ND values, that imply decreasing zone width and small magnets, are correlated with decreasing machine weight, even while the machine voltage rises in proportion with ND.

[0030] In line with the above, large ND values and thus small zone widths are typically beneficial. Next, for increased voltage and high machine efficiency, also the wall thickness of the rotor set, T, is advantageously made as small as possible. This is so because the magnetic flux density, B, between magnetic field source pairs of opposite polarity which face each other across a gap of width >T, and to which magnetic flux density the Lorentz force is proportional, decreases steeply with increasing gap width. In multipolar machines, therefore, there is a premium on limiting the geometrical gap width between the pairs of magnetic field sources as close to the rotor wall thickness, T, as may be possible without causing undue friction and wear.

[0031] In preferred embodiments, therefore, T is made as small and ND as large as possible.

Further, in order to minimize demagnitization that will weaken B, adjoining magnetic field source poles of opposite polarity on the same side of the magnetic gap must have an adequate width and be spaced adequately far apart. The ratio of the optimal pole width and the free space between neighboring poles to the gap width needs still to be determined from case to case. Provisionally it has been assumed that the poles should optimally be-2. 5T, wide, and that poles of neighboring magnets on the same side of the rotor wall should be separated by similar distances. Thereby an upper limit on ND is established that is proportional to the rotor diameter D and inversely proportional to T.

[0032] Next, a lower limit of T and thereby an upper limit of ND arises as follows. The joule heat due to the maximum motor current, iM, that may be passed along a zone without overheating through Joule losses and to which the Lorentz force and thus the motor torque

MM is proportion-al, is inversely proportional to both the zone width and rotor wall thickness, i. e. is proportional to 1/T2. Independently T, and thus ND, are limited by the mechanical strength of the rotors which mechanically must transmit the machine torque without significant elastic deformation so as not to degrade the current channeling between correlated electrical brushes on the slip rings on either end of the zones. The resulting upper limit of ND is determined by a compromise between the ohmic internal machine resistance that rises with decreasing rotor wall thickness, as discussed, while the mechanical strength of the rotor decreases with decreasing wall thickness.

[0033] The number of individual concentric rotors per rotor, NT, primarily influences the machine voltage, VM. For otherwise same conditions VM is proportional to NDNTL with L the axial length of the zones penetrated by the radial magnetic field of the paired magnetic field sources. Therefore, NT 2 2 may be chosen in order to increase the machine voltage. The motivation for increasing NTND by dividing rotors into sets of NT > 2 concentric rotors, so as to increase machine voltage and decrease machine currents, is strong, because for these, ND is limited to ND = 1 and ND = 2, respectively. By contrast, multipolar machines may have sizeable ND values even for small machines. Meanwhile, NT > 1 complicates machine construction and cost, and also the number of electrical brushes and brush holders rises in proportion with NT. Therefore, unless high machine voltages are desired, preferably but not necessarily, multipolar machines will be constructed with NT = 1, i. e. single rotors.

4. Motor Operation with DC, AC or 3-Phase and/or Multiple Current Sources a) Almost Unlimited Possible Combinations of Current Sources in Operating a Multipolar Motor [0034] Due to current channeling in the rotor (s), each zone is electrically independent of all the others, except for possible electrical interconnection by means of electrically interconnected brushes, to the effect that each zone may be regarded as an electrically independent module of

homopolar machine. This fact permits electrically connecting the different zones in any desired combination of"in series"and"in parallel"configurations, and to drive them by any desired combination of current sources. Consequently, multipolar motors may be operated with direct (DC), alternating (AC), or three-phase current, independent of ND and NT. Also, they may be operated by a plurality of current sources, optionally of different voltages, that may be DC, AC and/or 3-phase in any arbitrary combination. Finally, the current sources may provide currents in opposite directions in any arbitrary combination, so as to mechanically oppose each other but add their Joule heat production through internal machine resistance. This last option permits combining motor and electric heater function in any arbitrary ratio. Moreover, since the electrical connections among the zones is accomplished through connecting the brushes appropriately, advantageously including the use of the already introduced brush pairs, while the brushes are all in close proximity, i. e. situated on two parallel slip rings at either end of a rotor of restricted length, modes of operation may be changed from one to the other by means of simple on/off current switches.

[0035] In spite of possibly very non-uniform distributions of currents among the zones, in terms of magnitudes, driving voltages and distribution about the rotor circumference in actual use, a multipolar machine will remain truly"homopolar". This is so because, even while a rotor or a plurality of lengthwise consecutive rotors on the same axle rotates, the location and current distribution in all of the zones is independent of angular orientation of the axle, except for perhaps a slight ripples due to possible non-uniformity in the distribution of conductors in the rotor or rotors and hence slight angular non-uniformity of internal resistance. As a consequence, under all use conditions, multipolar machines will be acoustically and electronically as quiet as any other homopolar machine.

[0036] A further advantage of the use of multiple current sources for driving multipolar motors with multiple current sources is simplification of motor control. Instead of having to control one very powerful current source, a plurality of current sources permits much greater flexibility, including, say, fine-tuning via one or more smaller current sources being switched on or off.

b) Safeguards Against Brush Failure [0037] In addition to the great flexibility that is afforded by the opportunity of teaming multipolar motors with different current sources, there is an advantage in doing so for the sake of machine reliability. Namely, one wants to avoid the condition that currents must pass through a large number of brushes which are connected in series so that the failure of any one of them causes machine failure. Independently of this opportunity for increased machine reliability afforded by multipolar machines, the problem of possibly failing brushes in long sequences of in-series"turns", has been addressed in [1]. The remedy envisaged there is dielectric barriers between consecutive current turns that will short-circuit any current turn in which the voltage rises above some predetermined critical value. That option remains valid.

However, and as already briefly indicated, the problem is much less urgent for multipolar machines, firstly. because these may be driven by, or may supply, individually monitored current sources or customers that, if needed, e. g. for replacement or making repairs, may be temporarily bypassed if in series or switched off if in parallel. Secondly, the number of required brushes is typically reduced and brushes tend to have large areas that may be split into two or more parallel and independently spring-loaded brushes, dubbed"split brushes". Thereby the failure of any one brush does not disrupt the circuit but simply shifts current to the one or more remaining parallel brushes in a"split brush". c) Motor Operation with a Single AC or 3-Phase Current Source

[0038] For operation of a multipolar motor with a single AC or 3-Phase current source, rectifiers may be used to produce two current lines that are rectified in positive and negative direction, respectively. These two current lines may be connected to different zones in opposite direction, so as to everywhere obtain the same current direction as in DC. Herein the selection and geometrical arrangement of the zones to be fed by the one or the other current line, may be chosen at will. For normal motor operation, connections must be made to let Lorentz forces everywhere be oriented in the same sense of rotation, as already indicated, but the selection of zones to be connected to one or the other current source is arbitrary.

[0039] To begin with, consider the most simple case of intended optimum machine operation by means of a single AC or 3-phase current source. If the machine should have a plurality of sets of rotors, e. g. should have two rotor sets in the"in tandem"arrangement introduced in [1], one half of the sets of rotors might be driven with the rectified positive current and the other with the rectified negative current from one AC or 3-phase source. Similarly, for motors with NT = 2 or any other even number of rotors, one half of the rotors may be driven by the rectified positive current, the other half by the rectified negative current. Alternatively, if there is only a single rotor, one half of the zones may be connected to the positive and the other to the negative rectified current. In fact, it is not necessary that the same number of zones is fed by the positive and negative current line. The current in one set of zones, say fed by the positive current line, may be much larger than in the other set of zones.

[0040] The geometrical arrangement of the zones supplied by the + and-rectified current is immaterial, provided that the electrical connections are made to ensure that the Lorentz forces, i. e. contributions to the machine torque, yield the desired sense of rotation. For example, the zones on one side of all rotors in a rotor set, e. g. in a horizontal rotor set the bottom half, might be driven by the negative rectified current, and the zones in the mirror image side of the rotors, i. e. in this example the top half, by the positive rectified current. Or else, alternating zones in

each rotor may be similarly connected. Further, also the geometrical arrangement of rotors within one set with NT > 2 rotors among the two rectified currents is immaterial. The actual choice will generally be made so as to simplify switching between operation with DC versus AC or three-phase current. With suitable choices, such switching may be readily accomplished by simply changing the connections to the current supplies as well as among the first and last brushes of the respective zones. d) Motor Operation with an Arbitrary Selection of Current Sources [0041] A motor may be driven by a multiplicity of current sources for a variety of reasons.

One of these is the added motor reliability that may be achieved as already indicated in section a) above. Another is greater versatility, e. g. using a fairly low-power, land-based AC source for a submarine motor/generator while the craft is being refurbished in port, and switching to all- DC at sea. Another objective may be to use a multipolar motor partly or wholly as a heater.

This may be done by reversing the current direction from its normal sign in, say, one half of the zones and adjusting its strength. For example, no power supplied in the"wrong"direction and full power in the right direction, causes the motor to work with 50% power, and the"loss" fraction L, of typically 3% or so, to be emitted as Joule heat. Raising the reverse current to full power will cause the torques due to the two inputs to cancel, so that the machine's rotor set is at rest, while doubling the heat output. Moreover, at equal and opposite current inputs into the two halves of the machine, no torque will be generated and the heating effect can be controlled up to the value of the loss L by raising or lowering the current. Doubtlessly numerous other uses of the discussed opportunity of operating multipolar machines with different current sources exist and may be exploited as the need arises.

5. Generator Operation

[0042] By supplying mechanical energy via rotating the at least one rotor by means of at least one externally applied torque, the Lorentz forces acting on the electrons in the metallic rotor move these and produce the corresponding currents and voltages, i. e. reverse the motor action, and a multipolar machine becomes a generator. Here, too, a very wide range of choices is available as to the manner in which the rotor is mechanically rotated and the number of lines from which electrical power is extracted, i. e. their voltages and currents drawn. In any case the electrical power that may be extracted falls short of the mechanical power input by the amount of the loss, L, due to mechanical friction and Joule heating. l0043] Specifically, a torque of arbitrary magnitude and direction to rotate the rotor may be applied by any arbitrary means, and any selection of torques may be applied simultaneously.

Albeit with a rigid rotor set of simple cylindrical shape of constant wall thickness, the resulting circumferential velocity, vR, of the rotor will be the same for all [0044] The voltage, say, Vn, between the two ends of, say, zone n, is the product of the axial length of the zone, Ln, the already mentioned circumferential speed of the rotor relative to the magnetic field sources facing each other across the thickness of the rotor wall, VR, and the magnetic flux density due to these magnetic field sources, Bn with two possible directions, i. e. radially inwards and outwards. For any one circuit from which power is drawn, the voltage, V, is the sum of the voltages of the zones through which the current passes sequentially, i. e. V = X Vn = E Ln VR Bn. Accordingly, all electrical power generated will be DC. From this, AC or three-phase current, if desired, will have to be obtained by electronic means.

[0045] For the remainder, since electrically each zone is independent of all others, as already explained, zones may be electrically connected in any desired sequence and orientations, so that one or more different voltages may be supplied depending on the number and selection of zones through which the current in any one circuit flows.

6. Transformer Operation with DC, AC or 3-Phase and/or Multiple Current Sources [0046] As indicated above, a multipolar machine may be driven in the motor mode by the application of electrical power from any desired power source or combination of power sources, including DC, AC and three-phase, supplied to any desired sequence of zones in series, or to any desired combination of zones in series and in parallel. Thereby the electrical power will be converted into mechanical motor power minus the loss L, to be used in any desired manner. If that motor power may is used to generate electrical power in the generator mode, in line with section 5. above, the machine has been made into, or is being used as, a transformer.

[0047] Accordingly, used as a transformer, a multipolar machine may optionally transform a primary DC voltage to a secondary DC voltage, or a primary AC or three-phase voltage to a secondary DC voltage, with adjustable magnitude of primary and/or of secondary voltage, or may accept power inputs from a plurality of primary current sources with optionally different voltages and transform these into one or more power outputs via currents that have one or more different secondary voltages, and/or may simultaneously convert mechanical energy into electrical energy or vice versa, in any of the following applications: 1. One DC primary power input of voltage Vp and one DC secondary power output of voltage Vs 2. A plurality of DC primary power inputs, optionally of different voltages Vpl, Vp2.. and one DC secondary power output of voltage Vs 3. One DC primary power input of voltage Vp and a plurality of DC secondary power outputs, optionally of different voltages Vsl, Vs2...

4. A plurality of DC primary power inputs, optionally of different voltages Vpl, Vp2.. and a plurality of DC secondary power outputs, optionally of different voltages Vsl, Vs2 5. Interchangeable use of a multipolar machine as a versatile transformer and as a motor.

6. Interchangeable use of a multipolar machine as a versatile transformer and as a generator.

7. Interchangeable use of a multipolar machine as a versatile transformer, a motor or generator.

8. Simultaneous use of a multipolar machine as a versatile transformer and as a motor.

9. Simultaneous use of a multipolar machine as a versatile transformer and as a generator.

10. Simultaneous use of a multipolar machine as a versatile transformer, as a motor and as a generator.

11. Simultaneous use of a multipolar machine in any of the above modes and as a heater.

7. Simultaneous Motor/Generator/Transformer/Heater Operation [0048] The types of simultaneous operation indicated in applications 8. to 11. in Section 6. above are possible on account of the discussed mutual electrical independence of each zone on any one rotor set, even while the zones are mechanically connected by virtue of being situated on the same rotor set rigidly rotating at some angular rotation speed. In summary, a multipolar machine may be simultaneously used as a motor, as a transformer, as a generator and/or as an electrical heater, and in each of these modes with the versatility discussed in sections 4,5 and 6 above.

8. Construction of Magnet Tubes [0049] The overall plan of the multipolar machine has already been briefly indicated in Section 1 above and is as follows: The rotor rotates in the gap between axially extended magnetic poles of sources of magnetization that surround it from the outside, and correlated axially extended

magnetic poles of sources of magnetization inside the rotor. Mechanically, the magnetic field sources whose poles generate the zones of magnetic field that penetrate the rotor are held in magnetic"tubes", i. e. in an outer magnet tube and an inner magnet tube in the gap between which the rotor rotates. The magnetic tubes extend over a mid-section of the rotor that projects beyond them at both ends to permit the installation of slip rings and optionally other structures such as cooling rings to facilitate machine cooling.

[0050] The detailed construction of the magnet tubes will depend on the type of magnetic field sources used. In principle, these can be permanent magnets, electromagnets or superconducting magnets, and any one magnet tube may comprise any combination of these types, without a constraint on their sizes, magnetic strength or order. Nor do the magnetic field sources have to be pair-wise correlated. Thus three closely magnetic north poles of different types and morphologies on the outer magnet tube may face a single magnetic south pole on the inside magnet tube. However, only matched pairs of magnet poles facing each other across the rotor wall will have low demagnetization and therefore be advantageous for use in multipolar machines. In fact, as a matter of practicality, it is believed that multipolar machines will operate most efficiently if (i) all of the axially extended magnetic poles in a multipolar machine are of same axial length (L) and of same circumferential width, namely mildly larger than Tm on the outside and mildly smaller than Tm on the inside of the rotor, with spaces of similar width between them, (ii) are of same magnetic strength, (iii) are uniformly spaced, (iv) alternate in polarity outside as well as inside of the rotor, and (v) are pair-wise correlated such that an N-pole outside the rotor faces an S-pole inside and vice versa.

[0051] By this geometry are created, in the rotor, axially extended uniformly distributed "zones"of width Tm that are penetrated by an on average radially oriented magnetic flux density of roughly constant magnitude B that alternates in sense of direction from zone to zone.

If a voltage is applied between the two ends of any one zone, namely by means of correlated electrical brushes of circumferential width-Tm aligned with the zones and sliding on the outside of the rotor on their opposite ends, a current flows consecutively along the zones, and is constrained by the axial current channeling from spreading sideways into the field free gaps on either side of the zones. By further arranging brushes of neighboring zones on the same end of the rotor pair-wise, i. e. into the already discussed brush pairs, with change of brush pairing from one end of a zone to its other end, the current is made to flow forward and back from one zone to the next and next, always such as to suffer a Lorentz force in the same direction because as the current direction alternates, so does the radial sense of the magnetic filed.

[0052] Which type of magnet is to be used will depend on conditions and goals, and as already indicated, it is well possible to employ a mixture of different types as particular needs may in- dicate. However, more often than not all of the magnets will be similar, as already indicated above. Further, in a preferred embodiment already introduced in sections 1 and 3, the magnetic field sources will have the form of axially elongated horseshoe-type magnets which stretch our alongside the rotor, inside as well as outside, like a series of parallel tunnels.

[0053] For this particular type of source of magnetization, the magnetic tubes would advantageously be a nearly cylindrical non-metallic strong matrix material in which the magnets are embedded, preferably with"retention"in the sense of dentistry, and leaving free the tunnel-shaped holes between the arms of the horseshoe-type magnets that face the rotor from each side.

[0054] Magnet tubes may be made indefinitely long because the axially extended magnets in them may be fitted together in short pieces that are mechanically retained in channels into

which the magnet segments are sequentially inserted. This is possible because the operation of a multipolar machine is insensitive to variations of the magnetic fields along the zones. For the same reason, also, the mechanical structure of the magnet tubes may be separated into lengthwise sections that are aligned but independently mechanically supported.

9. Construction of Rotors a) Rotors Made of Materials with Inherent Current Channeling Structures [0055] Whether rotor sets are single rotors or are subdivided into NT : 2 rotors, in preferred embodiments rotor sets may be made in one piece of a material with an inherent channeling structure as previously disclosed in [1]. Examples of such materials, preferably of low density and high electrical conductivity, include man-made composite materials comprising continuous, axially extended metal conductors, e. g. of copper, silver, aluminum, lithium, beryllium or gold and their alloys, or still other metals and alloys, not necessarily all of the same kind, that are embedded in a nonconductive matrix or are provided with nonconductive, adhesive surface layers that are bonded together. Herein the conductors could all be of the same uniform cross section, e. g. be rod-like or plate-like or tube-like in any desired morphology, or could be a mixture of any such shapes. It is believed that suitable materials with inherent current channeling structures are commercially available or can be commercially produced on demand at reasonable cost. The electrical insulation among parallel adjoining conductors could be achieved or increased through surface films such as oxides, e. g. as obtained through anodizing aluminum.

[0056] Another example of inherent current channeling are materials in which the microstructure provides the desired channeling means in the form of one or more axially elongated highly conductive phases that are individually surrounded by one or more phases with much higher electrical resistivity. No specific examples of this kind of material come to

mind at this point but it is not doubted that (1) the described mixture of phases with greatly different electrical conductivities either already exists in various examples or can be produced, and that (2) their microstructures may be suitably axially extended by means of directional solidification, strong directional deformation such as through rolling or drawing, compaction, extrusion and/or other.

[0057] Some of materials with inherent current channeling properties, whether man-made or due to their microstructure or other, may be capable of extrusion into tubing of desired dimensions. For rotors with NT = 1 this would be a preferred direct method of rotor manufacturing. Rotor sets with NT > 1 could be produced from such extruded cylindrical rotors by gluing together graded, concentric individual rotors by means of an electrically non- conductive adhesive. b) Rotors Made of Assembled Individual Conductors [0058] Rotors may also be made by assembling macroscopic elongated conductors and bonding them together by means of non-conductive glues or embedding them in a non- conductive matrix material. In one preferred method, modules are made of well-aligned, continuous slender elements of, among others, copper, silver, aluminum, lithium, beryllium or gold and their alloys, embedded in a nonconductive matrix that are subsequently assembled into individual rotors and/or rotor sets. Advantageously, such modules will have the shape of axially extended cylindrical arcs that may be assembled into rotors by means of insulating adhesives along their axially extended joints. Molds for the indicated modules would be lengthwise sections of cylindrical tubing of suitable shape and surface finish from which the modules are removed after hardening of the adhesive. For NT > 1, modules of suitably graded diameters may be similarly glued together. Optionally the incidentally resulting cylindrical, non-conductive adhesive layer between adjoining rotors in sets of rotors

could serve as sufficient delineation between them. Alternatively, insulating layers may be utilized as separators between adjoining rotors in rotor sets. c) Rotors Wound from Current-Channeling Sheets or Foils [0059] As disclosed in [1], a rotor set comprising at least one rotor, may be wound on a cylindrical spindle in the form of continuous sheets or foils of conductive material that are provided with eddy current barriers, e. g. in the form of axially oriented cuts (eddy cuts) that may be filled with an insulating material [1]. Alternatively, and preferably, the sheet material possess an inherent current channeling structure, either due to microstructure or man-made.

In either case, individual rotors in a set of NT ! 2 rotors may be physically delineated by at least one intervening winding of an insulating material.

[0060] Or, as also disclosed in [1], a rotor set may be formed by the following steps: (i) stack together to the intended wall thickness of the set of rotors, layers of metal sheet that have been provided with eddy cuts that preferably are filled with insulating material; (ii) at the desired thickness of the rotors, insert sheets of insulating material (iii) carefully shape the perimeter of the stack and laminate the stack with some suitable binder material; (iv) while the bonding material between the layers is pliable (either because it has not yet been cured or because it is thermoplastic and has been heated) bending the stack into tube shape, (v) carefully align the layers so that all opposite edges of the same sheet abut; (vi) complete the rotor set by joining the abutting edges of the sheets in an electrically conductive manner.

Again, in lieu of making eddy barrier cuts, one may advantageously use sheet material with an inherent current channeling structure, whether man-made or due to microstructure. d) Rotors Made by Filling-in the Annular Gaps Between Nested Insulating Cylinders [0061] As another possibility, a singular, (i. e. NT = 1) current channeling rotor may be constructed by filling-in, with mutually electrically insulated but parallel slender conductors, the cylindrical gap between two, preferably thin-walled, cylindrical concentric tubes, wherein the average cross sectional diameter of the slender conductors is smaller than the width of the annular gap. Preferably, the individual conductors will be parallel to the cylinder axis and extend the whole length of the annular gap. The conductors could all be of the same uniform cross section, e. g. be rod-like or plate-like or tube-like in any desired morphology, or could be a mixture of any such shapes. Or the slender conductors could be flat or curved uniform strips that axially extend the whole length of the tubes and extend from wall to wall in substantially radial orientation. Advantageously, the slender conductors may be glued together with an individually applied electrically non-conductive adhesive or may be embedded in a nonconductive matrix material that fills in the gaps between them while fluid and subsequently hardens.

[0062] If made of insulating material, the concentric tubes could remain in place and form a permanent surfacing of the rotor, except for the required removal of the outer insulating cylinder material at the slip rings at both ends of the rotor. Advantageously, the partial or complete removal of the insulating cylinders, which will indirectly permit higher values of the magnetic flux density, B, will be effected through chemical dissolution.

[0063] Rotor sets with NT > 1 could be produced by similarly filling-in the annular gaps between nested thin-walled concentric tubes made of insulating material. In this case it is probable that the insulating cylinders will have to be left in place, except at the slip rings,

because of the difficulty of extracting the current-channeling rotors from the annular gaps. Therefore, since necessarily, for reasons of mechanical strength, the insulating cylinders must be somewhat thicker than other possible insulating layers, this method has the disadvantage of increasing the wall thickness of the rotor sets, T, and thus of the gap width between the poles of the sources of magnetization, with the attendant reduction of the magnetic flux, B. e. Rotors with Axially Extended Conductors whose Thickness Equals the Rotor Wall Thickness [0064] In a preferred embodiment, the radial thickness of the axially extended conductors that effect the current channeling in the rotors, is made equal to the rotor wall thickness, and their circumferential width is made of similar magnitude or even moderately larger. These generous dimensions of the current channeling elements are considered to be permissible because the Lorentz forces have virtually no radial component, while the orbital radius of the electrons due to the Lorentz forces is believed to be always much smaller than the rotor wall thickness, and stray currents outside of the zones that impair machine efficiency will still be modest (see below). Most importantly, such relatively large dimensions of the current conducting elements in the rotors greatly simplify the construction of rotors and rotor sets, even while they improve rotor stiffness and strength. Specifically, in method b) above, the number of conductors per rotor will rarely exceed one hundred and their assembly will be correspondingly simple. Also, construction of slip rings and insulation between adjoining rotors in a set is greatly simplified in this method since the non-conducting circumferential joints between the conductors can at the same time serve as the only needed insulating barriers between adjoining rotors in a set. f. Strengthening the Ends of Rotors by Means of Mechanical Support Rings

[0065] The rotor wall thickness at its ends may be greatly reduced, especially for NT > 1, even while the brushes are loaded against them with some perhaps not insignificant spring pressure. Therefore the rotor ends may be mechanically strengthened by means of support rings. g. Fitting Together Lengthwise Segments of Rotors.

[0066] Unlike the case of magnet tubes, fitting together lengthwise segments of a rotor is problematic, especially if NT > 1, because the current path along any one zone and from one zone to the next and next, must not be interrupted, even while the alignment of the current conducting elements must remain closely intact along the whole lengths of the zones with minimal or no mismatch between zones that would lead to shorts. For this reason, the already indicated option of making the conductive elements as thick as the individual concentric rotors in the set is highly favored. Namely, the thickness of an individual concentric rotor in a stack with NT > 1, will rarely fall below, say,-1/2 cm, and the number of conductors par rotor will rarely exceed 100. Consequently, connections may be made individually, e. g. by means of soldering or gluing with a conductive adhesive.

[0067] More problematic is the joining of lengthwise rotor stack segments in the case of materials with inherent current channeling. In that case care must be taken to align and join the different concentric rotors as carefully as may be possible. h. Electrically Insulating Adhesives, Glues and Matrix Materials [0068] Examples of suitable electrically insulating adhesives, glues and/or matrix materials include polymers of a variety of types including thermoplastics and thermosetting materials, as well as ceramics such as glasses and cements.

10. Construction of Slip Rings [0069] As outlined in section 8, in an operating multipolar machine, suitably shaped electrical brushes are positioned in line with the zones that are penetrated by the radial magnetic field of the magnetic field sources. These brushes permit current flow in the conductors that are covered by the correlated brush foot prints at either end, i. e. with proper brush alignment permit current flow in the zones but not outside of them. For proper operation of these brushes, suitable slip rings are provided, preferably of low surface resistivity and smoothed to minimize brush wear.

[0070] In all multipolar machines with NT > 1, the construction of slip rings on the outer surfaces of the rotors at the two ends of the zones is complicated by the need to prevent as much as possible stray currents between adjoining rotors (i. e. the between parallel slip rings or"tracks"), even while the voltage between adjoining tracks can amount to thousands of volts. Next, typically there are two similar sets of slip rings, each comprising one slip ring per track (i. e. concentric rotor), one each situated at the two rotor ends. The lowest width of the slip rings is limited by the required area per brush, i. e. the permissible current density, and the width of the zones within which the brushes pick up the currents. Additionally, for NT > 1, provision must be made for physical, insulating"separators"between adjacent tracks in order, firstly, to inhibit arcing or stray currents between adjoining rotors, and secondly the accidental contact between brushes on neighboring tracks.

[0071] For the case of current conductors whose thickness equals the rotor wall thickness (e. g. strips that extend from wall to wall in substantially radial orientation as introduced in section 8c or the method of section 8d above), all of the current can be extracted by brushes that run on the outer surface of the different rotors in a set. Correspondingly, for such, no machining for the production of slip rings may be required except for properly trimming the different rotors in a set to their correct length and perhaps for reducing"run-out"to a

minimum since run-out leads to machine noise and increased brush wear rates. However, machining of slip rings to taper them to expose all current conductors in them is required in all other cases. For this purpose the two ends of the rotor set are shaped into slip rings that expose, for potential contact with electrical brushes, substantially all conductors that are geometrically intersected by the slip rings.

[0072] If the rotor set is physically subdivided into separate rotors, the foot print of the brushes on the different slip rings should preferably extend over most of the width of their respective slip rings in order to make full use of the electrical conductivity of the rotors, but brushes must be prevented from intruding into neighboring slip rings since this could cause disastrous short-circuiting between tracks, as already indicated, and for the same reason electrical contacts between brushes on adjoining slip rings must be avoided.

[0073] The already mentioned separators may be used to prevent those short circuits. Even so, depending on conditions, a rotor set made of a material with an inherent channeling structure may not need physical barriers between adjoining rotors, especially not if the voltage between adjacent tracks is fairly low. In this case the slip rings may be shaped to delineate the rotors by the simple method outlined in connection with Figure 22F in [1] or an improved modification thereof discussed in conjunction with Figure 11 below.

[0074 [Further, in general care should be taken that significant stray currents do not inadvertently pass between neighboring slip rings outside of brushes. None-the-less, again depending on conditions, direct cooling through immersion of the machine into water will be feasible, as discussed in section I 10, I 12, III 13 and III 14 below, especially with NT = 1, and for multiple rotors in a set if the machine voltage is not high and/or the separator walls are high enough to reduce stray currents to a small fraction of the machine current. Also, in the case of direct cooling by immersion in water, there should be an increased circumferential interval between the first and last zone because the whole machine voltage is applied between

these, whereas the electrical potentials of neighboring brushes on the same track are either the same, e. g. in brush pairs, or zones differ by the voltage drop of the two"turns"between them, i. e. normally by 2V1.

[0075] If for some reason this should be advantageous, the zones need not be strictly parallel to the axis but may have any desired shape, provided only that the generated Lorentz force has the same direction (almost everywhere) along their length, and provided that the correlated brushes connect their respective ends, as already indicated.

11. Interrelations Between Machine Power and Dimensions [0076] A persistent concern with homopolar machines of any type is the number of the electrical brushes. Specifically, at machine power WM and machine voltage VM, the machine current iM = WM/VM (1) will normally pass through at least one brush on each of two slip rings per turn, i. e. through NB 2 2NDNT (2) brushes. Since there is a maximum current density, jmax to which electrical brushes may be operated, already introduced in section 2 as at least 3. 1#106 A/m2, the total required brush area, in any singular brush or in parallel components of a"split brush", is AB 2NDNT iM/Jax = 2NDNT WM/(Vmjmax) However, for if all zones are alike, the machine voltage is VM=ViNDNT (4) where Vl is the voltage per current turn so that the total brush area becomes AB=2WM/Vij (5)

independent of ND and NT. Typically, Vl is made as large as reasonably possible, in order to re-strict the machine current at given machine power and thereby also to reduce the brush area AB.

[0077] The machine length, L, plays a significant role herein because Vl is proportional to L, as already stated in section 3). Yet, opportunities for increasing L are limited because manufacturing of long rotors with the typically desired tight tolerances poses difficulties, and both the machine weight as well as the machine volume that should typically be kept as small as possible, are roughly proportional to L. Even so, for large ship drive motors, for example, L could range up to several meters. For the sake of mechanical strength, such long rotors may require significant wall thicknesses, T, that in [1] were estimated up to T = 0.2m. But at comparable machine performance, in multipolar machines, L and T will be significantly smaller than they would be in bipolar machines, with typically L ranging between O. lm and 2m and T between 0. 1cm and 3cm. Therefore, advantageously T will rarely rise much above 2cm unless NT is made sizeable, e. g. up to NT 20.

[0078] More important yet than the zone length, L, is the rotor diameter, D, (i) because for given circumferential width of the zones, Tm (which pending detailed modeling is assumed to be equal to the distance between neighboring zones, Tg), No is proportional to D, (ii) because Vl is proportional to the circumferential velocity, v,, that for given rotational frequency, v, is also proportional to D, and (iii) because the motor torque, MM, is proportional to D on account of the Lorentz forces'lever arm length of D/2. Thus, for same rotational velocity, eo = 2 v, same zone length, L, same magnitude of magnetic flux density, B, and same current, iM, the machine power, WM = Moo), is proportional to D3. Very powerful machines therefore require large rotor diameters, for large multipolar ship drive motors up to perhaps D = 2. 5m or even 3m.

12. Machine Efficiency and Machine Cooling [0079] As previously derived in [1], for otherwise same conditions, the machine mass is proportional to the percentage power loss, L. Further, the machine power is proportional to the machine current, iM, while the ohmic loss through internal electrical resistance in the current turns (the major contributor to the machine loss) as well as in the brushes, is proportional to iM2. That connection between machine power and loss is highly significant because the cooling needs of machines are proportional to L and cooling tends to be a problem. For this reason power losses above 3% become increasingly unacceptable for many if not most practical applications. Meanwhile, if cooling were of no concern, a doubling of machine power at the expense of a rise of L from 3% to 6%, say, with the corresponding almost halving of machine mass per unit of power, would seem to be a bargain. Hence efficient machine cooling will indirectly aid in raising machine power per unit of machine mass.

[0080] Cooling of multipolar machines may be done in various ways. In a preferred embodiments already introduced in section 8, the sources of magnetization are axially extended horse shoe-type permanent magnets whose geometry resembles that of tunnels whose passage openings face the rotor, i. e. form channels parallel and in close proximity to the rotor set. The cooling medium, whether gaseous or liquid, may advantageously be guided through those channels between the two arms of any one horseshoe-type magnet. This is apt, also, because the bulk of the waste heat is typically generated in and on the rotors, i. e. on the slip rings, in close proximity to the described channels. Those channels may optionally be closed against the rotor by some wall or membrane. Specifically for liquid coolants, this will prevent flooding of the machine. However, such flooding may in fact be beneficial because it can provide most effective cooling. For this reason, in one preferred embodiment, the outer magnet tube with its tunnels is sealed off from the slip rings by means of seals, and a cooling

medium, either water or some other fluid, perhaps an organic coolant, is circulated, perhaps assisted by a pump, through the tunnels by means of"cooling rings"on either side of the outer magnet tube. In this design, cooling through the inner magnet tube does not appear to be required or offer any particular advantages, although this possibility is not excluded.

[0081] Much simpler yet, as already introduced in section 10 and outlined in [1], homopolar machines are capable of operating while immersed in water, optionally sea water, provided that fouling through barnacles etc can be avoided and the voltages are not too large so that leak currents are small enough to be tolerated. This permits enclosing multipolar machines in pods for ship drives or ship maneuvering, but some precautions may be needed that will be discussed below.

[0082] The option of direct cooling through immersion in water is especially but not exclusively attractive for NT = 1 and when the machines are operated with metal fiber brushes that have been provided with a high cross resistance, such that the electrical resistance among fibers within a brush is high, even while the lengthwise resistance is quite low. Namely, in that case, macroscopically the brushes act as insulators through which current may be piped, and these brushes physically cover the electrical conductors of the zones exposed at the slip ring surfaces, whereas the remainder of the conductors exposed on the slip rings carry no current. Thus stray current conduction through surrounding water, whether ordinary cooling water or sea water, is expected to be dwarfed by the machine current, thus permitting cooling by direct immersion.

[0083] If the cooling medium is air or any other fluid in the machine, it may be advantageous to provide rotor ends with vanes that act to circulate the fluid when the machine is running.

13. Mechanical Structure

[0084] The rotor must be firmly, rigidly connected to the machine axle in order to rotate it in the motor mode or to be rotated by it in the generator and transformer mode. The axle, in turn will be held in some hearings supported by some foundation of the machine or by some base plate or other support. Also the outer magnet tube is, directly or indirectly, mechanically supported by that foundation or base plate or other, so as to prevent it from rotating. A steric problem is encountered by the mechanical support of the inner magnet tuber which, like the outer magnet tube is permanently stationary.

[0085] The drawings clarify the geometry involved. As will be seen, if it is not already clear from the present description, in regard to lateral motions, if it were unconstrained, the magnet tube inside the tube-shaped rotor would drop down on account of its weight to rub from the inside against the lower part of the rotor while widening the gap between it and the upper part of the rotor. This is prevented by means of at least one bearing that is rigidly connected to the inner magnet tube within which the machine axis rotates.

[0086] A preliminary analysis indicates that rotation of inner magnet tube is prevented, without any auxiliary mechanical constraints, simply through the mutual attraction of the magnet pole pairs across the rotor wall when in proper alignment versus their strong repulsion when N-poles face N-poles and S-poles face S-poles. If this automatic constraint should be predicted to fail at the highest torques within the design capability of a particular multipolar machine, one may stabilize the rotor by means of one or more gyroscopes attached to support linking the inner tube to the machine axle. Also, one may stabilize the inner magnet tube by means of gravity, i. e. weighting it at its intended bottom. However, this is not a desirable solution on account of expected oscillations, besides the added machine weight that is typically highly detrimental.

14. Multiple Rotors on the Same Axle

[0087] A multipolar machine may embody a plurality of rotors sequentially aligned along the same axle. This option may be chosen when, for example, there is a strong restriction on machine length but not diameter. Or, when one may wish to team a generator and a motor; or one may want to drive a ship by means of one rotor while idling the other except when full power is needed. Further, in case of AC power, the positive rectified current could drive one of two rotors and the negative current the other. Or three rotors could be used for three- phase. Or other.

BRIEF DESCRIPTION OF THE DRAWINGS [0088] A more complete appreciation of the present invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein Figure 1 is a schematic perspective view of a rotor and its mounting.

Figure 2 as Figure 1 but also including two pairs of magnetic field sources, two slip rings and four brushes.

Figure 3A is a schematic view of part of a rotor in cross section with surrounding pairs of different magnetic field sources that are resistant to demagnitization.

Figure 3B as Figure 3A but with all similar horseshoe-type magnets.

Figures 4 clarifies the assembly of magnet modules for the construction of tunnel-shaped magnets, including joints in lengthwise and crosswise orientation (A), slotted joints (B), centering holes in modules (C) and slanted and curved joints (D).

Figure 5A is a cross section through part of a rotor and outer and inner magnet tubes Figure 5B as Figure 5A but with mildly different magnets and additional features, including some dimensions needed for assessing the machine characteristics.

Figure 6 is a schematic cross section through a multipolar machine including mechanical supports, bearings and housing.

Figure 7 is a perspective view of part of a multipolar machine including a superconducting magnet module.

Figure 8 is a plan view of the overall foot print of slanted brushes with intervening gaps that facilitate moisture access as required for many brushes.

Figure 9 is a schematic perspective view of the basic components of a multipolar machine including three pairs of magnetic field sources.

Figure 10 is a schematic perspective view of a rotor with zones produced by paired tunnel- shaped magnets.

Figure 11 shows a schematic, perspective view of a lengthwise cut through a multipolar machine including preferred embodiment of slip rings and brushes.

Figure 12 illustrates possible cross sectional shapes of boundaries between adjoining slip rings.

Figure 13 is a schematic lengthwise cut through the end of a multipolar machine with three individual rotors and components for mechanical strengthening and cooling.

Figure 14 is a schematic cross sectional view of a multipolar machine with reduced slip ring diameter compared to the rotor diameter in the mid-section.

Figure 15 shows a schematic cross section of a multipolar machine with one possible way of constructing the mechanical support the rotor and of the inner magnet tube.

Figure 16 as Figure 15 but with improved mechanical rotor support and two lengthwise sections of an inner magnet tube.

Figure 17 is a simplified perspective drawing of vanes attached to a slip ring for cooling Figure 18 is a schematic cross sectional view of a multipolar machine of the type of Figure 16 but with different features and further construction details.

Figure 19 clarifies the current path and electrical connections in a multipolar machine with an NT=4 rotor when driven by a single DC current source.

Figure 20 clarifies the current flow and electrical connections when a machine like that in Figure 19 is driven by (A) two DC current sources, (B) an arbitrary number of DC current sources of optionally different voltages, (C) an AC or 3-phase current source, (D) a potentially arbitrary selection of AC or 3-phase current sources.

Figure 21 indicates possible ways in which a machine may be driven by a plurality of current sources and may be switched between DC and AC/3-phase operation.

Figure 22 is a schematic plan view of zones and current flow directions when used as a simple transformer with one a primary DC source and a secondary DC output.

Figure 23 as Figure 22 but with a different choice of the number of primary and secondary zones.

Figure 24 as Figures 22 and 23 but for a transformer with three primary and two secondary circuits.

Figure 25 as Figure 22 but with the primary DC power source replaced by the positively and negatively rectified components of one AC or three-phase power source.

Figure 26 as Figure 23 but as a generator, with five secondary circuits and driven by a mechanical power input (not shown).

Figure 27 illustrates making a rotor composed of two concentric tubes whose tubular gap is filled with a composite of slender conductors.

III. DESCRIPTION OF PREFERRED EMBODIMENTS [0089] Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, the present invention will now be described.

1. Basic Construction of the Rotor (Figure 1) [0090] Figure 1 is a schematic perspective view of rotor 2 and axle 10 of a multipolar machine that is rigidly mechanically connected to foundation 19 (that in this case is indicated as a base plate but could also have other forms such as a housing) by means of axle supports 23 (1) and 23 (2). The rotor may be unitary or may comprise NT> 1 concentric, mechanically fused but electrically insulated concentric rotors and is fastened to axle 10 by means of end plate 70 and structural part 61.

[0091] For the sake of clarity of the geometry, end plate 70 has been indicated as a uniform disk of the same material as the rotor. However, while the rotor will be at least partly of current-channeling material, the function of end plate 70 is strictly mechanical. Therefore it may be made of any suitable material and have any shape so as to firmly secure rotor 2 to axle 10 via structural part 61. By means of this construction, on rotation the cylindrical outer surface of rotor 2 rigidly rotates about the common rotation symmetry axis (in Figure 1 and subsequent figures indicated by a dash-point-dash line) in unison with axle 10, whether the machine is used as a motor that is driven by Lorentz forces in the rotor, or whether the machine is used as a generator that is driven by an external torque applied to axle 10.

[0092] End plate 70 (i) may be mechanically fastened to rotor 2 by any suitable means including but not restricted to screwing, riveting, soldering, welding, friction welding, gluing or other, (ii) may have any suitable shape, e. g. include shapes resembling spokes of a wheel, and (iii) may be of one piece with structural part 61 or be fastened thereto by any suitable means including but not restricted to screwing, riveting, soldering, welding, friction welding, gluing or other. Structural part 61 could, for example, be a sleeve about axle 10 or may be a

hole in end plate 70, or other, and may be secured to axle 10 by any suitable means, including but not restricted to screwing, gluing, soldering, welding, friction welding, shrink- fitting or other.

[0093] As an aid in understanding the quantitative relationships between the various parameters, including machine dimensions, rotation speed, machine power and currents, Figure 1 also indicates the rotor diameter, D, and wall thickness of the rotor, T. Herein, D is the average diameter of the NT 21 individual, concentric rotor (s) that constitute the rotor.

This approximation is deemed to be adequately accurate since multipolar machines will generally have fairly large D/T ratios, say, of about 10 and up.

[0094] Not indicated are zones, i. e. axially extended areas of the rotor wall extending over at least one mid-section of the rotor, that are penetrated by radial magnetic fields. Also not shown are sources of magnetization that generate the zones. Both zones and sources of magnetization will be further discussed below. The length of the zones, L, is less than the rotor length, if for no other reason than that there needs to be space for slip rings. Besides, there may be a plurality of sets of zones between slip rings that are arranged lengthwise sequentially along the length of the rotor. The reasons why one might choose to employ two or more lengthwise arranged sets of zones on the same rotor would be much the same as the reasons for using a plurality of lengthwise sequentially arranged rotors on the same axle that were named in section I. 14 above. Moreover, L need not be the same for all sources of magnetization for any set of zones disposed about a rotor if for some reason that will seem to be advantageous.

2. Permitted Variety of Rotors, Magnetic Field Sources and Channeling Patterns.

[0095] In order to perform the function of passing current forward and back from end to end within zones that are disposed between slip rings and that are penetrated by radial magnetic

fields, as further clarified by means of Figure 2, the current-carrying part of the rotor is made to be"current-channeling". The term"current channeling"designates the property of high electrical conductivity in channeling direction but high electrical resistance at right angles thereto, so as to constrain electrical current paths to follow the lines of a predetermined current channeling pattern. Further, the channeling patterns in multipolar machine rotors are made such that a typical current flow line extends, without retrograde meanders, from a slip ring, through at least one rotor midsection comprising zones, to another slip ring. Thus, in the midsections of any of the NT > 1 current-channeling, concentric rotors that comprise zones, current paths are constrained to extend between any two or more electrical brushes resting or sliding on slip rings on either side of a set of zones, whose"foot prints"are disposed on opposite ends of at least one common line of the current channeling pattern. Hence currents can thus flow through a zone, or part of a zone, only to the extent that the zone is traversed by at least one line in the current channeling pattern on which the foot print of at least one brush on each of the two slip rings is disposed.

[0096] Currents can be led into and out of different zones by suitably connecting electrical brushes and brush pairs, if any, on the two slip rings among each other and/or with current supplies in the case of motors and transformers or"customers"in the case of generators or transformers.

[0097] In accordance with the present invention and the above general description, it is not necessary that any or all of the rotor or rotors in a multipolar machine be uniformly cylindrical, rather than conical or bulbous, or have the same combination of these shapes.

Further, it is not necessary that the current channeling pattern is the same in all NT 2 1 concentric rotors in a single macroscopic rotor, or that multiple rotors in the same multipolar machine all be alike, or that any of the channeling patterns in a multipolar machine be straight and parallel to the rotation axis, although the latter is the most obvious and believed

to be optimal pattern. Rather, if for some reason this should be desirable, the rotors in any one multipolar machine could have an arbitrary selection of shapes, including bulbous, conical, cylindrical or a combination of these shapes, and they could comprise an arbitrary selection of current channeling patterns, e. g. sinusoidal along the axis direction or spiraling or arbitrarily curved. Further, the sources of magnetization in any one multipolar machine could comprise an arbitrary selection of permanent magnets, electro magnets and superconducting magnets of various shapes, sizes and magnetic flux densities. However, since (i) the end- points of the current paths in the rotor are determined by the positions of the brushes on the slip rings as described, and (ii) since the brushes are stationary relative to the sources of magnetization and thus are stationary relative to the zones, whether the rotor is at rest or rotates, and (iii) since in a homopolar machine the current must not change with changing angular rotor position, all current channeling pattern should be distributed over the rotor without angular dependence. Also this last restraint on angular uniformity of the current channeling pattern may be violated and still permit a multipolar machine to operate as a motor, a generator, a transformer and/or a heater, but it would not be any longer homopolar in the strictest sense band exhibit the corresponding electrical noise, especially if the magnetic field sources produced different magnetic flux densities and/or the zones were of different widths.

[0098] In summary of the above general considerations, note that for any construction, the currents in the available current paths between brushes along the channeling pattern of a rotor will be acted on by, or will produce, Lorentz forces through their interaction with the radial magnetic fields of the magnetic field sources. Herein it is not necessary that the zones be straight, or be of uniform width, or all be similar, or follow the pattern of the current channeling, or that the radial magnetic field in them be all of same strength, or that the radial magnetic field in them have uniform strength from one end of the zones to the other, or

indeed that the magnetic field in a zone be continuous or be strictly radial. None of these restrictions need to be maintained if this seems to be advantageous for one or the other reason. However, in preferred embodiments, multipolar machines have thin-walled cylindrical rotors with uniform current channeling pattern parallel to the rotation axis, and zones of uniform width extending parallel to the rotation axis that are penetrated by magnetic flux densities that are substantially uniform along the length of any one zone. In the following, therefore, these last conditions will be assumed, while recognizing that the present invention permits all of the above indicated deviations in rotor number and shapes, as well in design of channeling patterns in the rotor or rotors, and in choice and disposition of magnetic field sources, and that in many cases one may wish to make use of the various modifications.

[0099] In a preferred embodiment, therefore, axially aligned magnetic poles of pairwise similar geometry and magnetic pole strength are radially aligned to face each other across a gap within which a rotor comprising an axially aligned current channeling pattern rotates; and electric brushes, optionally in the form of brush pairs and/or split brushes, are disposed on slip rings at both rotor ends, in axial alignment with the zones that are generated by the magnetic pole pairs.

[0100] Preferably such alignment is done carefully. Namely, if the potentially current- carrying strip of rotor wall established by correlated brushes at opposite zone ends protrudes circumferentially on either or both sides beyond the correlated zone, part of the current can flow in paths that are not penetrated by the full radial magnetic field, which part of the current will therefore not be acted on, or produce, the full Lorentz force. On account of the thereby reduced impedance, in the motor mode a disproportionate fraction of the current will flow in the strip (s) with no or decreased B value, and thereby will contribute less to the torque, thereby reducing motor efficiency. Similarly when operated as a generator, the

indicated low-B strips will short-circuit the zones of strong magnetic flux density and thereby reduce the generated voltage.

[0101] In fact, as already indirectly indicated, the magnetic flux density B between any two magnetic field sources that face each other across the wall of a rotor set and thereby establish a zone, does not terminate abruptly at the edges of the projection of the magnetic field sources on the rotor wall. Nor is the magnetic flux density, B, within any one zone uniform but it peaks at the center. This is expected to cause a non-uniform current distribution within zones with a relative minimum of current density at the center. Meanwhile, the extra width of available conductive area increases proportionally with the overlapping width of the brush foot prints at the two zone ends. Hence increasing the brush foot print width reduces waste joule heat, thereby ameliorating the discussed detrimental effect of brush footprints that tangentially protrude beyond a zone. The optimal width of brushes relative to the zone width, taking into account the indicated opposing effects, should therefore be determined by detailed analysis. Pending this, in the present patent application, tangential brush widths are assumed to equal the correlated zone widths and these, in turn, to equal the morphological width of the sources of magnetization and of brush foot prints.

3. Current Channeling Means in Rotors [0102] The desired strong anisotrop of electrical resistivity for current channeling, typically with very low electrical resistance in axial direction and very high electrical resistance at right angles thereto, may be effected through a variety of current channeling means, or "channeling means"for short, some of which have already been introduced in section 9 and/or in [1]. These include"eddy cuts"or"eddy current cuts", being physical cuts in the desired direction of current flow that optionally may be filled in with insulating material.

Eddy cuts need not be continuous over the whole length of the intended current flow but it is

sufficient that they have a high length to spacing aspect ratio. Another form of channeling means is represented by microstructures in directionally solidified or strongly directionally deformed materials that comprise at least two phases with greatly different electrical resistivities.

[0103] A further embodiment of channeling means are composites in which continuous elongated metal components that are embedded in non-conducting matrix material or are assembled such that cross conduction between them is inhibited. Particular examples are highly conductive wires, rods or strips embedded in a suitable polymer or ceramic, as also highly conductive wires, rods or plates that are covered with some insulating surface layer and are glued together or are pressed together mechanically (compare section 9). Examples of insulating surface layers include oxide films, other non-metallic films such as may be applied though chemical reaction or electrochemical plating, e. g. anodizing of aluminum.

Suitable highly conductive materials include, among others, aluminum and aluminum alloys, copper and copper alloys, silver and silver alloys, and other noble metals and noble metal alloys. The cross sectional shapes of the length-wise extended conductors is optional, including circular (as in ordinary wire), ring-shaped (as in tubing), rectangular (as in strips of foils sheet or plates) or irregular in almost unlimited morphologies, e. g. star-shaped, sinusoidal, elliptical etc. Preferably, though, cross sections should not unduly vary along the conductors because local electrical resistance is inversely proportional to cross sectional area and is integrated from brush to opposite brush.

[0104] Elongated conductors may be held together by means of continuous embedments such as is the case in commercial composites wherein the matrix material is typically some plastic. Or else the conductive components may be glued together by thin layers of, say, epoxy or any other suitable glue. Or the conductors may be held together by mechanical means. In one preferred embodiment this is done by filling the annular cavity between two

concentric thin-walled tubings with wires or plates that are supplied with an insulating surface layer.

[0105] A further form of channeling means are weaves or meshes in which one set of parallel fibers or strands (e. g. the weft) are metallic and the other (e. g. the warp) is non- metallic. Thus rotors may also be fashioned of such weaves or meshes, e. g. by winding them onto suitable spindles and then fixing their shape, e. g. by infiltrating with some non- conductive hardenable material such as a polymer.

4. Placement and Mechanical Support of Sources of Magnetization (Figure 2) [0106] Figure 2 repeats and expands Figure 1 with the addition of two pairs of magnetic field sources, comprising inner magnetic field sources 5 (1) and 5 (2) paired with outer magnetic field sources 6 (1) and 6 (2), respectively. In the example of Figure 2 these magnetic field sources are straight and extend parallel to the rotation axis of the rotor, i. e. parallel to axle 10.

These magnetic field sources generate in the rotor two stationary, straight, axially extended, strip-shaped zones (not shown) that are penetrated by a radial magnetic field, namely one zone in the magnetic gap between the magnetic field source pair 5 (1)/6 (1) and a second zone in the magnetic gap between field source pair 5 (2) /6 (2). In the generator mode, those two zones generate electric voltages on account of Lorentz forces, and in the motor mode those two zones are acted on by Lorentz forces, as they move relative to the rotor material when the rotor rotates. Also shown are four brushes, namely brushes 27 (la) and 27 (lb) that are correlated with the 5 (1)/6 (1) magnetic field source pair and brushes 27 (2a) and 27 (2b) correlated with the 5 (2)/6 (2) magnetic field source pair. Herein it is assumed that the current channeling in rotor 2 is linear and parallel to the rotation axis of axle 10 everywhere so that the current in the zones will be parallel to the current channeling pattern in rotor 2.

[0107] Brushes 27 (la) and 27 (2a) slide on slip ring 34 (a) at or near the a-end end of rotor 2, outside of the mid-section of rotor 2 about which the magnetic field sources are disposed, being the arbitrarily named end of rotor 2 that in Figure 2 points towards the right. Similarly, brushes 27 (lb) and 27 (2b) slide on slip ring 34 (b) at or near the other, the arbitrarily named b-end of the rotor that in Figure 2 is at left. With the implied current channeling pattern parallel to the rotation axis in rotor 2, brushes 27 (la) and 27 (1b) are positioned to conduct current into and out of the zone generated by the magnetic field source pair 5 (1)/6 (1) at the ends of the zone generated by magnetic field source pair 5 (1)/6 (1). Similarly brushes 27 (2a) and 27 (2b) are positioned to feed current into and out of the zone generated by magnetic field source pair 5 (2) /6 (2).

[0108] Magnetic field source pair 5 (1)/6 (1) is indicated as a pair of permanent magnets and magnetic field source pair 5 (2) /6 (2) as a pair of electromagnets (requisite electrical leads not shown). In fact, it is possible also that either or both of magnet pair 5 (1)/6 (1) and 5 (2) /6 (2) would be superconducting magnets. Further, the two components of any magnetic field source pair could be unlike, as illustrated in Figure 3A. For example, a permanent magnet inside may be paired with an electromagnet outside. Any of such possibilities could be attractive for large rotor diameters D, e. g. in space or for large ship drives for which D could range up to about 2m. For mid-sized and small multipolar machines, permanent magnets are expected to be the preferred choice because they can be more compactly made with lower weight than electromagnets or superconducting magnets. However,"Extended-Reach" electromagnets (see p. 3269 of the 2002 McMaster-Carr catalogue) could serve well at medium and perhaps up to large sizes. Experience in this regard will be invaluable.

[0109] Inner magnets 5 (1) and 5 (2), respectively, are fastened, directly or indirectly, to the housing or base plate 19 by means of a mechanical supports 29 (1) and 29 (2) that exit the central cavity of the rotor set opposite to end plate 70. Thereby supports 29 do not. interfere

with machine rotation. Specifically, magnet 5 (1) is fastened to axle support 23 (2) by means of mechanical support 29 (1), and magnet 5 (2) is fastened to base plate or housing 19 by means of mechanical support 29 (2). Both mechanical supports are shown in the form of curved or bent rods but could have any desired suitable shape. Support 29 (1) could be fastened to magnet 5 (1) and its equivalents in any other machine by any suitable means, among them those already enumerated for fastening end plate 70 to rotor 2 and structural part 61, respectively, and for fastening structural part 61 to axle 10. Mechanical supports 29 serve the function of keeping inner magnets 5 in place relative to the rotor and to their correlated outer magnets 6.

[0110] Magnet 5 (1) is shown also to be supported by axle 10 via mechanical support 26 and low-friction bearing 35. Support 26 via 35 is optional as indicated by the fact that none is shown for magnet 5 (2). If teamed with one or more optional low-friction bearings between inner magnet (s) 5 and rotor 2, as indicated in Figures 6 and 7, such mechanical support centered on axle 10 stabilizes both rotor 2 and inner magnet (s) 5. That can be advantageous for axially long machines when rotor 2 and inner magnet (s) 5 are rigidly fastened to opposite ends of the machine, i. e. each only at one end, in the designs indicated in Figures 14 and 16, so as to permit rotation of rotor set 2 in the gap between inner (5) and outer magnets (6).

However, optional low-friction bearings (35) between rotor 2 and inner magnets (5) have severe disadvantages and are best avoided, which is possible through the basic design indicated in Figures 15 and 17.

[0111] In contrast to inner magnets 5, the mechanical rigid support of outer magnets 6 relative to axle 10 is unproblematic since it may be located anywhere outside of the outer diameter of rotor 2 and be fastened to base plate or housing 19 directly or indirectly.

Therefore and in order not to add to the complexity of Figure 2, only the support 25 of magnet 6 (2) is shown. However, there will be a strong force of attraction between the inner

and outer magnets that need to be supported. We shall return to this point in connection with Figures 15 and 17.

5. Magnet Shapes, Magnet Material and Estimated Cost (Figures 3 and 4) [0112] In the absence of flux returns, the magnets shown in Figure 2 are bound to be inefficient on account of demagnitization, the more so, the shorter their radial extent. The same feature argues also against magnets in the form of two fairly thin-walled concentric ferro-magnetic tubes that are axially strip-wise magnetized through their thickness with alternating sense of magnetization, and similarly against assemblies of axially extended arced strips of such tubing spaced with appropriate gaps between oppositely magnetized strips.

Geometrically cylindrical magnets and assemblies of arced strips magnetized through their radial thickness can be suitable for constructing multipolar machines. In fact, precision fabricated magnets are commercially available as made of advanced magnetic materials including NIB (neodym iron boron). Currently, MCE Inc. (Magnetic Component Engineering, Inc, 23145 Kashiwa Court, Torrance CA 90505, http ://www. mceproducts. com, Tel. (800) 989-5656) markets precision fabricated magnets in various forms, e. g. rings with optionally distributed magnetization direction though their thickness, as well as arced sections of cylinders, of up to about 4"diameter in the case of rings and similar width in the case of arced strips.

[0113] Precision fabricated magnets are made with very tight dimensional tolerances and could be manufactured on demand, e. g. such that they could be readily stacked or radially assembled into magnet tubes. This could be a favored option, especially for small machines.

For example, according to the MCE product information center, two concentric Tubes of about 0. 2" wall thickness and T = 0. 2"gap width between them, would provide about B = 0.8 Tesla in the gap. Due to severe demagnetization on account of their small radial

thickness, this is several times lower than the material's intrinsic flux density. MCE Inc quotes the magnets at between $100 and $200 per cubic inch. This rather high cost is some- what offset by the elimination of much machining effort. and magnet assembly beyond, say, gluing or attaching by any other means, short rings or arced segments together so as to form the desired tubes.

[0114] Considering cost and availability the discussed superior magnets could be attractive for small multipolar machines but would seem to be unsuitable for medium-sized to large machines. For these, magnets of less costly material whose cross sectional shapes resist demagnitization would be more advantageous. Magnet shapes that fulfill the requirement of low demagnitization include horseshoe, bridge and channel magnets. According to the Edmund Scientific Catalogue and the McMaster-Carr catalogue, Alnico magnets in all three of these forms are available with an intrinsic maximum magnetization of about 3 Tesla, at currently about $15/in3 or about $106/m3. Presumably this cost will decrease for large magnet assemblies.

[0115] Figure 3A shows, in cross section, five pairs of radially aligned magnetic field sources arranged about part of rotor 2. They comprise one horseshoe magnet (5 (1)), two bridge magnets (5 (4) and 6 (4) ), two channel magnets (6 (2) and 6 (5) ), and three irregular magnets ( (5 (3), 5 (5) and 6 (3) ), plus two bipolar ("extended reach") electromagnets (6 (1) and 5 (2) ) whose current leads are not shown and are likely to be located at either end of the rotor set. In terms of resistance to demagnetization, all of these magnet types would be greatly superior to the examples of magnetic field sources in Figure 2, as well as to any thin-walled magnets composed of advanced magnetic materials already discussed. Two of the pairs, 5 (3)/6 (3) and 5 (4) /6 (4), comprise essentially the same magnets on both sides of rotor set 2.

These are irregular magnets (5 (3) and 6 (3) ) with three poles each, and bridge magnets 5 (4) and 6 (4). The other three pairs consist of horseshoe magnet 5 (1) teamed with bipolar

electromagnet 6 (1), bipolar electromagnet 5 (2) teamed with channel magnet 6 (2), and irregular magnet 5 (5) in the form of an elongated horseshoe magnet with an elliptical piercing, teamed with channel magnet 6 (5). Herein, magnet 6 (5) is composed of three magnet modules, namely two similar rectangular rods of magnetic material and a strip of (not necessarily the same) magnetic material. The three modules of magnet 6 (5) are assembled into U-shape and magnetized in the fashion of normal channel-magnets with axially extended N-and S-poles, e. g. like 6 (2). The modules of magnet 6 (5) are joined together along joint 62 by any suitable means, including soldering or gluing.

[0116] Figure 3A clarifies that axial zones along rotor set 2 that are penetrated by a radial magnetic field so that axial currents will suffer Lorentz forces or conversely in which a mechanical rotation of rotor set 2 will generate axial currents, may be established by any pairing of any arbitrary arrangement of magnetic field sources. Thus the opposing poles of a magnet pair need not have the same circumferential width, as illustrated for magnetic field source pairs 5 (1)/6 (1) and 5 (2) /6 (2), their magnetic flux density may not be of equal strength (which among others would permit B of magnets 6 (1) and 5 (2) to be arbitrarily regulated through controlling the current input into them) and indeed one of any magnet pair may not even be a magnet but could be"keeper", e. g. magnet 6 (1) could be replaced by a"keeper".

More radically yet, one of the magnet tubes could be replaced by a continuous flux return [0117] The definite restrictions applying to pairs of magnetic field sources for multipolar machines are in fact very few, as already outlined in section 2 above. In summary and partly additionally to the points already made, individual magnets need not to be symmetric about their radial mid-plane; their geometrical mid-plane may be inclined against the correlated radial plane of rotor set (at corresponding weakening of the radial component of B which is responsible for the rotative Lorentz force);

the magnet pairs need not to be spaced evenly about rotor set 2; they need not be provided with curved pole faces for generating a uniform gap between pole face and rotor set 2 (although that will typically be desirable); the gap width between magnetic pole faces and rotor set 2 may very arbitrarily ; along any one zone they need not generate the same strength off ; along any one zone the line of magnet poles may comprise arbitrary variations in circumferential width and strength of B ; along any one zone the sense of direction of B may change arbitrarily ; the line of magnets along any one zone may be discontinuous; and zones may not be linear or axially oriented but they could, for example, be spiral shaped, provided that brushes at the ends of the zones are correlated.

[0118] The two basic conditions governing any of the above possible modifications are (i) that current, i, can flow only through conductors of which both ends are within the footprint of a brush, and (ii) that the Lorentz force generated in any one zone is F = J f [txB] dA dL (6) integrated over the overlapping area of the brushes at the opposite ends of the zone and over the current path length between the brushes at the opposite ends of the zone.

[0119] Motivations for instituting any one of the deviations from regularity enumerated above may be found from case to case. For example, in small machines there may not be space enough for housing magnets inside of the rotor set and therefore"keepers"may be used instead. As another example, in order to provide for an effective method of braking a machine, one may wish to selectively reverse the magnetic flux over selected zones or pre- determined parts of zones by means of reversing the current direction in one or more strategically placed bipolar electro-magnets. Next, it may be intended to provide two or more

selectable machine power levels by activating groupings of zones by means of different independently controllable current sources (see section 111. 9. ), and one may determine that, say, for low-power machine operation, horseshoe-type magnets are the most economical, while a few electromagnets may be used to boost power to top levels. Similarly, on account of the larger space available for the outer as compared to the inner magnets one may decide to use space-saving but more expensive permanent horseshoe magnets of advanced magnetic material for the inner magnet tube and more voluminous but cheaper bipolar electromagnets that can generate the same high values of B for the outer magnet tube.

[0120] The particular choice of magnet type and shape will depend on a variety of features, including but not restricted to machine performance, construction cost, maintenance and operation cost, availability of magnets, space requirements, weight and ease of machine assembly. These different considerations may in fact point to the use of different magnets for the inner and outer magnet tubes as already indicated above. Further, even for uniform arrangements of a selected magnet type as in Figure 3B, the exact shape, spacing and size of the magnets relative to the gap between the poles of opposing pairs of magnets, within which the rotor set slides, will have to be determined by detailed analysis. Symmetry considerations suggest for the optimal arrangement, which yields the optimal compromise between the magnetic flux density in the zones and the number of zones per circumference, that the tangential extent of the magnetic poles, Tm, and of the gap width, Tg, between the poles, will be nearly equal and will be two to three times larger than the radial distance between opposite poles across the gap width, T, as already introduced in section 1. 3. Namely, if neighboring magnetic poles on the same side of the rotors are progressively moved closer to each other, an increasing fraction of the magnetic flux will pass between poles on the same side instead of to the correlated poles across the gap, thereby diminishing the strength of the radial flux

density, B, through the zones. Conversely, if the poles are too widely spaced a reduced fraction of the available rotor wall area is utilized for zones.

[0121] In line with the above varied considerations, Figure 3B shows a very simple but presume-ably quite effective arrangement of inner and outer magnets, all of the same horseshoe type. Another advantageous choice, especially in regard to low cost and ease of manufacture would be channel-type magnets with flat pole pieces that are assembled like magnet 6 (5) in Figure 3A. This is so because permanent magnets in the shape of rods and strips are more readily obtainable and at greater axial length and lower cost than other shapes.

Further, for ND > =-l 0, the variation of gap width between a rotor and a flat pole piece become increasingly small and the resulting reduction of B compared to the smallest gap width in the middle of a flat pole piece is negligible, whereas shaping pole pieces into cylinder arcs is liable to be costly.

[0122] The construction of magnet tubes will be greatly simplified through assembling of permanent magnets from"modules" (4) as illustrated in Figure 4. The possibility of assembling magnets from modules has already been introduced in connection with channel- type magnet 6 (5) in Figure 3A, i. e. as constructable from strips that are glued, soldered or joined by suitable means, Figures 4A to 4D clarify geometries for the assembly of magnet modules, e. g. into axially elongated horseshoe-type shapes. Herein, axially oriented joints between modules are labeled 62 and cross-wise joints, i. e. joints normal to the rotor axis, are labeled 63.

[0123] While in Figure 4A, joint 62 happens to be in the mid-plane of the magnet, and while this is likely to be a favorite choice, this is not necessary. In fact there is a very wide variety of possible shapes, locations, means of joining, surface condition and details of surface morphology of the two sides of a joint before assembly, e. g. to facilitate alignment and/or bonding strength. All of these are meant to be included in the present invention disclosure.

For example, joint surfaces may be slotted in male and female shapes as indicated for the case of an axially oriented, slotted joint 64 in Figure 4B, or magnet modules 4 may be provided with axially aligned centering holes 66 through which rods may be passed for lengthwise alignment of magnet modules as indicated in Figure 4C. Bonding may be done by gluing, soldering, friction welding or any other method, and surfaces may be prepared by etching, spraying, painting, sandblasting, photolithography, scoring, or providing the desired surface relief in the molds in which the segments may be cast, pressed and/or sintered. Also, joints may be irregular in various ways, e. g. be wavy or be inclined to the axis as indicated by means of wavy joint 64 (1) and inclined joint 64 (2) in Figure 4D.

[0124] All of these choices are liable to be made based on cost and manufacturing efficiency, but since the steps therein would all be evident candidates for mass production techniques that would be no more demanding, difficult or costly than comparable techniques in the manufacture of small magnets for industry or research. Since such costs are already included in the retail magnet prices indicated above, the discussed preparation of magnet modules for assembly into axially extended sources of magnetization, they are unlikely to significantly raise the cost per unit weight of magnets suitable for multipolar machines above the estimate already given.

[0125] The discussed joints will not be heavily stressed in machine operation and they will be held together by magnetic forces. Therefore joining operations are no expected to be critical in terms of strength. But they will commonly be critical for achieving tight dimensional tolerances. Correspondingly in favored embodiments, modules 4 may favorably be glued together by means of thin layers of epoxy or other advanced adhesive so as to obtain minimal deviations from the intended shape of assembled magnets. Further, joints 63 will not interfere with the magnetization of the assembled magnets, whereas axial (62) and irregular (65) joints have a small potential of such interference. For this reason axial and irregular

joints (65) should preferably be avoided. For the same reason, also, possible centering holes 66 ought to be made of small diameter.

6. Basic Overall Morphology in a Preferred Embodiment (Figure5,6 and 7) [0126] As indicated in section III. 4, there is latitude in constructing the requisite mechanical supports for outer as well as inner magnets. Specifically, magnets could be individually supported such as in Figure 2. Or they could be collectively supported in various groupings wherein the magnets in any one group comprise a plurality of magnets from two up to their whole complement on either side of the rotor. Herein magnets could be separated by spacers made of metal, wood, other organic materials, ceramics or plastics, and be connected to these and among each other by means of bolts, rivets or screws, or by means of soldering, welding or gluing, or any other means.

[0127] In a preferred embodiment magnets are molded or cast or inserted into magnet tubes of the general type shown in Figure 5, wherein the matrix materials, labeled 55 and 56 for the inner and outer tube, respectively, will typically be some lightweight (i. e. compared to structural metals) high-strength polymer such as a rosin, an epoxy, Teflon, a reinforced composite, a phenol or similar. Alternatively, matrix material 55 and/or 56 may be at least partly of metal and may be produced by means of machining, casting, molding, spark cutting, extruding, pressing or sintering. Matrix material 55 and/or 56 will be variously selected for stiffness, mechanical strength, light weight, low melting point, castability, corrosion resistance, machinability, suitability for sintering, or suitability for spark cutting, wherein the weight placed on the different criteria will depend on the size and intended use of the machine. Including the already mentioned polymeric materials, candidate materials include but are not restricted to a selection from aluminum, an aluminum alloy, lithium, a lithium alloy, beryllium, a beryllium alloy, tin, a tin alloy, zinc, a zinc alloy, cadmium, a cadmium

alloy, titanium, titanium alloy, copper, a copper alloy, favorably among these a bronze, steel, stainless steel, a noble metal, a noble metal alloy, a commercially proven casting metal, a commercially proven metallic, polymorphic, ceramic or glassy sintering powder, a metallic, polymorphic, glassy or ceramic material suitable for casting as a slurry, an experimental casting metal and an experimental sintering powder.

[0128] Magnets-may be directly cast, molded or sintered into the magnet tube channels, depending on the properties of matrix material 55 and 56. Or suitably shaped channels for the magnets may be provided by means of casting, machining, sintering, extrusion, pressing, spark cutting or any other method of shaping, to be filled with magnets, preferably in the form of modules to be slid or mechanically pressed into the channels from either or opposite sides. Advantageously, the channels and magnets will be shaped to provide"retention"in the sense of dental fillings, as indicated in Fig. 4. This will not only provide extra mechanical strength for ordinary machine operation but additionally provide shock resistance as is a precondition for use in US Navy vessels.

[0129] As already indicated, magnet modules may be piecewise, successively inserted into preformed smooth-surfaced shaped channels of suitable size and shape. This may simplify construction of outer and/or inner magnet tubes as well as reduce manufacturing costs.

Favorably, magnet modules being inserted into such channels may be coated with some suitable adhesive or a lubricant that on drying will harden into an adhesive, or they may be soldered together.

[0130] Also shown in Figure 5 are electrically insulating wear resistant low-friction coatings (24) on rotor 2 and/or the outer and inner magnet tube. Further, the tunnel-shaped channels formed by the arms of the horseshoe-type magnets (45 and 46 for the inner and outer magnets, respectively) are indicated as being closed against the gap between magnet tubes and rotor in Figure 5A but open to that gap in figure 5B. Both of these modifications are

possible and may be optionally used. The open-gap version is advantageous for machine cooling in which the tunnel-shaped channels 46 of the outer magnet tube and adjoining gap to rotor 2 are flooded by a liquid coolant such as water or an organic coolant as envisaged in Figure 13 and 18.

[0131] Figures 5A and 5B are not to scale. Specifically, while the width of the poles, Tm, and the width of the circumferential gaps between the poles, Tg, will optimally be similar to each other as indicated in Figure 5, they will typically be rather larger than the gap width between the outer and inner magnet tubes, TM, and this in turn will be only mildly larger than the wall width, T, and the thickness of coating 24 will be quite small compared to T.

[0132] Figure 6 shows a possible cross section of a multipolar machine in line with the above considerations. In addition to the features already discussed in conjunction with Figure 5, it includes a housing 19 to which the outer magnet tube 6 is rigidly connected through mechanical supports 25 that correspond to mechanical support 25 in Figure 2. Supports 25 are required to supply the counter-torque against the torque exerted on the rotor by the Lorentz forces, i. e. supports 25 serve the function of counter-balancing the machine torque and must have the corresponding strength. The morphology of supports 25 is widely variable and may attach the outer magnet tube to a base plate much as the magnetic field source is supported by the base plate 19 via support 25 in Figure 2, or in any other suitable morphology.

[0133] Shown also in Figure 6 are mechanical supports 26 between inner magnet tube 5 and bearing 35 surrounding axle 10. These components correspond to support 26 and bearing 35 of Figure 2 that keep inner magnet tube 5 in place that have already been discussed.

Especially support structure 26 may have a wide variety of shapes and be made of various different materials. Additionally, low-friction bearings (35) may be provided between rotor 2 and either or both of the magnet tubes as indicated in Figure 6. The function of these

bearings, like that of support structure 26 and the bearing 35 that centers on axle 10, is to stabilize the relative positions of rotor 2 and magnet tubes 5 and 6. However, either or both of these kinds of bearing may be unnecessary as will be further discussed in conjunction with Figures 14 to 17. Namely, inner magnet tube 5 is inhibited from rotating through the magnetic attraction of the opposite poles on tube 6 facing it across the rotor wall. Up to some limiting torque on inner tube 5 on account of its interaction with rotor 2, no mechanical support 29 between it and housing or base plate 19, may be necessary to prevent inner tube 5 from rotating. In that case only its mechanical weight needs to be supported and this may be taken up through pressure between inner tube 5 and rotor 2 at the lower end, i. e. the six-o- clock position.

[0134] In contemplating the question of bearings, mechanical supports and choice of matrix materials 55 and 56 (which may in fact be physically the same material), account must be taken, also, of the rotationally symmetric magnetic force between tubes 5 and 6 that results from the mutual attraction of the north and south poles of the magnets facing each other across the rotor wall. Its effect is to cause an overall compressive stress in the outer magnet tube and a tensile stress in supports 25. Given even a modest compressive strength of magnets 6 and material 56, those stresses are likely to be harmless. More problematic are the complementary tensile hoop stress in the inner magnet tube and tensile stresses in supports 26, if any. In conjunction with the radially outward direct force on the individual magnets 5, the indicated hoop stress could cause magnets 5 to detach from material 55. In order to forestall such possible de-bonding,"retention"in the sense of dentistry is may be used as indicated in Figure 5 and already discussed. Also, care may be taken to establish firm bonding between magnets 5 and material 55. To this end, the surfaces of magnets 5 could, for example, be chemically treated with a bonding agent or they could be mechanically roughened before molding the inner ring.

7. Multipolar Machines with Electromagnets [0135] As indicated by means of Figure 3A, electromagnets may be used, singly, partly or exclusively, for powering multipolar machines. Their particular advantage is a typically controllable magnetic flux density B which may exceed that of permanent magnets. Aside from special considerations already discussed in connection with Figure 3A, whether to use electromagnets and if so in what proportion relative to other magnetic field sources, is mainly a question of bulk, cost, machine efficiency and increased complexity. No simple answer seems to be possible without careful analysis from case to case. The advantage of permanent magnets above electromagnets is almost certain to decrease with machine size but it is questionable at what size, if any, electromagnets will be definitely superior to permanent magnets. This indeed will greatly depend on the cost, relative ease of manufacture and weight of permanent magnets that, in turn, significantly depends on machine size (see section 5. above).

8. Superconductinç Multipolar Machines (Figures 7 and 8) a) Advantages and Liabilities [0136] Much the same considerations in weighing the choice between electromagnets versus permanent magnets discussed in section 7 above, apply to superconducting magnets. The decisive advantage of superconducting magnets in the construction of homopolar machines of all types is their ability to generate controllable, and an order of magnitude greater, magnetic flux densities, B, than permanent and electromagnets. This is of critical importance because at otherwise same machine construction, increased B values translate into proportionally higher torque, power, voltage and/or induced current strength. Meanwhile the options available to increase machine voltages and torques in traditional homopolar machines are

limited because there is only ND = 1 turn per individual concentric rotor and, secondly, only one magnet to supply the magnetic field for all of the machine which greatly restricts the dimensions of the rotor. These conditions make the use of superconductive magnets almost mandatory for traditional homopolar machines. The disadvantages of superconducting magnets compared to permanent and electromagnets include greater complexity, higher cost and increased machine volume. However, the technology of superconducting magnets has made great strides in recent years and continues to develop rapidly. Therefore superconducting multipolar machines may well become competitive with permanent magnet multipolar machines in time, even though at this point the forecast cost efficiency and performance of multipolar machines with conventional permanent magnets significantly outclasses that of conventional superconducting machines. The decisive points are discussed in the following sections. b) Reduced Number of Turns (N_) per Rotor on Account of Bulky Magnets [0137] As already discussed in conjunction with Figure 3A, the magnets of multipolar machines may be selected largely independent of each other, not only from zone to neighbor zone but even along the length of any particular zone. Further, it will be advantageous to assemble also super-conducting magnets, like other magnets, in the form of modules (compare section III. 5 and Figure 4A above). These two facts together generate the possibility for many different ways in which superconducting magnets may be used in any one multipolar machine, singly or in any proportion up to exclusive use of superconducting magnets. Figure 7 illuminates the issues involved by means of a single superconducting magnet module as follows.

[0138] Figure 7 shows magnet module 4 which houses superconducting coil 8 surrounded by an unseen coolant which will probably be circulated into and out of module 4 by means of a

pump and tubing that are not shown in Figure 7. A current is passed through the many turns of superconducting coil 8 (whence the high magnetic flux density B) by means of leads into and out of module 4 that also are not shown in Figure 7.

[0139] Module 5 forms part of outer magnet tube 6 (of undetermined construction outside of module 4). In Figure 7 module 4 extends for about one sixth of the circumference of rotor 2, and extends along an undetermined fraction of the length thereof. The magnetic poles of the superconducting magnet in module 4, of circumferential width Tm, are marked N and S on the annular front face of module 4 and extent substantially along the axial length of module 4.

Between them, the north and south pole pieces leave a gap of circumferential width Tg, as indicated in Figure 7. In line with previous Figures 3 to 6, so also in Figure 7 gap width Tg is assumed to be of similar as the pole width, Tm, and much larger than the rotor wall width, T.

This is not a necessary condition, though, and Tg could in principle be as narrow as z 2. 5T while practically speaking Tm is liable to be rather larger than that.

[0140] In rotor 2, the two superconducting magnetic poles (N and S) generate two zones of circumferential width Tm, provided that they are opposed by essentially the same magnetic pole face geometry in a correlated module on the other side of the rotor set wall 2, as will be assumed in the interest of good machine efficiency, even though this may be practically impossible on account of space constraints, except in rather large machines. In any event, the construction of superconducting coils and surrounding thermal insulation will put a lower limit on Tm whereas in multipolar machines with permanent magnets T will typically range between a few millimeters to a few centimeters. Consequently, for Tm necessarily rather larger than-2. 5T as would be typical for permanent magnets, ND with super-conducting multipolar machines will fall well short of ND _ 7rD/5T expected with permanent magnets.

Since, further, Vl= vLB = v11DLB and VM = NTNDVi = NTNDv7rDLB, the discussed shortfall of ND (by some factor that decreases with machine size but will be significant for

small machines), will have the same effect as reducing B by the same factor. For this reason, even though B for superconducting machines can be three times and more larger than for permanent magnets, superconducting magnets will, at least for the time being, be impractical for small to medium multipolar machines, while they could be superior for large machines. c) Extended Slip Rings [0141] Superconducting magnet module 4 of Figure 7 acts in the machine like any other magnet of same dimensions. Correspondingly, electrical brushes will be aligned with the zones defined by the two poles as for other magnets. In Figure 7 the position and width Tm of the brushes are indicated by brush foot prints 12 (1) and 12 (2) on slip ring 34 that are marked by shading in axial direction. However, as already discussed in section I 2, ordinary metal fiber brushes as also monolithic brushes may not be used on footprints exceeding some upper limit of width that at this time, albeit so far without proper experimental proof, is believed to be Tm > 3cm = 1.2". This is so because of depletion of adsorbed moisture at brush/slip ring interfaces, that is necessary for currently available metal fiber or monolithic brush sliding on metal in the open air or a suitably controlled atmosphere such as humid C02 [2].

[0142] At this time, zones wider zones than the discussed limit of about 1. 2" = 3cm, will require"slanted brushes", i. e. assemblies of brushes with parallelogram-shaped cross sections that extend up to about 1. 2" in sliding direction and are separated by gaps wide enough to permit moisture access for re-adsorbing water in the wake of a sliding brush (at present estimated at about 1. 2" for typical operation in open air and moisturized C02). An example of the resulting division of a brush foot print 12 into parallelogrammatic strips 14 (1) to 14 (6) covered by slanted brushes is shown in Figure 8. In the example of Figure 8 the parallelogrammatic strips have the same width as the gaps between them and are inclined about 45° against sliding direction indicated by the arrow labeled v,. For electrical brushes

available at this time, this design is believed to be required for the purpose of preventing moisture depletion in brush-slip ring interfaces and permitting adequate access of moisture for re-adsorption between brushes.

[0143] The above is but an example and dimensions as well as angles may be chosen in accordance with circumstances, preferences and experience. Specifically, at this time high sliding speeds may require a widening of the zones with the associated widening of the brushes. However, most recent developments of metal fiber brush technology, already discussed in section I 2, suggest that the outlined restriction on brush use on account of required adsorbed humidity, will be overcome in due course. Pending such a favorable development, future experience will probably pin-point optimal values and designs for brush footprints with slanted brushes. At any rate, use of slanted brushes roughly doubles the width, A, of slip rings and thereby adds to overall machine length. Also slanted brushes are liable to be more expensive. For these reasons, it is advantageous to avoid the need for slanted brushes by limiting T to about 1/2"and zone widths to Tm <_ 1. 5". Yet, in accordance with the considerations of section b above, this may be impossible for multipolar machines with superconducting magnets. d) Increased Machine Diameter and Its Effects [0144] Like Tm, so also the radial height (i. e. extension in radial direction from axis 10) of module 4 will have a minimum value determined by the needs of superconducting coil design, cryogenic cooling and thermal insulation of modules. To the degree that this, together with necessary support structures to fasten module 4 to the foundation or machine housing 19, is larger than the radial height of permanent magnets and their support structures, use of superconducting magnets will increase the overall machine diameter. If the discussed radial heights differ by, say, AH, then for the same outer machine diameter, same machine

length, presumably nearly the same weight and at the same current and rotation speed, the rotor set diameter could be increased by the factor (1+2AH/D), i. e. to D'=D (1+2AH/D) (7) which would cause ND, VI, VM, MM and WM to rise accordingly, namely to ND'= ND (1+2AH/D) (8) V1=VI (1+2AH/D) (9) <BR> <BR> <BR> <BR> <BR> VM'= ND'V,'= VM (1+2AH/D) 2 (10)<BR> <BR> <BR> <BR> <BR> <BR> WM'= iM VM'= WM (1+2AH/D) 2 (11) MM'=WM'/# = WM (1+2AH/D) 2 (12) [0145] Thus, height differences AH between superconducting modules and the permanent magnets that they would replace, essentially degrade machine power and torque by the factor of 1/ (1+2AH/D) 2. This negative impact would affect large machines much more than small ones, but would decrease with shrinking dimensions of superconducting magnet modules.

For example, at constant B, values of AH = 3"and 8"would reduce the power and torque of a large D = 6ft machine to the fraction 1/(1+2#3"/72")2=85% and 1/(1+ 2x8"/72") 2 = 67%, respectively, whereas mid-sized D 3ft machines would be degraded to 1/(1+2#3"/36")2 = 73% and 1/ (1+ 2x8"/36") 2 = 48%, respectively. Again, for multipolar machines with superconducting magnets to be competitive with permanent magnets, these factors would have to be over-compensated by increased B values of superconductors versus permanent magnets which they replace. Assuming that superconductors might attain 4 Tesla and above as compared to 0. 8 Tesla for permanent magnets, this could be easily possible for mid-sized to large machines, including also the contribution to ND'/ND on account of extra circumferential width of superconducting modules already discussed in section 8. b above.

The value of superconducting magnets for multipolar machines thus critically depends on the compact sizes to which superconducting magnet modules and thus AH may be reduced. e) Increased Structural Forces and Stresses [0146] For same rotor dimensions, the forces and stresses in multipolar machines are expected to rise roughly in proportion with the magnitude of NDB, independent of the type of magnetic field sources used.. If so, and if B might be increased to 10 Tesla at no or only modest decrease of ND, the stresses considered in section III 6 would increase tenfold. Thereby they could become large enough to require strong structural supports between modules 4 and foundation/housing 19 and/or axle 10. Similarly, structural reinforcements would be needed among the modules 4 on either side of rotor wall 2, i. e. in magnet tubes 5 and 6, as well as between those two tubes. Importantly, also, the coils within the modules will have to be made mechanically strong enough to support their mutual attraction at the distance T plus twice the thickness of the thermal insulation. At this point, writing without specific information on superconductive magnet design, these problems seem to be manageable. On the other hand, correspondingly increased torsional stresses in the rotor set (see section I. 8. b) may demand increased rotor set wall thickness, i. e. increased T. This in turn increases machine weight that could be problematical with permanent magnet machines, but may be of less concern for superconducting magnets on account of their high magnetic field strengths. f) Increased Cost, Weight and Complexity,-Conclusions [0147] The impact of the increased cost, weight and complexity associated with superconducting magnets on account of their need for deep refrigeration is much harder to assess quantitatively than the impact of increased module dimensions discussed in sections 8b) to 8e above. The conclusions in this critically depend on the steadily advancing state of the

technology of superconducting magnets. If costs and volume of superconducting magnet modules 4 can be sufficiently reduced then, with the already achieved reported reliability of cryogenic systems and supermagnetic coils, there is a good prospect that large superconducting multipolar machines will become widespread.

[0148] The future will tell to what minimum rotor diameters superconducting multipolar machines will become accepted. To a large extent, this will depend on the intended application, i. e. which particular features are more important compared to others. Herein space applications (compare section 1. 11) may represent a special case. In view of the low ambient temperature in space (provided objects are shaded from exposure to direct sunlight) superconducting magnets may be especially attractive. A problem still to be solved in this connection is the operation of fiber brushes in space that has already been mentioned above. It is assumed that this problem (mainly of materials science) will be solved in due course.

9. Current Paths, Lorentz Forces and Electrical Brushes (Figures 9 and 10) [0149] Figure 9 is a perspective drawing of a machine of the kind of Figures 5 and 6, although for clarity of drawing, many details are omitted, including magnetic tube matrix materials and support structures. Also only three horseshoe-type magnets, i. e. six zones per magnet tube are shown, with the outer magnets 6 (1), 6 (2) and 6 (3) facing the inner magnets 5 (1), 5 (2) and 5 (3), respectively. As in the previous figures, the polarities of the magnetic poles alternate about the circumference of rotor set 2, of diameter D, and change sign across the gap so as to generate six parallel zones 21 (j) of alternating sense of radial magnetization. Of the six zones, only 21 (1), 21 (2) and 21 (3) are visible and labeled in Figure 9. All zones extend for the length (L) of the two magnet tubes. The described pattern of magnetization is indicated by the letters"N"and "S", signifying north and south, at the various magnetic poles, in agreement with accepted convention and the previous Figures.

[0150] Slip rings 34 (1) and 34 (2) are positioned at the two ends of rotor set 2, beyond the axial length, L, of magnets 5 (1) to 5 (3) and 6 (1) to 6 (3). Further, also for the sake of clarity of drawing, the brushes are not shown but only their footprints (12). The six footprints which are visible in Figure 6 are labeled 12 (1) to 12 (6) and are indicated by shading with lines that are parallel to the axle 10, in the same manner as in Figure 7.

[0151] Figure 9 clarifies the geometry of the current path (22) by means of a bold, inside the rotor broken, line. In Figure 9 the current enters brush footprint 12 (1) as symbolized by a curved line with an arrow labeled"i"that starts near the top middle of the figure. Physically, the current could have come directly from the positive terminal of a DC current source, for example, or it could have come from an unseen neighboring brush on slip ring 34 (1) that is aligned with the zone generated by the S pole of magnet 6 (3) and the N pole of magnet 5 (3).

[0152] After entering brush footprint 12 (1) on slip ring 34 (1), namely physically through an unseen brush that slides on footprint 12 (1), current i (i. e. in Figure 9 the broken bold line 22) passes along zone 21 (1) to brush footprint 12 (2) on slip ring 34 (2), and via an upward arching, bold arrowed line labeled"i"into brush footprint 12 (3). That arching line between brush foot prints 12 (2) and 12 (3) symbolizes current passage from the end of zone 21 (1) into and through an unseen brush that slides on footprint 12 (2) and from there via an electrical connection into and through an unseen brush that slides on footprint 12 (3) to the start of zone 21 (2). From there current i traverses zone 21 (2) in opposite axial direction from that in zone 21 (1), reaches brush footprint 12 (4) at the end of zone 21 (2) and, again symbolized by an upward arcing arrowed line labeled"i", passes through unseen brushes sliding on footprints 12 (4) and 12 (5) into the start of zone 21 (3). With this, current i has traversed two parallel zones, i. e. 21 (1) and 21 (2), in opposite directions, but since the sense of the radial magnetic field, B, in the two zones has reverse sense, namely radially towards the axle in zone 21 (1) and radially outwards away from axle 10 in zone 21 (2), the rotational sense of the Lorentz force F is the same, namely

clockwise, in both zones that is also indicated by the arrow labeled eo about the front end of axle 10.

[0153] This geometry is indicated by the two sets of three each mutually perpendicular arrows labeled F, i and B which symbolize the three mutually perpendicular vectors F, i and B in the usual notation by the right-hand rule and are shown along line 22, one in zone 21 (1) and the other in zone 21 (2). In line with the present exposition as well as Figure 7, brush footprints 12 (1) and 12 (2) are geometrically aligned with zone 21 (1), and brush footprints 12 (3) and 12 (4) are geometrically aligned with zone 21 (2). And the brushes (not shown) that slide on these footprints are pair-wise electrically connected (advantageously in the form of brush pairs, to guide current, i, systematic-ally from one zone to the next as indicated by the arrowed, arched, bold lines labeled"i". From brush footprint 12 (4) on, the pattern is repeated. The arrowed, arched line between footprints 12 (4) and 12 (5) corresponds to the curved line by which the current enters at the top of the drawing.

[0154] Thus, to summarize, by means of the described pair-wise interconnection between neigh-boring brushes on the same slip ring, the current reverses direction every time that it reaches the end of a zone and passes over into the next. Since also the magnetic flux density vector B, changes sign from one zone to the next, as discussed and indicated by the sets of three mutually perpendicular arrows labeled F, i and B, the Lorentz force, F, has the same sense of orientation in all zones, i. e. in this case clockwise, as already mentioned..

[0155] The described pattern of current flow, which is central to the invention of multipolar machines, is depicted still more clearly in Figure 10. Herein Figure 10 is a semi-schematic repetition of Figure 9 in which the outlines of magnets 5 and 6 are only faintly indicated, while the course of the current (22) is shown as a broken line of short arrows. The zones (of which zones 21 (1), 21 (2) and 21 (3) are the same as in Figure 9) are indicated by parallel broken lines on either side of the line of current flow line 22. Also as in Figure 9, the brushes are not shown

and, again, the passages of current, i, from the end of one zone into one brush, into an electrically connected neighboring brush and on into the start of the next zone are indicated by arrowed arching lines (in the present Figure 10 labeled 22).

10. Construction of Slip Rings (Figures 11 to 14) [0156] In [1] much attention was paid to the problem of how best to provide the end of a rotor set with mutually insulated parallel slip rings. This is especially challenging for small wall thicknesses T/NT with slip ring widths, A, that are several to many times larger than T/NT.

Several solutions were proposed in [1]. In addition to these, Figure 11 illustrates a favored embodiment of the present invention by the example of a rotor set with NT = 3 rotors that is seen in a perspective view with a lengthwise cut. The method applies to rotor sets composed of physically distinct rotors that are separated by boundaries of insulating layers, as well as to rotor sets made of material with an inherent current channeling structure without physical boundaries between the adjacent rotors.

[0157] Various examples of materials with inherent current channeling structures were introduced in section E. 3. Among others, these include man-made composites of parallel conductors embedded in an insulating matrix. , and layered weaves or meshes in which one set of parallel fibers or strands (e. g. the weft) is metallic and the other (e. g. the warp) is non- metallic, and which weaves are hardened into a rigid rotor set 2 by means of some suitable infiltrated non-conducting material. Accordingly, rotor set 2 in Figure 11 may consist of three concentric rotors, each with a fine-scale current channeling structure, that are separated by insulating boundaries 43 (1) and 43 (2) as indicated, or it may be made of a material with an inherent current channeling structure in which case boundaries 43 (1) and 43 (2) delineate neighboring current turns (or'tracks") but are not physical structures.

[0158] As a first important feature, in order for any particular brush to electrically contact all conductors in the current channeling pattern through the wall thickness of its correlated rotor, slip rings 34 (1) to 34 (3) at the end of rotor set 2 are inclined against the rotation axis by an angle, say a (not shown in Figure 11). Thereby, in the course of rotor rotation, all axially extended conductors through the rotor wall thickness are exposed to the brush foot prints on the slip rings. Depending on the choice of a slip rings of arbitrary width A may be constructed even for small wall thicknesses T/NT, since the slip ring width, is given by A= (T/NT)/sina (13) [0159] Preferably but not necessarily, the overall conical shape of the end of rotor set 2 and the features thereon including, in general terms, slip rings 34 (j) and physical slip ring boundaries 44 (j) separating slip rings 34 (j) and 34 (j+1), may be formed through shaping one or both ends of rotor set 2 by any suitable means, e. g. mechanically through turning in a lathe, grinding etc, or electro-chemically by means of currents in conjunction with electrolytes, or by means of spark cutting, or other. Alternatively, the overall conical end of a rotor set 2 with slip rings 34 (j) and boundaries 44 (j) may be produced separate from rotor 2, all in one piece or in various parts that are later assembled and joined to rotor set 2 in any suitable, electrically conductive manner, e. g. as in examples that were discussed in [1]. The advantage herein is that rotors may be long, bulky and hard to handle, while the slip rings etc may require complex, high-precision shaping operations.

[0160] In the specific case of Figure 11, neighboring slip rings are separated by boundaries 44 (1) and 44 (2) whose shape may be chosen within a wide range of possible modifications, among them the triangular shape of Figure 11 and those shown in Figure 12. In general, the function of slip ring boundaries 44 (j) is to provide electrical insulation between slip rings 34 (j) and 34 (j+1) and the electrical brushes sliding thereon, as discussed in conjunction with Figure 11 and Figurel2 below:

In order to efficiently describe the manner by which boundary 44 (j) fulfils its function, consider the"upper edge"of boundary 44 (j), i. e. the line of separation between slip ring boundary 44 (j) and slip ring 34 (j), assuming that (as in Figure 11) the slip rings on either side of the rotor are consecutively numbered in the direction from the rotor center to its ends, so that the rotation radii of the slip rings correspondingly decrease with rising number j. Said upper edge of slip ring boundary 44 (j) is made to have a radial distance from the rotation axis that is equal to or smaller than the radial distance from the rotation axis of any part of slip ring 34 (j), and conversely to be larger than or equal to the radial distance from the rotation axis of any part of slip ring 34 (j+l). hi this construction, then, a brush situated on slip ring 34 (j) at the end of, say, zone (k) intersects all possible current paths of zone (k) in rotor 2 (j) but none in either rotor 20-1) or rotor 2 (j+1). Correspondingly, a neighboring brush on adjoining slip ring 340+1) that is aligned with the same zone (k), intersects all current paths of rotor 20+1) in zone (k) but none in the neighboring rotors (i. e."tracks").

[0162] Any two brushes along zone k on neighboring tracks have a voltage difference equal to the potential difference between zone (k) in rotors 20) and 20+1). In a multipolar machine with all similar zones that are connected consecutively, this amounts to a voltage difference of NDV1 which will typically be less than 100V in small machines but can amount to thousands of volts in large homopolar machines. Accordingly, any accidental electrical contacts between neighboring brushes on adjoining slip rings will be avoided because, at best, they will cause leak currents and at worst disastrous short circuits.

[0163] Slip ring boundaries 44 are designed to inhibit accidental contacts between neighboring brushes on adjacent tracks in three different ways.

By generating a current-free zone between neighboring slip rings, namely the physical width of the boundary.

By being shaped to prevent mechanical contact with the brushes on their two sides, the efficiency of that function depending on the width, radial height and shape of the boundary with different examples shown in Figures 12A to 12E.

By means of an insulating surface finish. This last feature, e. g. a coat of paint, a coat of lacquer, an anodization film or other, would be generally advantageous and therefore is expected to be typically present, even though none is shown in Figures 11 and 12 in order not to confuse the drawings.

[0164] Figures 12A to E show a selection of boundary morphologies from among an almost inexhaustible possible range. These may be chosen as deemed appropriate for different brush sizes and brush inclination against the rotation axis, if any, as suggested by the examples of Figures 11 and 12. All of these shapes will perform the function of electrically insulating neighboring slip rings from each other subject to appropriate consideration of the radial thickness (in contrast to the already discussed axial width) of boundaries 43 between neighboring rotors as follows.

[0165] For sets of rotors separated by insulating layers 43, indicated by double lines in Figures 12A and 12B, ideally the upper and lower radial edges of any one slip ring should lie physically within a boundary 43 that electrically separates the concentric rotors to which the slip rings on either side of boundary 44 belong, and do so over the whole rotor circumference. Thus the upper and lower edge of slip ring 34 (j) should ideally coincide with boundaries 430-1) and 43 (j) of rotor 2 (j), respectively. However, insulating boundaries (43) between adjacent rotors in a rotor set cannot be mathematical cylinders of zero thickness, and precision of shaping slip rings 34 is limited at a minimum by machining precision and rotor eccentricity. Therefore, if insulating boundaries 43 between rotors in a set are made of, say, thin plastic foil, coincidence of the edges of slip ring boundaries (44) with rotor boundaries (43) will be difficult if not impossible to achieve, especially for rotor sets of medium to large diameter. Therefore, either

insulating boundaries 43 between must have adequate radial extent so as to permit the construction of slip rings without short circuiting, or slip ring boundaries 44 must be shaped to inhibit short circuiting by any of the means indicated in Figures 12C to 12E.

[0166] Firstly, leak currents and/or short circuits between neighboring slip rings 34 (j) and 340+l) may be inhibited by shallow cuts (42) on either side of slip ring boundary 44 (j) as indicated by the examples of Figuresl2C and 12D. The depth of cuts 42, if any, will be chosen to optimize the balance between reduced current flow and reduced leak current, as resulting from deeper and shallower cuts, respectively, and is exaggerated in Figures 12C and 12D.

[0167] Conditions are different for rotor sets made of materials with inherent current channeling and without physical boundaries between adjoining rotors (43) because in these the current conducting elements do not delineate precise boundaries between adjoining rotors (43).

Rather, even given nearly perfect alignment of conductors in the current channeling pattern, boundaries 43 between adjoining rotors have an effective width equal to the average diameter of the conductors in the structure. Any misalignments of the current channeling structure along the distance between opposite slip rings adds to that effective boundary width. For NT > 1, therefore, the conductors in current channeling structures should favorably have a small diameter, provided axial alignment does not deteriorate with decreasing dimensions of the conductors. In any event one will make a compromise between perfection of alignment, size of conductors, mechanical strength, conductive cross sectional rotor area lost through insulating matrix material and cost. Anyway, the radial distance from the rotation axis of the lower edge of slip ring 34 (j), on a rotor set with inherent current channeling, should preferably exceed that of the upper edge of slip ring 340+1) by at least the average conductor diameter. The squiggly zones indicating boundaries 43 in Figures 12C, 12D and 12E are meant to indicate the discussed boundary zone between adjacent concentric rotors in a set that is due to the overlap

of cross sections among neighboring conductors whose axes would delegate then to neighboring rotors, respectively.

[0168] Included in cost considerations will be the ease and perfection with which the various patterns in Figure 12 may be achieved. Perhaps the cylindrical shape of boundaries 44 in Figure 12A is favorable in this regard but it has the disadvantage of making control of the brush sliding path and thereby effective spatial separation of neighboring brushes on adjoining slip rings more difficult. At same axial width, even less control of brush sliding path would be provided by the patterns in Figures 12A and 12B, that could be easily machined. Next in line may be the triangular pattern of Figure 11 that combines simplicity with good control of brush path and still better presumably are the patterns of Fig. 12C and 12D. At any rate, the protective effect of boundaries 44 against short-circuiting among neighboring brushes rises with width and height of slip ring boundaries 44. If they are made as suggested in Figures 11 and 12 this height is limited by the position of boundaries 43 and the outer rotor diameter. Therefore it may be advantageous to increase the height of the boundaries towards the ends of the rotor.

[0169] Conditions are simpler in a preferred embodiment in which the current conducting elements are dimensioned so as to each extend through the radial wall thickness of their respective rotor, as envisioned in Figure 13. This embodiment has the advantages of (i) particularly simple mechanical construction; (ii) minimum of space wasted by matrix or adhesive material and therefore reduced Joule heat loss in the rotor; (iii) for same conductor material, high mechanical stiffness on account of fewer joints between conductors, thereby permitting increased machine torque and machine power before elastic twist in the rotor causes unacceptable misalignment of brushes on opposite sides of zones; (iv) simple construction of slip rings since these do not need tapering.

[0170] Figure 13 depicts an example with of such a rotor, i. e. wherein the typical conductor extends through the whole rotor wall width. As in the case of Figure 11, also Figure shows a

rotor composed of NT = 3 concentric, mechanically fused rotors, namely 2 (1), 2 (2) and 2 (3).

These are mutually electrically insulated by means of boundary layers 43 (1) and 43 (2).

[0171] As the slip rings are not tapered because, as already indicated, each of the three rotors is fully conductive in radial direction, shaping of the rotor end in order to generate boundaries between the respective slip rings is not required. Instead the needed barriers to prevent accidental contact between neighboring brushes on the same zone but on different tracks are, in this example, take the form of insulating separators 11 (al) and 11 (a2). Herein the"a"in the labels of Figure 13 refers to the arbitrarily named"a"-side of the machine. Plausibly, but not necessarily, the mirror symmetrical structures will be present on the other, the"b"side of the rotor. However, the slip rings on the"b"-side could well be tapered and barriers of type 44 could be shaped on them.

[0172] Specifically, Figure 13 depicts separator walls 11 (al) and 11 (a3) between the slip rings, as well as separator wall 11 (a3) at the outer edge of the outermost slip ring, i. e. at the edge of slip ring 34 (a3). These separator walls are shown to be rigidly attached to, or be integral parts of, rings of insulating material which rings in the case of 34 (al) and 34 (a2) are tapered to extend axially only some restricted distance into the rotor. The function of these optional tapered rings is to mechanically strengthen the rotor end. This stiffening function is very obvious for the case of mechanical support ring 32a, from which separator wall 11 (a3) extends, and that is much thicker and wider than the two tapering rings.

[0173] Also shown in Figure 13 is part of a possible cooling system, comprising among others cooling ring 47 (a), that will be further discussed in connection with Figure 17.

11. Slip Rings with Reduced Diameters (Figure 14) [0174] On occasion, one would wish to have a powerful large multipolar machine, requiring a large rotor diameter, but is restricted by the maximum sliding velocity of the electrical brushes,

being at this time z50m/sec or moderately higher, as introduced section I 2. Figure 14 shows one possible design by which to overcome this difficulty, namely by reducing the slip ring diameter below that of the rotor, and thereby reducing the surface speed at same machine rotation speed. An example of a case in which machine performance may be limited by the sliding speed of the electrical brushes, can be light-weight generators for possible space applications.

[0175] The construction of slip rings with reduced diameter will not only permit achieving higher machine rotation speeds and voltages, but at the same time reduce brush wear rates and thereby lengthen brush service life. On the down-side, the axial slip ring width, A, would have to be increased because of increased current density in the brushes as their width in sliding direction is reduced in proportion with the slip ring diameter. Indeed, independent of the possible necessity to employ slip rings of reduced diameter but increased axial width, A, in order to achieve fast machine rotation speeds, this option may be used also in order to increase brush lifetimes.

[0176] Figure 14 illustrates an example of a multipolar machine with slip rings of reduced size.

The basic construction of the machine is the same as already explained in conjunct-ion with Figure 2 as follows: Rotor set 2, whose cylindrical part of wall thickness T rotates in the gap between magnet tubes 5 and 6, is rigidly fastened to axle 10 by means of structural part 61. The mechanical support of inner magnet tube 5 is as follows: (i) At its right end, inner magnet tube 5 is rigidly fastened to base plate 19 by means of support 29 that is rigidly fastened to foundation 19 via axle support 23 (2) ; (ii) At its left end, inner magnet tube 5 is mechanically supported by means of mechanical part 26 that is rotatably supported via bearing 35 that encircles axle 10. For the purpose of providing slip rings of reduced diameter, i. e. significantly smaller than the diameter D of the cylindrical part of rotor set 2, support 29 is, in the example of Figure 14, shaped as an annular disk whose outer circumference is rigidly attached to the

right end of magnet tube 5 and which as its inner aperture is extended into a tube that encircles axle 10 and at its right end is rigidly fastened to motor axle support 23 (2). The needed rigid mechanical support of outer magnet tube 6 that would correspond to parts 25 in Figure 2 and Figure 6, is assumed to not be intersected by the cross section shown in Figure 14 and is therefore not shown. As in Figure 6, optional bearings 35 between rotor set 2 and magnetic tubings 5 and 6 may be included to stabilize the relative positions of the cylindrical part of rotor set 2 and the two magnet tubes. Optionally, similarly stabilized by means of bearings 35, is the tube extension of part 29 relative to axle 10 where it extends to support 23 (2) beyond the edges of tubes 5 and 6 at the right side in Figure 14.

[0177] Potential slip ring sites 36 (1) and 36 (2) at the left and 36 (5) and 36 (6) at the right are situated on symmetrical extensions of rotor set 2 that geometrically resemble support 29, i. e. in the example of Figure 14 are annular disks that extend into tubes which encircle axle 10. On the left side, said tube extension of rotor set 2 is fastened to the circumference of part 61, and is an integral part of the rigid mechanical attachment of rotor set 2 to axle 10. Figure 14 shows the mirror-image extension of rotor set 2 on the right as not being attached to any other part of the machine. However, this is not necessary and the extension of rotor set 2 at right could equally well be rotatively supported by axle 10 via bearings between it and the tube-extension of part 29.

[0178] As described and shown in Figure 14, the two extensions of rotor set 2 afford opportunity for slip rings of reduced diameters in locations 36 (1) and 36 (2) at left and 36 (5) and 36 (6) at right. These may be optionally used in various (but not unrestricted) combinations, together also with the normal slip ring locations 36 (3) and 36 (4).

[0179] The advantages of running brushes at reduced speed with increased lifetimes, on slip rings in any of locations 36 (1), 36 (2), 36 (5) and 36 (6), are offset by the extra complexity and expected extra construction cost of the design in Figure 14. Specifically, for locations 36 (2)

and 36 (5) the axial current channeling pattern of the conductors in the cylindrical part of rotor set 2 must be continued in a starburst pattern in the annular extensions of 2, and this must be accomplished without significantly disturbing their mutual alignment so that correlated brushes on opposite ends of the zones, i. e. at left and right of Figure 14, electrically contact the respective ends of closely the same selection of conductors. For slip ring sites 36 (1) and 36 (6) the problem is aggravated by the need to further continue conductors into much the same cylindrical pattern as in the central part of rotor set 2 but at reduced diameter.

[0180] The practical difficulty of the described construction is expected to sharply increase with decreasing diameter of the current-channeling conductors. The above indicated restrictions in the variety of combinations in which the discussed slip ring locations may be utilized arises for conductors whose cross section is more or less equiaxed for which slip rings have to be tapered, as indicated for sites 36 (1) and 36 (6) in line with Figure 11, in order to intersect all conductors in a zone. This restriction does not exist for radially oriented strips or ribbon-like conductors. Correspondingly, slip ring sites 36 (1) to 36 (3) could be used together, and slip rings could be used in any combination in the case of radially oriented strip-shaped conductors in rotor set 2 but not for conductors with roughly equiaxed cross sections.

12. Mechanical Supports for Rotor and Inner Magnet Tubes (Figures 15 and 16) [0181] The mechanical support of the rotor and of the inner magnet tube is of profound importance for the construction of multipolar machines. As first introduced via Figure 2, the mechanical support of outer magnet tube (s) 6 pose no problem. They may be simply supported by any part of the surrounding structures that are sufficiently strong and are at rest relative to the machine. Much more problematic is the mechanical structure and stability of rotor 2 and inner magnet tube 5, the former rotating with axle 10, the latter at rest relative to outer magnet tube 6. Further, rotor 2 must be quite firmly connected to axle 10 as it must rotate it with full

machine torque in motor mode and by which it is rotated with full machine torque in generator mode.

[0182] Sterically, the nesting of rotating rotor 2 in the gap between stationary magnet tubes 5 and 6 requires at least one rotating mechanical support structure for the rotor that extends from rotor 2 to axle 10, e. g. structural supports 61,70 and/or 27 in Figures 6,14 and 15. This/these mechanical supports between rotor 2 and axle 10 form at least one rotating barrier against any mechanical support of inner magnet tube 5 that extends through the length of the machine so as to support magnet tube 5 at two ends. And similarly, the presence of stationary magnet tube 5 prevents supporting rotor 2 at both ends if inner magnetic tube 5 requires stabilizing against rotation from outside of the machine. Thus both rotor 2 and magnet tube 5 can each be supported at only one end if magnet tube 5 requires mechanical stationary support from outside of the machine.

[0183] This feature causes the somewhat awkward structure of Figure 14 with the extended bearing 35 about the right side of axle 10 and its rigid connection to stationary axle support 23 (2). It is awkward because it requires a potentially long rotor to be fastened at only one end.

Much less problematical is the mechanical restraint of the similarly a potentially long and heavy inner magnet tube 5 against rotation, e. g. via member 29 in Figure 14, because the weight of inner magnet tube 5 may be readily borne by bearings that encircle the axle, such as the two bearings labeled 35 in Figure 14.

[0184] Figure 15 repeats the basic construction involved more clearly. Herein, rotor 2 is mechanically firmly supported only via rotating structural elements 61 and 50 fastened to axle 10 at its left end. For the remainder, rotor 10 may be stabilized via sliding contact with the outer magnet tube 6 that is firmly supported from the outside, and the inner magnet tube that in turn is supported against rotation only via structural element 29 connected to the axle support 25 (2).

For additional mechanical stability, inner magnet tube 5 is secured to axle 10 by means of

bearing 35 (2). While such constructions as in Figures 14 and 15 are feasible, they are problematic for long machines as the rotor will be prone to elastic sagging and mechanical vibrations, whereas for smooth functioning the slip rings 34 (1) and 34 (2) in Figure 15, should be free of significant vibrations and have only small"run-out", e. g. about 0. 001" = 0.025mm.

[0185] A remedy for this potential difficulty is based on the realization that (i) the weight of inner magnet tube 5 can be readily supported by bearings 35 about axle 10, as already discussed, and (ii) that with firmly supported outer magnet tube 6, so as to provide the reaction to the machine torque, the torques acting on inner magnet tube 5 tending to rotate it, are moderate and according to preliminary analysis will be overcome by the strong mutual attraction among the paired magnetic poles up to the highest expected machine torques.

[0186] With this, the construction of Figure 16 in manifold modifications is possible. Herein, the rotor is supported at both ends as well as in the middle, namely by mechanical supports 61 (1), 61 (2) and 61 (3), while inner magnet tube 5 is separated into two sections, 5 (1) and 5 (2), each of which is supported by mechanical supports 26 (1), 26 (2), 26 (3) and 26 (4). The remnant torque on inner magnet tube through Lorentz force interactions with the currents in the rotor as well as through sliding friction against the rotor will be balanced by the already mentioned magnetic attraction between the radially aligned magnetic poles of the magnets in the outer and inner magnetic tubes. Thus, the inner magnet tube 5 (and its sections) will remain stationary while the rotor is in motion. Additionally, if required, inner magnet tubes could be stabilized against rotation by means of gyroscopes, e. g. attached to or embedded in a selection of supports 26. Alternatively, also, inner magnet tubes 5 could be stabilized gravitationally by weighting them near the bottom. This would be a cost effective simple solution, -if ever it should be needed, -provided machine weight is not an issue, which it would be in moving applications, e. g. in ships, aircraft and cars.

[0187] The design indicated in Figure 16 is but one particular example in a wide range of possibilities. The division of inner magnet tubes 5 into lengthwise sections is readily feasible because of the feature discussed in conjunction with equation (6) that neither constancy nor continuity of magnetic flux density, B, along any one zone is required for proper functioning of multipolar machines. Moreover, as discussed in connection with Figure 4, magnets in magnet tubes are advantageously assembled from modules in any event. This permits the equivalent assembly also of both inner and outer magnet tubes in modules, both lengthwise and radial, in morphologies equivalent to those shown in Figure 4 and any that may be derived therefrom.

Thus not only inner but also outer magnet tubes may be assembled from, or be divided into, as many lengthwise sections as may be deemed favorable, e. g. for ease of manufacture, assembly, maintenance and repair, as also to permit as many supports 61 of the rotor as may be desired.

In fact, magnet tubes could be manufactured in arc-shaped modules or any desired angular extent in lieu of whole cylindrical shapes as may be deemed most favorable from case to case. sections, arc sections with such arcs preferably fitted together along axial planes.

[0188] Lastly, multipolar machines in which the magnetic tubes are cylindrical arcs rather than full cylinders are also possible and some good use may be found for them, e. g. for installation in very restricted spaces.

13. Machine Cooling and Other Aspects (Figures 17 and 18) [0189] Large multipolar machines and many medium-sized or even small multipolar machines will require forced cooling by means of specially designed cooling systems, unless they may be immersed in a suitable liquid, especially water, optionally see water (see section 17, 110 and I 12). Cooling through direct immersion in water may requires extra high separator walls 11. Also, it may be necessary to leave a wider gap between the first and last zones of any one rotor because there the voltage difference between neighboring brushes on the same track is not the

sum of the voltage drop of two successive current turns, as is the maximum everywhere else about the slip ring circumference with regularly distributed zones, but is the sum of the voltage drops of all zones about the slip ring.

[0190] For smaller machines, fan cooling comparable to that of car engines by means of a fan in front, and similarly of personal computers by cooling fans inside the chassis, will be sufficient. Section 1. 7 introduces the possibility that such cooling may be provided, or be assisted, by means of vanes affixed to either or both rotors near at or near their ends that circulate a cooling medium, e. g. air, about the machine. Figure 17 illustrates this option for the machine in Figure 9 to which rotor extensions 31 (1) and 31 (2) have been added. Vanes 30 (1) to 31 (6), of which only 30 (1) to 30 (3) are visible in the drawing, are affixed to extension 31 (1) and vanes 30 (6) to 30 (12) to extension 31 (2).

[0191] The shape of vanes 30 is arbitrary provided that they perform the desired function.

Figure 17 shows but one example wherein the vanes are arranged to generate an air or other fluid flow through the hollows in the magnets and in the spaces between the magnets, from extension 31 (2) to 31 (1) in the indicated clockwise rotor rotation, and the reverse direction with opposite rotation.

[0192] In order not to confuse Figure 17 unnecessarily, similar vanes are not shown on the inside of rotor set 2, but such would be no less, and perhaps even more useful and may optionally be added or used alone, with similar or different shapes and numbers for any set of vanes.

[0193] More commonly, especially for large machines, cooling will be done through circulating some suitable fluid through or about the machine in some at least partly predetermined path. Figure 18, which is a cross section of a machine of the general type of Figure 16 but without sub-divided inner magnet tube, illustrates one preferred embodiment of multipolar machine cooling. Herein, the space between outer magnet tube 6 and rotor 2 is

flooded with a cooling fluid that might be water or a watery solution or any other suitable liquid such as a commercial organic coolant that at the same time acts like a lubricant. In Figure 16 the cooling fluid is confined to said space between outer magnet tube 6 and rotor 2 by means of seals 49 (a) and 49 (b) that extend between"cooling rings"47 (a) and 47 (b) and rotor 10 on the a-and b-side of the machine, respectively.

[0194] Cooling rings 47 (a) and 47 (b) encircle the rotor on both sides of outer magnet tube 6.

They act as reservoirs in the path of circulating coolant from one side of the machine to the other, i. e. in Figure 18 from the b-side to the a-side of the machine. In its passage through the machine, the coolant in the embodiment of Figure 18 flows mainly through the tunnel-shaped spaces, 46, of the outer magnet tube 6, but also along the cylindrical gap 38 between the rotor and the outer magnet tube 6 outside of spaces 46.

[0195] The coolant may be water (sweet or salt or purified) or some other coolant, favorably among the choices electrically insulating fluids that also serve as lubricants, including a number of commercial products. In the case water and similarly air, the cooling fluid may be taken in and flow out from the outside without further tubing except as may be required for circulation the coolant by means of pumping or other. Other coolants will have to be confined to some circulatory piping system including pumping means.

[0196] A detail of part of cooling ring 47 (a) and seal 19 (a) is included in Figure 13. Among others it shows seal 49 (a), made of some suitable material such as an elastomer, e. g. Viton or other, that serves to isolate the coolant so as to prevent its escape out of the machine, where it could cause short circuiting or contaminate the slip rings and brushes. Also, escaping coolants may cause environmental hazards and in any event coolants other than freely available air or water will typically need to be replenished at financial cost.

[0197] Seal 49 (a) (and by implication similarly 49 (b) on the b-side of the rotor) is a doublet.

This is an optional refinement wherein the"leak space"39a (and by implication a similar leak

space 39 (b) on the b-side of the rotor) between the two parts of the seal doublets, labeled 49a and 49b in Figure 18, serves the purpose of bleeding off any leaked coolant through a drain hole at the bottom (not shown). This will prevent seeping of the coolant to the slip rings and brushes where it might cause short-circuiting as already indicated or, conversely, could cause increased brush resistance and/or sparking. For machines with high voltages, the use of an electrically insulating organic coolant would provide an extra safeguard in this regard.

[0198] In Figure 18, the coolant is indicated as entering the machine through cooling ring 47 (b) at top right and as leaving it through cooling ring 47 (a) at bottom left. However, this is just one possible embodiment in which to circulate coolant through the spaces between rotor 2 and at least one outer magnet tube 6. By the extensive contact of the coolant with outer tube 6 and rotor 2 in the embodiment of Figure 18, cooling will be very effective, and thereby make cooling the rotor from its inside, i. e.. through part or all of spaces between rotor 2 and at least one inner magnet tube 5 unnecessary, although this is a possible option, in addition to as well as in lieu of the indicated cooling through part or all of spaces between rotor 2 and outer magnet tube 6. Further, it is believed that indirect cooling via heat conduction through rotor 2 will be sufficient also to cool the slip rings and brushes. If this should be, or judged to be, insufficient, additional cooling by any other means, such as for example through vanes 30 mounted on rotor 2, as already discussed in connection with Figure 17, may be employed. Alternatively, especially for small machines, cooling via coolant that circulates in any part or all of the spaces between rotor 2 and either or both of inner and outer magnetic tubes 5 and 6 may be omitted in favor of other types of cooling, e. g. as by means of vanes 30, or perhaps gaseous coolant blown at or over the machine by means of some type of fan.

[0199] The weight of, and possible inertial forces on, inner magnet tube 6 in Figure 18 is, as in Figure 16, supported by axle 10 via members 26 that include bearings 35. Additionally constraining inner magnet tube 5 from rotating by structural means of the kind of member 29 in

Figures 14 and 15 is believed to be unnecessary on account of the mutual attraction between the opposing magnetic poles in the inner and outer magnet tube already discussed. If need be the constraint through the mutual attraction between opposing magnet poles may be assisted by at least one gyroscope and/or gravitationally through weighting magnet tube 5 so as to shift its center of gravity below the rotation axis.

[0200] For small machines, also members 26 with bearings 35 may be unnecessary. Such a construction may be preferred in order to lighten the machine, or to save cost, or to provide extra interior space, or to facilitate cooling. In that case the weight of magnet tube 35, to the extent that it may not be supported by the mutual attraction between opposite magnetic poles across the rotor, would in horizontal machines be supported by a lower portion of the circumferential area between rotor 2 and magnetic tube 5. For smooth sliding and low wear, at least one of the opposing surfaces of an outer magnetic tube 6 and rotor 2, and similarly at least one of the opposing surfaces between an inner magnetic tube 5 and rotor 2 should for this reason and/or in order to reduce drag through sliding friction, be provided with a low-friction, wear resistant coating 24. An example of coating on only one side is shown in Figure 5B, and an example for coatings on both sides is shown in Figure 13. Additionally, at least the opposing surfaces between any or all inner magnet tube (s) 5 and rotor 2 could be lubricated by conventional means, and similarly for outer magnet tube 6 unless such lubricants should interfere with machine cooling. Thereby the coefficient of friction between rotor 2 and magnetic tubes 5 and 6 would be reduced from, say, p=5% for an unlubricated low-friction coating, to less than, say, zut 1% for conventional lubrication with or without a coating 24.

[0201] Since the together all of inner magnet tubing 5 will account for less than 30% of the machine weight, mM, the power loss and torque on account of the discussed friction when the weight of at least one inner magnet tube 5 is allowed to rest on the lower part of the inner surface of rotor 2, i. e. if support 26 is eliminated for at least one inner tube 5, is small if a low-

wear coating 24 is provided at the sliding interface. According to numerical estimates the accompanying power loss will be less than 1 % of machine power in typical cases. Such a loss will be further decreased, i. e. to well below 1%, if conventional lubrication is used with or without low-friction coating 24. Even so, the use of a structure 26 in conjunction with at least one low-friction bearing 35 about axle 10 is liable to reduce loss of machine torque and machine power through fiction between rotor 2 and magnetic tube 5 to the lowest possible level and will be part of preferred embodiments.

[0202] The particular structure chosen in Figure 18 is but an example and a wide range of modification is possible. In particular both the inner magnetic tube 5 and the outer magnetic tube 6 could be separated into lengthwise sections in the manner indicated for inner magnetic tube 5 in Figure 16. Further, the number of supports 26 for at least one inner magnet tube is optional and may be chosen in accord with considerations of cost, mechanical stability, ease of construction, weight and other.

[0203] It should be noted that by the use of conventional lubrication with or without low- friction coatings 24, the weight of rotor 2 may be at least partially supported by inner magnet tube 5 and/or outer magnet tube 6. This is the converse of the already discussed at least partial support of the weight of at least one magnet tube 5 or at least one lengthwise section of an inner magnet tube, by rotor 2. In fact, in view of (i) the occasionally desired long length of rotor 2, (ii) that unlike magnet tubes 5 and 6, rotor 2 must be continuous, i. e. cannot contain spatial gaps, and (iii) the typically advantageous relatively small wall thickness, T, of rotor 2, this option can have considerable advantages, especially for large machines.

III 14. Brush Holders, Brush Pairs and Split Brushes [0204] On the one extreme, brushes 27 may be individually guided in individual brush holders, and on the other extreme all brushes in a machine may be guided in a single brush holder that en-circles the rotor and extends over all"tracks", i. e. over all slip rings. In preferred

embodiments the hypothetical unitary brush holder is divided into a plurality of brush holder sections (in Figure 18 labeled 33 (a) and 33 (b) according to their position on the a-side and b- side) that each guide at least two and in general an arbitrary number of brushes that need not be the same for all brush holder sections, in lieu of, or supplemented by, individual brush holders.

[0205] On account of the rotational symmetry of the rotor, brush holder sections 33 will be overall arc-shaped as seen in axis direction but on a detailed scale they may be faceted or have more complex shapes. Brush holder sections 33 correlate with at least two neighboring zones and more typically with an arbitrary multiplicity of zones with which they are geometrically aligned, as may be deemed desirable. Correspondingly, each brush holder section will (i) hold a plurality of electrical brushes such that they are electrically insulated from each other except for excellent electrical conductivity between"brush pairs", i. e. neighboring brushes on the same slip ring that transfer current between neighboring zones), (ii) apply the appropriate brush force, and (iii) permit brush advance in brush axis direction in the course of brush wear.

[0206] The brushes forming brush pairs should be at as closely the same electrical potential as possible. According to the present invention this may be accomplished either by rigidly joining two neighboring brushes by means of a metallic, low-resistance joint and guiding the so-formed brush pair in a suitably enlarged brush holder, or by"short-circuiting" (i. e. creating a low- resistance electrical connection between) individual brushes and their respective holders, and form brush pairs through electrically connecting short-circuited brush holders pair-wise.

Advantageously, such short-circuiting may be accomplished by means of a resilient multi- contact metal material.

[0207] Further, optionally any one brush or any one brush pair may be divided into a"split brush"or"split brush pair"comprising an arbitrary number of between 2 and, say, 5, electrically parallel, independently electrically connected and independently mechanically loaded brushes that are positioned in close axial proximity to each other on the same slip ring in

the same radial position. No electrical insulation between the members of split brushes and split brush pairs is required or desirable, but splitting brushes into parallel components will increase machine reliability in line with the explanation already given in section 4 b.

[0208] In preferred embodiments, therefore, a current moving through zone n from the b-side to the a-side, will be led to the neighboring zone n+1 by means of neighboring brushes (or split brushes) 27 (a, n) and 27 (a, n+1), or brush pair or (split brush pair) 27 (a, n) /27 (a, n+1), sliding on slip ring, say, 34 (a). From there the current will flow back to the b-side through zone n+1 where it will be picked up and transferred to zone n+2 by single brushes (or split single brushes) or brush pair (or split brush pair) 27 (b, n+1)/27 (b, n+2) sliding on slip ring 34 (b), to repeat the pattern back to slip ring 34A and so on.

[0209] If brushes 27 (a, N) and 27 (a, n+1) are joined into a brush pair, they will necessarily have a common axis direction, i. e. the"brush pair axis direction". Therefore in preferred embodiments brush holders and brush holder sections 33 are provided with mutually electrically insulated guiding channels with smooth parallel walls for individual brushes or split brushes and/or brush pairs or split brush pairs, that permit their smooth, low-friction advance in axis direction in the course of brush wear. Advantageously, brush holders and brush holder sections 33 incorporate means for the application of mechanical force, e. g. constant force springs, or spiral springs, or a suitable pressurized fluid, for providing a pre-determined pressure between brushes and slip rings, preferably independent or nearly independent of momentary brush length.

[0210] Advantageously, but not necessarily, within any one brush holder and brush holder section, the axis directions of brushes and/or brush pairs (unitary or split) include the same angle of inclination against the local slip ring surface normal, e. g. 20° trailing, or 10° leading, or 0°, etc. Accordingly, within any one brush holder section 33, brush guiding channels are advantageously mutually inclined in accordance with their local radial position relative to the

rotor axis. Specifically for the present example, in the course of wear brush pair 27 (a, n) /27 (a, n+1) will move toward slip ring 34 (a) in its brush pair axis direction, guided in a channel of brush holder section 33 (a) whose walls are parallel to the axis direction of brush pair 27 (a, n) /27 (a, n+1) that is inclined by a specified angle relative to the local slip ring orientation.

Similarly brush pair 27 (b, n+1)/27 (b, n+2) will advance towards slip ring 34 (b) in its channel in brush holder section, at a mildly different orientation in accordance with its different radial orientation to the rotor. Thus any one brush holder section will advantageously accommodate at least one brush pair, and commonly more than one.

[0211] Any one brush holder section will comprise at least two brush channels for one each single brush (or one each single split brush) at its two ends. Namely, whether at the a-or b- end, currents are fed into and out of brush holder sections 33 via single brushes (or single split brushes) typically from, say, the right end of one brush holder section to the left end of the adjoining brush holder section, or else the current is supplied by or fed into some external electrical circuit. In order to facilitate the indicated electrical connections to the outside, the ends of brush holder sections may be provided with electrical terminals 40, optionally including switches 77, as schematically indicated in Figure 18 wherein terminals 40 (a) and 40 (b) with symbolically indicated switches are situated on the a-and b-side, respectively.

[0212] In preferred embodiments, brush holders or brush holder sections will be attached, in an electrically insulating manner, to the outer walls of cooling rings 47 (a) and 47 (b), respectively, as shown in Figure 18. Alternatively, if there should be no cooling rings, brush holder sections 33 could be attached to the outer magnet tube 6, or they may be attached to machine base plate or housing 19, or may be attached to at least one mechanical support connecting outer magnet tube 6 to machine base plate or housing 25. In fact brush holders or brush holder sections 33 could also be attached to inner magnet tube 5 in which case slip rings 34 would be fashioned on

the inside of rotor 2. While this would be feasible it has the disadvantage of impaired accessibility of the brushes for installation, monitoring, inspection and replacement.

[0213] The primary functions of brush holder sections 33 are to electrically isolate brushes, except for brush pairs, from each other and to mechanically load and guide brushes 27 in their axial direction so as to make reliable, low-resistance electrical connection between brushes 27 and slip rings 34, as already discussed above. Optionally, brush holders and brush holder sections may be mechanically fused which will simplify installation and may add to their mechanical strength. This choice and the correspondingly increased choice of placement of brush holder section ends about the rotor circumference, impacts the number of terminals 40 and switches 77 at any one location, namely one (or a set of parallel) terminal per each single brush, being equal to the number of parallel slip rings serviced by any one particular brush holder section 33.

[0214] Brush holders 33 and/or brush holder sections 33 may deliberately be designed to leave one or more gaps wherein zones are not traversed by a current. Such gaps may be made to increase the physical distance between neighboring brushes in order to lower the electrical fields that may drive leak currents, e. g. in case of cooling by direct immersion in water of any kind, i. e. sweet, salt, de-ionized or distilled, as already indicated in section in 10. Further, such gaps may be made on account of space constraints in regard to terminals 40, i. e. physically on account of their number and/or the maximum machine current. Namely, and as already stated, typically a terminal will be required for every brush at either end of a brush holder section 33, because the current flow will be permanently interrupted at any end brush of a brush holder section that is not connected to a terminal. Therefore, when all brush holder sections on neighboring slip rings are mechanically fused (as contemplated for the a-but not the b-side of Figure 18), the left and right ends of two circumferentially adjoining brush holders 33 will face each other with one terminal attached to each of NT slip rings (equal to three in Figure 18). E. g.

in a machine with brush holders that are mechanically fused across NT = 6 slip rings, the gap between the ends of circumferentially adjoining brush holder sections will have to physically accommodate 2xNT = 12 terminals attached to the NT = 6 brushes at each of the brush holder section ends across the gap between them. For large machine currents and large NT the requisite terminals may physically be stout bus bars that need more space than equal to the interval between neighboring zones. Additionally there may be other reasons for providing enlarged gaps between the ends of a brush holder or of adjoining brush holder sections, such as to provide for simplified switching of brushes and terminals within the machine, for providing geometrical barriers against leak current flow and other.

[0215] Note: Construction details of brush holders, beyond the above principles of machine architecture, are the subject of an independent patent application.

15. Multiple Current Sources, Primary and Secondary Circuits (Figures 19 to 26) a) Method of Graphical Presentation [0216] In line with the preceding exposition, each current"turn"in a multipolar machine, i. e. each current passage between two brushes at opposite ends of a zone, may be regarded as a machine module that is potentially independent of all other current turns/machine modules. In other words, a multipolar machine may be regarded as an assembly of electrical machines that may be arbitrarily grouped and be arbitrarily connected"in series"and/or"in parallel".

Correspondingly, a multipolar motor may be driven by an almost unlimited choice of number and kinds of current sources, limited only by the number of turns, NDNT, of the machine.

This principle and resulting options have already been outlined in section I 4. They are illustrated and further explained by means of Figures 19 to 21 as follows: [0217] Figure 19 shows the current flow in a multipolar motor that is powered by a single DC current source. It uses the example of part of a rotor set of NT = 4 rotors with an arbitrary number ND of current turns per rotor, seen in plan view as if the rotor set were slit in axial

direction and flattened. Herein zones 21, i. e. current turns in axially extended strips of rotor set 2 that are penetrated by radial magnetic field B, are shown as vertical parallel strips with diagonal shading in two different orientations, symbolizing opposite sense of orientations of B. These orientations are shown to systematically alternate from zone to zone as expected for magnetic field sources with two (or in general an even number of) opposite poles, in line with Figures 3B, 5,9, 10 and 17. As a result, zones 1 and ND have opposite sense of radial magnetization. While this will be a common case, it is not a necessary condition, as shown by the example of the magnet pair 5 (3) /6 (3) in Figure 3, with three poles per magnet facing each other across the rotor wall [0218] In Figure 19, a (convenient but arbitrary) numbering of the zones is indicated at both ends of the rotor set composed of NT concentric, mutually electrically insulated rotors. The two rotor ends are arbitrarily dubbed"A"and"B"for above and below the zones in Figure 19, respectively, whereas physically the rotor could have any arbitrary orientation, e. g. vertical in spite of the fact that, mostly for convenience of drawing as well as most practical cases, all examples herein have assumed an axle in horizontal orientation. Further, the zones, and the brushes that connect the conductors in the zones, are numbered in ascending order from right to left, in the order of.... ND-2, ND-1, ND, 1,2, 3....

[0219] The slip rings at the"A"and"B"ends of the machine are shown as horizontal lines of symbols that represent the brushes that slide on them. Relative to the zones they are numbered in the same order as in Figures 11 and 13, namely. 1, 2,... NT (with in this case NT = 4) outward from the zone ends. The symbols for the brushes are solid dots (T), small open circles (o), crossed open circles, and open circles with a central dot, for brushes on slip rings 34 (1), 34 (2), 34 (NT-1) and 34 (NT), respectively.

[0220] In the described depiction of zones, slip rings and brushes in Figure 19, the pattern of the current flow is indicated by means of solid lines with arrows pointing in the direction of positive current flow. b) Multipolar Machines in DC Operations [0221] In the simplest possible current flow pattern for multipolar machines, as shown in Figure 19, the current enters from the positive terminal of a DC current source into brush 1 on slip ring 1 on the B side at the square symbol with light center, marked C in From there, the positive current follows the current flow line in the direction of the arrows, i. e. travels through zone 21 (1) to brush 1 on slip ring 1 on the A side and on to the neighboring brush, i. e. brush 2 on the same slip ring. As indicated by the short horizontal line with arrow, brushes 1 and 2 on slip ring 1 on the A side are electrically connected, i. e. brushes 1 and 2 on slip ring 1 on the A side form a brush pair of the kind discussed in section 13 above (and similarly all brushes connected by a horizontal arrow in Figure 19). The further current path continues through zone 21 (2) to brush 2 on slip ring 2 on the B side, where brush 2 is similarly electrically connected to, and forms a brush pair with, neighboring brush 3 on slip ring 1 of the B-side, again as indicated by the short current flow line with arrow, and so on.

In this manner the current will pass from zone to zone, always changing current flow direction as the magnetic flux B changes sign so that the Lorentz force acts on the current in the same direction in every zone. Reversal of current direction correspondingly reverses the sense of rotation.

[0222] After having traversed every zone in rotor 1, the current arrives at brush ND on slip ring 1 on the B-side. If there were only a unitary rotor, i. e. if NT were equal to one, the current would exit the machine at this point. However when NT > 1, as in the example of Figure 19 with NT = 4, the current will next enter rotor 2 via the indicated diagonal

connection between. brush ND on the B-side of slip ring 1, to brush 1 on slip ring 2 on the B- side, and so on until all zones have been traversed in all NT rotors and the current exits at brush ND on slip ring NT In Figure 19 that exit point is marked with a solid black square labeled Cout.

[0223] In line with section 1. 4, and as already emphasized, the above is but the most simple circuit, using just one DC source, while the choice of how to power a multipolar machine is very wide indeed. Figure 20 illustrates this fact by means of a variety of examples wherein, for convenience of drawing, all connections between brushes and current sources as well as between brushes on adjoining slip rings are shown for the B side. Figure 20 uses the same symbols and manner of representation as Figure 19 and again the positions at which current source terminals are connected to brushes are also in this figure marked by the already introduced square symbols for the case of direct current. By contrast, the widely used circular symbol for rectified current indicate terminals of AC or three-phase current sources They are used in two orientations depending on whether the positive or the negative rectified current is concerned. Further, small arrows attached to the circumference of these circular symbols are used to indicate the sense of the current flow, i. e. of the positive and negative rectified current components into or out of the current source. The labels used are these are as follows: 71 = terminal for positive DC current in i. e. negative current out; 72 = terminal for positive DC current in i. e. positive current out; 73 = terminal for positive rectified AC or three-phase current in; 74 = terminal for positive rectified AC or three-phase current out; ; 75 = terminal for negative rectified AC or three-phase current in 76 = terminal for negative rectified AC or three-phase current out.

[0224] Specifically, Figure 20A illustrates the use of two similar DC current sources, each of which drive the current through two consecutive rotors, i. e. one source drives the current from terminal 71 (1) connected to brush 1 on slip ring 1 on the B-side, to the exit terminal 72 (1) connected to brush ND on slip ring 2 on the B-side. The other current source drives the current from terminal 71 (2) connected to brush 1 on slip ring 3 on the B-side, to the exit terminal 72 (2) connected to brush ND, on slip ring 4 on the B-side.

[0225] If the two current sources are operated with the same current magnitude, the effect is the same as substituting two similar in-series DC sources for one DC source. However, the possibility of connecting two instead of a single current source to a multipolar motor offers novel opportunities. Specifically, the two sources may be operated with different currents in any desired ratio. This option may be utilized, for example, in controlling ship drives, e. g. at half power only one of the current sources might be operated. At lower than half power the current from that current source could be throttled back to any desired level. For higher power, the second current source would be gradually brought into play, up to full power.

[0226] Another application of two independent DC current sources follows from operating them in opposite direction of current, e. g. the polarity at the connections 71 (2) and 72 (2) in Figure 20 could be reversed. If so, and as already indicated in section 14, the Lorentz forces in the zones powered by the second current source would oppose those of the first source and the machine torque would be the difference of the contributions due to the individual current sources. In the case of equal and opposite current from the two sources, no net torque would be generated and as a result the multipolar machine would have been converted into an electric heater to the limit of L. For any combination of current strengths and direction between the two current sources, the machine would act simultaneously as a motor rotating in either direction as may be chosen, and as a heater, and do so in freely adjustable proportions.

[0227] A third application is the reverse, namely using a multipolar machine as a generator that simultaneously supplies two different sets of batteries.

[0228] The above considerations regarding two independent DC current sources may be generalized into any arbitrary number of current sources. This possibility is indicated in Figure 20B by means of terminals 71 (1)/72 (1) for current source 1, terminals 71 (2) /72 (2) for current source 2, and terminals 71 (3)/72 (3) for current source 3. As shown in Figure 20B, the different sources need not operate integral numbers of rotors, e. g. two different current sources may operate on the same slip ring, nor need they operate the same number of current turns. Rather, possible choices of the number N of current turns driven by any one current source range between 0 N < NaNr current turns. By way of illustration, current sources 1 and 3 in Figure 20B drive fewer than ND zones, and source 2 drives more.

[0229] Similarly, a generator may supply an arbitrary number of secondary circuits, e. g. in the case or more different secondary circuits, e. g. in the case of three secondary circuits may simultaneously charge two different sets of batteries and drive an electric motor, whereby the voltages and currents are limited by the available power and number of"turns".

[0230] Due to the restrictions of drawing, the total number of zones in Figure 20 is small (namely 8 zones that generate 4x8 = 32 current turns for the NT = 4 rotors depicted). For an actual machine, a complete drawing would typically show many more zones and thus current turns, and these could be distributed among the three, and in the general case any arbitrary number of, current sources in any desired proportion. c) Multipolar Motors Driven by AC or 3-Phase Current [0231] The major thoughts in this and the next section have already been introduced in section 14 above. They shall now be explained in greater detail by means of the same method of presentation, and using and same number of rotors and zones, as before. Herein, Figure

20C presents the operation of a multipolar motor by means of an AC or 3-Phase Current source for the simplest case, namely applying the rectified positive current to rotors 1 and 2, and applying the negative rectified current to rotors 3 and 4. Opportunities for combining the negative and positive current sources in imaginative ways are restricted in that the positive and negative current components are generated at equal magnitudes. However, they may be applied to different numbers of current turns which might have advantages for special purposes. d) Combinations of AC and DC Sources and Switching Operation Between Them [0232] Another variation of applying a multiplicity of current sources to multipolar machines is combining direct and alternating and/or three-phase current sources. An example is presented in Figure 20D, wherein the positive and negative rectified current components of an AC or three-phase current source are teamed with a DC current source. Herein, the DC current source is connected between terminals at brush (N-1) on slip ring 2 and brush (N-2) on slip ring 3, and is geo-metrically bracketed by the two rectified current components.

Namely, the positive rectified cur-rent flows between brush 1 on slip ring 1 and brush (N-2) on slip ring 2, and the negative rectified current component flows between brushes (ND-1) on slip ring 3 and (ND-2) on slip ring 4. Again, currents from the two sources may be adjusted at will and the resulting torques will add.

[0233] For most purposes such combinations will be less interesting or valuable than the opportunity to switch between DC and AC and/or 3-phase current operation that was already introduced in section I 4. This appears to be especially applicable to submarines that might be favorably powered by AC while in port and by DC while submerged. The right hand part of Figure 21 illustrates a method by which motor operation may be easily switched between DC and AC. This figure uses the same type of view and symbols as Figures 19 and 20 but

shows more zones and only one rotor. This will clarify the drawing and the reader will by now understand that multipolar machines may be conveniently understood as an array of NDNT independent current turns which all may serve as machine modules, independent of their physical location in the machine, e. g. whether all may be situated on a single rotor or whether they are arbitrarily distributed over an arbitrary number of rotors.

[0234] Turning, then, to switching between DC and AC operation, note that the terminals of both, current sources S4 and S5, are connected across brushes 1 to 8, in a in-parallel arrangement, such that opening or closing switches 77 (5) to 77 (8) will activate one or other of the two. Specifically, closing switches 77 (5) and 77 (6) while switches 77 (7) and 77 (8) are open will permit direct current to flow consecutively through all of the zones, i. e. all current turns from 1 to 8. Opening switches 77 (5) and 77 (6) and closing switches 77 (7) and 77 (8), by contrast, will cut off the DC source but will permit positive rectified current to flow through current turns 5 to 8, and rectified negative current through current turns 1 to 4.

[0235] Additionally, on its left side, Figure 21 shows how very few restrictions apply to the use of multiple current sources on a single multipolar machine. Thus one may observe that the terminals of any one current source may be attached to brushes on opposite ends of the rotor, as is shown for current sources Si and S2. Figure 21 also shows that current sources may be readily switched on or turned off, namely via switches 77 (1) to 77 (5). e) Transformer Operations-Background [0236] The use of multipolar machines has already been outlined in section I 6. It is further clarified by means of Figures 22 to 26. Herein the same type of graphic representation is used as in the preceding figures 19 to 21.

[0237] Transformer action depends on the following relationships: An axial primary current flow ipn, due to a primary current source of voltage Vp, in zone n, penetrated by radial magnetic flux density Bn over length Ln, will suffer a Lorentz force Fn = [ipnxBn] n => Fn = ipn BnLn (14) independent of the applied voltage and independent of the currents, voltages and Lorentz forces in any of the other zones. The vector notation is used to emphasize the possible two different senses (i) of the Lorentz force to cause clockwise or anti-clockwise rotation, (ii) of the current flowing in the positive or negative sense of rotation axis orientation, and (iii) of the orientation of the radial B field, i. e. the N-magnetic pole inside or outside of the rotor. In regard to the latter, the two different inclinations of the shading lines of the zones in Figures 22 to 26 indicate the two different senses of orientation of the radial (i. e. normal to the plane of the drawing) B field.

Following equation (14), in a rotor of diameter D = R/2, the torque due to current ipn in zone n will be Mn == [FnX R] or by magnitude Mn = inBnLn D/2 (15) and if the rotor should rotate at angular velocity # = 271 v, i. e. with surface velocity Vr ='4 coD = zDv (16) the zone will make the contribution mWn = (DMn = inBnLn Vr = Fn Vr (17) to the mechanical work done by the machine if it is operated as a motor.

[0239] Conversely, if the brushes at either end of zone n should be electrically isolated except for the connection between them through zone n, no current will flow in zone n, but the tangential surface velocity vr of the conducting metal in the zone, penetrated by radial magnetic flux density Bn over length Ln, will induce the voltage Vn = [Vr xBn] Ln or by magnitude Vn = vr Bn Ln (18) If the two brushes at the two ends of zone n were electrically connected to permit current flow in through zone n, this would dissipate the electrical work eWn = in Vn = in Bn Ln Vr = mWn (19) Some of work eWn would be dissipated as Joule heat in the internal resistance of the zone and of the brushes, but the remainder could be supplied to a secondary circuit, i. e. could serve as a secondary voltage in a generator or a transformer. Similarly, some of mWn would be dissipated as mechanical friction, but the remainder could be used as motor power to, say, drive a ship's propeller.

[0240] Thus equation 19 demonstrates, that in a rotating machine, each zone may indeed be independently supplied with current to do mechanical work or, conversely, may serve as the current output for a generator or transformer and in the process counteract the driving torque.

In view of the mutual independence of the zones, therefore, a multipolar machine may not only be used as a motor or a generator but may also be used as a transformer, wherein a primary current supply is used to rotate the rotor, and the energy input is withdrawn as electrical energy at some different secondary voltage. In practice one would normally not use individual turns for the primary"coil"and the secondary"coil", but connect groups of zones in series, as desired and as indicated in Figures 22 to 26.

f) Transformer Operations-Multiple Circuits [0241] In general, identifying zones that receive current input from a primary current source by the subscript p, identifying zones from which current is withdrawn by the subscript s, and neglecting friction and Joule losses, it will be in the absence of mechanical power input or output, Wp= (EBpLp.) ip= (EBsjLsj) is=Ws (20) Hence, with equations 18 and 19, and considering that the tangential velocity vr is the same for all zones in a multipolar machine (barring minor differences if nested rotors of slightly different diameters are used) we obtain the transformer formula i,/ip = (EBpj Lpj)/ (SBsn Lsn) = Vp/Vs (21) [0242] For the most simple case in which all of the zones have the same length, L, and same magnetic field strength, B, as implied in Figure 22, equation 21 simplifies to is/ip = NpBL/Ns BL = Np/Ns = Vp/Vs (22) with Np and NS the number of zones used as primary zones (i. e. receiving current input from some primary source at voltage Vp) and secondary zones (i. e. delivering current at transformed voltage Vs), respectively.

[0243] As already indicated, in uniformly cylindrical rotors, the velocity vr is the same for all zones, but by virtue of possible differences among the sources of magnetization, zones may be penetrated by different magnetic flux densities, Bn (compare Figure 3A). For the simplest case of all zones having the same values of L and B, as implied in Figure 22, equation 22 holds. In that case the secondary voltage, Vs, may be varied by varying the primary voltage Vp which means changing the rotation velocity (see equation 18). Alternatively, at same Vp, the ratio of

VS/Vp may be varied by suitably moving the terminals of the primary and secondary circuits, e. g. from Np = 4 and Nu-12 for Vs = (12/4) Vp = 3Vp, as in Figure 22, to Np = 10 and Ns = 6 for Vs = (6/10) Vp = 0.6Vp as in Figure 23.

[0244] Whether or not B and L are the same for some or all of the zones, changes of Vs by other means than simple changes of rotation speed, will require moving, say, the negative terminal of the primary circuit and the positive terminal of the secondary circuit (both as viewed from the outside), as seen by comparing Figures 22 and 23. Similarly, also, changing primary and/or secondary voltages in more complex situations, e. g. as indicated in Figure 24, as indeed changing output voltages also in the case of generators (compare Figure 26), will require moving the positions of terminals.

[0245] A simple practical way to physically move terminals with little effort would be to supply, as needed, multipolar machines with, firstly, switches in lieu of at least some of the fixed electrical connections between adjacent brushes that in Figures 22 to 26 are indicated as short horizontal lines with arrows indicating the direction of the current flow and, secondly, to supply receptacles for power input or output as needed. At this point, neither of these modifications for equipping multipolar machines for use as transformers with variable input/output voltages, and similarly for use of generators with variable output voltages, pose any foreseeable difficulties.

[0246] While it will be convenient to make the connections all on one side between adjacent, physically close brushes as in Figures 22 and 23, this is not a necessary restriction. This is demonstrated in Figure 3 that also indicates the possibility of employing multiple primary and/or secondary circuits. Herein, at the typically small friction and joule heat losses, and in the absence of any mechanical input or output, the decisive condition is equation (20), i. e. that Ws = Wp, or ideally that Ws = Wp. It is therefore possible to simultaneously use a plurality of primary current sources, the ni primary current source supplying power Wu,, =

ipnVpn to zone n through which current ipn flows, and/or to draw off electrical energy Wsj = isjVj 6'om the jth secondary circuit of a plurality of secondary circuits, all of which may be operated independently of each other. Thus in case of multiple primary and/or secondary circuits and without any mechanical power input or output, it is Win-X ipnVpn = Wout-S isjVsj (23) [0247] Herein the individual voltages and currents are governed by equations (14) and (18), since now only the velocity vr is common to all zones, and this will adjust according to the input/output power, unless there should also be a mechanical or other power input from, or output to, the outside, e. g. through the application of an external torque [0248] Specifically, in Figure 3 electrical power is supplied by three primary current sources that deliver voltages Vol, Vp2 and Vp3, respectively, and electrical power is abstracted through two secondary circuits with secondary voltages Vsl and Vs2 g) Transformer Operations-AC/DC or 3-phase/DC Transformation [0249] In the manner outlined in Fig. 21 one or more AC and/or 3-phase current power supplies may be used as inputs into multipolar machines, i. e. also as primary current supplies.

Herein for any one AC source, two rectifiers are employed to generate a positive and a negative current component, and these are connected in lieu of primary DC power sources. Figure 25 illustrates this method for the case of Figure 22 wherein the one primary power supply of Figure 22 is replaced by the positively and negatively rectified components of an AC or three- phase power supply labeled 1. The positive and negative rectifiers are labeled 2 and 3, respectively. Also there is indicated an optional ground wire (4). Additional AC sources may

be similarly substituted for DC power sources. AC current output would require"chopping" and electronic means.

[0250] In summary, independent of the validity of the above derivation, in line with section 16 and as discussed in connection with Figures 22 to 26, a multipolar machine may be operated at least in the following different transformer modes: 1. One DC primary power input of voltage Vp and one DC secondary power output of voltage Vs ; 2. A plurality of DC primary power inputs at optionally different voltages of Vpl, Vp2... and one DC secondary power output of voltage Vs ; 3. One DC primary power input of voltage Vp and a plurality of DC secondary power outputs, optionally of different voltages Vsl7 VS2 4. A plurality of DC primary power inputs of optionally different voltages Vpl, Vp2... and a plurality of DC secondary power outputs, optionally of different voltages Vsl, Vs2... ; 5. One primary power input through the rectified currents of at least one AC or three-phase current of optional voltages and at least one secondary voltage output; 6. A plurality of primary power inputs at optionally different voltages through the rectified currents of at least two of AC or three-phase current sources of optional voltages and at least one secondary voltage output.

16. Multiple Simultaneous Machine Use and Reliability of Multipolar Machines [0251] The values of the voltages in multipolar machines used as transformers such as illustrated in Figure 24 would vary depending on power used in the two secondary circuits.

Unlike traditional electrical transformers, the secondary voltages could not be controlled via the input voltage. Rather, keeping the secondary voltages constant, will require control of vr. This would not necessarily have to be done via controlling any or all of the input voltages but could

be done mechanically, e. g. by an auxiliary mechanical power source that provides a controllable rotational speed.

[0252] In case that an external mechanical torque (optionally at fixed rotation speed) should be employed and be the only power source, this would constitute an electrical generator component, optionally with multiple secondary circuits. Specifically, in case the three primary electrical power sources in Figure 24 were eliminated, a generator as in Figure 26 would result, wherein the mechanical power source is not shown. Anyway, the electrical induction in the secondary circuits does not depend on the origin of the torque that generates the rotation speed, i. e. co = Dvr. Therefore a plurality of independent mechanical torques could be applied at the same or different positions of the axle of the rotor set or single rotor of a multipolar machine.

[0253] Hence, with a mechanical power input, a multipolar machine used as an electrical generator could simultaneously supply an arbitrary number of secondary circuits, with an arbitrary number and selection of voltages, limited only by the number of available"turns", as in fact has already been pointed out above. Optionally, each of the secondary circuits could draw variable currents at their own specified constant voltage, provided that the mechanical input power source is controlled to maintain a constant rotation speed, i. e. a constant value of Vr.

[0254] In accordance with the above considerations, there may be not only positive but also negative mechanical power input, i. e. motor action or braking, and there may be any arbitrary number of simultaneous mechanical torque inputs whose sum but not the magnitudes and directions of the individual contributions, multiplied with the angular velocity (see equation 17), will be the relevant value in the energy balance.

[0255] Finally, any arbitrary part of the electric and/or mechanical power input may be used in motor action. Thus, in summary, whatever the power source or combination of power

sources may be, the multipolar machine may be simultaneously used as a motor, a generator and a transformer.

[0256] It may be noted that the switching of current sources in transformer as well as motor action will be a simple matter because (i) the number of brushes is typically much lower than for conventional homopolar machines (ii) brushes are very accessible, being positioned outside of the magnetic field (iii) in large machines, brushes are typically hefty and operate in appropriately hefty brush holders.

In combination, these three features of multipolar machines are valuable because they simplify machine operation and machine servicing.

[0257] As an attendant advantage, the ease of accessing the brushes and their decreased number compared to traditional homopolar machines of same power, permits monitoring, and if need be replacing brushes in case of malfunction or wear. In further combination with the use of multiple current sources, multipolar machines may be constructed with greater reliability than traditional homopolar machine types.

[0258] Importantly, as has already been pointed out above and is illustrated in Figures 20 and 21, multiple current sources may be connected and disconnected independently, e. g. for maintenance or repairs, or may be physically removed for repairs and/or replacement, without interruption of machine operation. This feature enhances reliability and safety of machine operation. Additionally the already indicated optional introduction of split brushes, i. e. the splitting of any one brush or brush pair into two or more parallel and independently spring- loaded brushes or brush pairs (see section I 4b), is a further safety feature since thereby the failure of any one brush does not disrupt the circuit but simply shifts current to the one or more remaining parallel brushes.

l0259] Optionally one may add the further safety feature already introduced in [1], namely of arranging dielectric barriers between current turns that are designed to electrically break down at some specified voltage and thereby short-circuit brushes that may have failed.

Advantageously, this may be accomplished by connecting neighboring brush pairs on the same slip ring by means of conductors with interposed dielectric barriers of the indicated kind, e. g. aluminum with an interposed oxidation layer that will electrically break down when the voltage significantly exceeds that expected across two consecutive current turns. However, in view of the excellent demonstrated reliability especially of metal fiber brushes, that fairly expensive precaution appears to be unnecessary, especially also because in the preferred embodiments of Figures 11,13 and 18, brushes may be readily monitored and replaced. Further, with brushes and connections typically in easy view and reach, and with axle and rotor the only moving parts, multipolar machines are expected to be trouble free.

17. Methods of Rotor and Slip Rins Construction (Figure 27) a) Making Rotors/Rotor Sets [0260] Rotor manufacture, at least for NT=1 and not undue lengths, is relatively simple if materials with inherent current channeling structures or suitable composites should be commercially available at acceptable quality and cost. In that case suitable tubing may be directly commercially available, or else rotors may be machined from bulk material, may be extruded, or if current channeling sheet or foil material should be available, rotors could be made by winding such sheet onto a spindle and inter-layering it with electrically insulating sheet or fail as may be needed to produce rotors with NT > 1.

[0261] If materials with inherent current channeling structures should not be obtainable in suitable shapes and/or at reasonable cost, the preferred, most simple method of making rotors is through assembling rectangled current conducting elements that for NT = 1 have a radial

thickness equal to T, the intended unitary rotor wall width, and or for NT > 1 have a radial wall thickness close to T/NT, i. e. the wall thickness of individual concentric rotors in the rotor set, while their circumferential dimension may be, say, 1. 5T or 1.5 T/NT, as the case may be.

Since practically speaking even for very large machines, T will rarely exceed 2. 5cm = 1"and for the smallest machines T/NT will hardly ever fall below 1/2 mm, the conductors with such a choice will be of a convenient size are of modest numbers, e. g. some tens to a few thousand for any one machine, so that they may be assembled by hand or by robots.

[0262] Whether the indicated conductors of radial thickness T or T/NT and of similar circumferential thickness are used, or any other individual elongated conductors, current- channeling rotors may be fabricated by the following general method that is believed to be superior to the methods disclosed in [1]. It has already been briefly introduced in section 15 and is partly illustrated in Figure 27 that applies to a unitary rotor or any one in a set of NT concentric, mechanically fused but electrically insulated rotors. The method involves the following steps which, however, may be modified in various ways, whose order may be changed in accordance with preferences and/or experience and to which other steps may be added: 1) Procure two suitable cylindrical tubes 78 and 79 and fit them together concentrically such that the annular gap between them is uniform and provides a suitable mold for the desired rotor.

2) Procure suitable axially extended conductors, e. g. (nearly) rectangular bars having the radial dimension of the rotor wall thickness, or wires, slender rods, tubing, profiles and/or thin strips of a suitable metal such as copper, silver, aluminum, lithium, beryllium, gold, copper alloys, silver alloys, aluminum alloys, lithium alloys, beryllium alloys and gold alloys, and cut their length to appropriate size, i. e.

equal to or moderately longer than the intended ultimate length of the rotor set including slip rings.

3) Provide the axially extended conductors with an electrically insulating surface layer that will in the completed rotor will serve as an insulating layer between them, i. e. will stick them together in electrically insulating fashion and/or will serve as a filler material for the spaces between the slender conductors.

4) Optionally assemble a number of the axially extended conductors into modules shaped as cylindrical arcs to fit the shape of the intended rotor, i. e. so as to fit into the space between tubes 78 and 79.

5) In case that assembling by modules is the favored method, provide at least one of the cylindrical surfaces of the modules with an electrically insulating surface layer that will after curing serve as an insulator between the modules, will stick them together in electrically insulating fashion and preferably will before curing lubricate to facilitate insertion between tubes 78 and 79.

6) After preparation according to steps 3) or 4) and 5) above, as the case may be, place the axially extended conductors into the annular gap between tubes 78 and 79, either singly, or in groups, or in the form of modules in accordance with 4) and 5) above, and fuse them together by any of the following means: (i) curing the surface layer according to 3) above; (ii) infusing the spaces between the axially extended conductors or modules, as the case may be, with a suitable, electrically insulating matrix material and harden it; or (iii) combine methods (i) and (ii).

7) If cylinders 78 and 79 have been chosen to be thin walled of insulating material, they may be kept in place when assembling an NT > 1 rotor. Or shape a rotor set and slip rings, either directly from the assembly of the two cylindrical tubes and the fused slender conductors in the annular gap between them, or after removing all or

part of the cylindrical tubes by any of a variety of means, including sliding the current channeling cylinder out of the gap between cylinders 78 and 79, or removing either of both of cylinders 78 and 79 by machining, peeling off, etching, chemical dissolution, melting or perhaps still other means.

[0263] To somewhat flesh out the above general description, note that slender conductors with roughly equiaxed cross sections are suitable for rotor sets with NT ! 1 in line with the preceding descriptions including Figures 11 and 12. Slender conductors in the shape of radially oriented strips that extend across the radial width of the at annular gap between the two tubes e. g. in the form of modules 80 and 82 between outer tube 78 and inner tube 79 in Figure 27, are a preferred embodiment. The potential drawback of circumferentially wide modules of type 82 in Figure 27 is that they generate current paths which circumferentially protrude beyond the zones, i. e. beyond the projected width of the magnet poles. This phenomenon has already been discussed in section III 2 above and is not believed to cause a significant degradation of machine performance. Also the possibly increased intensity of eddy currents and the machine loss due to them is believed to be minor.

[0264] A quantitative analysis for determining the optimal width of the axially extended conductors in the current channeling rotor is planned. In any event, the circumferential width of conductors such as in module 82 of Figure 27 should be made as large as reasonably possible without degrading machine efficiency since for otherwise same materials this will simultaneously yield the simplest most cost-effective rotor construction, and on account of the minimized volume fraction of cements or adhesives, will yield the greatest mechanical strength, the greatest elastic stiffness and the lowest Joule heat losses in the rotor Further, since current channeling must extend from end to end of the conductive part of the rotor in order to avoid short-circuiting of zones, also cost of slip ring construction and slip ring performance in terms of electrical resistance to brushes as well as length of brush life-times, rise with the

circumferential extent of the conductors. Finally, fitting together separately manufactured slip rings and rotors, as also fitting together lengthwise sections of long rotors, with minimal impairment of motor performance, is also facilitated by large circumferential dimensions of the conductors in the rotor.

[0265] Step 7) deserves further comment, especially in case the newly formed rotor is stuck to cylinders 78 and/or 79 so as to preventing it from being slid out of the annular gap. In that case tubes 78 and/or 79 could be slit lengthwise and be peeled off or be removed after suitably bending them away from the current-channeling material. Either of these methods might be facilitated by the use of a suitable lubricant or mold release material which inhibits sticking between the tubes and the composite. Such removal might also be accomplished, or be assisted, by heating or cooling in order to make use of differential thermal expansion or contraction, as the case may be. Other possible methods for the removal of at least one of the at least two tubes include but are not limited to, softening by heating (e. g. of tubes made of a plastic), cutting operations such as machining in a lathe, other means of mechanical removal such as filing, dissolving in a solvent, etching off by means of an acid or caustic, burning off, removing electrochemically, removing by means of chemical reaction and/or promoting brittle fracture that will permit subsequent mechanical removal by chemical reaction, e. g. by heating in chlorine, hydrogen or other.

[0266] According to the present invention, a favored method of overcoming the difficulties that are potentially associated with step 7) as discussed is the use of arc-shaped cylindrical sections in lieu of full tubing of 360° angular extent such as 78 and 79 in Figure 27. In such, modules of full length but extending through an angular range of, say, 180°, 120°, 90°, 60° may be made. This will permit production of rotors from two, three, four, six or more modules that are assembled through joining along radial, axially extended joints. Because they do not intersect the current paths, such joints may be bonded by any suitable means such as soldering,

gluing without interfering with current channeling, The principal advantage of employing arc- shaped cylindrical sections of tubing for making rotor modules as indicated is that they pose no steric hindrance so that the modules can be readily removed, especially if an easily released material such as Teflon is used. b) Long Rotors Made from Lengthwise Sections [0267] Long rotors may be assembled from lengthwise sections made by any of the above methods. Joining these with adequate mechanical strength and without interfering with current channeling may require shaping the macroscopic interface so as to provide torsional strength beyond that of a simple planar joint normal to the rotation axis. Examples of such shapes include but are not limited to planar slanted against the rotation axis, conical, stepped, slotted with one or more interlocking slots or teeth, interlocking in some arbitrary pattern, or other.

[0268] In order to on the one hand not introduce unacceptably high electrical resistance at the interface and on the other hand not to provide low-resistance current paths between adjoining individual rotors in the case of NT > 1 requires (i) good geometrical alignment, (ii) electrically conductive bonding means such as an electrically conductive adhesive, solder or brazing, or direct metallic bonding between the metallic conductors on the two sides such as through induction heating, spot welding or other, (iii) that the conductive bonding means does not permit significant radial electric conduction, and in particular not between adjoining rotors.

[0269] The third requirement is the more readily fulfilled, the thicker an insulating layer separates adjoining individual rotors is, and the larger the radial dimensions of the axially elongated conductors in the rotor are. For otherwise same conditions, further, conduction of leak currents between adjoining individual rotors at joints decreases with decreasing thickness of the bonding layer. This feature gives an advantage of thin layers of conductive adhesives to over other bonding means. Altogether satisfactory bonding between lengthwise sections of

long rotors will be possible but the means chosen should be adapted to prevailing circumstances. c) Slip Rings [0270] An important requirement for making rotor sets is the ability to shape slip rings, e. g. in conformity with Figures 11 and 12. The most straightforward method for this purpose presumably is machining in a lathe. This requires firm, machinable bonding among the axially elongated conductors that effect the current channeling which according to relevant practical experience is not believed to pose a problem.

[0271] Advantageously, slip rings may be machined or otherwise shaped in units that effectively are rotor ends but made separately from the rotor, as already discussed in section m 10. Repeating the previous argument, the advantage herein that high-precision slip ring manufacture, e. g. to run-outs of preferably less than 0.001", is not encumbered by clumsy, possibly quite bulky and heavy rotors. However, it requires the extra step of joining the rotor ends that carry the slip rings, to the rest of the rotor, not only with sufficiently high torsional strength but without significantly impairing the current channeling or introducing unacceptably high local electrical resistance. The same considerations and solutions apply to the slip ring/rotor joining as discussed above for the joining of lengthwise sections of rotors.

LIST OF REFERENCES 1. D. Kuhlmann-Wilsdorf, "Bipolar Machines-A New Class of Homopolar Motor Generator", Patent Application, filed May 6,2002, Pub. No. 2003/0052564A1, Pub. Date March 20,2003.

2. "Metal Fiber Brushes", D. Kuhlmann-Wilsdorf, (Chapter 20 in"Electrical Contacts: Principles and Applications", Ed. p. G. Slade, Marcel Dekker, NY), 1999, pp. 943-1017.

3. "Production and Performance of Metal Foil Brushes", P. B. Haney, D. Kuhlmann-Wilsdorf and H. G. F. Wilsdorf, WEAR, 73 (1981), pp. 261-282.

MULTIPOLAR MACHINES-OPTIMIZED HOMOPOLAR MOTOR/GENERATORS <BR> <BR> <BR> <BR> <BR> TABLE of CONTENTS p. A SYMBOLS p. B LIST OF LABELS (alphabetical order) p. D LIST OF LABELS (alphabetical order) p. E MULTIPOLAR MACHINES - OPTIMIZED HOMOPOLAR MOTOR/GENERATORS/TRANSFORMERS p. l CROSS-REFERENCE TO RELATED APPLICATIONS p. 1 FIELD OF THE INVENTION p. l I. GENERAL DESCRIPTION OF THE INVENTION p. 4 1. Basic Design p. 4 2. Electrical Brushes p. 9 3. Significance of the Various Parameters p. 11 4. Motor Operation with DC, AC, 3-Phase and/or Multiple Current Sources p. 13 a) Almost Unlimited Possible Combinations of Current Sources in Operating a Multipolar Motor p. 13 b) Safeguards Against Brush Failure p. 15 c) Operation with a Single AC or 3-Phase Current Source p. 16 d) Operation with an Arbitrary Selection of Current Sources p. 17 5. Generator Operation p. 18 6. Transformer Operation p. 19 7. Simultaneous Motor/Generator/Transformer/Heater Operation p. 20 8. Construction of Magnet Tubes p. 21 9. Construction of Rotors p. 23 a) Rotors Made of Materials with Inherent Current Channeling Structures p. 23 b) Rotors Made of Assembled Individual Conductors p. 24 c) Rotors Wound from Current-Channeling Sheets or Foils p. 25 d) Rotors Made by Filling-in the Annular Gaps Between Nested Insulating Cylinders p. 26 e) Rotors with Axially Extended Conductors whose Thickness Equals the Rotor Wall Thickness p. 27 i) Strengthening the Ends of Rotors by Mechanical Support Rings p. 28 g) Fitting together Lengthwise Segments of Rotors p. 28 h) Electrically Insulating Adhesives, Glues and Matrix Materials p. 29 10. Construction of Slip Rings p. 29 11. Interrelations Between Machine Power and Dimensions p. 31 12. Machine Efficiency and Machine Cooling p. 33 13. Mechanical Structure p. 35 14. Multiple Rotors on the Same Axle p. 36 II. BRIEF DESCRIPTION OF THE DRAWINGS p. 36 in. DESCRIPTION OF PREFERRED EMBODIMENTS p. 37 1. Basic Construction of the Set of Rotors (Figure 1) p. 39 2. Permitted Variety of Rotors, Magnetic Field Sources and Channeling Patterns. p. 41 3. Current Channeling Means in Rotors p. 45 4. Placement and Mechanical Support of Sources of Magnetization (Figure 2) p. 46 5. Magnet Shapes, Magnet Material and Estimated Cost (Figures 3 and 4) p. 49 6. Basic Overall Morphology in a Preferred Embodiment (Figures 4,5 and 6) p. 56 7. Multipolar Machines with Electromagnets p. 60 8. Multipolar Machines with Superconducting Magnets (Figures 7 and 8) p. 60 a) Advantages and Liabilities p. 60 b) Reduced Number of Turns (ND) _ per Rotor on Account of Bulky Magnets p. 61 c) Extended Slip Rings p. 63 d) Increased Machine Diameter and Its Effects p. 65 e) Increased Structural Forces and Stresses p. 66 f) Increased Cost, Weight, Complexity, -and Conclusions p. 67 9. Current Paths and Lorentz Forces and Electrical Brushes (Figures 9 and 10) p. 67 10. Construction of Slip Rings and Brushes (Figures 11 and 12) p. 70 11. Slip Rings with Reduced Diameters (Figure 13) p. 77 12. Mechanical Supports for Rotor and Inner Magnet Tubes (Figures 15 and 16) p. 80 13. Machine Cooling and other Aspects (Figures 17 and 18) p. 83 14. Brush Holders, Brush Pairs and Split Brushes p. 88 15. Multiple Current Sources, Primary and Secondary Circuits (Figures 19-21) p. 92 a) Method of Graphical Presentation p. 92 b) Multipolar Machines in DC Operations p. 94 c) Multipolar Motors Driven by AC or 3-Phase Current p. 98 d) Combinations of AC and DC Sources and Switching Between Them p. 98 e) Transformer Operations-Background p. 100 f) Transformer Operations-Multiple Circuits p. 102 g) Transformer Operations-AC/DC or 3-phase/DC Transformation p. 104 16. Multiple Simultaneous Machine Use and Reliability of Multipolar Machines p. 105 17. Methods of Rotor and Slip Ring Construction (Figure 27) p. 108 a) Making Rotor/Rotor Sets p. 108 b) Long Rotors Made from Lengthwise Sections p. 113 c) Slip Rings p. 114 REFERENCES p. 115 CLAIMS p. l 16 ABSTRACT p. 141 FIGURES 14 foot print of"slanted"brush 37 gap between rotor and inner magnet tube 38 gap between rotor and outer magnet tube 15 gold plating or other low-resistance surface 5 inner magnet (s) or inner magnet tube 83 individually placed elongated conductors for making rotor with inherent current channeling 22 intended current direction 43 insulating boundary layer between neighboring individual rotors 24 insulating, low-friction, wear resistant coating 65 irregular (i. e. curved, slanted..) joint between magnet modules 62 joint between magnet modules in axial orientation 63 joint between magnet modules normal to the rotor axis 19 machine base plate or housing 39 leak space between seals with drain hole at bottom to prevent coolant from reaching slip rings 70 machine endplate 4 magnet module 7 magnetic gap 55 matrix material for assembling inner magnets into inner magnet tube 56 matrix material for assembling outer magnets into outer magnet tube 23 mechanical support for axle to machine base plate or housing 26 mechanical support for inner magnet (s) or inner magnet tube to axle via bearings 25 mechanical support for outer magnet (s) to machine base plate or housing 32 mechanical support ring for rotor end (also carries separator 11 at end of rotor) 80 module of strip-shaped conductors for making rotor with inherent current channeling 81 module of fine fibers for making a rotor set with inherent current channeling structure 82 module of conductors of maximum radial dimension for making a current channeling rotor 6 outer magnet (s) or outer magnet tube 78 outer tube for making a rotor set with inherent current channeling structure 9 pole piece 36 possible slip ring site 3 rim 3 2 rotor or set of rotors 49 seal between cooling ring and rotor 11 separator wall between slip rings, i. e."tracks" 34 slip ring 44 slip ring boundary 64 slotted joint between magnet modules 39 space between seals with drain hole at bottom to prevent coolant from reaching slip rings 54 spring for loading brush 8 superconducting magnet coil 23 support for axle 10 to machine base plate or housing (19) 26 support for inner magnet (s) or inner magnet tube to axle via ball bearings 25 support for outer magnet (s) or outer magnet tube to machine base plate or housing 61 structural part for fastening rotor to axle 77 switch 40 Terminal attached to brush holder for making electrical connection to the outside Multipolar Machines-LABELS (numerical order) 2 rotor or set of rotors 3 rim 4 magnet module 5 inner magnet (s) or inner magnet tube 6 outer magnet (s) or outer magnet tube 7 magnetic gap 8 superconducting magnet coil 9 Pole piece 10 axle 11 separator wall between slip rings, i. e."tracks" 12 brush footprint 14 foot print of"slanted"brush 15 low-resistance surface (typically gold plating) 16 brush box 17 brush guide, sliding in brush box as brush wears 18 brush metal fibers embedded in brush guide (17) 19 machine base plate or housing 21"zone"i. e. axially extended strip of rotor that is penetrated by a radial magnetic field 22 intended current direction 23 mechanical support for axle 10 to machine base plate or housing (19) 24 insulating, low-friction, wear resistant coating 25 mechanical support for outer magnet (s) or outer magnet tube to machine base plate or housing 26 mechanical support for inner magnet (s) or inner magnet tube to axle via bearings 35 27 electrical brush (advantageously a metal fiber brush) 28 connector plate conducting current between brushes on neighboring zones or strips 29 mechanical support for inner magnet (s) or inner magnet tube to base plate or housing 30 vane for circulating coolant 31 extension of rotor beyond slip ring 32 mechanical support ring for rotor end (also carries separator 11 at end of rotor) 33 brush holder or brush holder section 34 slip ring 35 low-friction bearing 36 possible slip ring site 37 cylindrical gap between rotor and inner magnet tube 38 cylindrical gap between rotor and outer magnet tube 39 leak space between seals with drain hole at bottom to prevent coolant from reaching slip rings 40 terminal attached to brush holder for making electrical connection to the outside 42 cut through boundary zone between neighboring slip rings 43 boundary layer or zone between neighboring individual rotors 44 slip ring boundary, i. e. boundary or zone between neighboring slip rings 45 possible channel for coolant of inner magnet 46 possible channel for coolant of outer magnet 47 cooling ring 48 wall of cooling ring 49 seal between cooling ring and rotor 50 tubing at inner wall of rotor used for mechanical strengthening 51 edging for protection of inner edge of 50 54 spring for loading brush 55 matrix material for assembling inner magnets into inner magnet tube 56 matrix material for assembling outer magnets into outer magnet tube 61 structural part for fastening rotor to axle 62 joint between magnet modules in axial orientation 63 joint between magnet modules normal to the rotor axis 64 slotted joint between magnet modules 65 irregular (i. e. curved, slanted..) joint between magnet modules 66 centering hole in magnet module 70 end plate for rotor 71 terminal for positive DC current in, i. e. negative current out 72 terminal for negative DC current in, i. e. positive current out 73 terminal for positive rectified AC or three-phase current in 74 terminal for positive rectified AC or three-phase current out 75 terminal for negative rectified AC or three-phase current in 76 terminal for negative rectified AC or three-phase current out 77 Switch 78 outer tube for making a rotor set with inherent current channeling structure 79 inner tube for making a rotor set with inherent current channeling structure 80 module of strip-shaped conductors for making a current-channeling rotor 81 module of fine fibers for making a current channeling rotor 82 module of conductors of maximum radial dimension for making a current channeling rotor 83 individually placed elongated conductors for making rotor with inherent current channeling Multipolar Machines - Labels (alphabetical order) 10 axle 10 35 low-friction bearing 43 boundary layer between neighboring individual rotors 44 boundary zone between neighboring slip rings 44 27 electrical brush (advantageously a metal fiber brush) 16 brush box 33 brush holder or brush holder section 12 brush foot pint 17 brush guide, sliding in brush box as brush wears 18 brush metal fibers embedded in brush guide 66 centering hole in magnet module 66 45 channel for coolant for inner magnets 46 channel for coolant for outer magnets 66 centering hole in magnet module 28 connector plate conducting current between brushes on neighboring zones or strips 47 cooling ring 22 current direction 42 cut through boundary zone between neighboring slip rings 51 edging for protection of inner edge of 70 endplate for motor 31 extension of rotor beyond slip ring 27 electrical brush (advantageously a metal fiber brush) 71 terminal for positive DC current in i. e. negative current out 72 terminal for negative DC current in i. e. positive current out 73 terminal for positive rectified AC or three-phase current in 74 terminal for positive rectified AC or three-phase current out 75 terminal for negative rectified AC or three-phase current in 76 terminal for negative rectified AC or three-phase current out 50 tubing at inner wall of rotor used for mechanical strengthening 30 vane for circulating coolant 48 wall of cooling ring 21"zone"i. e. axially extended strip of rotor that is penetrated by a radial magnetic field