AND SYSTEMS FORMED THEREWITH

RELATED APPLICATION

[001] This application claims priority to United States Provisional Patent Application Serial No. 63/165,107, titled “Discrete Flux-Directed Magnet Assemblies”, filed March 23, 2021.

FIELD OF THE INVENTION

[002] The invention relates to synchronous electrical machines and, more specifically, embodiments of the invention include systems and methods for improving power and torque density in motors and generators.

BACKGROUND

[003] Increasing the power to mass and torque to mass ratios in electrical machines, i.e., power and torque densities, is key to deploying electric power in a wider variety of new applications where mass and size of the machines are critical, such as for aircraft, turboshaft power generation and wind power generation. With existing machine technologies, power densities on the order of 5 kW/kg are achievable but constitute a limiting factor for many new applications. Further design improvements in higher power and torque densities will also benefit existing applications, such as electric vehicles. The potential benefits include higher efficiencies in both energy conversion and transmission, as well as reductions in carbon footprint, thermal generation, and regulated emissions.

[004] In theory, the highest power and torque densities can be achieved with fully superconducting, synchronous machines, for which power densities on the order of 25 kW/kg or higher appear possible. However, AC losses in superconducting stator windings can only be accommodated at low RPMs. Partially superconducting machines with DC rotors could, in principle, generate an airgap flux density of several Tesla, and thereby offer the potential of reaching higher power and torque densities. However, saturation of the required back iron limits the flux density in the airgap to values below 2 Tesla, and the heavy weight of the back iron further limits achievable power and torque densities. The required cryogenics and the complexity of quench detection and protection for a rotating superconducting system complicates wide-spread use of superconducting machine technology unless much higher power levels and torque densities can be reached.

[005] In 1973 John C. Mallinson, a British-American physicist, published a magnetic theory for a new class of magnetization patterns for planar structures in which the magnetization direction is a spatially rotating flux with constant amplitude. Such an ordered array of permanent magnet segments augments the magnetic field on one side of the array while canceling the field to near zero on the other side of the array. See Mallinson, J. C., IEEE Transactions on Magnetics, Vol. MAG-9, No. 4, pp 678 - 682, December 1973. The spatially rotating pattern of magnetization direction channels the flux from segment to segment in an arrangement of magnetic segments. An application of these assemblies is exemplified in the Halbach Array, invented by Klaus Halbach in 1980 for charged particle beam optics in accelerators and corresponding beam lines. See Halbach, Klaus, Nuclear Instruments and Methods, 169 (1): 1-10 "Design of Permanent Multipole Magnets with Oriented Rare Earth Cobalt Material" (1980).

[006] For particle accelerator applications it is necessary to bend, focus and apply chromatic corrections on charged particle beams. This is done with electromagnetic coils containing a fixed number of precisely arranged pole pairs. A dipole arrangement for bending a charged particle beam consists of a single pole pair, i.e., n = 1, having one north pole and one south pole. For focusing a charged particle beam, the coil configuration has an n = 2 quadrupole arrangement containing two pairs of north poles and two pairs of south poles. Chromatic corrections, which focus particles with different momenta to a precise focal point, call for higher-order arrangements of n = 3 or more pole pairs. In general, any desired magnetic field in the cross section of an aperture of infinite length can be described or synthesized as a superposition of so-called multipole components, that is, a combination of select multipoles, e.g., dipoles, quadrupoles, sextupoles, etc. The magnetic fields used for charged particle beam optics must be highly accurate, analogous to the stringent requirements for conventional optical lenses. Mathematically, this accuracy requirement is fulfilled when each magnet comprises a single multipole order, e.g., a pure quadrupole (n = 2), without any contribution of lower or higher-order terms.

[007] Halbach arrays offer the required high field uniformity needed for charged particle beam optics. In these magnet assemblies, the flux direction at any point is given by the following equations in polar coordinates: (Eqn 1) and (Eqn 2), where B _rem is the magnitude of the remanent flux density and p is an integer specifying the number of pole pairs. The subscript “r “ denotes the radial component of the field and the subscript “0“ denotes the tangential component of the field. A positive value of p produces a field that is directed in the radially outward direction of the array, and a negative value of p produces a field that is directed in the radially inward direction of the array, i.e., toward the central axis of the cylinder.

[008] Electrical machines also require the same multipole configurations as needed for charged particle beam optics, but the field uniformity requirements are less stringent than for charged particle beam optics. For the rotors of synchronous machines, permanent magnet Halbach arrays enable a simple and energy-efficient realization of generating the required multipole configuration and the augmentation of flux density on one side of the arrays yields increased power and torque density. However, the high cost of manufacturing Halbach arrays, in particular those with high pole numbers, has prevented the widespread use.

[009] To achieve significant improvements in the performance of synchronous machines in respect to power and torque density as well as efficiency, new design topologies are needed that integrate proven concepts with improved manufacturing technologies and optimization methodologies. New topologies are also needed to implement the advantages of flux channeling demonstrated with Halbach arrays, e.g., extended to superconducting coil configurations. The invented concept presents a solution for significantly increasing the performance of synchronous machines with a novel approach for flux channeling which avoids the complexities of Halbach array manufacturing.

SUMMARY OF THE INVENTION

[010] Multiple improved designs are provided for electrical machines that enable unprecedented power and torque densities as well as increased efficiency. The concepts are applicable to machines based on permanent magnets as well as superconducting coils. Using permanent magnets as the field-generating system avoids the complexity of cryogenics and the need for supplying electrical energy to a rotating system. On the other hand, superconducting rotors offer the potential for much higher flux densities. The present invention also enables realization of magnetic gear boxes and integration of magnetic gear boxes with electrical machines. The following example embodiments are illustrative but not limiting of the scope of the invention.

[011] It is well known that Halbach arrays offer significant advantages for the field- generating rotor of a synchronous machine over the conventional magnet assemblies consisting of alternating north-south pole structures. Due to the flux channeling in a circumferential array, the flux density on one side of the array, where flux is needed, is enhanced while the flux density on the opposing side, where no flux is needed, is reduced to near zero. A design concept is disclosed that produces the required flux channeling as in Halbach arrays. Unlike the Halbach array, the design concept offers scalability from very small to very large systems with higher mechanical stability as needed for machines operating at high RPM, at significantly reduced manufacturing costs. The disclosed systems and methods of flux channeling are directly applicable to superconducting rotors.

[012] In one embodiment the efficiency of the machine is increased by eliminating magnetization losses in the back iron required for field shaping in the airgap and reducing the fringe magnetic field. In another embodiment a significant increase in power and torque density is achieved by eliminating the back iron. [013] Further improvement in applied power and torque density of electrical machines is achievable with magnetic gearing that may be integrated with a motor or generator. For magnetic gearing, the disclosed flux channeling concept offers: (i) high mechanical strength at significantly reduced cost in comparison to conventional Halhach arrays, (ii) significantly higher power transfer per unit mass than conventional mechanical or magnetic gearing, (iii) a gearing efficiency which may exceed 99 %, and (iv) intrinsic overload protection with minimal or no maintenance.

[014] Further optimization of power and torque density in an electrical machine also requires increased current loading in the stator windings and, therefore, highly effective heat dissipation and cooling to assure reliable operations. Highest current loading of the stator winding can be achieved with Bitter-Magnet technology (See: Soobin An, A Feasibility Study to Apply the Bitter Magnet to Electric Power Devices, MT-26, Sept, 2019), in which the conductor consists of copper sheets that contain optimized hole patterns for the flow of a coolant with direct contact between the coolant and the heat- generating conductor. The Bitter-Magnet technology provides excellent heat dissipation while using cost-effective manufacturing methods.

[015] In accord with exemplary embodiments of the invention, there is provided a magnetic system suitable for use in a rotating machine or a gear box, comprising at least a first array structure containing at least a first plurality of like discrete magnetic segments and extending along a central axis, with each segment in the first plurality: (i) having an elongate length, relative to its width, extending along a major side thereof in a direction parallel with the central axis; (ii) including a pole with a like characteristic field distribution including a maximum field strength direction and the same maximum field strength; (iii) having a surface, with a predefined shape in cross section, from which the maximum field strength direction points outward therefrom, about which surface the segment is axially rotatable prior to fixed placement of the segment in the first array of like magnetic segments circumferentially positioned about the central axis; (iv) fixedly arranged with its major side extending in a direction parallel to directions which the major sides of other segments in the first plurality extend; and (v) positioned to extend in a direction parallel with the central axis to collectively form, in combination with others in the first plurality, the first array of like magnetic segments, which first array is configured as a first ordered sequence having field poles of the magnetic segments rotated with respect to one another as a function of position in the first sequence, this resulting in shifts in angular orientations of the field poles among the magnetic segments in the first sequence. Segments in the first plurality in the magnetic system may be positioned in contact with, or in sufficient proximity to, one or more other segments to additively combine or reduce fields from different segments and thereby impart net field strengths about the first array structure wherein an augmented magnetic field strength results on one of the inner side or the outer side of the array relative to a reduced magnetic field strength on the other of the inner side or the outer side of the array. In one series of embodiments the magnetic segments are in an ordered sequence wherein the magnetic segments are axially rotated with respect to other magnetic segments to sequentially shift orientations of the characteristic maximum field strength direction among the segments and thereby effect the augmented magnetic field strength on one side of the array. The magnetic system may further include a support structure with which: the magnetic segments of the first plurality occupy fixed positions relative to the central axis and relative to one another, and the relative shifts in orientations of the characteristic maximum field strength directions among the field poles is fixed. The support structure may include a series of channels or grooves in which the magnetic segments are placed. The magnetic segments and the channels or grooves may have complementary shapes or mating features which lock the rotational positions of segments in place to fix the relative shifts in field orientation in place. In another embodiment the magnetic system includes a support structure having a series of apertures therein and formed along the central axis, with discrete magnetic segments in the first plurality axially rotated and positioned within the apertures to sequentially provide the shifts along the array. The support structure may comprise a series of stamped laminations joined against one another wherein the laminations comprise nonmagnetic material.

[016] In accord with further embodiments of the invention, the magnetic system further includes a second array structure comprising at least a second plurality of like discrete magnetic segments, and extending along the central axis, with each segment in the second plurality: (i) having an elongate length, relative to its width, extending along a major side thereof in a direction parallel with the central axis; (ii) including a pole with a like characteristic field distribution including a maximum field strength direction and the same maximum field strength; (iii) having a surface, with a predefined shape in cross section, from which the maximum field strength direction points outward therefrom, about which surface the segment is axially rotatable prior to fixed placement of the segment in the second array of like magnetic segments circumferentially positioned about the central axis; (iv) fixedly arranged with its major side extending in a direction parallel to directions which the major sides of other segments in the first plurality extend; and (v) positioned to extend in a direction parallel with the central axis to collectively form, in combination with others in the second plurality, the second array of like magnetic segments, which second array is configured as a second ordered sequence having field poles of the magnetic segments rotated with respect to one another as a function of position in the second sequence, this resulting in shifts in angular orientations of the field poles among magnetic segments in the second sequence. In an example embodiment the second array of magnetic segments is configured to provide a sequence of elements comprising rotationally shifting angular orientations of magnetic field patterns where the angular orientation of field patterns rotates among different magnetic elements in directions orthogonal to the central axis. In other embodiments of the system the spatial rotation of the field patterns configures the flux in a manner which provides an augmented magnetic field strength on one of the inner side or the outer side of the first array relative to providing a reduced magnetic field strength on the other of the inner side or the outer side of the first array. Also, in other embodiments the first array includes n magnetic segments and the field pattern among every one of the n segments is characterized by a rotational shift in the angular orientation relative to the angular orientation of the field pattern of the next element in the sequence. In another embodiment the second array includes m magnetic segments and the field pattern among every one of the m segments is characterized by a rotational shift in the angular orientation relative to the angular orientation of the field pattern of the next element in the sequence. The first array may include n magnetic segments with the field pattern among fewer than every one of the n segments characterized by a rotational shift in the angular orientation relative to the angular orientation of the field pattern of the next element in the sequence.

[017] Also in accord with the invention, there is provided a synchronous electrical machine having a first rotor and a stator winding each coaxial with respect to the other about a central axis extending in a direction along a frame, with the stator fixedly attached to the frame and the first rotor attached to the frame for rotation relative to the frame and the stator winding. The first rotor and the stator winding each have a circumferential surface extending along the central axis. The first rotor includes a first plurality of discrete magnetic segments with each segment: (i) having an elongate length, relative to its width, along a major side thereof, in a direction parallel to the central axis; (ii) including a pole with a like characteristic field distribution including a maximum field strength direction and the same maximum field strength; (iii) having a surface, with a predefined shape in cross section, from which the maximum field strength direction points outward therefrom, about which the segment is rotatable prior to fixed placement in a first array of like magnetic segments circumferentially positioned about the central axis; (iv) fixedly arranged with its major side extending in a direction parallel to the major sides of other segments in the first plurality; (v) extending along the central axis to collectively form, in combination with others in the first plurality, the first circumferential array of magnetic segments having an inner side facing the central axis and an outer side facing away from the central axis; and (vi) positioned in sufficient proximity to one or more other segments to additively combine or reduce fields from different segments and thereby impart net field strengths about the first circumferential array wherein an augmented magnetic field strength results on one of the inner side or the outer side of the array relative to a reduced magnetic field strength on the other of the inner side or the outer side of the array. The major sides of the segments in the first plurality may, for example, be cylindrically shaped or elliptically shaped such that the predefined shape in cross section is circular or elliptical. The major sides of the segments in the first plurality may be but are not limited to shapes which are axially symmetric. In one series of embodiments all magnetic segments in the first array consist only of the segments in the first plurality. In another series of embodiments all segments in the first array are dipole magnets. The first array of magnetic segments may be configured to provide a sequence of elements comprising rotationally shifted angular orientations of magnetic field patterns where, along the sequence, the angular orientations of field poles among different ones of the discrete magnetic segments are rotated as a function of position in the sequence, in directions orthogonal to the central axis, thereby providing a sequence of rotations in the angular orientations of the field poles, including rotations in maximum field strength directions. The magnitude of the augmented magnetic field strength, on one of the inner side or the outer side of the array relative to the reduced magnetic field strength on the other of the inner side or the outer side of the array, may depend in part on the number of segments per pole and the specific sequence of and angle(s) of rotation of the field poles. For another series of embodiments, with the first array including n magnetic segments the field pattern among every one of the n segments is characterized by a rotational shift in the angular orientation relative to the angular orientation of the field pattern of the next element in the sequence. When the first array includes n magnetic segments, the field pattern among fewer than every one of the n segments may be characterized by a rotational shift in the angular orientation relative to the angular orientation of the field pattern of the next element in the sequence. The major sides of magnetic segments in the first array may be spaced apart from one another or in contact with one another.

[018] Embodiments of the afore described synchronous electrical machine may include a second rotor where: the stator winding extends between an inner stator winding distance Wi and an outer stator winding distance Wo, each stator winding distance Wi and Wo measured from the central axis; the first rotor is an inner rotor, IR, extending between an inner distance IRi and an outer distance IRo, each distance IRi and IRo measured from the central axis, where IRo < Wi. With the machine comprising the second rotor positioned as an outer rotor, OR, relative to the inner rotor, IR, and attached to the frame for rotation relative to the frame and the stator winding, the second rotor, OR, extends between an outer rotor inner distance ORi and an outer rotor outer distance, ORo, with each distance ORi and ORo measured from the central axis, the outer rotor, OR, having a circumferential or cylindrical-like surface extending along the central axis. The outer rotor, OR, comprises a second plurality of discrete magnetic segments, each segment in the second plurality having a characteristic field pattern and: (i) fixedly arranged in spatially parallel orientations with respect to one another; (ii) extending along the axis to collectively form a second circumferential array; (iii) positionable in a second stabilizing structure; and (iv) rotatable about the central axis to interact with the stator winding for torque generation.

[019] For the afore described machine comprising a second rotor, the second array of magnetic segments may be configured to provide a sequence of elements comprising rotationally shifting angular orientations of magnetic field patterns where the angular orientation of field patterns rotates among different magnetic elements in directions orthogonal to the central axis. The spatial rotation of the field patterns may configure the flux in a manner which provides an augmented magnetic field strength on one of the inner side or the outer side of the second array relative to providing a reduced magnetic field strength on the other of the inner side or the outer side of the array. With the first array including n magnetic segments, in one embodiment the field pattern among every one of the n segments is characterized by a rotational shift in the angular orientation relative to the angular orientation of the field pattern of the next element in the sequence. Where the second array includes m magnetic segments, according to another embodiment the field pattern among every one of the m segments is characterized by a rotational shift in the angular orientation relative to the angular orientation of the field pattern of the next element in the sequence. For a different series of embodiments, with the second array including n magnetic segments, the field pattern among fewer than every one of the n segments is characterized by a rotational shift in the angular orientation relative to the angular orientation of the field pattern of the next element in the sequence.

[020] In accord with another series of embodiments, there is provided a synchronous electrical machine, comprising a first rotor and a stator winding each coaxial with respect to the other about a central axis which extends in a direction along a frame, with the stator winding fixedly attached to the frame and the first rotor attached to the frame for rotation relative to the frame and the stator winding. The first rotor and the stator winding each have a circumferential surface extending along the central axis, with the first rotor comprising a first plurality of discrete magnetic segments with each segment: (i) having an elongate length, relative to its width, extending along a major side thereof in a direction parallel with the central axis; (ii) including a pole with a like characteristic field distribution including a maximum field strength direction and the same maximum field strength; (iii) having a surface, with a predefined shape in cross section, from which the maximum field strength direction points outward therefrom, about which surface the segment is rotatable prior to fixed placement in a first array of like magnetic segments circumferentially positioned about the central axis; (iv) fixedly arranged with its major side extending in a direction parallel to the major side of other segments in the first plurality; (v) including a pole having a like characteristic maximum field strength direction; and (vi) positioned to extend in a direction parallel with the central axis to collectively form, in combination with others in the first plurality, the first circumferential array of like magnetic segments, which array is configured in a sequence having the poles of the magnetic segments rotated with respect to one another as a function of position in the sequence, this resulting in shifts in angular orientations of the field poles among the magnetic segments.

[021] Major sides of the segments in the first plurality may be cylindrically shaped or elliptically shaped such that the predefined shape in cross section is circular or elliptical. Each major side of each of the segments in the first plurality may be axially symmetric. The first array may consist only of the discrete magnetic segments in the first plurality. All of the segments in the first array may be dipole magnets. Embodiments of the machine may require that multiple segments in the first plurality are not pie shaped elements and are not formed into asymmetrically shaped elements in which the maximum field strength direction changes as a function of position about the element shapes. In other embodiments multiple segments in the first plurality are not formed into asymmetrically shaped elements after magnetization so that the maximum field strength direction would vary as a function of position about different ones of the shaped elements. [022] According to disclosed embodiments of the invention, none of the segments in the first plurality are formed as identical magnetized elements, then shaped or machined from identical elements into different shapes and then ordered as a series of differently shaped elements among which the maximum field strength direction varies as a function of position about the element shapes. According to other embodiments, none of the segments in the first plurality are shaped and ordered as a series of elements among which the maximum field strength direction varies as a function of position about the element shapes. For the afore described machine, with the first circumferential array of magnetic segments having an inner side facing the axis and an outer side facing away from the axis, an augmented magnetic field strength results on one of the inner side or the outer side of the array relative to a reduced magnetic field strength on the other of the inner side or the outer side of the array. Also according to other embodiments, when the first circumferential array of magnetic segments rotates about the central axis, the field on the side of the array exhibiting the augmented magnetic field strength primarily interacts with fields of the stator winding for torque generation. Embodiments of the afore described machine include a support structure having a series of apertures therein and formed along a cylindrically shaped plane with each in the first plurality of discrete magnetic segments rotatably positioned within one of the apertures to provide the shifts. Such a support structure may comprise a series of stamped laminations joined against one another wherein the laminations comprise nonmagnetic material. The afore described machine may include an inner rotor and an outer rotor. For example, with the stator winding radially extending between an inner stator winding distance Wi and an outer stator winding distance Wo, and each stator winding distance Wi and Wo measured from the central axis, the first rotor is positioned an inner rotor, IR, extending between an inner distance IRi and an outer distance IRo, each distance IRi and IRo measured from the central axis, where IRo < Wi. The machine further comprising an outer rotor, OR, positioned as an outer rotor relative to the inner rotor, IR, and attached to the frame for rotation relative to the frame and the stator winding, the second rotor, OR, extending between an outer rotor inner distance ORi and an outer rotor outer distance, ORo, each distance ORi and ORo measured from the central axis, the outer rotor, OR, having a circumferential or cylindrical-like surface extending along the central axis. The outer rotor, OR, comprises a second plurality of discrete magnetic segments, each segment in the second plurality having a characteristic field pattern and: (i) fixedly arranged in spatially parallel orientations with respect to one another; (ii) extending along the axis to collectively form a second circumferential array; (iii) positionable in a second stabilizing structure; and (iv) rotatable about the central axis to interact with the stator winding for torque generation. The second array of magnetic segments may be configured to provide a sequence of elements comprising rotationally shifting angular orientations of magnetic field patterns where the angular orientation of field patterns rotates among different magnetic elements in directions orthogonal to the central axis. The spatial rotation of the field patterns may configure the flux in a manner which provides an augmented magnetic field strength on one of the inner side or the outer side of the array relative to providing a reduced magnetic field strength on the other of the inner side or the outer side of the array. The first array may include n magnetic segments and the field pattern among every one of the n segments may be characterized by a rotational shift in the angular orientation relative to the angular orientation of the field pattern of the next element in the sequence. According to another embodiment, with the second array including m magnetic segments the field pattern among every one of the m segments is characterized by a rotational shift in the angular orientation relative to the angular orientation of the field pattern of the next element in the sequence. According to still another embodiment, with the second array including n magnetic segments, the field pattern among fewer than every one of the n segments is characterized by a rotational shift in the angular orientation relative to the angular orientation of the field pattern of the next element in the sequence.

[023] There is also provided a method of assembling a synchronous machine. A first rotor and a stator winding are attached about a frame, each of the first rotor and the stator winding being coaxial with respect to the other about a central axis which extends in a direction along the frame, with the stator winding fixedly attached to the frame and the first rotor attached to the frame for rotation relative to the frame and the stator winding. Each of the first rotor and the stator winding is formed having a circumferential surface extending along the central axis, wherein the first rotor is formed with at least a first plurality of discrete magnetic segments configured in a first array, with each segment: (i) having an elongate length, relative to its width, extending along a major side thereof in a direction parallel with the central axis; (ii) including a pole with a like characteristic field distribution including a maximum field strength direction and the same maximum field strength; (iii) having a surface, with a predefined shape in cross section, from which the maximum field strength direction points outward therefrom, about which surface the segment is axially rotatable prior to fixed placement of the segment in the first array of like magnetic segments circumferentially positioned about the central axis, the first array of magnetic segments having an inner side facing the central axis and an outer side facing away from the central axis; (iv) fixedly arranged with its major side extending in a direction parallel to directions which the major sides of other segments in the first plurality extend; and (v) positioned to extend in a direction parallel with the central axis to collectively form, in combination with others in the first plurality, the first array of like magnetic segments, which first array is configured as a first ordered sequence having field poles of the magnetic segments rotated with respect to one another as a function of position in the first sequence, this resulting in shifts in angular orientations of the field poles among the magnetic segments in the first sequence, the shifts resulting in an augmented magnetic field strength on one side of the first array relative to a lower magnetic field strength on the other side of the first array.

[024] There is also provided a magnetic system suitable for use in a rotating machine or a gear box, having at least a first array structure containing at least a first plurality of like discrete magnetic segments and extending along a central axis with each segment in the first plurality: (i) having an elongate length, relative to its width, extending along a major side thereof in a direction parallel with the central axis; (ii) including a pole with a like characteristic field distribution including a maximum field strength direction and the same maximum field strength; (iii) having a surface, with a predefined shape in cross section, from which the maximum field strength direction points outward therefrom, about which surface the segment is axially rotatable prior to fixed placement of the segment in the first array of like magnetic segments circumferentially positioned about the central axis; (iv) fixedly arranged with its major side extending in a direction parallel to directions which the major sides of other segments in the first plurality extend; and (v) positioned to extend in a direction parallel with the central axis to collectively form, in combination with others in the first plurality, the first array of like magnetic segments, which first array is configured as a first ordered sequence having field poles of the magnetic segments rotated with respect to one another as a function of position in the first sequence, this resulting in shifts in angular orientations of the field poles among the magnetic segments in the first sequence.

[025] In one series of embodiments of the magnetic system, segments in the first plurality are positioned in contact with, or in sufficient proximity to, one or more other segments to additively combine or reduce fields from different segments and thereby impart net field strengths about the first array structure wherein an augmented magnetic field strength results on one of the inner side or the outer side of the array relative to a reduced magnetic field strength on the other of the inner side or the outer side of the array. The magnetic segments may be entirely in an ordered sequence wherein the magnetic segments are axially rotated with respect to other magnetic segments to sequentially shift orientations of the characteristic maximum field strength direction among the segments and thereby effect the augmented magnetic field strength on one side of the array. The magnetic system may further include a support structure with which: the magnetic segments of the first plurality occupy fixed positions relative to the central axis and relative to one another, and the relative shifts in orientations of the characteristic maximum field strength directions among the field poles is fixed. The support structure may include a series of channels or grooves in which the magnetic segments are placed. Accordingly, the magnetic segments and the channels or grooves may have complementary shapes or mating features which lock the rotational positions of segments in place to fix the relative shifts in field orientation in place. In disclosed embodiments, the support structure may include a series of apertures formed therein and formed along the central axis, with discrete magnetic segments in the first plurality axially rotated and positioned within the apertures to sequentially provide the shifts along the array. The support structure may be formed of a series of stamped laminations joined against one another wherein the laminations comprise nonmagnetic material. [026] The afore described magnetic system may further including a second array structure comprising at least a second plurality of like discrete magnetic segments, and extending along the central axis, with each segment in the second plurality: (i) having an elongate length, relative to its width, extending along a major side thereof in a direction parallel with the central axis; (ii) including a pole with a like characteristic field distribution including a maximum field strength direction and the same maximum field strength; (iii) having a surface, with a predefined shape in cross section, from which the maximum field strength direction points outward therefrom, about which surface the segment is axially rotatable prior to fixed placement of the segment in the second array of like magnetic segments circumferentially positioned about the central axis; (iv) fixedly arranged with its major side extending in a direction parallel to directions which the major sides of other segments in the first plurality extend; and (v) positioned to extend in a direction parallel with the central axis to collectively form, in combination with others in the second plurality, the second array of like magnetic segments, which second array is configured as a second ordered sequence having field poles of the magnetic segments rotated with respect to one another as a function of position in the second sequence, this resulting in shifts in angular orientations of the field poles among magnetic segments in the second sequence. The second array of magnetic segments may be configured to provide a sequence of elements comprising rotationally shifting angular orientations of magnetic field patterns where the angular orientation of field patterns rotates among different magnetic elements in directions orthogonal to the central axis. Also, the spatial rotation of the field patterns may configure the flux pattern in a manner which provides an augmented magnetic field strength on one of the inner side or the outer side of the first array relative to providing a reduced magnetic field strength on the other of the inner side or the outer side of the first array. In one embodiment, with the first array including n magnetic segments, the field pattern among every one of the n segments is characterized by a rotational shift in the angular orientation relative to the angular orientation of the field pattern of the next element in the sequence. In another embodiment, with the second array including m magnetic segments, the field pattern among every one of the m segments is characterized by a rotational shift in the angular orientation relative to the angular orientation of the field pattern of the next element in the sequence. In another embodiment, with the first array including n magnetic segments, the field pattern among fewer than every one of the n segments is characterized by a rotational shift in the angular orientation relative to the angular orientation of the field pattern of the next element in the sequence.

[027] The embodiments of electrical machines according to the invention may include back iron, positioned radially outward from the first plurality of magnetic segments in the first array of the first rotor and coaxial with the first rotor, with windings of the stator extending along an air gap between the first rotor and the back iron, to generate an enhanced radial flux density in the air gap. The hack iron may be mechanically coupled to rotate with the rotor in synchrony to avoid, reduce or eliminate the presence of a changing field which would cause magnetization to occur in the back iron.

[028] When the machine includes flux directing inner back iron, e.g., positioned radially inward from the first plurality of magnetic segments in the first array of the first rotor and coaxial with the first rotor, the inner back iron may be mechanically coupled to rotate with the rotor in synchrony to avoid, reduce or eliminate the presence of a changing field which would cause magnetization to occur in the back iron.

[029] When the magnetic system includes the second array structure comprising magnetic elements, the system may also include a circumferential array comprising ferromagnetic segments positioned between the first array and the second array in coaxial alignment with each.

BRIEF DESCRIPTION OF THE DRAWINGS

[030] Features, and advantages of the present invention will be better understood when the following detailed description is read with reference to the accompanying drawings, where:

[031] Figure 1 provides a view in cross section of a conventional prior art synchronous machine;

[032] Figure 2a is a partial view a cylindrical magnet assembly consisting of pie-shaped elements for which magnetization directions are anti-parallel in adjacent segments; [033] Figure 2b is a partial view a cylindrical magnet assembly consisting of pie-shaped segments for which magnetization directions sequentially rotate between adjoining segments by 45°;

[034] Figure 3 is a side view in cross section of a synchronous machine taken along the shaft with a segmented rotor magnet assembly;

[035] Figure 4 is a side view in cross section of a synchronous machine with a segmented rotor magnet for which the hack iron is not fixed to the machine housing but, rather, is mechanically coupled to rotate with the rotor;

[036] Figure 5 is a side view in cross section of a synchronous machine with a segmented rotor magnet assembly is located on the outer periphery of the machine and the back iron is located adjacent the machine shaft and is attached to the machine housing;

[037] Figure 6 is a side view in cross section of a synchronous machine with a segmented rotor magnet assembly where instead of being fixed to the machine housing the back iron is mechanical coupled for rotation with the rotor;

[038] Figure 7 is a side view in cross section of a synchronous machine with a dual segmented rotor assembly and which does not contain any back iron;

[039] Figure 8 is a view in cross section taken along the shaft of a machine illustrating two concentric discrete flux directed arrays each having 5 pole pairs comprising cylindrically shaped magnetic segments with the inner flux-directed array comprising three segments per pole and the outer flux directed array comprising five segments per pole;

[040] Figure 9 is a view in cross section taken along the shaft of a machine illustrating a support structure in the shape of a ring for supporting the rod-shaped magnetic segments with exemplary elliptical apertures, the arrows indicating orientations for the major axis of each in a cylindrical array of elliptical aperture and possible field orientations for magnetic segments inserted therein;

[041] Figure 10 is a view in cross section of a machine illustrating two concentric flux- directed magnet arrays, each having 5 pole pairs incorporating elliptical apertures into which elliptically-shaped magnetic segments are inserted; [042] Figure 11 is a perspective view of a machine with an exemplary magnetic segment composed of multiple permanent magnet subsegments shown inserted end-to-end within one exemplary aperture of the support ring shown in Figure 9; and

[043] Figure 12 is a view in cross section, taken along a plane transverse to a cylindrical axis of symmetry, of a magnetic gear system having an exemplary' cylindrical array comprising magnetic poles each assembled with elliptical -shaped magnetic segments and rectangular-shaped ferromagnetic segments in the airgap.

[044] Discrete magnetic segments or associated apertures in which the segments are placed are indicated in the figures with circular or ellipsoidal shapes. Arrows drawn within the shapes correspond to magnetization directions or rotational shifts of the placed segments or orientations of ellipsoid shaped apertures in which the segments are placed. Like reference numbers are used throughout the figures to denote like components. Features of the invention are illustrated schematically, it being understood that various details, connections and components of an apparent nature are not shown in order to emphasize features of the invention. Various features shown in the figures are not to drawn scale.

DETAILED DESCRIPTION OF THE INVENTION

[045] Before describing in further detail the particular features related to embodiments of the invention, it is noted that the present invention resides primarily in a novel and non-obvious combination of components and process steps. So as not to obscure the disclosure with details that will be readily apparent to those skilled in the art, certain conventional components and steps have been omitted or presented with lesser detail, while the drawings and the specification describe in greater detail other elements and steps pertinent to understanding the invention. The disclosed embodiments do not define limits as to structure or method according to the invention, but only provide examples which include features that are permissive rather than mandatory and illustrative rather than exhaustive. Further, to assure clarity in describing the invention and the scope of what is claimed, a brief explanation of terminology is provided. [046] “Circumferential” as used herein refers to a configuration which extends partly or entirely around an axis or a body shape, e.g., a rotor, a stator, or an array of segments. For example, the outer surface of a closed body shape, e.g., a stator winding, which extends along a straight axis and completely around the axis, has a circumferential shape because the outer surface extends partly or completely around the axis. The closed body shape may, for example, be that of an electrical winding, e.g., having a cylindrical, or cylindrical-like, body shape extending along the axis.

[047] “Circumferential array” refers to an array of segments arranged circumferentially about an axis or around a body shape.

[048] “Cylindrical array of segments” refers to an array of discrete segments configured in a series, e.g., a series of bar magnets, which extends partly or entirely circumferentially around an axis or a body shape where the segments may be arranged as a sequence of parallel segments to provide spatial attributes along a real or imaginary cylindrical surface. The spatial attributes may relate to spatial geometric features or to magnetic field distributions and magnetic flux densities as a function of position about the real or imaginary cylindrical surface.

[049] “Cylindrical-like” refers to a shape which is similar to or sufficiently approximates the shape and symmetry of a cylindrical body even though the body may have multiple distinct wall portions or variations in diameter.

[050] “Discrete magnetic segment”, also referred to as a segment, is a permanent magnet or an electromagnet (e.g., an electromagnetic coil). In the case of a permanent magnet, the segment may be in the form of a rod-shaped, i.e., elongate, structure. The structure may be monolithic or may comprise of multiple subsegments, i.e., multiple magnets, which are smaller in size and arranged end to end, i.e., pole to pole, to realize a desired length of the segment. A permanent magnet segment is not limited to any particular shape in cross section and such segments, disclosed for use in embodiments of the invention, have an elongate shape extending along a straight axis without being limited to any specific set of shapes in cross section, i.e., sectional views taken along planes orthogonal to the axis. Such segment cross-sectional shapes may, for example, be circular, cylindrical, elliptical, symmetric, or asymmetric.

[051] “Flux channeling”, in the context of magnetic fields, refers to a net field pattern due to interaction of flux emanating from multiple magnetic sources. By way of example, for an array of circumferentially arranged magnets, flux channeling may result in an asymmetric field distribution about an array of individual magnets. For a conventional Halbach array, the field interactions may result in an augmented magnetic field strength on one side of the magnet array relative to a reduced magnetic field strength on another side of the array.

[052] “Rod shaped structure” means an elongate member extending along a straight axis without limitation on the shape of the structure as viewed along a plane orthogonal to the major axis. Discrete magnetic segments used to form arrays according to the invention are generally elongate, extending about a major axis, and may have a variety of shapes in cross section, i.e., along a plane orthogonal to the major axis.

[053] “Shape in cross section” means, with respect to a discrete magnetic segment or a coil, a shape along a plane orthogonal to the major axis of the segment, e.g., a straight axis along the direction in which the elongate shape extends.

[054] A prior art embodiment of a conventional synchronous machine is shown in Figure 1. The concept is identical for generators and motors. In the case of a generator, mechanical energy is supplied to the rotating shaft 104 of the machine. The mechanical energy is converted to electrical energy made available as an output from the stator windings 102. In the case of a motor, for any kind of propulsion, electrical energy is supplied to the stator windings 102 and converted to mechanical energy made available at the rotating shaft 104. [055] The schematic layout shown in Figure 1 illustrates the basic function of a synchronous electrical machine. The stator 102 and the rotor 100 are concentrically situated along a common axis with the stator windings 102W configured such that current flowing in each winding is primarily in the axial direction, i.e., along the direction of the shaft 104. The stator of a synchronous machine may consist of multiple windings 102W (not shown) with appropriate phasing to generate a rotating magnetic field. Ideally and optimally, it is desirable for the field lines of the rotor of a conventional machine to extend radially from the common axis, i.e., in a radial direction orthogonal to the primary directions of current flow in the stator windings.

[056] The rotor 100, which transfers mechanical energy into or out of the system, is coupled to the machine shaft 104. The rotor is surrounded by the concentric back iron

103, along which the so-called airgap 102 resides between the rotor and the back iron.

The stator windings 102W are located in the air gap, G. Consisting of permanent magnets or electromagnets 101, the rotor 100 provides a magnetic field in the airgap for coupling with the field generated by the stator windings 102W. To convert mechanical energy to electrical energy, when the rotor 100 is turned by an application of torque to the shaft

104, interaction between the changing flux of the rotor and current flow in the stator windings induces an electromotive force (emf) at the terminals of the stator winding and the system operates as a generator. In the case of motor operation, when alternating voltages with appropriate phase shifts between them are applied to excite the stator windings 102W, a rotating magnetic field is generated around the axis of the machine. Interaction between the rotating field generated by the stator windings and magnetic fields of the rotor magnets 101 turn the rotor in synchronization with the frequency of the alternating voltage applied to excite the stator winding.

[057] To achieve the maximum energy transfer between the rotor magnets 101 and stator windings 102, the field in the stator winding airgap, G, must be oriented in radial direction. As described for a conventional motor, the Lorentz force, F, acting on a conductor of the stator winding is given by F = IxB, where all quantities are vectors. I represents the current in the stator winding 102 and B is the magnetic flux density provided by the rotor magnets in the airgap, which interacts with current flowing through the stator windings. The force given by the vector cross product has its maximum value when the direction of current, I, and the direction of the flux density, B, are perpendicular to each other. The Lorentz force is zero when the angle between the two quantities is 0°. As can be seen from this relationship, the machine power is optimized when the field direction of the rotor is in the radial direction relative to the common axis, since the conductors of the stator winding are oriented in the axial direction. With the back iron 103 surrounding the field generating rotor, the field lines of the rotor can be more closely aligned to the radial direction.

[058] The power of a synchronous machine is given by the relationship: where w represents the rotational speed, L is the axial length of the machine. D is the average diameter of stator windings in the airgap, B _R is the fiux density in the air gap and As is the current loading of the stator winding. The equation shows that the power of the machine is proportional to the flux density in the airgap at the stator winding. The flux density of a cylindrical system as needed for the rotor can be enhanced if the system comprises a flux channeling array of magnetic elements as present in a cylindrical Halbach array. For this magnet configuration each magnetic pole is segmented into elements, and the magnetization directions of the individual elements change in orientation from element to element. While a conventional permanent magnet has a north pole and a south pole on opposing sides of the array, by appropriately rotating the magnetization direction from element to element in the array appropriately, the flux of a magnet can be bent, i.e.. channeled, to almost entirely emerge on only one side of the array. In this case, a ring assembly of magnets, which can consist of permanent magnets or electromagnets, can be produced which has substantially only an inward or only an outward directed magnetic flux. Due to the field bending (referred to as flux channeling), the emerging flux is not only largely limited to one side of the system but also leads to a significant enhancement of the emerging flux density in comparison to a conventional magnet with opposing north and south poles. In some cases, the field bending achievable with the flux channeling array according to the invention can be enhanced by as much as a factor of two.

[059] In principle, the power of a synchronous machine can be significantly enhanced if the field-generating rotor system is implemented as a flux-channeling array, e.g., with a conventional Halbach array comprising pie-shaped magnetic segments, instead of the conventional assembly of magnets that have opposing north and south poles. Advantages of the system incorporating a flux-channeling array over the conventional system are evident from a comparison between performance for the conventional magnet assembly as illustrated Figure 2a, and performance for a system incorporating flux channeling arrays as illustrated in Figure 2b.

[060] Figure 2b illustrates two magnetic poles of a complete Halbach array in which each pole consists of four elements 121. Each pie-shaped element 121 of the array has a different magnetization orientation. The field strength of a permanent magnet depends on the shape of die magnet and the field is strongly dependent on the presence of ferromagnetic material in the vicinity instead of air. For the assembled pie-shaped segments the field lines are channeled from segment to segment based on the lower reluctance of ferromagnetic material in comparison to air. If, on the other hand, the same pie-shaped element is in air, some of its field lines would return through the element itself, thereby reducing the field that can be measured on the outside. If all pie-shaped elements of a Halbach array are magnetized to the same remanent field B _rem , the assembled system can he a very good approximation to the ideal field configuration given by Eqn 1 and Eqn 2.

[061] Based on the flux channeling in a complete Halbach array, the flux density on the inside 122 of the ring can be enhanced and the flux density on the outside 123 can be canceled, or vice versa, in which case only the outside of the ring shows any flux density. Practically, however, manufacture of pie-shaped permanent magnets with varying magnetization directions 121 about the longitudinal axis of each segment is rather complicated, time consuming and expensive. This is due to the fact that permanent magnets are produced as rectangular with identical magnetization directions 121. The magnetized parallelepipeds are then individually machined to obtain a required magnetization direction. Based on the brittleness and hardness characteristics of permanent magnet materials and the strong forces acting in the vicinity of other ferromagnetic materials, the manufacturing and assembly processes are complicated, challenging and less practical than desired for many applications.

[062] Furthermore, assembling the pieces in a donut-iike shape, in the presence of strong opposing magnetic forces, and then bonding them to one another, is a complex process. The resulting assembly would then normally be overwrapped to achieve mechanical robustness. For many applications, the final cost of such assemblies exceeds the resulting advantages such that it appears more economical to increase power and torque simply by increasing the size of a conventional machine.

[063] However, with flux-channeling arrays according to the invention, comprising discrete magnetic segments which, in exemplary embodiments, all have identical magnetization directions (see Figure 10), it becomes more practical and economically feasible to realize synchronous electrical machines yielding the same benefits as expected from conventional Halbach arrays,

[064] An embodiment of an exemplary _' system 130 according to the invention is shown in Figure 3 with a flux -channeled permanent magnet array 107 attached to the shaft 104 of the machine to form the field-generating rotor. The representation of the magnet array 107 is schematic. The four indicated subsegments of array 107 are only meant to indicate that this segment is an assembly of individual magnetic subsegments. It does not show how the magnetic segments are oriented in the assembly. With the help of the concentric back iron 103, positioned radially outward from the rotor and coaxial with the rotor, an enhanced radial flux density is generated in the air gap, G, between the field of the rotor 100 and the back iron 103 where the stator windings 102W are located. [065] The efficiency of an electrical machine is strongly affected by magnetization losses in the back iron, which is exposed to the changing magnetic field of the rotating field of the rotor. These magnetization losses can be significantly reduced if the back iron is mechanically coupled to the rotor, as for the system 135 shown in Figure 4. In this case, with the back iron 111 is mechanically coupled to rotate with the rotor 108 in synchrony so that there is no changing field causing magnetization to occur in the back iron Hi.

[066] According to another embodiment of the invention shown in Figure 5, a flux- channeled array 113 is positioned on the outside of the stator 102, facing away from the central axis with the flux-directing iron 112 positioned on the inside of the stator 102 and facing the central axis. With this configuration it becomes possible to produce an even higher flux density in the air gap, G, between the stator 102 and the rotor magnet array 113 for the same dimensions of the machine and therefore a higher power and torque density. Also, with reference to the system 45 of Figure 6, if the iron 112 is again mechanically coupled to the flux-channeling array 113 the magnetization losses in the iron will be reduced.

[067] According to still another embodiment of the invention, the system 150 shown in Figure 7 illustrates a further improvement in flux density in the air gap 102 for an electrical machine achieved with the outer back iron (e.g., shown in Figures 3 to 6) replaced with another flux channeling array comprising discrete magnetic segments 110. lit this ease, as before, the inner flux-channeling array 109 generates an outward directed flux and the outer flux channeling array 110 that replaces the back iron generates in inward directed flux. The opposing flux-channeling arrays (109 and 110) provide: (i) the desired radial flux direction, (it) lead to a further enhancement of the flux density in the air gap which is now' given by the superposition of the inner and outer flux-channeling arrays, and (iii) no further shielding of a fringe magnetic field is required. The two opposing, flux -channeling arrays (109 and 110) are mechanically coupled to the rotor 108 and thereby to the shaft 104. [068] In contrast to a machine configuration that requires back iron, with opposing flux- channeling arrays, higher flux densities in the airgap become feasible. Since iron shows magnetic saturation near 2 Tesla, flux densities in the air gap have to be limited to this value or the iron will act like air losing its purpose. Even below two Tesla, the thickness of the back iron must increase with the flux density in. the airgap to direct the field in the airgap in the radial direction and to contain the fringe magnetic field, increased iron thickness leads to an increase of the machine weight which counteracts the increase in power and torque density resulting from the increase in flux density. With the concept of opposing flux-channeling arrays this limitation is removed and using superconducting dipole coils instead of permanent magnets with flux densities in the airgap of several Tesla become feasible.

[069] In United States Patent Application US2018/0226190 a manufacturing process is disclosed for Halbach arrays in which an entire array is magnetized in a single step. This is achieved with the help of magnetization coils that generate a continuously changing flux direction as a function of azimuthal position around the Halbach ring (See Eqn 1 and Eqn 2) . Application of this technique is best suited to a limited range of array diameters between 50 mm and 200 mm and maximum pole numbers of less than 12. Magnetization of permanent magnet material such as, NdFeB, requires a flux density of several Tesla. This renders fabrication of large continuous Halbach arrays, such as required for wind generators, impractical. The required magnetization coils would be very large with accordingly very large inductances. To generate the required pulsed magnetic field with a flux density of several Tesla requires very high voltages and high power. A further difficulty exists for the magnetization of rings for electrical machines that require pole numbers of more than 20 with sufficient radial thickness. The inside field of any multipole coil, as needed for the magnetization process, falls off with an increasing exponent toward the center of the system. For a quadrupole, i.e., a system with four poles, the flux density falls off in a linear manner as a function of radius. For the general case of n poles, the flux density falls off as 1/r _n- ¹ . Due to the steep decline of flux density towards the center, it becomes increasingly difficult to achieve a sufficient flux density for magnetization on the inside of a ring-shaped magnet of a given radial thickness. To overcome this effect, very large magnetization fields are required to penetrate the ring with the required flux density for uniform magnetization in the radial direction.

[070] As afore described, the manufacturing complexity of conventional Halbach arrays consisting of pie-shaped, appropriately magnetized segments has prevented their widespread application. For many applications, the final cost of such assemblies exceeds the resulting advantage, and it is more economical to increase power and torque by enlarging the size of a conventional machine.

[071] According to the invention, manufacturing difficulties of incorporating conventional Halbach arrays into rotating machines can be avoided based on designs other than those requiring continuous ring geometries or cylindrical assemblies formed with discrete pie-shaped pieces, Embodiments of the invention provide a flux-directed magnet assembly comprising discrete, permanent magnets or current carrying normal or superconducting coils arranged in an array which extends along the contour of a cylindrically shaped surface, i.e., a cylindrical plane. Individual magnets in the array extend in a direction parallel with the central axis of the cylindrically shaped surface.

[072] Referring to Figure 8, a view in cross section illustrates two flux-directed magnetic assemblies in a concentric arrangement suitable for operation as a rotating electrical machine or magnetic gear. Each of the circles 303 is a rod-shaped permanent magnet or a dipole coil, referred to herein as a magnetic segment. In an advantageous embodiment, all magnetic segments 303 in one of the rings are identical with identical magnetizations. However, the elements are rotated relative to each other to produce the magnetization direction needed for flux channeling. The required magnetization direction of each individual magnetic segment is indicated by an arrow. The magnetic segments of the inner ring (302) can also be identical to the elements of outer ring 300. [073] The illustrated embodiment is suitable for operation as a dual rotor motor or generator. Other embodiments may consist of a single flux-directed magnet assembly applicable to machinery having a single rotor as shown in the concept figures 4, 5 and 6. Referring to Figure 8, each flux-directed magnet assembly 300 and 302 may comprise of coils or a series of permanent magnets in the form of rod-like elements, referred to as pole segments. For embodiments where the segments are permanent magnets, the segments may be spaced-apart front one another, but the surfaces of adjacent pole segments, referred to as major sides, may be adjoining or in contact with one another. The view of Figure 8 is taken along a plane transverse to a cylindrical axis of symmetry common to each array of rod-like segments, lire inner array of rod-like segments 302 in the concentric pair projects a radially outward-directed flux, and the outer array 300 in the concentric pair projects a radially inward directed flux, determined by the indicated magnetization directions. Each exemplary array of rod-like magnetic elements (300 and 302) is configured as a flux-directed magnetic assembly with the appropriate magnetization directions of the individual magnetic rod-like segments. The embodiment shown in Figure 8 generates a field with 5 pole pairs. Each such assembly of discrete magnets extends within a cylindrical plane in the direction of the axis of symmetry. For the inner magnetic array 302, with an outward projected flux, each pole consists of 3 segments. In the outer magnetic array 300, each pole consists of 5 segments. The indicated magnetization directions can be obtained by the Eqn 1 and Eqn 2 which for convenience are presented here again:

B _{r ~} B _rem * cos(p * Θ) (Eqn 1) and

B _Θ = B _rem * sin(p * Θ) (Eqn 2),

The ideal configuration given by Eqn 1 and Eqn 2 is best approximated by a large number of segments per pole. However, it can be shown that five segments per pole can provide a suitably close approximation of an ideal configuration for practice of the invention.

[074] The concentric arrangement of two arrays 300 and 302 of rod-like segments shown in Figure 8 can be used as a rotor for synchronous electrical machines and the underlying concepts may also be applied for operation of magnetic gears. In motor applications, the stator windings will be placed in the air gap between the inner 302 and outer 300 arrays of rod-like magnetic segments. The concentric opposing arrays each produce a radially directed flux density as needed for an optimized torque, since the stator current flows in a direction perpendicular to the plane along which the view is taken and the Lorentz forces on a conductor in the stator winding is given by the cross- product F = IxB of the current flowing in the conductor and the surrounding magnetic flux.

[075] For practical applications of electrical machines, and magnetic gears incorporating the concentric arrays of these rod-like elements, the number of pole pairs, the number of segments per pole, the shapes in cross-section of the individual magnets, the air gap between the two magnet arrays, and the radial thickness of the arrays can each be optimized for the best possible flux channeling.

[076] The shape of each rod-like magnet, he,, a permanent magnet or a dipole coil, in a flux-directed magnet array may be of varied symmetric or asymmetric shape when so viewed in cross section.

[077] In one embodiment the rod-like magnetic segments are in a series of identical and uniformly spaced-apart cylinders which collectively form the cylindrical array pattern of each flux-directed magnet assembly. In this example, with the permanent magnets each having a magnetization direction transverse to the axial direction of the cylindrical shape, the magnets may he individually rotated as a function of position about the assembly to provide the required magnetization direction for a cyclically shifting pattern of magnetization directions along the poles, akin to the pattern in a conventional Haibach array, and for any specified multipole configuration, n. [078] The exemplary rod-shaped permanent magnets (schematically shown in Figure 8 as cylindrical in shape) are each inserted in a series of apertures or bore holes 601. The apertures may be formed in a cylindrically shaped support structure 600, such as shown in Figure 9. The support structure can be produced with stamped laminations having precision apertures 601 for insertion of the permanent magnet segments therein. .Such stacked laminations can be manufactured with accuracies of 0.01 mm or less at a relatively low cost. The material of these laminations can be non-magnetic and. for example, can predominantly comprise titanium, to provide a relatively high strength, low density support structure.

[079] During motor excitation, the individual magnets in the illustrated concentric arrays of flux-directed magnetic segments experience torques that could impart rotation of their positions within the cylindrically shaped support structures in reaction to the acting Lorentz forces. Such rotations can he prevented, for example, by using magnets with an elliptical cross-section as shown in Figure 10 with the apertures of the support structure having complimentary shapes that lock the rod-shaped magnetic segments in place under the acting Lorentz forces. Alternatively, the rod-like magnets can be chemically bonded, e.g., with an appropriate epoxy, into the support structure to prevent any rotation or axial movement, or the surfaces of the major sides, which may be circular-like in cross section may include a key which interlocks in a mating keyway in the support structure.

[080] A feature of the disclosed embodiments is that the arrays may comprise discrete magnets of the type which can be produced with any available permanent magnet material, including NdFeB of the highest available grade (e.g., N52). No further development of permanent magnet manufacturing and magnetization processes is needed. For applications with highest power and torque densities requiring very large flux density B _R (see Eqn 3) in the airgap, superconducting dipole coils can be used as the magnetic elements. In this case all coils of the two rings can be in series or, if preferred, the current in the outer ring can be different from the current in the inner ring. [081] For designs requiring arrays having significant segment length in the axial direction, as shown for one in a plurality of bore holes in the partial view of Figure 11, multiple discrete subsegments of permanent magnets 400 can be inserted end-to-end within each bore hole in the laminated support structure 401 No repulsive forces need to be overcome to place multiple magnets in the same aperture and the magnets inserted end-to-end in the same aperture should not need to be bonded together.

[082] The disclosed discrete arrays of spaced-apart magnetic elements are expected to have significantly higher mechanical robustness over conventional Haibaeh arrays formed with discrete pie-shaped pieces and are therefore well-suited for electrical machines operating at high RPM. Conventional Haibaeh arrays consist of segments of brittle material glued together and typically overwrapped with fiberglass epoxy.

[083] When compared to a conventional Halbach array, manufacture of the disclosed discrete flux -directed magnet assembly is a more economical process by which magnetic flux is redirected across a small air gap. Notably, all rod-like magnetic segments in the assembly can be identical. If magnetic segments with long axial lengths are assembled of shorter individual magnets, a sorting process can be applied to make sure that all rods within a ring have equal remanent fields. In manufacturing of permanent magnets, variations in remanent field of a few percent from magnet to magnet are typically found. By measuring all magnets and sorting them accordingly, variations in field strengths between rods can be minimized, thereby avoiding torque ripple of the machine.

[084] The feasibility of producing cost-effective discrete flux-directed magnetic assemblies of almost any size and with highest flux density in the air gap makes this technology well suited for magnetic gear boxes such as disclosed in U.S. Patent 3,378,710. [085] Figure 12 schematically illustrates another embodiment of discrete, spaced-apart, rod-like magnetic segments 505 in a pair of concentric cylindrical arrays (500 and 502) containing flux -channeled magnet assemblies. A third ring 503, containing a number of ferromagnetic segments 504 is located in the gap between the two flux-channeling magnet array rings. The illustrated embodiment comprises two rings (500 and 502) containing permanent magnets and an inserted ring with ferromagnetic segments 503. The two rings are flux channeling assemblies.

[086] Figure 12 shows a view in cross section along a plane transverse to the common axis of symmetry of the two arrays. Elements (505) in each cylindrical array extend along one of two imaginary concentric cylindrical surfaces as in previous figures (Figure 8 and Figure 10). During rotation of one of the arrays about the common axis, and as magnets (505) and ferromagnetic segments (504) in different rings approach each other, the different elements attract or repel one another, exhibiting behaviors functionally akin to meshing teeth of mechanical gears on two rotatable rings. Although the arrays of magnetic elements provide a motion ratio like that of a traditional mechanical gear, the magnetic gears work without contacting one another. They are therefore immune to mechanical wear of interacting/mating surfaces and create no noise. The gears may slip without damage. With an equal number of pole pairs on the inner and outer arrays of magnetic elements, the system works like a conventional clutch with a maximum allowable torque transfer. The discrete flux· directed magnet assemblies provide an advantageous gear system over conventional north-south magnet assemblies, in part because conventional assemblies require back iron and do not yield the same high flux density in the airgap. The invention provides a cost-effective magnetic gear system with a high torque transfer density.

[087] The magnetic gearing can be coupled with the disclosed embodiments of synchronous electrical machines. In case of a wind generator with the very low RPM, he,. less than 20 RPM, the magnetic gears can be connected to the wind-driven propeller, but with the implementation of the magnetic gears, the generator can be driven by a significantly higher RPM. Since the power of an electrical machines is proportional to the RPM, the size of the generator can be reduced accordingly, and the increased output frequency of the generator facilitates the required rectification. Since mechanical gear boxes in wind generators have been found to constitute the element with the shortest meantime between failure of the whole system, a magnetic gear box with the intrinsic slippage capability, will significantly improve reliability.

FEATURES AND DISTINCTIONS OF THE INVENTION

[088] The invention enables use of flux channeling without the constraint which have constrained the technology to limited applications.

[089] Figure 2b illustrates two magnetic poles of a complete Halbach array in which each pole consists of four elements 121. Each pie- shaped element 121 of the array has a different magnetization orientation. The field strength of a permanent magnet depends on the shape of the magnet and the field is strongly dependent on the presence of ferromagnetic material in the vicinity instead of air. For the assembled pie-shaped segments the field lines are channeled from segment to segment based on the lower reluctance of ferromagnetic material in comparison to air. If, on the other hand, the same pie-shaped element is in air, some of its field lines -would return through the element itself, thereby reducing the field that can be measured on the outside. Pie-shaped pieces 121 with arbitrary magnetization directions have no symmetry in respect to their magnetization direction. Because of this broken symmetry, pieces with different magnetization directions as shown in Figure 2b, that do not touch, will show significant differences in their inner and outer flux densities. Consequently pieces with different magnetization directions as shown in Figure 2b, that do not touch, will not exhibit the same maximum field strength. How ever, if all pie-shaped elements of a Halbach array are magnetized to the same remanent field B _rem , and touch each other as shown in Figure 2B, the assembled system can be a very good approximation to the ideal field configuration given by Eqn 1 and Eqn 2. [090] In one embodiment an array for use in a rotating machine contains a plurality of like discrete magnetic segments. When the segments are spaced apart, such as prior to placement in the array, each includes a pole having the same maximum field strength. Flux channeling can be effected when the segments are (i) formed in a circumferential array with rotated fields in a sequence along the array, and (ii) with each segment positioned in sufficient proximity to the next segment in the sequence along the array for the fields to interact with one another. Among different embodiments of the invention, for flux channeling to occur the segments may be in physical contact with one another or they may be spaced-apart but in such sufficiently close proximity that the fields between segments next to one another in the array interact to effect flux channeling.

[091] While the invention has been described with reference to particular embodiments, it will be understood by those skilled in the art that various changes may be made, and equivalents may be substituted for elements thereof without departing from the scope of the invention.