Technical Field The invention relates to the field of electrical machines, in particular to the insulation of a conductor for an electrical machine. The invention further relates to several insulation layers provided on and around the conductor.

Background Art

Electrical conductors for electrical machines, such as coils for an electromotor or generator, are insulated for avoiding contact between the single windings of the coils, but also for avoiding a short between the coil and other conductive components of the electrical machine, for example the stator of a electromotor. For instance, the main wall insulation (e.g. mica tape and impregnated resin) is used nowadays to insulate a conductor on full potential to the stator core on ground potential. Currently, the so-called vacuum pressure impregnation (VPI) technology is used and widely applied by many machine manufacturers. In this process, layers of mica tape are wound on conductors. The layers of mica tape are impregnated with thermosetting resins and thermally cured subsequently to obtain the so-called main wall insulation - the final mica-resin composite. In case of motors and small generators (< 15 kV) complete stators with inserted form-wound coils are fully impregnated in a global VPI process. For large generators, insulated Roebel bars are manufactured and impregnated individually (single VPI).

The principle of using mica tape and resin impregnation has not changed for almost one century and is well established to produce main wall insulation on a complex conductor shape and overall size, such as coils or Roebel bars for large electrical machines. To create a finished stator coil and Roebel bar today, the widespread application of robotics for coil forming, insulation taping and consolidation have improved the known process. However, these insulations have poor heat conducting properties for electrical machines. In particular, mica tapes known to be used in electrical machine windings have good dielectric strength and partial discharge resistance, but poor heat conductivity properties.

As the produced losses in the form of heat are usually the bottle neck of the design of electrical machines, the low thermal conductivity of insulations contributes to design limitations significantly. For many materials suitable for electrical insulation, thermal and electric conductivity is assumed to go hand in hand, so an electrical insulator is seen as a thermal insulator, too. This is due to the fact that the free movement of electrons, which corresponds with electric conductivity, is also seen as the major contributor of heat conduction. Brief summary of the invention

In view of the above, an electrical machine according to claim 1 and the use of diamond particles in an insulation layer of an electrical machine according to claim 15 are provided. Further aspects, advantages, and features of the present invention are apparent from the dependent claims, the description, and the accompanying drawings. According to an aspect of the invention an electrical machine having a conductor arrangement is provided. The conductor arrangement includes an electrical conductor and an electrical insulation that is at least partially provided around the conductor. The electrical machine is adapted for applying a voltage up to a rated voltage Vmax to the conductor arrangement. The electrical insulation includes a diamond containing insulation layer which includes diamond particles having a diameter of at least 1 μιη in a direction substantially parallel to the conductor surface. The diamond containing insulation layer provides the highest dielectric strength and/or discharge resistance of the electrical insulation. The diamond containing insulation layer has a thickness td according to the following formula (1) t _d [mm] = V _max [kV] * k _d where 0.0005 < k _d < 0.0555.

Generally, diamond can be a good electrical insulator and a heat conductor at the same time. The effects are due to the fact that diamond can conduct heat (phonon transfer) by lattice vibrations instead of utilizing electrons. Therefore, a better heat conductivity and a higher dielectric strength than mica based insulations can be provided by the conductor arrangement according to embodiments described herein. Using diamond particles for the insulation of the conductor arrangement allows for a more compact electrical machine design, higher voltages and thereby for higher efficiency and/or energy density. Also, novel thermal management methods for electrical machines are possible, further enhancing performance.

Embodiments described herein allow for utilizing the extremely high heat conductivity with thinner insulation layers than known.

Brief Description of the Drawings

The subject matter of the invention will be explained in more detail in the following text with reference to preferred exemplary embodiments which are illustrated in the drawings, in which:

Figure 1 is a schematic drawing of an electric machine having a coil as conductor arrangement;

Figures 2 and 3 show schematic front views of conductor arrangements according to embodiments described herein;

Figure 4 shows a schematic perspective view of a wound conductor arrangement according to embodiments described herein;

Figure 5 is a schematic drawing of a conductor arrangement provided with an insulator according to embodiments described herein;

Figure 6 is a schematic partial and more detailed view of the electrical conductor arrangement provided with an insulator according to embodiments described herein;

Figures 7 to 10 show schematic views of insulation layers including diamond containing insulation layers of conductor arrangements according to embodiments described herein;

Figure 11a to l id show schematic plan views on a tape according to embodiments described herein;

Figure 12 shows a schematic drawing of a conductor arrangement with an insulator according to embodiments described herein; Figure 13 shows a schematic drawing of an electron discharge path according to embodiments described herein;

Figure 14 shows a schematic front view of the slot region with a conductor arrangement arranged in the slot region according to embodiments described herein; Figure 15 shows a schematic cross-sectional view of the slot region according to embodiments described herein;

Figure 16 shows a schematic front view of the slot region according to embodiments described herein; and

Figure 17 shows a flowchart of a method of insulating a conductor according to embodiments described herein;

Preferred Embodiments of the Invention

According to embodiments described herein, an electrical machine including a conductor arrangement is provided. For instance, the electrical machine according to embodiments described herein may be at least one of electrical motor, generator, transformer and/or other electromagnetic device e.g. actuator and/or electromagnet. Typically, the conductor arrangement may include a wound conductor like e.g. a coil of the electrical machine.

Figure 1 shows an example of a wound coil as a conductor arrangement in a basic structure of an electrical motor. The electrical motor 100 includes a stator 101 and a rotor 102. The stator 101 is exemplarily shown having a stator core 105, which is for instance provided in a cylinder- like shape and which is provided with six wound conductors 106 or multi -turns, such as coils or windings, which are connected to a power source. The magnetic rotor 102 is adapted for rotating about an axis 104 pointing in the plane of the drawing sheet. By providing current in the windings 106, a magnetic field is induced. The magnetic rotor 102 is rotated. Due to the magnetic forces between the rotor 102 and each winding 106, which reject and attract each other, the rotor 102 is continuously rotated. In this way, a rotational movement of the rotor 102 is achieved. The skilled person may understand that an electrical machine as referred to herein is not limited to the design shown in Figure 1.

Figures 2, 3, and 4 show a simplified example of an electrical conductor 201 of a conductor arrangement 200. The simplified drawings show the conductor 201 having a rectangular cross-section. The electrical conductor 201 is surrounded (at least partially) by an electrical insulation 203. The electrical insulation contains a total thickness ttot.

The total thickness ttot of the electrical insulation is described according to the following formula (2): (2) t _tot [mm] = V _max [kV] * k _tot with 0.0690 < k _tot <0.103.

The electrical insulation 203 includes a diamond containing insulation layer 330. The diamond containing insulation layer 330 has a thickness td. The thickness td of the diamond containing insulation layer is described by the following formula (1):

(1) t _d [mm] = V _max [kV] * k _d with 0.0005 < k _d <0.0555. The lower thickness limit for td (with kd = 0.0005) is made possible due to the excellent dielectric strength of the diamond layer, allowing even an extremely thin layer to still withstand a given dielectric voltage. Such a thin layer is preferably suitable for rated voltage Vmax of at least 0.1 kV, preferably at least 1 kV. A preferred lower limit for kd is 0.001, a more preferred lower limit is 0.005, and a particularly preferred lower limit is 0.015. The lower limit of 0.001 is especially relevant in case of the diamond containing layer being applied by direct infusion, and the lower limit of 0.005 is especially relevant for the case of the diamond containing layer being applied by taping.

On the other hand, even the upper thickness limit (with kd = 0.0555) still allows for a reasonable thickness, while allowing for excellent dielectric strength and still good cooling properties, due to the excellent thermal conductivity of the diamond layer. A preferred upper limit for kd is 0.03, and a particularly preferred lower limit for kd is 0.02.

The small thickness td of the diamond containing insulation layer, as well as the excellent insulating and heat conducting properties of diamond, also allow the small total thickness ttot of the electrical insulation, as described by formula (2) above. The circumference of the electrical conductor 201 is surrounded by the electrical insulation 203, while the front sides of the conductor are not covered by the electrical insulation 203. Figure 2 shows a cross-section in the x-y-plane of the conductor shown in a perspective view in Figure 4. Figure 3 shows that the electrical insulation 203 of the electrical conductor 201 comprises two insulation layers 330 and 202. The insulation layer 330 is a diamond containing insulation layer. The two insulation layers 330 and 202 have different insulation properties, such as different values of electrical conductivity. The diamond containing insulation layer 330 provides the highest dielectric strength and/or discharge resistance. The electrical conductor has a longitudinal axis or z-direction. The insulation layers 203, 202 are arranged in the longitudinal direction of the electrical conductor 201.

Figure 5 shows a conductor arrangement 200 including insulation in the form of a tape 210 having a diamond containing insulation layer for electrically insulating the conductor. The example of Figure 5 shows a longitudinal conductor, of which a section is drawn. The tape is wound about the conductor in a winding direction W in a helical matter. The winding direction W substantially corresponds to the longitudinal z-direction of the conductor arrangement 200. Figure 6 shows an enlarged section of the conductor arrangement of Figure 5. Figure 6 shows the insulation in the form of a tape 210 having overlapping portions 214, 215, and 216, where the tape 210 used for forming the insulation overlaps with the previously wound tape section.

The tape 210 in the examples of Figures 5 and 6 includes a diamond containing insulation layer that contributes to the escape of heat through the insulation layer and to the insulation of the electrical conductor.

Figure 7 shows a more detailed view of the structure of the electrical insulation 203 which includes the diamond containing insulation layer 330 and the carrier 310 of the tape. The thickness td describes the height of the diamond containing insulation layer 330 which is perpendicular to the conductor surface whereas the thickness 302 is the height of the whole tape. In the example of the tape, the tape thickness 302 is similar to the total insulation thickness of the electrical insulation 203. The diamond containing insulation layer includes diamond particles 320 that are provided as flakes 334 which are arranged on the carrier 310. The carrier 310 is a web or a film. The carrier 310 can also include a carrier material like a (non-woven) polyester web, a polyester film, glass cloths, non-woven glass cloths, polyimide and the like. The diamond flakes 334 are arranged in successive diamond flake layers parallel to the conductor surface in an at least partially staggered manner such as to disallow any direct straight discharge path through the diamond containing insulation layer. Figure 8 shows an example of a diamond containing insulation layer 330 which is provided by a diamond powder 331. Although the example of Figure 8 is shown without a carrier 320, the diamond containing insulation layer 330 of Figure 8 may also be provided on a carrier 320, such as a carrier described above with respect to Figure 7, e.g. for forming a tape.

Figure 9 shows a further example for a diamond containing insulation layer 330 including diamond blocks 333 which are provided in a carrier material 332. The diamond blocks 333 have different shapes and sizes.

Figure 10 shows a diamond containing insulation layer 330 being a closed solid diamond surface 340. The closed solid diamond surface 340 is provided without a carrier and is directly applied on the electrical conductor (not shown) e.g. by direct infusion.

Figures 1 la to l id show a schematic plan view on a tape 210 which includes a first and a second area that are arranged as stripes. In the example of Figure 11a, two of the stripes contain mica and one stripe contains diamond particles. The diamond containing stripe 335 is arranged between the two mica containing stripes 350. The stripes run in parallel to the longitudinal direction (z-direction) of the tape. Figures l ib and l id show similar tapes having 3 or 5 of mica containing stripes 350 and 2 or 4 diamond containing stripes 335, respectively. Figure l id shows another arrangement with discontinuous diamond containing stripes 335. The diamond containing stripes 335 allow for heat conduction and electrical insulation at the same time.

Figure 12 shows a schematic drawing of a conductor arrangement 200 including insulation in the form of a tape with overlapping regions. The tape 210 includes three stripes of material like Figure 11a. In this example, the two mica containing stripes 350 overlap whereas the diamond containing stripe 335 is single-layered. Like in Figure 5, the winding direction W of the tape is in the longitudinal direction (z-direction) of the conductor arrangement. The single-layered diamond containing insulation layer provides excellent heat conductivity for the whole insulation arrangement along and across the conductor (surface).

Figure 13 shows a schematic drawing of an electron discharge path through a diamond containing insulation layer 330 wherein the diamond particles 320 that may be provided as diamond flakes 334 are arranged in parallel. Although the diamond containing insulation layer 330 is thin, the discharge path is comparably long to other strong insulation layers. Thus, a tape as shown in Figure 7 contains ideal heat conductivity and insulation characteristics.

Figure 14 shows a schematic front view of the slot region 401 of the core of the electrical machine, with an electrical conductor 201 comprising an electrical insulation 203 arranged in the slot region 401. The insulation 203 separates the conductor 201 from the core 402. The insulation 203 has the thickness . For example, the core 402 can be the stator core 105 of Figure 1 and the electrical conductor can be a segment of the coil 106 of Figure 1. However, the conductor can also be a conductor bar. The core 402 is ferromagnetic and conductive. Thus, the insulation of the conductor 201 is desirable to prevent any turn-to- turn faults. By providing insulation 203 having a diamond containing insulation layer with a very low thickness ttot, the amount of active conductor material can be increased resulting in higher applicable voltages while an excellent heat conductivity and electrical insulation is ensured. Figure 15 shows a schematic top cross-sectional view of the slot region 401 of a core of the electrical machine with the conductor arrangement 200 arranged therein. The slot region 401 includes a core 402 and a local heat sink region 403. The conductor arrangement includes the conductor 201 that is insulated with a tape 210 that is wound in a winding direction W. The winding direction W of the tape is in the longitudinal direction (z-direction) of the conductor. The tape 210 includes a diamond containing insulation layer. The single windings 412 of the tape are arranged such that a direct heat flow is allowed towards the next local heat sink. Thus, the tape includes a tape width 406 of typically 20 mm to 35 mm and a resulting winding angle 407 of typically 10 degrees to 25 degrees. The heat escapes along the insulation, across the insulation and/or longitudinally with respect to the tape direction and/or to the conductor surface through the diamond containing insulation layer of the tape.

Figure 16 shows a schematic front cross-sectional view of the conductor arrangement arranged in a slot region 401 of a core of the electrical machine, wherein the enhanced heat flow is indicated by black arrows. The conductor arrangement again has a conductor 201 and an insulation 203 including a diamond containing insulation layer. The lateral side surfaces of the conductor arrangement are in contact with the core material, and the bottom side surface of the conductor arrangement is in contact with a slot wedge 405 at the opening side of the slot. In addition, a yoke air duct 408 is arranged in a yoke region 404 of the core and in thermal contact with the top side surface of the conductor arrangement.

The core material, the slot wedge 405 and the yoke air duct 408 act as heat sinks that allow the escape of heat away from the conductor 201. Herein, the slot wedge 405 and the yoke air duct 408 are the most efficient heat sinks. More generally, the conductor is thermally coupled to multiple heat sinks having different heat absorption rates.

The heat flow from the conductor to these heat sinks is shown by the thick arrows: As can be seen, the heat flows not only across the insulation layer to the immediately neighboring core region, but a substantial portion of the heat also flows along the insulation layer (parallel to the conductor surface) to the heat sinks having higher heat absorption rates, i.e., to the slot wedge 405 and the yoke air duct 408.

Thus, the heat escapes in the direction along the insulation layer and/or directly to the slot region 401. The heat escapes through the yoke air duct 408 of the yoke region 404 and/or the heat escapes through the core 402. The core 402 contains heat sinks (not shown) that allow the escape of the heat away from the conductor 201. The heat escapes through the slot wedge region 405. The heat escapes in a direction along the insulation, across the insulation and/or axially through the diamond containing insulation layer of the tape 210. Novel thermal management technologies and/or higher voltages can be used, which lead to new machine performance levels. Due to the changed situation regarding the thermal characteristics with diamond insulation, the heat flow in electrical machines can be designed much more efficiently.

Figure 17 shows a flow chart 500 of an embodiment of the method. In step 501, an electrical conductor is provided, wherein the electrical conductor includes a surface. Step 502 includes insulating the electrical conductor with one or more insulation layers and a diamond containing insulation layer.

Generally, it may be understood that embodiments of the invention are not limited to the embodiments shown in the figures. Rather, the embodiments shown in the figures are only examples, e.g. examples for conductors. Further examples may include other conductor arrangements being used in an electrical machine for generating a magnetic field. DEFINITIONS In the following definitions for general terms used throughout the document are given.

The skilled person may understand that an electrical conductor as referred to herein may be understood as a conductor having any suitable shape, such as a cylinder on a substantially round shape, a wound conductor including several windings, or the like. The skilled person may understand that conductive material as referred to herein may be electrically insulated in different ways. The electrical insulation as referred to herein may therefore be understood as including the insulation of single strands of a conductor as well as the insulation of the whole (wound) conductor (ground insulation). Further, the terms "insulation" and/or "insulation layer" etc. as used herein refer to an electrical insulation. Mica may be understood as a silicate material, in particular a sheet silicate mineral. Mica may for instance be described as a complex silicate with aluminum and alkali metals. Some varieties of mica may contain iron, magnesium, lithium, fluorine, barium, manganese and vanadium. The skilled person may understand that mica is generally a material, which may be used in different shapes and sizes, e.g. by being split into flexible and transparent thin films. According to some embodiments, mica may be a silicate material having a dielectric strength of about 110-120 MV/m (e.g. 118MV/m). Further, mica may be provided as flakes.

The term "substantially" as used herein means that there may be a certain deviation from the characteristic denoted with "substantially." For instance, the term "substantially parallel" refers to an arrangement of an element which may have certain deviations from the exact parallel arrangement, such as a deviation from the parallel arrangement of up to about 15°. The term "substantially no holes", e.g. on the surface, as used below may include single holes, which may for instance be present due to fabrication defects or the like. The longitudinal direction of the electrical conductor may be understood as an axis of the electrical conductor running in the direction of the largest extension of the electrical conductor. In the case that a wound conductor is provided, such as a coil having a ringlike shape or the like, the longitudinal direction may correspond to an axis running along the circumferential direction of the wound conductor. In some embodiments, the y- direction may be a direction being perpendicular to the longitudinal direction, such as the height of the electrical conductor. The x-direction may also be described as being perpendicular to the longitudinal direction, such as the width direction of the electrical conductor. Both the x- and the y-direction may be described as directions normal to the conductor surface if a wound conductor is referred to. As used herein, the extension of diamond particles in a direction substantially parallel to the conductor surface may be described as the extension of diamond particles in any local plane and/or surface as the x-z plane or the y-z plane. A direction along the insulation may be understood as parallel to the local plane defined by the insulation or the conductor surface. A direction across the insulation may be understood as orthogonal to the local plane defined by the insulation or the conductor surface. The terms "axial" and "circumferential" may be understood as referred to the local spatial arrangement of the conductor arrangement and not as referred to the local spatial arrangement of the electrical machine.

The diamond particles may be understood as particles that have a diameter of at least 1 μιη. The diamond particles may be provided as diamond flakes and/or diamond powder. Embodiments which are described herein in terms of diamond flakes may be understood as embodiments that also work with other diamond particles (e.g. diamond powder). The diameter of diamond particles may be understood as any diameter in a plane parallel to the (local) conductor surface.

The diamond containing insulation layer including continuously provided diamond particles may be understood as a layer, in which the diamond particles stand in contact with each other, in particular through the whole diamond containing insulation layer, e.g. through the whole thickness of the diamond containing insulation layer. Standing in contact with each other does not necessarily mean that the diamond particles have to be in contact with other diamond particles over the whole surface, but a contact over a part of the surface or even a punctual contact may be sufficient. The diamond containing insulation layer as referred to herein may be provided in the form of a paper like structure with one or more layers of continuously provided diamond particles.

A discharge path as described herein may be understood as a path along an inter-grain region of the diamond containing insulation layer allowing an electrical discharge.

The voltage Vmax as described herein may be understood as the rated (maximum) voltage of the electrical machine. With respect to ground maximal voltage the electrical machine is adapted to supply to the conductor. In case a maximum is not defined any supported voltage that is suitable may be used.

The thickness td of the diamond containing insulation layer is to be understood as any thickness e.g. average thickness substantially perpendicular to the conductor surface. Thus, the parameter kd of the thickness may vary within the defined range of kd along the conductor surface.

The total thickness of the electrical insulation is to be understood as any thickness e.g. average thickness substantially perpendicular to the conductor surface. Thus, the parameter ktot of the thickness may vary within the defined range of ktot along the conductor surface. If a carrier is present, the carrier may be part of the total thickness ttot.

GENERAL ASPECTS AND MODIFICATIONS

Next, individual aspects of the electrical machine and its conductor arrangement and the use thereof are described in more detail. Therein, the reference to Figures and their reference numbers is merely for illustration. The aspects are not limited to any particular embodiment. Instead, any aspect described herein can be combined with any other aspect(s) or embodiments described herein unless specified otherwise.

According to embodiments described herein, an electrical machine including an conductor arrangement, typically a wound conductor arrangement, is described. The (wound) conductor arrangement includes an electrical conductor having a longitudinal direction and comprising a conductor surface and an electrically conductive material (such as copper, iron, steel, and the like). The conductor arrangement further includes an insulation for insulating the electrical conductor including one or more insulation layers being at least partially provided around the conductor. The one or more insulation layers typically include a diamond containing insulation layer including continuously provided diamonds with diamond particles having a diameter of at least 1 μιη in a direction substantially parallel to the (local) conductor surface. Further, the diamond containing insulation layer provides the highest dielectric strength of the one or more insulation layers, and/or the diamond containing insulation layer provides the highest partial discharge resistance of the one or more layers. CONDUCTOR/MACHINE The electrical conductor may be made from copper or the like. Typically, the conductive material of the conductor may include copper. According to some embodiments, the electrical conductor may have any suitable shape, e.g. a shape which is configured for the application in an electrical machine. In some embodiments, the electrical conductor may be a wound conductor. The conductor may be a conductor coil or conductor bar for a high voltage (HV) rotating machine.

The conductor may be wound into a plurality of strands. The electrical insulation may be arranged for insulating the single strands of the (wound) conductor, such that the single wires of the coil may be understood as being isolated against each other. For instance, the single strands or wires may be coated with an isolated material before being wound to a wound conductor for the conductor arrangement. However, due to the application of the wound conductor in electrical machines, it is also desirable to have the whole wound conductor isolated against other (e.g. grounded) components of the electrical machine, such as magnets, conductive materials, electrical lines and the like. Additionally, the electrical insulation may be arranged for ground insulation of the conductor.

Embodiments described herein may also refer to an electric machine, in particular an electromotor, having a conductor arrangement according to any of the herein described embodiments. For instance, an electrical machine as shown in Figure 1 may be equipped with the conductor arrangement according to embodiments described herein. For instance, the wound conductors 106 or multi-turns, such as coils or windings, shown in Figure 1 may at least partially be surrounded by an insulation including a diamond containing insulation layer according to embodiments described herein.

According to an embodiment, the rotor 102 shown in Figure 1 may also include a wound conductor having an electrical insulation as described herein. As an example, the coil may be arranged in a rotor. Generally, an electrical machine as referred to herein may be an electrical machine for high voltages. For instance, the electrical machine and the conductor arrangement according to embodiments described herein may be adapted for a rated voltage between 0.1 kV and 100 kV. The rated voltage Vmax is particularly larger than about 1 kV. More particularly the rated voltage Vmax is larger than about 15 kV, and even more particularly the rated voltage Vmax is larger than about 30 kV. In some embodiments, the electrical machine and the conductor arrangement according to embodiments described herein may be adapted for an electric machine, such as a motor or a generator, for supplying an AC current to the conductor arrangement, the AC current having a frequency of about 5 to 1 kHz.

The electrical machine is not limited to electrical motors but may also be at least one of generator, transformer and/or other electromagnetic device e.g. actuator and/or electromagnet. Typically, the conductor arrangement may include a wound conductor like e.g. a coil of the electrical machine

INSULATION

The insulation 203 of embodiments described herein provides a respective topology to restrict the migration of electrons through the insulation, e.g. by a continuous surface topology. In particular, the topology of the insulation does not have short paths of holes through the insulation, which makes it hard to cross for an electrical discharge. The topology is chosen for the purpose of restricting electron migration and forcing the electrons on a zig-zag path in the insulation (which is suggested in Figure 13). The higher dielectric strength of the insulation according to embodiments described herein can enable the use of a thinner insulation. The combined effect of the reduced insulation thickness and the higher heat conductivity of the insulation containing a diamond containing insulation layer may further lead to an amplified positive effect on the heat conductivity of the insulation system. In some embodiments (which will be described in detail below), a thinner carrying material for the insulation material may be used due to the lower mass of the diamond containing insulation layer. The electrical insulation may comprise more than one insulation layers and/or a carrier. The total thickness of the electrical insulation may be described according to the following formula (2):

(2) t _tot [mm] = V _max [kV] * k _tot with 0.0690 < k _tot <0.103; wherein the preferred lower limit of k _to t is 0.07 and/or the preferred upper limit of k _to t is 0.09. The total thickness may not be constant over the whole conductor surface but may vary within the given range of ktot. The total insulation thickness may include all insulation layers and/or carrier. The carrier may have a lower limit for the thickness of 0.01 mm.

According to some embodiments, diamond particles may be included in the insulation. Typically, diamond has higher dielectric strength and much higher thermal conductivity compared to materials used for insulation purposes in electrical machines, e.g. mica. This allows the diamond based insulation to be much thinner and thermally more conductive than mica based insulations. Thinner insulation with higher heat conductivity leads to better thermal management and to more space for other active materials like copper and iron. In some embodiments the heat conductivity of the electrical insulation is between 0.2 W/mK up to 2200 W/mK. The electrical insulation may comprise more than one insulation layer.

Embodiments described herein may be used for novel electrical machine design utilizing higher efficiency and/or energy density. The described embodiments result in an economical improvement due to a better heat conductivity and a possibly higher dielectric stress than e.g. mica based insulations. Due to the better dielectric strength (and, consequently, smaller insulation thickness) and better heat conductivity, novel electrical machine concepts are enabled. Embodiments described herein allow for utilizing the newly freed space for more copper or iron and/or for utilizing the new thermal management opportunity to create novel high efficiency (colder running) and/or high energy density (surviving bigger currents thermally) electrical machines.

Utilizing the high heat conductivity with thinner insulations according to embodiments described herein, novel thermal management technologies can be created, which may lead to unknown machine performance levels. Due to the changed situation regarding the thermal characteristics with a diamond insulation according to embodiments described herein, the heat flow design in electrical machines can be done in previously impossible ways and in a much more efficient manner.

TAPE

The insulation layer(s) exemplarily and simplified shown in Figures 2 to 4, especially the diamond containing insulation layer(s), may be realized in different ways, which will be explained in detail in the following.

According to some embodiments, the diamond containing insulation layer 330 may be provided by a tape 210. According to embodiments, the tape may be wound around the electrical conductor. For instance, the tape may include a carrier and diamond particles on the carrier. The diamond particles may be provided as diamond flakes. Typically, the tape 210 providing the insulation includes a carrier and diamond particles which may be provided as diamond flakes (as shown and explained in detail with regard to Figure 7). According to some embodiments, the diamond flakes are provided on a carrier forming together the tape. According to an embodiment, the flakes may have a ratio of flake thickness to flake diameter of at least 1 : 10 and/or at most 1 : 10000. The ratio of flake thickness to flake length may be 1 : 5, in particular 1 : 10, and even more particularly 1 : 15. In some embodiments, the ratio of flake thickness to flake length is 1 : 10 or greater. The flake length extends in the direction of the conductor surface and the flake thickness extends perpendicularly to the flake length and to the conductor surface. Particles may be heterogeneously and/or homogenously distributed on the carrier or on the conductor surface.

The flake length may be any extension of the flake in a z-y plane or a z-x plane (as illustrated in Figure 6), while the thickness of the flakes may be measured in x-direction or y-direction (depending on the geometry of the conductor, but in any case perpendicular to the longitudinal axis of the conductor). In the case of a wound conductor, the flake length may be measured as one extension of the flake in circumferential direction, while the flake thickness may be measured in a direction across the insulation. According to embodiments, the diamond particles may be provided as flakes having a diameter of at least 10 μιη and/or at most 1000 μιη. In some embodiments, the tape has a thickness of less than 0.2 mm, particularly less than 0.1 mm, and even more particularly less than 0.02 mm. The thickness of the tape may be measured perpendicular to the longitudinal direction (z-direction) of the tape.

In some embodiments and as shown in Figure 5, the tape is wound about the conductor in a winding direction W in a helical matter. Typically, the winding direction W may substantially correspond to the longitudinal z-direction of the conductor arrangement.

In some examples, every winding of the helically wound film may include a portion, which overlaps with the insulator already present on or around the conductor, or a previous section of the tape itself. In some embodiments, the tape may be a multi-layer tape. Additionally or alternatively, two or more films to form the insulation may be helically wound on top of another, e.g. by consecutively winding the films on the conductor (and/or the already present insulator on the conductor) or by alternatively winding the films on the conductor and/or the already present insulator on the conductor.

According to embodiments the tape comprises a first area and a second area arranged as stripes extending parallel to each other in a longitudinal direction of the tape (as illustrated in Figures 1 la to l id). The first and second areas differ in at least one of diamond content and/or heat conductivity and dielectric strength. The first area may comprise diamond particles and/or the second area may comprise essentially no diamond particles. For example, the second area may comprise a higher amount of mica particles and/or a lower amount of diamond particles than the first area. According to embodiments, the tape may comprise more than 5% by volume mica. For instance, the tape may comprise more than 5% by volume mica but less than 50% mica by volume.

According to embodiments, the tape is wrapped around the conductor in multiple turns, in such a manner that two subsequent turns at least partially overlap with each other, in such a manner that one of the first and second areas of the two subsequent turns overlap with each other and/or that the other one of the first and second areas is non-overlapping between the two subsequent turns. There may be essentially no overlap of different areas of the two subsequent turns. The overlapping portion may be less than 80% of the tape width, preferably less than 50%>.

For example, the tape may be divided into three stripes (as illustrated in Figure 11a) wherein two stripes may contain mica flakes and one stripe may contain diamond particles. The stripes may be arranged on a carrier. According to embodiments described herein, the tape may be wound around a conductor such as two similar stripes overlap each other. A certain pattern may be formed where mica stripes and diamond stripes follow each other in sequence. According to embodiments described herein, the diamond particles may provide an essentially continuous heat path across the insulation through the diamond-containing layer and preferably through the electrical insulation. As may be understood by the person skilled in the art, the tape may be not limited to the number of stripes described in this embodiment. It is rather possible to include as many stripes of different contents as desired. For instance and according to the embodiment, the two areas may be discontinuous (as illustrated in Figure l id). The two areas may also be arranged in a pattern in longitudinal direction of the tape. With the embodiment of a tape including the diamond containing insulation layer, a winding insulation with long life time and high thermal conductivity can be provided. Thereby, the tape insulation may include a carrier and diamonds in the form of diamond particles that may be provided as flakes and/or diamond powder. As mentioned above, also the embodiment with the tape allows for a thinner and better heat conducting insulation with known, readily applicable tape insulation technology. All benefits of diamond insulation may be provided in a quickly implementable form for short term to long term use. Diamond based winding insulation refers to the replacement of the previously used materials by a material having a better thermal conductivity and a suitable dielectric strength.

The insulation 203 may include a diamond containing insulation layer 330 and a carrier 310 and diamond particles 320 that may be provided as diamond flakes on the carrier 310 (as illustrated in Figures 5 and 6). Typically, the diamond flakes 320 form the diamond containing insulation layer 330 of the insulation of the conductor arrangement according to embodiments described herein. According to some embodiments, the carrier 310 may be a web or a film. In some embodiments, the carrier 310 may include a material like a (non-woven) polyester web, a polyester film, glass cloths, non-woven glass cloths, polyimide and the like.

The diamond particles 320 which may be provided as diamond flakes may have a larger extension in the z-direction being substantially parallel to the surface of the conductor than in y-direction corresponding to the thickness of the flakes substantially perpendicular to the surface of the conductor. As described above, the diamond containing insulation layer 330 of the insulation 203 does not provide a direct path for electrons through the layer. For instance, an electron would need to go in a zig-zag manner between the flakes when desiring to go through the insulation layer. The result is a much higher resistance compared to known insulations of electrical conductors. Providing diamond in flake shape as described in embodiments herein, electron flow through the insulation can sufficiently be restricted, e.g. similar to a diamond layer with a continuous surface with substantially no holes in the surface. According to embodiments, the diamond particles are arranged in successive diamond particle layers parallel to the conductor surface in an at least partially staggered manner such as to disallow any direct straight discharge path through the diamond containing insulation layer. The diamond particles may contact each other to form a macroscopic interconnected web extending along the conductor surface.

The skilled person may understand that all embodiments that are described in terms of the tape are also combinable without the tape and/or other embodiments.

DIAMOND CONTAINING INSULATION LAYER

According to some embodiments, the surface of the diamond containing insulation layer may be a continuously closed diamond surface. For instance, the diamond may be provided as a coating, which yields a continuously closed diamond surface. According to embodiments, diamond particles may protrude from the diamond containing insulation layer. Different embodiments for forming the diamond containing insulation layer will be explained in detail below.

The diamond containing insulation layer may be applied by any one of a tape, vapor deposition, sputtering, extrusion, placing separate diamond blocks and the like. The diamond particles may be directly infused in the conductor.

The skilled person may understand that the diamond particles provided as a diamond powder are continuously provided in the carrier material.

According to some embodiments described herein, the diamond particles are provided as diamond powder 331 having a diameter as defined herein of at least 1 μιη. In particular, the size of the diamond powder may be measured as a diameter of the diamond particles in any direction in a plane parallel to the conductor. According to some embodiments, the size of the diamond particles is measured as the diameter in any one of the x-, y, or z- direction of the conductor arrangement. In some embodiments, the size of the diamond particles of the diamond powder may be measured substantially parallel to the surface of the conductor.

According to one embodiment, the diamond blocks have a size of typically about 0.5 mm to about 10 cm, more typically between about 1 mm and about 5 cm, and even more typically between about 5 mm and about 5 cm. The size of the diamond blocks may be measured as a diameter of the diamond blocks in any of the x-, y-, or z-direction. The carrier material 332, in which the diamond blocks are provided, may be the same carrier material as described with respect to Figure 8. According to some embodiments, diamond powder compressed blocks may be used, especially as slot insulation of a wound conductor. For instance, compressed diamond powder blocks are available in a variety of shapes, and can be applied as a solid diamond powder block layer as slot insulation. The skilled person may understand that not only the diamond blocks may be used as a slot insulation but that all embodiments described herein may be used for the slot insulation in an electrical machine.

According to some embodiments, the diamond containing insulation layer may also be provided in the form of a diamond coating. For instance, the diamond coating may be formed on the electrical conductor by vapor deposition (such as chemical vapor deposition or physical vapor deposition), sputter technology and the like. Using a coating process for proving the diamond containing insulation layer may allow forming both inter turn and slot insulations applied by a chemical vapor deposition technique. A fully diamond covered winding could be cooled by direct cooling methods, improving e.g. the machine performance.

According to embodiments, a closed surface may be achieved by a coating process or the like as described above. The diamond containing insulation layer 330 may be formed by direct infusion of a diamond layer on the conductor material or on top of an inter turn insulation of the conductor. The diamond coating may be seen as a diamond particle of at least 1 μιη in diameter according to embodiments described herein. According to embodiments that can be combined with any other embodiment described herein, the diamond-containing layer further contains "diamond like" carbon structures.

The advantages of the above described embodiments refer to a thinner and better heat conducting insulation, with a great potential for life time benefits. Not only the benefits in view of high dielectric strength and heat conductivity of diamond can be used, but also a potentially "everlasting" winding insulation according to the present electrical machine life time perspective. Nowadays, the winding insulation life time usually determines the life time of the electrical machine in practice. A conductor winding provided with a diamond containing insulation layer could have a strong mechanical protection, which could extend the practical life time of electrical machines to extreme time extensions. Generally, the diamond containing insulation layer of the insulation of the conductor arrangement according to embodiments described herein may directly be provided on the surface of the conductor. In some embodiments, the diamond containing insulation layer of the insulation may be provided on top of a layer on the conductor, such as on top of a winding insulation of the conductor. For instance, the layer between the diamond containing insulation layer and the conductor may be an intermediate layer. The intermediate layer may have a value of electrical conductivity between the value of the conductor and the value of the diamond containing insulation layer. In some embodiments, the intermediate layer includes a mixture of diamond powder, a holding matrix and/or metallic components, wherein the diamond content of the intermediate layer is less than in the diamond containing insulation layer. The diamond content of the intermediate layer may be as low as 0% by volume. The intermediate layer further may include diamond powder. The intermediate layer may be conductive, in particular semi-conductive, to improve thermal conductivity. According to embodiments, the thermal expansion coefficient of the intermediate layer may be between the thermal expansion coefficient of the conductor material and the thermal expansion coefficient of diamond.

In some embodiments, which may be combined with other embodiments described herein, the diamond content of the diamond containing insulation layer is larger than 50% by volume of the diamond containing insulation layer, in particular larger than 80% by volume. With a diamond content of larger than 65% by volume (e.g. by one of the above discussed embodiments of a tape, a powder, diamond blocks or a coating), the main insulation of the electrical conductor may substantially be provided by the diamond containing insulation layer. Typically, the mica content within the diamond containing insulation layer is between 5% by volume and 50% by volume, in particular more than 10%. The insulation effect of the insulation layer, especially the diamond containing insulation layer, is provided in large parts by the diamond in the diamond containing insulation layer. In particular, it can be said that the partial discharge resistant part of the insulation is provided by the diamond containing insulation layer. The diamond containing insulation layer may have a dielectric strength of 18 MV/m to 2200 MV/m. Preferably, the dielectric strength may have a lower limit of 100 MV/m and/or an upper limit of 800 MV/m. As described above and with respect to embodiments describes herein, the total thickness of the insulation layers may be drastically reduced by insulations including diamond particles. The total insulation thickness is described by the parameter ttot. The thickness td of the diamond containing insulation layer is described by the following formula: (1) t _d [mm] = V _max [kV] * k _d with 0.0005 < k _d <0.0555

The preferred lower level of the parameter kd of equation (1) may be 0.005 whereas the preferred upper level of the parameter kd may be 0.025.

The thickness of the diamond containing insulation layer may increase with decreased diamond particle content and/or a higher rated voltage applied to the electrical conductor. Although the thickness of the insulation layer is reduced no direct discharge path may be provided through the diamond particles. The total thickness may vary according to the variation of the diamond containing insulation layer. The carrier may vary according to the thickness of the diamond containing layer. The carrier additionally may vary according to the diamond content and/or size of diamond particles. The total insulation thickness may vary according to the carrier.

According to some embodiments, the diamond containing insulation layer acts as the main insulation of the electrical conductor. Typically, the main insulation is a partial discharge resistant part of the insulation of the electrical conductor. Typically, the main or main wall insulation is used to insulate a wound conductor on full potential to the stator core on ground potential. Typically, the insulation layer or the diamond containing insulation layer provided in embodiments described herein is configured for providing the main insulation or main wall insulation of an electrical conductor. According to some embodiments described herein, the applicability of the insulation to be used as a main insulation for the electrical conductor depends inter alia on the AC breakdown strength of the pure material and the dielectric properties.

In some embodiments, the insulation of the conductor may include different layers, e.g. layers having different material properties, such as dielectric strength, thermal conductivity, density, elasticity and the like. The diamond containing insulation layer may thus be the layer of the insulation being most suitable to achieve the insulation effect (and in particular most suitable for the main wall insulation), e.g. by having the greatest dielectric strength among the layers of the insulation of the electrical conductor and/or the highest partial discharge resistance among the layers of the insulation of the electrical conductor.

According to some embodiments, the diamond containing insulation layer has a thermal conductivity of between about 0.2 W/mk and about 2000 W/mK. The preferred lower limit of the thermal conductivity may be 0.5 W/mK and/or the preferred upper limit of the thermal conductivity may be 1000 W/mK. Typically, the thermal conductivity is measured in a direction perpendicular to the conductor surface, e.g. substantially perpendicular to the longitudinal direction of the electrical conductor, or, in the case of a wound conductor, in a direction across the electrical insulation being substantially perpendicular to the longitudinal direction circumferential direction of the conductor.

According to some embodiments, values of properties of the diamond containing insulation layer may be achieved by the diamond containing insulation layer as a whole. For instance, the diamond containing insulation layer may include a carrier material, in which the diamond particles or blocks are placed. The carrier material may have an influence on the above cited values. Consequently, the above cited values may be averaged values through the whole diamond containing insulation layer.

The continuously provided diamond particles can be described as not offering a discharge path through the diamond containing insulation layer, in particular in a direction perpendicular to the longitudinal direction of the conductor (as illustrated in Figure 13). Typically, the continuously provided diamond particles prevent a continuous discharge path through the diamond containing insulation layer (similar to the percolation theory). The diamond containing insulation layer with the continuously provided diamond particles may be described as acting as an insulator restricting the passage of electrons through the diamond containing insulation layer. In some embodiments, the continuously provided diamonds may force an electron trying to pass through to go on a kind of zig zag path, which may hinder the electron to pass through the diamond containing insulation layer, especially the whole thickness of the diamond containing insulation layer. The skilled person may understand that, generally, the diamond containing insulation layer or the surface of the diamond containing insulation layer is not necessarily un-punctered, but that small holes may be present without influencing the insulator characteristic of the diamond containing insulation layer and/or without interrupting the continuously provided diamond particles.

The presence of diamond particles in the insulation layer may lead to thinner insulation layers by providing similar or even better insulation and heat conductivity properties than state of the art insulation layers.

According to an embodiment, the conductor arrangement may be arranged in the core 402 of an electrical machine. The conductor arrangement may be part of the slot region 401 by being inserted in the slot between e.g. iron bars. The total insulation thickness may vary according to the type of insulation. For example, when the insulation includes higher diamond content, the insulation thickness may decrease. The content of active materials may be increased. The core 402 may be made from a conductive material e.g. iron.

According to an embodiment that can be combined with any embodiment described herein, the slot region may comprise at least one local heat sink 403. The at least one local heat sink 403 may be arranged within the core 402. The core 402 may be ferromagnetic. The at least one local heat sink 402 may be a plurality of heat sinks spaced apart from each other in an axial or circumferential direction of the conductor arrangement 200. According to an embodiment, the at least one local heat sink is arranged in contact with the conductor arrangement for cooling the conductor arrangement 200. The at least one local heat sink may be arranged at a respective axial or circumferential position of the conductor arrangement 200. According to embodiments, the electrical machine comprises a ferromagnetic core 402, and the local heat sink is provided in the core in direct contact with the conductor arrangement 200. In an example, the local heat sink 403 comprises an air duct provided in a plane essentially orthogonal to the axis of the conductor arrangement 200. Additionally, the local heat sink may comprise an air duct provided in a head portion of the core and extending essentially along an axis of the conductor arrangement 200.

According to an embodiment, the conductor arrangement 200 may include at least one insulation layer. The insulation layer may comprise a diamond containing insulation layer. The diamond containing insulation layer may be provided by a tape 210. The tape may have a width 406. The tape width 406 may be between 10 mm to 40 mm. Preferably, the lower limit of the tape width may be 20 mm and/or the upper limit of the tape width may be 35 mm. The tape may be arranged in a winding angle 407 allowing the tape to lead in a direct way to at least one of the at least one local heat sinks 402. The tape may be wound around the conductor with a minimum winding angle of 5 degrees to 60 degrees. Preferably, the lower limit of the winding angle may be 10 degrees and/or the upper limit of the winding angle may be 25 degrees. According to one embodiment, the taping angle direction may be both - one directional overlapping and/or back and forth reverse overlapping. According to an aspect, the tape comprises a one directional overlapping only. In an example, the diamond-containing layer is arranged for conducting heat from the electrical conductor in a direction along the insulation of the conductor surface towards the at least one local heat sink 403. The arrangement of the tape 210 may enable an anisotropic heat flow to the at least one local heat sink 403 in a direction along the insulation of the conductor.

An enhanced heat flow may be enabled by the diamond containing insulation layer (as illustrated in Figure 16). The heat flow may be anisotropic. The slot region 401 may contain a ferromagnetic core having a yoke extending along a yoke axis, wherein the conductor arrangement 200 is at least partially inserted in the slot region 401. The heat may be transferred to the core 402 and or to the yoke region 404. Additionally, the heat may be transferred to the slot wedge region 405. The heat may be transported axially, in a direction across the insulation and/or in a direction along the insulation of the conductor arrangement 200. At the yoke region, the heat may escape through a yoke air duct 408, which may enhance the heat transport away from the conductor arrangement.

As an example for the new electrical machine design the electrical machine may comprise a ferromagnetic core having a yoke extending along a yoke axis, wherein the conductor is at least partially inserted in the slot region. The conductor fills a major portion of a cross- sectional area of the slot region. The cross-sectional area may be substantially perpendicular to the yoke axis. Further, the electrical insulation may fill only a minimal portion of the cross-sectional area of the slot region.

USE

According to some embodiments, the use of diamonds in an insulation layer for an electrical conductor, especially a wound conductor, is provided. The electrical conductor includes a surface and a direction across the conductor surface. The diamonds are typically provided in a diamond containing insulation layer including continuously provided diamonds with diamond particles of a diameter larger than 1 μιη in a direction substantially parallel to the conductor surface, as e.g. described in detail above. According to embodiments described herein, the diamond containing insulation layer includes more than 5% and less than 50% by volume mica. The diamond containing insulation layer may in particular be used in a winding insulation in an electrical machine winding, as for instance described with respect to Figure 1. Using diamond insulation in electrical machine windings is a substantial change in the insulation concept and enables the improvements of having a winding insulation with long life time and high thermal conductivity. The use of the diamond containing insulation layer may be realized via a tape insulation made from diamond particles that may be provided as diamond flakes and/or diamond powder, a direct infusion of a diamond layer on the conductor surface or on top of inter turn insulation, diamond powder compressed blocks as slot insulation. Variants of embodiments of diamond containing insulation layer are also described with respect to Figures 5 to 10. By using a diamond containing insulation layer according to embodiments described herein, a thinner and better heat conducting insulation with huge potential life time benefits can be provided. Not only the benefits of high dielectric strength and heat conductivity of diamond may be considered, but also a potentially almost "everlasting" winding insulation from present electrical machine life time perspective. Consequently, new electrical machine design utilizing higher efficiency and / or energy density may be developed. Due to the better dielectric strength (smaller insulation thickness) and heat conductivity, novel electrical machine concepts are enabled by embodiments described herein. Utilizing the newly freed space for more copper or iron and /or utilizing the new thermal management opportunity, novel high efficiency (colder running) and / or high energy density (surviving bigger currents thermally) electrical machines can be developed.

Alternatively the thinner high performance diamond insulation could be used to develop higher voltage level machines with same insulation thickness. A combination of increasing active material content and voltage level is also possible by a combined utilization of the freed up insulation material space. Typically, the dielectric strength of diamond is up to about 2000 MV/m (from about 18 MV/m to about 2000 MV/m), while mica has up to about 118 MV/m dielectric strength. This difference may result in a diamond layer being more than 10 times (16.9 times) thinner than a corresponding mica layer that has the same dielectric strength. A medium voltage mica tape insulation has 2.5 mm thickness on both sides of the winding. A corresponding diamond containing insulation layer with equivalent dielectric strength can be provided with a thickness of 0.15 mm according to embodiments described herein.

Conversely, the amount of diamonds to replace a certain amount of mica would be less than 1/lOth in mass (the factor of 1/16.9 discussed above, times the density ratio. Specifically, the density of diamond is 3510 kg/m ³ and different mica types range from 2700 - 3300 kg/m ³ , using the most conservative 3510 vs 2700 kg ratio, a given mass m _m of mica can be replaced with a mass ma of diamonds, where md is less than m _m by a factor of f = 16.9*2700/3510, which is approximately 13. Therefore, m _m . = f* ma * , approximately 13*md. Therefore, with a direct simple implementation with existing industrial safety factors a significant total insulation thickness reduction is possible. Also the discharge resistance of diamond is greatly increased compared to mica or other typical insulation materials.

According to some embodiments, the beneficial properties of diamond result from the physical properties of diamond. For instance, when diamond is bombarded with high energy particles, unlike other materials (e.g. mica), the material structure remains unaffected and no "destruction channel" is created through the material. In practice, the diamond conducts the heat so fast away from the impact channel that the incoming energy cannot stay there to destroy the material structure.

Typically, the situation of thermal expansion in a slot of a winding in an electrical machine according to embodiments described herein has to be considered. For instance, the interface between the conductive material and the diamond, especially with regard to the different thermal expansion behavior may be considered when using embodiments described herein.

Though the present invention has been described on the basis of some preferred embodiments, those skilled in the art should appreciate that those embodiments should by no way limit the scope of the present invention. Without departing from the spirit and concept of the present invention, any variations and modifications to the embodiments should be within the apprehension of those with ordinary knowledge and skills in the art, and therefore fall in the scope of the present invention which is defined by the accompanied claims.