Thermal Energy Transfer Device

Abstract

The present invention relates to a thermal energy transfer device for use in transferring thermal energy from a coil of an electrically drivable motor, the device comprising a plurality of thermally conductive members arranged in thermal communication with at least one coil of the electrically drivable motor, and a thermally conductive portion connected to the plurality of thermally conductive members, each of the plurality of thermally conductive members being directly electrically insulated from the other plurality of thermally conductive members.

Description

[Technical field]

[0001] The present invention relates to electric propulsion systems and the removal of unwanted heat that accumulates during operation of such propulsion systems. [Background technology]

[0002] Electric propulsion systems have many advantages over combustion propulsion systems, especially with regard to chemical emissions etc. It is widely known that electric propulsion systems can make transportation more viable in the long term. Summary of the Invention [Problem to be solved by the invention]

[0003] However, there are several problems inherent in the use of electric propulsion over conventional combustion propulsion systems. Attempts have been made to overcome such problems in an attempt to increase the viability of electric propulsion. Further advances in this field are provided herein. [Means for solving the problem]

[0004] Aspects of the invention are set out in the accompanying claims.

[0005] In view of a first aspect, there is provided a thermal energy transfer apparatus for use in transferring thermal energy from a coil of an electrically driveable motor, the apparatus comprising a plurality of thermally conductive members arranged in thermal communication with at least one coil of the electrically driveable motor, and a thermally conductive portion connected to the plurality of thermally conductive members, each of the plurality of thermally conductive members being directly electrically insulated from the other plurality of thermally conductive members.

[0006] Thus, in accordance with the invention, heat energy generated in an electrically drivable motor can be efficiently and effectively removed from the system without the generation of current that can cause additional undesirable heat energy and reduced efficiency, particularly at less than a ten-fold reduction in such energy over conventional systems.

[0007] In fact, multiple heat transfer paths are provided, each electrically isolated from adjacent channels to prevent current build-up. Reducing the additional heat generation in such systems is particularly desirable due to the large ripple effects. More heat energy can be effectively transferred while at the same time providing a smaller heat conducting section to handle the heat energy generation from the electrically drivable motor. This provides a smaller, lighter and therefore more flight efficient system. When deployed in aircraft, for example, this increases the viability of electric propulsion and therefore the likelihood of its use over combustion engines. This in turn has favorable environmental impacts.

[0008] In one example, the plurality of thermally conductive members are formed from the same material as the coils of the electrically drivable motor.

[0009] Such an arrangement reduces the effects of thermal expansion or contraction at the joints between the components due to their common thermal expansion coefficients. Indeed, since the system is concerned with the transfer of thermal energy, it is advantageous from a structural and reliability standpoint to prevent differential expansion. The system is therefore more robust in such an arrangement and has a corresponding increase in lifespan.

[0010] In one example, the thermally conductive members are elongated and have a diameter of less than about 1 mm. Advantageously, the thermally conductive members have a diameter of about 0.1 mm.

[0011] Such an arrangement further reduces the generation of undesirable electrical currents (such as eddy currents) that can increase the amount of thermal energy that is generated that must then be transferred away from the electrically drivable motor, and thus reducing the amount of thermal energy generated increases efficiency. A diameter of approximately 0.1 mm has been found to be particularly effective in allowing effective heat transfer and allowing effective insulation while balancing the demands of ease of manufacture and manufacturing tolerances. This arrangement also allows complex geometries of the thermal paths to be used, thus realizing compact motor designs.

[0012] In one example, the multiple thermally conductive members take the form of multiple adjacent strands of individually insulated and optionally wrapped around each other electrical wire, such a wire arrangement is often referred to as a Litz wire.

[0013] Such wires are examples of long, thin, narrow conductive members. Litz wire is relatively easy from a manufacturing standpoint to manufacture and integrate into systems.

[0014] In an example, the thermally conductive members are formed from high purity aluminum.

[0015] High purity aluminum has been found to allow for highly efficient conduction of thermal energy, and in certain instances, the purity may be greater than about 99.99%, or greater than about 99.95%.

[0016] In one example, the thermal energy transfer device further includes a cryogen source containing a cryogen, the thermally conductive portion being in thermal communication with the cryogen. The cryogen can be hydrogen, helium, nitrogen, etc. in a liquid, gas, supercritical, or solid phase. In one example, the cryogen can be frozen nitrogen or cryogenically frozen water.

[0017] Active cooling of the heat conducting parts would be more difficult to implement, but is shown herein to be beneficial for thermal energy removal, and in electric aircraft propulsion, such cryogens may already exist. In essence, this arrangement utilizes aspects that may already exist and thus provide improved thermal energy removal performance without additional manufacturing or construction difficulties.

[0018] In one example, at least a portion of the plurality of thermally conductive members are arranged on the cable, particularly in a spiral or helical winding.

[0019] Such an arrangement is particularly space efficient, easy to manufacture, and robust.

[0020] In one example, the apparatus is arranged such that, in use, the plurality of heat conducting members receive 0.1 watts of residual eddy heating. In one example, the apparatus is arranged such that, in use, each of the plurality of heat conducting members receives extremely low heating power due to eddy currents. This generation of heat energy resulting from the generation of eddy currents in the conductors may be referred to herein as "eddy current heating power." The arrangement in modern state-of-the-art systems produces approximately 10 watts of excess power that is converted into heating. In contrast, the arrangement disclosed herein produces approximately 0.1 watts of excess power. This is therefore a clear and significant improvement.

[0021] The present invention provides a significant reduction in thermal energy generation from eddy currents in conductive elements for removing heat from coils of electrically drivable motors. In one arrangement, the present invention is capable of reducing this heating by a factor of about 100. This is therefore a significant improvement over current systems.

[0022] In one example, each of the plurality of thermally conductive members has an outer layer of electrically insulating material, which in one example can be a resin or the like.

[0023] This prevents current passing through the thermally conductive member from forming additional undesirable currents in nearby conductive members. In particular, it is advantageous to maintain electrical insulation of the thermally conductive members from one another to prevent current from flowing from member to member and thereby generating heating. In such instances, the electrically insulating material helps to prevent direct electrical connection between the thermally conductive members. Eddy currents are generated as a by-product of the moving magnetic field in electrically drivable motors.

[0024] In one example, each of the plurality of thermally conductive members has an outer layer of epoxy resin, hi another example, the motor coil and the heat shunt can be potted together in epoxy resin.

[0025] Epoxy resin has been found to be particularly effective and relatively simple from a manufacturing standpoint to provide electrical insulation. By embedding the motor coil and heat shunt in epoxy resin, mechanical stability is improved as the coil becomes a self-supporting block. Thus, there is improved electrical insulation provided by the epoxy resin for the electrical elements within the epoxy resin. Optionally, a vacuum can be utilized around the elements within the device to prevent heat transfer from the multiple thermally conductive members to the environment. In this way, further improvements can be provided to the retention of heat in the wires before being passed to the thermally conductive portion.

[0026] In view of another aspect, there is provided a thermal energy transfer apparatus for use in transferring thermal energy from a coil of an electrically drivable motor, the apparatus comprising a plurality of thermally conductive members disposed in thermal communication with at least one coil of the electrically drivable motor, a thermally conductive portion connected to the plurality of thermally conductive members, and a layer of insulating material disposed between at least a portion of any adjacent pair of the plurality of thermally conductive members.

[0027] In such devices, the layer of insulating material serves to prevent direct electrical communication between any two adjacent thermally conductive members.

[0028] In view of yet another aspect, a cooling apparatus for an electric coil winding of an electric motor is provided, the cooling apparatus comprising a plurality of elongated thermal conductors disposed adjacent at least a portion of an inner surface and / or an outer surface of the electric coil winding, each of the plurality of elongated thermal conductors being electrically insulated from both (a) other adjacent elongated thermal conductors and (b) the electric coil winding.

[0029] In such an arrangement, the elongated thermal conductor is adjacent to either the inner or outer surface of the electric coil windings that are known to heat up during use. The thermal conductor can transfer this heat away from the motor coil. The insulation allows for efficient removal of thermal energy while mitigating current transfer between adjacent conductors.

[0030] In one example, a plurality of elongated thermal conductors are arranged in a closely packed array and contact the inner and / or outer surfaces of the electrical coil windings.

[0031] This improves contact to the electrical coil windings and therefore improves conduction of thermal energy away. It also improves the arrangement for physical manipulation in that the connections are less likely to be disturbed due to vibration or other movement, etc.

[0032] In view of yet another aspect, there is provided an electric motor for use in an aircraft comprising an electric coil winding and a cooling arrangement according to any of the above aspects.

[0033] While this arrangement provides benefits for any electric motor, the arrangement disclosed herein may be particularly effective for aircraft, and particularly aircraft engines that utilize or retain a low temperature source for low temperature power generation.

[0034] One or more embodiments of the present invention will now be described, by way of example only, with reference to the following drawings, in which: [Brief description of the drawings]

[0035] [Figure 1]1 shows a schematic diagram of a current state of the art thermal energy transfer device for use in an electrically drivable motor. [Figure 2a] 1 shows a schematic diagram of a thermal energy transfer device according to an example of the present invention. [Figure 2b] 1 shows a schematic diagram of a thermal energy transfer device according to an example of the present invention. [Figure 2c] 1 shows a schematic diagram of a thermal energy transfer device according to an example of the present invention. [Figure 3a] 1 shows a schematic diagram of a thermal energy transfer device according to an example of the present invention. [Figure 3b] An expanded portion of FIG. 3a is shown. [Figure 4A] FIG. 1 shows a schematic diagram of a Litz wire according to an example of the present invention. [Figure 4B] FIG. 1 shows a schematic diagram of a Litz wire according to an example of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] Any reference to a prior art document in this specification is not to be considered as an admission that such prior art is widely known or forms part of the common general knowledge in the art. As used herein, the words "include", "comprises", and similar words are not to be construed in an exclusive or inclusive sense. In other words, they are intended to mean "including but not limited to". The present invention is further described with reference to the following examples. It will be understood that the invention as claimed is not intended to be limited in any way in these examples. It will also be recognized that the present invention encompasses not only the individual embodiments but also combinations of the embodiments described herein.

[0037] The various embodiments described herein are presented only as aids in understanding and teaching of the claimed features. These embodiments are provided only as representative samples of embodiments and are not intended to be comprehensive and / or exclusive. It is to be understood that the advantages, embodiments, examples, functions, features, structures, and / or other aspects described herein should not be considered as limitations on the scope of the invention as defined by the claims or limitations on the equivalents of the claims, and that other embodiments may be utilized and modifications may be made without departing from the spirit and scope of the claimed invention. Various embodiments of the present invention may suitably include, consist of, or essentially consist of suitable combinations of the disclosed elements, components, features, parts, steps, means, etc., other than those specifically described herein. In addition, the present disclosure may include other inventions not claimed herein but which may be claimed in the future.

[0038] The invention described herein relates to thermal energy transfer for use with electrically drivable motors. A particular system of the invention may be a low temperature electrically drivable motor or an aircraft having an electrically drivable motor that utilizes energy generated in a low temperature environment.

[0039] Figure 1 shows a simple schematic diagram of a current state of the art thermal energy transfer device 10. The current state of the art thermal energy transfer device 10 comprises a slotted plate 11 and a heat sink 12. The device 10 is arranged around a motor coil winding 100. The motor coil winding 100 may be operated with alternating current (AC). Such an arrangement is often used in state of the art systems.

[0040] The inventors of the system disclosed herein have recognized that the system allows for improved eddy current suppression and that this has a significant impact on the efficiency of the overall system.

[0041] Fig. 2a shows a simple schematic diagram of a thermal energy transfer device 200. The device 200 shown in the example of Fig. 2a comprises a plurality of thermally conductive members 210 arranged in thermal communication with at least one coil 2000 of an electrically drivable motor. The device 200 comprises a thermally conductive section 220. The thermally conductive section 220 is connected to the plurality of thermally conductive members 210. The plurality of thermally conductive members 210 are directly electrically insulated from the other plurality of thermally conductive members 210.

[0042] Here, "directly" refers to electrical isolation between adjacent thermally conductive members 210. Thermally conductive members 210 are connected to thermally conductive sections 220. Thus, electrical current can be conducted through a particular thermally conductive member, through thermally conductive section 220, and into another thermally conductive member also connected to thermally conductive section 220. However, electrical current cannot pass directly (without going through a third component) from any one thermally conductive member 210 to any other, or in one example, any other adjacent thermally conductive member 210.

[0043] The devices disclosed herein can be advantageously used with any electrically drivable motor. In particular, the devices can be used with cryogenic arrangements, such as superconducting motor arrangements, or motors that contain superconducting elements therein. Additionally or alternatively, the devices can be used with cryogenic arrangements, such as hyperconducting motor arrangements, or motors that contain hyperconducting elements therein. Each of these motor arrangements can be operated using alternating current.

[0044] The thermally conductive portion 220 may be a heat sink or the like for removing thermal energy from the thermally conductive member 210. The device 200 may have one or more thermally conductive portions 220. In the example of FIG. 2a, the device 200 has two thermally conductive portions 220 arranged at either end of the motor coil 2000. Multiple thermally conductive members 210 may be connected to both thermally conductive portions 220. The thermally conductive portion 220 may be a cooling block or a large thermally conductive block connected to a cooling arrangement for removing thermal energy from the device 200. The thermally conductive portion 220 may have a thermal mass of about 10 times or more than the thermal mass of the thermally conductive member 210. This allows the thermally conductive portion 220 to effectively dissipate the thermal energy received from the thermally conductive member 210. The thermally conductive member 210 is arranged to effectively transfer thermal energy, while the thermally conductive portion 220 is arranged to store and dissipate thermal energy.

[0045] In one example, the plurality of thermally conductive members 210 are formed from the same material as the coil 2000 of the electrically drivable motor. In this way, when temperature changes occur, the physical connections between the elements do not distort due to thermal expansion / contraction. In particular, there is no physical disconnection that occurs between the elements when conducting thermal energy from the coil 2000. This ensures a more robust arrangement in use.

[0046] In one example, the plurality of thermally conductive members are elongated and have a diameter of about 0.1 mm. The diameter of the thermally conductive members may be about 1 mm, 0.9 mm, 0.8 mm, 0.7 mm, 0.6 mm, 0.5 mm, 0.4 mm, 0.3 mm, 0.2 mm, 0.1 mm, or 0.05 mm. It has been found that 0.1 mm provides a balance between reducing the generation of undesirable eddy currents in the device 200 and ease of manufacture. In a particular example, the plurality of thermally conductive members may be Litz wire.

[0047] In one example, the plurality of thermally conductive members are formed from high purity aluminum. The high purity aluminum may be aluminum having a purity of about 99%. The high purity aluminum may be aluminum having a purity of about 99.9%. The high purity aluminum may be aluminum having a purity of about 99.99%. Such materials typically have a residual resistivity ratio (ratio between resistances at 273 and 4K) of about 500, which has been found to be advantageous for use in the device.

[0048] The motor coils may be formed from other materials with similar properties, such as niobium-titanium, high temperature superconductors, or magnesium diboride. Such options offer the advantage of superconducting properties, where the electrical resistance, which is effectively zero, can result in extremely high electrical efficiency. However, such materials have relatively low thermal conductivity. Thus, these materials can be advantageously used in low temperature alternating current motors for the motor coils. Such materials do not have preferential thermal energy conductivity for use in multiple heat conducting members.

[0049] FIG. 2a shows a schematic example of an apparatus according to the invention. Element 210 may represent a plurality of heat conducting members. The heat conducting members may be bundled together, for example a cable of wires. This may be referred to as a Litz cable. A Litz cable is a bundle of insulated strands. In one example, element 210 in FIG. 2a represents a Litz cable comprising a number of individually electrically insulated wires. Each of these wires may be a heat conducting member. A Litz cable may comprise approximately 100-200 strands, each of approximately 0.1 mm in diameter. The strands need not be circular in cross section, and the use of "diameter" here is exemplary for purposes of measurement. A Litz cable may or may not be individually insulated from other Litz cables. In the example shown in FIG. 2a, the Litz cable is formed into a rectangular cable. A Litz wire consists of a number of thin strands of wire bundled together, individually insulated from each other. Such an arrangement advantageously impedes the generation of eddy currents when the conductive material is in a moving magnetic field.

[0050]

[0033] Referring now to Figures 2b and 2c, there are similar views to that shown in Figure 2a. Like features have like reference numbers, for example Figures 2b and 2c show a thermally conductive member 210 connecting to a thermally conductive portion 220.

[0051] In particular, Fig. 2b clearly shows the arrangement of the heat conducting members 210. The motor coils have been omitted from the view shown in Fig. 2b in order to improve the visibility of the heat conducting members 210. Again, for the sake of improved visibility, slightly fewer heat conducting members 210 are included in the view of Fig. 2b. In fact, this arrangement has better thermal conductivity with a larger number of heat conducting members 210.

[0052] Referring now to Fig. 2c, a diagram similar to Fig. 2a and Fig. 2b is shown. The diagram of Fig. 2c has a similar "spaced" arrangement of thermally conductive members 210, but also includes a motor coil 2000. It can be seen that some of the thermally conductive members 210 have a curve in their configuration before contacting the thermally conductive portion 220. This curve can be advantageous in that it allows for thermal expansion in the configuration during use. In particular, this formation allows for expansion and contraction during the transfer of thermal energy without inducing high levels of mechanical stress in the configuration.

[0053] 3a, an example of an apparatus 300 having an electrically drivable motor coil 3000 is shown. The apparatus 300 includes a plurality of thermally conductive members 310 and a thermally conductive section 320. The apparatus 300 also includes a cryogen source 330 that contains a cryogen. The thermally conductive section 320 is in fluid communication with the cryogen contained in the cryogen source 330.

[0054] The term "cryoagent" is used to refer to an actual substance at a low temperature. In most arrangements, such substances are contained in tanks, containers, or the like. The low temperature clearly depends on the substance in question, but low temperature behavior has been observed in substances up to -50°C. Thus, low temperature is interpreted herein to refer to temperatures below -50°C. The cryogen can be any of hydrogen, helium, nitrogen, etc. in liquid, gaseous, or supercritical phase. The cryogen may be helium cooled to cryogenic temperatures without liquefaction. Such cryogens are particularly suitable for use in aircraft. In one example, the cryogen can be frozen nitrogen, or cryogenically frozen water.

[0055] The thermally conductive portion 320 in the example of Fig. 3a is actively cooled by cryogen from a cryogen source 330. This results in a more robust removal of thermal energy, allowing the apparatus 300 to remove a greater amount of thermal energy. Active cooling of the thermally conductive portion 320 can be provided by a mechanical device, such as a cryocooler, which does not contain any cryogenic fluid other than a closed cycle within the cryocooler. Cooling in this example can be by conduction.

[0056] In one example, at least a portion of the plurality of thermally conductive members 310 are disposed within the cable, for example, by windings. The windings can be spiral or helical windings. Such an arrangement allows individual strands within the cable to transition from being centrally disposed within the cable to being disposed outwardly within the cable. In this manner, each strand can more effectively contribute to the overall cooling of the motor coil.

[0057] In one example, the apparatus is arranged such that, in use, each of the plurality of heat conducting members 310 receives extremely low heating power due to eddy currents. In the presently disclosed arrangement, the cable generates approximately 0.1 watts of excess power compared to approximately 10 watts of excess power in modern state of the art systems that are converted to heating. This is therefore a clear and significant improvement.

[0058] Modern arrangements that have been found to provide approximately 10 watts include arrangements such as those utilizing slotted aluminum in place of multiple thermally conductive members.

[0059] Thus, the present arrangement provides a system that can reduce unwanted heating by a factor of about 100. This improves the overall performance of the device, particularly in terms of handling the removal of thermal energy and not causing additional unwanted heating to conduct away from the device.

[0060] In one example, multiple thermally conductive members 310 can be glued to the coil surface of the motor coil 3000. This glue ensures a strong physical connection between the elements, thus improving the thermal conductivity between the two elements. This glue can be epoxy impregnated or the like.

[0061] In one example, each of the plurality of thermally conductive members 310 has an outer layer of an electrically insulating material. Such a layer provides a barrier against the generation of additional undesirable eddy currents. In a particular example, each of the plurality of thermally conductive members 310 has an outer layer of epoxy resin. Epoxy resin is an example of an electrically insulating material that is easy to manufacture and provides the desired electrical insulation.

[0062] Referring now to FIG. 3b, an enlarged view of portion A of FIG. 3a is shown. FIG. 3b clearly shows the serpentine bends in the thermal transfer member 310. The bends can be serpentine or similar shapes with curvature of the elements. The bends help to take thermal expansion into account, as explained above. This allows the arrangement to be more resistant to physical stresses, thereby reducing the likelihood of physical damage occurring to the potentially delicate thermal transfer member 310. In this way, the overall lifespan of the arrangement is increased. In particular, over thermal cycles, materials can fatigue, which the arrangement overcomes. This results in an increased lifespan and reliability of the arrangement. Such reduced susceptibility to degradation is particularly useful in aerospace applications where safety is critical.

[0063] In one example, there is a thermal energy transfer apparatus for use in transferring thermal energy from a coil of an electrically drivable motor, the apparatus comprising a plurality of thermally conductive members disposed in thermal communication with at least one coil of the electrically drivable motor, a thermally conductive portion connected to the plurality of thermally conductive members, and a layer of insulating material disposed between at least a portion of any adjacent pair of the plurality of thermally conductive members.

[0064] In particular, a layer of insulating material is disposed between any adjacent pairs of portions to prevent electrical current from passing from one thermally conductive member to an adjacent thermally conductive member. The insulating material may be along the entire length of the thermally conductive members to ensure that electrical current cannot pass between adjacent thermally conductive members. In instances where one layer of electrically insulating material is used in a layered arrangement between thermally conductive members, less material is used than in instances where each thermally conductive member has a layer of electrically insulating material. Thus, such an arrangement may be less expensive to manufacture.

[0065] In one example, there is a cooling apparatus for an electric coil winding of an electric motor, the cooling apparatus comprising a plurality of elongated thermal conductors disposed adjacent at least a portion of an inner surface and / or an outer surface of the electric coil winding, each of the plurality of elongated thermal conductors being electrically insulated from both (a) other adjacent elongated thermal conductors and (b) the electric coil winding.

[0066] Although examples are disclosed herein with respect to arrangements in which multiple thermal conductors are adjacent to a portion of the inner and / or outer surface of the electrical coil windings, this should not be considered limiting. Advantageously, the conductors are adjacent to and secured to the electrical coil windings. This may be via the inner or outer surface, or the conductor (or several conductors) may be arranged to connect to the body of the coil. Such connections are also envisioned to be within the scope of the present invention. Such arrangements operate in essentially the same manner to achieve the same goal of operating through the removal of thermal energy from the coil by connection to at least some of the multiple thermal conductors.

[0067] 4A and 4B show examples of Litz wires 450, 460. Each wire 450, 460 contains a bundle of thermally conductive members 452, 462 surrounded by insulation 454, 464. The wires can be formed using wire drawing techniques. Alternatively, the wires can be printed with additional fabrication to provide a conductive portion of very small thickness combined with an insulating portion. The wire arrangement disclosed herein significantly reduces the generation of eddy currents in use. The arrangement can have a circular cross section 450 or a square cross section 460.

[0068] The further arrangements disclosed herein provide the advantages outlined above, particularly with regard to efficient thermal energy removal from the motor coils, whilst also reducing the undesirable generation of eddy currents.

[0069] In use, the apparatus herein may be arranged as part of an electric motor. The motor may be for use in an aircraft or the like. The motor has electrical coil windings and a cooling arrangement as described herein.

[0070] The motor can be kept cold, for example, using a cryogen. Cryogens that exist for use with fuel cells and the like in electric motors can be used for cooling the heat conducting parts in the arrangements herein. This advantageously takes advantage of features already present for secondary aspects in the apparatus of the present invention.

[0071] The invention described herein relates to thermal energy transfer for electric motors, particularly in the example of electric motors in aircraft, but it can also be applied in applications where thrust generation involves the production of unwanted heat that is transferred away from the point of generation.

[0072] These applications may include automotive, aerospace, domestic or commercial propulsion generation, and the like.

[0073] The systems herein are simple to manufacture, robust to physical changes such as during temperature transfer, and highly efficient. The systems herein are an improvement over current state-of-the-art systems.

[0074] The thermally conductive member may be manufactured through additive manufacturing to provide a particularly narrow conductive element combined with an insulating portion.

Claims

1. 1. A thermal energy transfer device for use in transferring thermal energy from a coil of an electrically drivable motor, said device comprising: a plurality of thermally conductive members disposed in thermal communication with at least one coil of the electrically drivable motor; a heat conductive portion connected to the plurality of heat conductive members; Equipped with A thermal energy transfer device, wherein each of the plurality of thermally conductive members is directly electrically insulated from other of the plurality of thermally conductive members.

2. 10. The thermal energy transfer device of claim 1, wherein the plurality of thermally conductive members are formed from the same material as a coil of an electrically drivable motor.

3. 3. The thermal energy transfer device of claim 1 or 2, wherein the plurality of thermally conductive members are elongated and have a diameter of 0.1 mm.

4. 4. The thermal energy transfer device of claim 1, wherein the plurality of thermally conductive members are Litz wires.

5. The thermal energy transfer device of any one of claims 1 to 4, wherein the plurality of heat conducting members are formed from high purity aluminum.

6. 6. The thermal energy transfer device of claim 1, further comprising a cryogen source containing a cryogen, said thermally conductive portion being in thermal communication with said cryogen.

7. A thermal energy transfer device according to any preceding claim, wherein at least a portion of said plurality of thermally conductive members are disposed within a cable.

8. A thermal energy transfer device according to any preceding claim, wherein, in use, the plurality of thermally conductive members are arranged to receive an eddy current heating power of 0.1 Watts.

9. A thermal energy transfer device according to any preceding claim, wherein each of said plurality of thermally conductive members has an outer layer of electrically insulating material.

10. 10. The thermal energy transfer device of claim 1, wherein each of said plurality of thermally conductive members has an outer layer of epoxy resin.

11. 1. A thermal energy transfer device for use in transferring thermal energy from a coil of an electrically drivable motor, said device comprising: a plurality of thermally conductive members disposed in thermal communication with at least one coil of the electrically drivable motor; a heat conductive portion connected to the plurality of heat conductive members; Equipped with A thermal energy transfer device, wherein a layer of insulating material is disposed between at least a portion of any adjacent pair of said plurality of thermally conductive members.

12. A method of operating a thermal energy transfer device according to any one of claims 1 to 11, said method comprising the steps of: Energizing a coil of an electrically drivable motor; conducting thermal energy from the coil along the plurality of thermally conductive members; A method comprising:

13. 13. The method of claim 12, wherein 0.1 Watts of eddy current heating power is generated in the plurality of thermally conductive members by actuating the coil of the electrically drivable motor.

14. 1. A cooling device for electric coil windings of an electric motor, said cooling device comprising: a plurality of elongated thermal conductors disposed adjacent at least a portion of an inner surface and / or an outer surface of the electrical coil winding; A cooling apparatus, wherein each of the plurality of elongated thermal conductors is electrically insulated from both (a) other adjacent elongated thermal conductors and (b) the electrical coil windings.

15. The cooling apparatus of claim 14 , wherein the electrical coil windings and the plurality of elongated thermal conductors are formed from the same material.

16. 16. The cooling device of claim 14 or 15, wherein the plurality of elongated thermal conductors have a diameter of 0.1 mm.

17. 17. The cooling device of claim 14, further comprising at least one heat sink connected to each of the plurality of elongated thermal conductors, the heat sink being connected to an end of a thermal path of each of the plurality of elongated thermal conductors.

18. 20. The cooling device of claim 17, wherein the at least one heat sink is axially disposed on at least one side of the electrical coil windings.

19. A cooling device according to any one of claims 14 to 18, wherein the plurality of elongated thermal conductors are in the form of electrical wires.

20. The cooling device according to any one of claims 14 to 19, wherein the plurality of elongated thermal conductors are arranged in a cable.

21. A cooling device according to any one of claims 14 to 20, wherein the plurality of elongated thermal conductors are in the form of Litz wires.

22. 22. The cooling device according to any one of claims 14 to 21, wherein the plurality of elongated thermal conductors are arranged in a dense array and contact the inner and / or outer surfaces of the electrical coil windings.

23. 1. An electric motor for use in an aircraft, comprising: [0023] An electric coil winding; A thermal energy transfer device according to any one of claims 1 to 11 or a cooling device according to any one of claims 14 to 22, An electric motor comprising:

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