Heat-pipe cooling system integrated in the winding of an electric machine

Abstract

The invention relates to a system for cooling a winding of an electric machine comprising a wound element, the wound element comprising a tubular body (110) extending in a longitudinal direction, and at least one coil which is arranged in the tubular body (110) and has a winding head extending out of the tubular body (110), at one longitudinal end of the tubular body (110), the cooling system comprising: at least one heat pipe (400), arranged fixedly with respect to the tubular body (110), the heat pipe (400) comprising an evaporation portion (410) extending above a winding head, and a condensation portion (420) extending along the tubular body (110) in the vicinity of a cold source; and at least one heat exchanger arranged in the vicinity of at least one winding head and configured to provide exchanges of heat between each winding head and the evaporation portion of the heat pipe (400).

Description

[0001] DESCRIPTION

[0002] Title of the invention: COOLING SYSTEM WITH HEAT PIPE INTEGRATED INTO THE WINDING OF AN ELECTRICAL MACHINE

[0003] Technical field of the invention

[0004] The invention relates to a winding cooling system for an electrical machine and more particularly to a winding cooling system for a wound element of a rotating electrical machine of the electric motor type, said system comprising heat pipes integrated as close as possible to the wound components.

[0005] Technological background

[0006] Among rotating electrical machines, electric motors can comprise a wound element such as a stator and a rotor mounted to rotate within said stator. The stator comprises a bundle of laminations, having a plurality of teeth or notches for receiving a winding.

[0007] In some cases, the rotating machine is started by electromagnetic induction between the stator armature winding and the rotor field winding. To limit efficiency losses in rotating machines, the winding must be cooled, as most of the loss is due to the Joule effect generated by the electromagnetic induction. This loss is even greater when the temperature of the winding conductors is high.

[0008] To ensure the dissipation of heat and the cooling of the coils, cooling systems incorporating fans or means of supplying air to heat sinks in the form of fins are common. In this way, air is drawn in after passing over the fins and / or coils and is then expelled around the perimeter of the housing.

[0009] In cases where the internal components of an electrical machine must be sealed, they cannot be cooled with a fan system. Cooling can only be achieved through the external casing or by a dedicated cooling system. Dedicated cooling systems generally use air or gas, and sometimes oil or coolant spray cooling. However, a seal must be installed between the moving and stationary parts of the machine, which adds complexity to the cooling system.

[0010] In some cases, the cooling system includes heat pipes comprising a closed chamber through which a two-phase heat transfer fluid circulates. This fluid can change its physical state to absorb and release heat through evaporation or condensation. These heat pipes are arranged to flow the heat transfer fluid between a heat generation zone and a heat dissipation zone.

[0011] Generally, the heat dissipation zone corresponds to the condenser section of the heat pipes and consists of fins positioned externally and away from the windings. This area is prone to fouling, which can reduce the cooling system's efficiency. Furthermore, this configuration presents the disadvantage of a fragile structure when the condenser and evaporator are connected by only one or more heat pipes. In addition, to keep the evaporator and condenser as close as possible to the hot and cold sources in these systems, a connection / disconnection mechanism is necessary, which could degrade the system's heat transfer performance.

[0012] Cooling systems are also known that include primary cooling achieved by conduction between the stator laminations and the housing in which they are mounted. This housing can be cooled by dynamic air using heat exchangers or by a liquid loop.

[0013] These systems typically include secondary cooling, external to the motor, configured to circulate within the motor and cool the stator's electrical conductors and the motor's moving parts. This secondary cooling is often complex to install. Furthermore, it can be a source of contamination (dust, conductive particles, etc.) and lead to deterioration of the electrical insulation system (EIS). This can result in a fault causing an electrical short circuit, or impair heat exchange capacity due to fouling.

[0014] Cooling systems for electric motor windings using heat pipes are also known. However, this cooling system is not optimal, as it can have shortcomings in electrical insulation when the voltage exceeds one hundred volts. This arrangement is also risky in terms of long-term reliability, as it relies solely on the primary insulation of the wire.

[0015] On the other hand, integrating heat pipes close to the winding in known cooling systems will generate additional losses, such as eddy current losses, because these cooling systems incorporate conductive components. Furthermore, a heat pipe is generally made from a conductive material, which can generate additional losses related to the magnetic field produced by the winding. In addition to degrading the overall motor performance, the localized heating of these losses ultimately contributes to the degradation of the wire's electrical insulation and leads to an electrical fault. Eddy currents can also disrupt the magnetic field and induce further losses in the winding.

[0016] The inventors therefore sought an alternative solution to obtain a cooling system that met the constraints of integrating heat pipes, insulation and cooling at the coil heads of an electrical machine.

[0017] Objectives of the invention

[0018] The invention aims to provide a cooling system for the winding of an electrical machine comprising a wound element by integrating heat pipes into the winding of said wound element.

[0019] The invention also aims to provide, in at least one embodiment, a cooling system offering the best compromise between cooling and insulation of the winding.

[0020] The invention also aims to provide, in at least one embodiment, a cooling system limiting eddy current losses, while optimizing heat transfer.

[0021] The invention also aims to provide, in at least one embodiment, a cooling system integrated as close as possible to the winding.

[0022] The invention also aims to provide, in at least one embodiment, a simplified and inexpensive cooling system enabling the optimization of the mass density of a wound element.

[0023] The invention also aims to provide, in at least one embodiment, a cooling system that simplifies its integration into a wound element.

[0024] The invention also aims to provide, in at least one embodiment, a cooling system that does not require secondary cooling.

[0025] The invention also aims to provide, in at least one embodiment, a cooling system to preserve the deterioration of the electrical insulation of a wound element and to prevent electrical defects in such an element.

[0026] The invention also aims to provide, in at least one embodiment, a cooling system that is less polluting and limits fouling.

[0027] The invention also aims to increase the radial thermal conductivity at the coil heads of a wound element.

[0028] Description of the invention

[0029] To this end, the invention relates to a cooling system for a winding of an electrical machine comprising a wound element, said wound element comprising: a tubular body extending in a longitudinal direction, at least one coil arranged in said tubular body, said coil having a first portion, called the coil core, extending coaxially inside said tubular body, and a second portion, called the coil head, extending coaxially outside said tubular body, at the level of a longitudinal end of said tubular body, said cooling system being characterized in that it comprises: at least one heat pipe arranged in a fixed manner with respect to said tubular body, said heat pipe comprising an evaporation portion extending at least partially above at least one coil head, and a condensation portion extending at least partially along said tubular body in the vicinity of a cold source,at least one heat exchanger arranged in the vicinity of at least one coil head and configured to ensure heat exchange by conduction between each coil head in the vicinity of which it is arranged and said evaporation portion of said heat pipe.

[0030] Throughout this text, the term "wound element" refers to any element comprising a winding of wire capable of forming a magnetic field when an electric current flows through the electrical machine. The term "wound element" thus refers to a body comprising such a winding of wire, or a coil arranged in or around said body.

[0031] Throughout the following text, and unless otherwise indicated, the tubular body is defined as a hollow body having a surface capable of being wound, preferably an internal surface capable of being wound.

[0032] The tubular body is made of a ferromagnetic material capable of forming an inductance. Furthermore, the tubular body may be enclosed within a housing.

[0033] Throughout the following text, and unless otherwise indicated, the terms "evaporation portion", "evaporation part", "evaporator part", and "evaporator portion" are equivalent and define a particular portion of the heat pipe arranged at the coil heads, said heads constituting a hot source.

[0034] For the purposes of this invention, it is understood that the evaporation portion of a heat pipe may be in direct or indirect contact with the coil heads.

[0035] In the case of indirect contact, an insulated heat exchanger, preferably electrically insulated, is arranged between the coils and the heat pipe.

[0036] Throughout the following text, and unless otherwise indicated, the terms "condensation portion", "condensation part", "condenser part" and "condenser portion" are equivalent and define a particular portion of the heat pipe arranged at the level of the tubular body and / or a cold source.

[0037] Throughout the following text, the cold source can be defined as a cooling method not specifically intended to cool the coil heads of a wound element of an electrical machine.

[0038] Furthermore, said tubular body comprises at least one coil, preferably a plurality of coils made of an electrically conductive material known to those skilled in the art. Throughout the following text, the description relating to a coil also applies to a plurality of coils arranged within said tubular body.

[0039] Thus each coil extends coaxially to the longitudinal direction of the tubular body and has a core portion of the coil and a head portion of the coil.

[0040] The portion known as the coil core corresponds to a portion of a coil or plurality of coils arranged inside said tubular body.

[0041] The so-called coil head portion corresponds to a portion of a coil or plurality of coils extending coaxially outside the tubular body, at one of its longitudinal ends. Thus, the tubular body may include a coil head portion extending at both of its longitudinal ends.

[0042] In addition, the reel head portion may include one or more reel heads.

[0043] The cooling system according to the invention comprises at least one heat pipe, preferably a plurality of heat pipes.

[0044] The heat pipes are arranged in a fixed manner relative to the tubular body and include an evaporation portion or evaporator, arranged at the level of at least one coil head on the one hand, or of said coil head portion, which constitutes a hot source, and a condensation portion, arranged at the level of the tubular body.

[0045] The condensing section of the heat pipes extends along the tube body in the vicinity of a cold source or a heat-dissipating element. This condensing section of the heat pipes may be located on at least a portion of the tube body or in an adjacent compartment.

[0046] It is understood that the heat pipes of the cooling system according to the invention can be capillary or gravity heat pipes comprising a two-phase heat transfer fluid known to a person skilled in the art.

[0047] The cooling system according to the invention also includes a heat exchanger arranged in the vicinity of at least one coil head and configured to ensure heat exchange by conduction between each coil head in the vicinity of which it is arranged and said evaporation portion of said heat pipe.

[0048] The heat exchanger is made of a thermally conductive material known to a person skilled in the art and allows the heat source formed by the coil head portion to be thermally connected with the evaporator part of at least one heat pipe.

[0049] The invention advantageously allows the integration of a heat pipe cooling system as close as possible to the winding, and in particular to the coil heads which constitute the hot source of an electrical machine.

[0050] The entire cooling system optimizes the cooling of the wound element of an electrical machine and limits the use of a dedicated secondary cooling system, which is complex and expensive to implement.

[0051] The cooling system according to the invention enables heat transfer between the coil heads and a cold source, such as the main cooling system of an electrical machine. In other words, the invention eliminates the need for secondary cooling conventionally used to cool the coil heads of a wound element, such as oil, oil vapor, or gas cooling.

[0052] With the heat pipes arranged in a fixed manner relative to the tubular body, the cooling system according to the invention is an integrated system providing efficient cooling that facilitates maintenance of the electrical machine and the wound element. Advantageously, and according to the invention, said heat exchanger comprises at least one annular fin with a longitudinal axis extending radially from a coil head, said annular fin being interposed between a longitudinal end of said tubular body and at least said coil head.

[0053] Thus, according to the invention, the system allows thermal conduction to be resumed as close as possible to the coil heads, with fins integrated into the winding.

[0054] Advantageously and according to the invention, each annular fin has a plurality of perforations with a longitudinal axis.

[0055] Thus, according to the invention, the perforations allow for better cooling at the coil heads.

[0056] Advantageously and according to the invention, the evaporation portion of said at least heat pipe extends longitudinally through a perforation along the longitudinal axis of an annular fin.

[0057] Thus, according to the invention, the heat pipes are held together with the fins to ensure better integration at the coil heads and efficient heat exchange.

[0058] Advantageously and according to the invention, the cooling system comprises a plurality of heat pipes, of which at least one heat pipe comprises at least one radial branch arranged at the level of its evaporation portion, said radial branch extending between the evaporation portion of this heat pipe and the evaporation portion of an adjacent heat pipe.

[0059] The radial branches of a first heat pipe may be joined, welded, or mechanically connected to a second heat pipe by any means known to a person skilled in the art. Alternatively, the radial branches may be arranged independently without mechanical connection to an adjacent heat pipe.

[0060] Thus, according to the invention, the cooling system optimizes heat exchange over the entire periphery of the coil heads of the wound element.

[0061] Advantageously and according to the invention, said heat exchanger comprises at least one shell arranged peripherally on at least one coil head.

[0062] Thus, according to the invention, the system improves cooling with peripheral thermal conduction.

[0063] Advantageously and according to the invention, the wound element comprises a plurality of coils.

[0064] Advantageously and according to the invention, said heat exchanger comprises a plurality of annular fins with a longitudinal axis extending radially from at least one coil head, said fins being interposed between a longitudinal end of said tubular body and each of the coil heads.

[0065] Thus, according to the invention, the system ensures optimized cooling of each coil.

[0066] Advantageously and according to the invention, the annular fins and the shell of the heat exchanger comprise a laminated material.

[0067] Thus, according to the invention, the cooling system makes it possible to limit the loss due to eddy currents and to improve the electrical resistivity of the heat exchanger.

[0068] Advantageously and according to the invention, the electric machine comprises a rotor and stator, and said stator comprises a wound element cooled by said system.

[0069] It is understood that the invention relates to a cooling system that can be applied in a non-limiting way to electrical machines comprising a wound element such as stators, rotors, transformers or any other electrical machine comprising a wound element capable of being cooled by a cooling system according to the invention.

[0070] The invention also relates to a cooling system characterized in whole or in part by the characteristics mentioned above and / or below.

[0071] List of figures

[0072] Other objects, features and advantages of the invention will become apparent from the following description, given by way of non-limiting example only, and which refers to the accompanying figures in which:

[0073] - [Fig. 1] represents a cooling system according to a first embodiment of the invention

[0074] - [Fig. 2] represents a cooling system according to a second embodiment of the invention

[0075] - [Fig. 3] represents a cooling system according to a third embodiment of the invention

[0076] - [Fig. 4] represents a schematic longitudinal section of a stator equipped with a cooling system according to an embodiment of the invention

[0077] Detailed description of an embodiment of the invention

[0078] In the figures, the scales and proportions are not strictly respected, for the purposes of illustration and clarity.

[0079] In the entire detailed description that follows with reference to the figures, unless otherwise indicated, each element of the cooling system according to the invention is described as it is arranged during its use.

[0080] Identical, similar or analogous elements are designated by the same references in all figures.

[0081] Figures 1, 2, and 3 each depict a different embodiment of a cooling system according to the invention, and more particularly a specific arrangement of the heat pipes and the heat exchanger. Furthermore, and notwithstanding other possibilities, each of Figures 1 through 4 relates to a stator comprising several coils. The tubular body of the stator has an external surface and an internal surface from which extend a plurality of radial teeth defining slots extending along the internal surface of said tubular body. The stator comprises a plurality of coils arranged in at least one slot.

[0082] It must be understood that the invention cannot be limited to an embodiment with a plurality of coils and that a winding within the meaning of the invention can be formed by at least one coil.

[0083] In addition, the particular coil shaping illustrated in figures 1 to 4 can be achieved through the coil compaction process described in patent application ER2102912.

[0084] The invention relates to a cooling system for the winding 200 of an electrical machine 100, preferably a rotating electrical machine of the electric motor type comprising a wound stator.

[0085] The electrical machine 100 comprises a tubular body 110 in which a plurality of coils of the winding 200 are housed. The winding 200 comprises a first portion 220, called the core portion, arranged inside the tubular body 110, and a second portion 210, called the head portion, arranged outside said tubular body 110. The tubular body 110 can thus comprise two head portions 210. Said portions 210 extend longitudinally on either side of each longitudinal end of said tubular body 110.

[0086] The tubular body 110 of the electrical machine 100 thus presents an internal wound surface corresponding to the core portion of the coil 220.

[0087] In the described embodiment, the cooling system comprises a plurality of heat pipes 400, each comprising a condenser portion 420 and an evaporator portion 410 extending respectively over a portion of the tube body 110 and over a coil head portion 210. This system includes a heat exchanger 300 comprising a shell 310 arranged peripherally around at least one coil head 210 of the winding 200.

[0088] The said ferrule 310 can be made in one or more pieces of a thermally conductive material and is configured to perform heat exchange with the plurality of heat pipes 400.

[0089] Furthermore, the heat pipes 400 can extend longitudinally on said ferrule 310. The ferrule 310 is thus thermally connected to said heat pipes 400. It can also be provided that the ferrule may include longitudinal grooves shaped to the form of the evaporator part 410 of the heat pipes 400, so that the latter may extend into said grooves.

[0090] The heat exchanger 300 also includes a plurality of annular fins 320 arranged intercalated between each coil of the winding 200. The annular fins 320 are thus integrated as close as possible to the coils at a coil head portion 210 of the winding 200. Said annular fins 320 extend radially between an inner and an outer portion of a coil head portion 210. Said annular fins 320 form discs projecting transversely to the longitudinal direction of the heat pipes 400 and the shell 310. The shell 310 and the annular fins 320 can be electrically insulated between the coils and the heat pipes 400.

[0091] In the described embodiment, each heat pipe 400 includes an evaporation portion 410 extending longitudinally over the ferrule 300 and through the perforations 321 of longitudinal axis of each of the annular fins 320.

[0092] The evaporator part 410 of each heat pipe 400 is thermally connected to the heat exchanger 300 via the ferrule 310 and the annular fins 320.

[0093] In addition, the condenser part 420 of each heat pipe is arranged on a portion of the tubular body 110 of the rotating electrical machine 100.

[0094] The condenser part 420 of the heat pipes 400 can be integrated into the surface of the tubular body 110 or pass through said tubular body 110 at orifices provided accordingly on the thickness of said tubular body 110. It is understood that such orifices are adapted and conform to the dimensions of the heat pipes 400.

[0095] The tubular body 110, on which the condenser portion 420 of the heat pipe is mounted, can be either a separate compartment thermally connected to the cold source, or directly the ferromagnetic part of the stator. In this case, the heat pipes 400 will be integrated into the surface of the tubular body to improve thermal conductivity with the cold source.

[0096] In the context of an electric motor, the integration of heat pipes can be done on the periphery of the stator lamination pack or in a dedicated compartment mechanically connected to the motor and in contact with the main cold source of said motor after assembly.

[0097] The coils can be electrically powered by a power source such as a DC power bus with a center tap. This configuration between the heat pipes 400 and the tube body 110 allows for better management of the electrical insulation between the coils, in addition to improving their cooling. Indeed, mounting the condenser section 420 of the heat pipes 400 on the tube body allows the reference potential of the tube body 110 to be applied to the coils. The heat pipes 400 ensure electrical continuity between the heat exchanger 300 integrated at the coil heads and the condenser section 420 of the heat pipes mounted on the tube body 110.In the case of a power supply with a midpoint on the DC bus, the voltage constraint between the coils can be replaced by a voltage constraint between phase and ground when the exchanger is connected to ground, for example.

[0098] Depending on the heat exchanger and its arrangement, a more homogeneous distribution of the electric field can be obtained and thus improve the partial discharge inception voltage threshold, better known by the acronym PDIV (Partial Discharge Inception Voltage).

[0099] The annular fins 320 and the ferrule 310 of the heat exchanger 300 can be electrically insulated with materials known to those skilled in the art and usable in electronics such as polyimide, insulating papers, bimaterial insulators, etc.

[0100] The cooling system may also include thermal interface materials or heat sinks to improve thermal conduction between the winding and the heat exchanger 300. Preferably, the cooling system may include a single material for electrical insulation and thermal interface depending on the integration of the heat pipes.

[0101] It is understood that the size, shape, material and number of heat pipes will be adapted and defined to optimize heat transfer between the winding and the tubular body 110.

[0102] [Fig. 1] represents a first embodiment of the cooling system in which the heat exchanger 300 comprises annular fins 320 and two ferrules 310 arranged on each coil head 210.

[0103] The coil heads 210 extend longitudinally outwards on either side of the tubular body 110 of the stator from a respective longitudinal end thereof. In this embodiment, the tubular body has a plurality of orifices into which the heat pipes 400 are inserted. In this embodiment, the entire set of heat pipes 400 extends longitudinally.

[0104] The condenser part 420 of the heat pipes 400 is thus integrated into the thickness of the tubular body 110. The evaporator part 410 of the heat pipes 400 extends longitudinally over the ferrules 310 and fits into the perforations 321 of the longitudinal axis of each annular fin 320 of the heat exchanger 300.

[0105] In addition, each annular fin 320 has a disc shape extending radially from the internal central axis of the winding outwards from said winding 200. The annular fins 320 project transversely from the plane of the ferrules 310 and are mechanically and thermally connected to the evaporator portion 410 of the heat pipes. This figure also shows a coil 201 of the winding 200 compacted according to the particular process according to FR2102912 at one end of the winding 200. [Fig. 2] represents a second embodiment of the cooling system not comprising a ferrule 310 and where the evaporator part 410 of the heat pipes 400 extends longitudinally at the level of the coil head portion 210. The evaporator part 410 includes radial branches 411 extending peripherally around each of the coils 201, 202 and 203 at the annular fins 320 of the heat exchanger 300.The condenser part 420 of the heat pipes 400 is arranged on the external surface of the tubular body 110.

[0106] The tubular body 110 is the body of an electric motor stator and it includes on its internal surface notches 111 and teeth 112 around which are wound the coils 201, 202, and 203 of the winding 200.

[0107] In this embodiment, the evaporation portion 410 of at least one heat pipe 400 includes a radial branch 411 extending peripherally around each of the coils 201, 202 and 203 of the winding 200.

[0108] The radial branches 411 in this embodiment extend radially between two heat pipes, but other configurations and / or possible connections between heat pipes are conceivable. In the described embodiment, the heat pipes can be bent between the condenser and evaporator sections and then radially shaped to conform to the shape of the coil.

[0109] [Fig. 3] represents a third embodiment of the cooling system where the heat exchanger 300 does not include a ferrule 310 arranged at the coil heads 210. The system of this embodiment includes a plurality of heat pipes 400 connecting several times the same radial branch 411 of the evaporator part 410 of a heat pipe in order to optimize the heat exchanges by conduction between the coil head portion and the tubular body 110.

[0110] [Fig. 4] schematically represents a longitudinal section of an electric stator of an electric motor equipped with a cooling system according to an embodiment of the invention. This section also shows the axis of symmetry of the stator in dashed lines. In this embodiment, the main cold source 500 of the electric motor is in contact with the tubular body 110 of the stator in order to cool the latter. The annular fins 320 of the heat exchanger 300 are interposed between each coil of the winding 200. The annular fins 320 are integrated at the level of each of the coils of the coil head portion 210 of the winding 200 and allow heat exchange from the hot source, namely the coil heads, to the evaporator portion 410 of the heat pipe 400. The condenser portion 420 is arranged on the external surface of the tubular body 110 directly exposed to the main cold source 500 of the engine.

[0111] The ring fins 320 have perforations 321 with a longitudinal axis into which the evaporator part of the heat pipes 400 are inserted.

Claims

DEMANDS 1. Cooling system for a winding of an electrical machine comprising a wound element, said wound element comprising: a tubular body (110) extending in a longitudinal direction, at least one coil arranged in said tubular body (110), said coil having a first portion, called the coil core, extending coaxially inside said tubular body, and a second portion, called the coil head, extending coaxially outside said tubular body (110), at a longitudinal end of said tubular body (110), said cooling system comprising: at least one heat pipe (400) arranged in a fixed manner with respect to said tubular body (110), said heat pipe (400) comprising an evaporation portion (410) extending at least partially above at least one coil head, and a condensation portion (420) extending at least partially along said tubular body (110). proximity to a cold source,at least one heat exchanger (300) arranged in the vicinity of at least one coil head and configured to provide heat exchange by conduction between each coil head in the vicinity of which it is arranged and said evaporation portion of said heat pipe (400), said system being characterized in that said heat exchanger (300) comprises at least one annular fin (320) with a longitudinal axis extending radially with respect to a coil head, said annular fin (320) being interposed between a longitudinal end of said tubular body (110) and at least said coil head.

2. System according to claim 2, characterized in that each annular fin (320) has a plurality of perforations (321) with longitudinal axis.

3. System according to claim 3, characterized in that the evaporation portion (410) said at least heat pipe extends longitudinally through a perforation (321) of longitudinal axis of an annular fin (320).

4. System according to any one of the preceding claims, characterized in that it comprises a plurality of heat pipes (400), of which at least one heat pipe comprises at least one radial branch (411) arranged at the level of its evaporation portion (410), said radial branch (411) extending between the evaporation portion (410) of this heat pipe and the evaporation portion of an adjacent heat pipe.

5. System according to any one of the preceding claims, characterized in that said heat exchanger (300) comprises at least one shell (310) arranged peripherally on at least one coil head.

6. System according to any one of the preceding claims characterized in that said heat exchanger (300) comprises a plurality of annular fins (320) with longitudinal axis extending radially with respect to at least one coil head, said fins (320) being interposed between a longitudinal end of said tubular body (110) and each of the coil heads.

7. System according to claims 5 and 6 taken together, characterized in that the annular fins (320) and the shell (310) of the heat exchanger (300) comprise a laminated material.

8. System according to any one of the preceding claims, characterized in that the wound element comprises a plurality of coils.

9. System according to any one of the preceding claims characterized in that the electrical machine comprises a rotor and stator and said stator comprises a wound element cooled by said system.

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