INTEGRATED COOLING WINDING AND ELECTRICAL MACHINE INCLUDING SUCH A WINDING

Abstract

INTEGRATED COOLING WINDING AND ELECTRICAL MACHINE COMPRISING SUCH A WINDING One aspect of the invention relates to a winding (100) comprising: an electrically insulating coil body (110) comprising: a first internal channel (111) delimited at least in part by a sealed wall (113); and a second internal channel (112) distinct from the first internal channel (111) and intended to receive a cooling fluid; and a winding of conductive wire (120) disposed inside the first internal channel (111); and wherein the sealed wall (113) is arranged so as to be in contact with the cooling fluid when the cooling fluid flows in the second internal channel (112). Figure to be published with the abbreviation: Figure 2C

Description

Title of the invention: WINDING WITH INTEGRATED COOLING AND ELECTRIC MACHINE COMPRISING SUCH A WINDING Technical field

[0001] The technical field of the invention is that of cooling electrical machines. The present invention relates more particularly to a winding having improved cooling and an electrical machine comprising such a winding. STATE OF THE ART

[0002] The development of electric aircraft increases the need for high-power electrical machines (of the order of a hundred kW to a few MW). The sizing of such an electrical machine requires taking into account thermal transfers, particularly at the level of the machine's windings.

[0003] The windings are in fact the site of significant losses due to the Joule effect, which dissipate in the form of heat. However, the maximum current density that the electrical machine can support is limited by the maximum temperature of the windings.

[0004] To be able to achieve high current densities while avoiding thermal runaway or premature aging of the electrical machine, it is therefore necessary to extract the heat produced by the windings. The solutions commonly used for cooling electrical machines are essentially of three types: natural convection, forced convection by air and forced convection by liquid.

[0005] Patent application FR3093252A1 also describes a solution consisting of cooling the coil heads of the windings by means of a heat sink comprising a phase change material (or PCM).

[0006] [Fig.l] represents an electrical machine 10 described in patent application FR3093252A1. The electrical machine 10 comprises an external rotor comprising a rotor yoke 12 and an internal stator comprising a stator yoke 16, concentric with the rotor. Permanent magnets 14 are arranged on an inner surface of the rotor yoke 12. The stator comprises at its periphery a plurality of magnetic teeth 18. Around each tooth 18 is arranged a winding 20 comprising a coil body 22 and conductors 23. Two coil heads 24 emerge at the ends of the coil body 22. A heat sink 26 is arranged at each coil head 24, in order to quickly extract the heat produced by the conductors 23. The heat sink 26, which is formed in two hollow parts 26A, 26B which can be fitted into each other, is interposed between the coil body 22 and the conductors 23. It comprises an internal cavity 26C for receiving in the liquid state a phase change material 28. The phase change material 28 is capable of absorbing an excess quantity of heat when the current density through the conductors 23 increases.

[0007] The heat sinks 26 comprising the phase change material are elements added to the coil body, which provide limited cooling to the coil heads. Their implementation is also delicate. Summary of the invention

[0008] There is a need to provide a winding with a more efficient and easier to use cooling function.

[0009] According to a first aspect of the invention, this need is tended to be satisfied by providing a winding comprising: • an electrically insulating coil body comprising: • a first internal channel delimited at least in part by a watertight wall; and • a second internal channel distinct from the first internal channel and intended to receive a cooling fluid; and • a winding of conductive wire arranged inside the first internal channel; the sealed wall being arranged so as to be in contact with the cooling fluid when the cooling fluid circulates in the second internal channel.

[0010] Thanks to its two adjacent internal channels, one containing the conductive wire winding and the other for the cooling fluid, the winding has a global cooling function, and not just limited to the winding heads. The use of the winding is further simplified, since the second internal channel forms a cooling circuit integrated into the winding from its manufacture.

[0011] Preferably, the conductive wire winding comprises a plurality of turns and the first internal channel comprises a plurality of annular portions, each annular portion of the first internal channel containing a single turn.

[0012] The sealed wall is advantageously arranged so that several annular portions of the first internal channel are in contact with the cooling fluid when the cooling fluid circulates in the second internal channel.

[0013] The winding according to the first aspect of the invention may also have one or more of the following characteristics, considered individually or in all technically possible combinations: • the second internal channel is arranged around the first internal channel; • the conductive wire winding is in contact with the waterproof wall; • the waterproof wall is made of an electrically insulating material having thermal conductivity greater than 5 Wm *.K1; • the waterproof wall is made of an electrically insulating material with an electrical conductivity of less than 10 12 S.cm; • the coil body is formed from a single piece; • the coil body is made of a single material, preferably a ceramic material, for example based on zirconia or alumina; • the coil body is made of a polymer material, for example polyethylene terephthalate (PET); and • the coil body is made of a refractory material.

[0014] A second aspect of the invention relates to an electrical machine comprising a winding according to the first aspect of the invention.

[0015] A third aspect of the invention relates to a method of manufacturing a winding comprising the following steps: • form an electrically insulating coil body comprising: • a first internal channel delimited at least in part by a watertight wall; and • a second internal channel separate from the first internal channel and intended to receive a cooling fluid; the sealed wall being arranged so as to be in contact with the cooling fluid when the cooling fluid circulates in the second internal channel; and • forming a winding of conductive wire inside the first internal channel.

[0016] Preferably, the coil body is obtained by an additive manufacturing technique.

[0017] In a first embodiment of the manufacturing method, the step of forming the conductive wire winding comprises a sub-step of inserting a molten metal into the first internal channel and then a step of solidifying the metal.

[0018] In a second embodiment, the step of forming the conductive wire winding comprises a sub-step of inserting a metal powder into the first internal channel, a step of melting the metal powder to form a bead of molten metal and then a step of solidifying the metal.

[0019] Preferably, the first internal channel is completely filled with the molten metal.

[0020] In a third embodiment, the step of forming the conductive wire winding comprises inserting a conductive wire into the first internal channel. BRIEF DESCRIPTION OF THE FIGURES

[0021] Other characteristics and advantages of the invention will emerge clearly from the description given below, for information purposes only and in no way limiting, with reference to the following figures.

[0022] [Fig. 1] schematically represents an electrical machine equipped with windings according to the prior art;

[0023] [Fig.2A], [Fig.2B] and [Fig.2C] represent a first embodiment of a winding with integrated cooling according to the invention;

[0024] [Fig.3A] and [Fig.3B] represent a second embodiment of the winding with integrated cooling according to the invention;

[0025] [Fig.4] schematically represents a manufacturing process for the cooling winding integrated development according to the invention.

[0026] For clarity, identical or similar elements are identified by identical reference signs throughout the figures. DETAILED DESCRIPTION

[0027] Figures 2A, 2B and 2C represent in an orthogonal reference frame of axes XX z a winding with integrated cooling 100 according to a first embodiment. Figure 2A is a complete perspective view, Fig. 2B is a top view (in the plane of axes X z) and [Fig.2C] is a perspective view, partial and exploded, showing the interior of the winding 100. These figures will be described jointly.

[0028] The winding 100 comprises a hollow, electrically insulating coil body 110 and a conductive wire winding 120 disposed inside the coil body 110.

[0029] The coil body 110 is advantageously formed from a single piece. Externally, it has a substantially annular shape. It comprises a central cavity 130 sized to receive a magnetic core, for example a magnetic tooth of an electrical machine.

[0030] The coil body 110 comprises a first internal channel 111, in which the conductive wire winding 120 is arranged, and a second internal channel 112 distinct from the first internal channel 111. The second internal channel 112 is intended to receive a cooling fluid, preferably a liquid such as oil or glycolated water, in order to extract the heat produced by the conductive wire winding 120 (when an electric current flows in the winding).

[0031] The first internal channel 111 is delimited, at least in part, by a first sealed wall 113, also called the internal wall, of the coil body 110. The second channel 112 is delimited by the first sealed wall 113 and a second sealed wall 114, called the external wall, of the coil body 110. Preferably, the first and second internal channels 111-112 occupy the entire interior volume of the coil body 110. They may also be called “cavities” or “sections.”

[0032] The first sealed wall 113 is arranged to be in contact with the cooling fluid when the latter circulates in the second internal channel 112. Thus, the heat produced by the conductive wire winding 120 disposed inside the first internal channel 111 (i.e. on the other side of the first sealed wall 113) is extracted by the cooling fluid. The first sealed wall 113 prevents the cooling fluid from coming into contact with the conductive wire winding 120, which could cause a short circuit in the case of an electrically conductive fluid.

[0033] The first sealed wall 113 is advantageously arranged so that the cooling fluid can circulate around the first internal channel 111. In this configuration, it can also be considered that the second internal channel 112 is arranged around the first internal channel 111. The first internal channel 111 can be delimited entirely by the first sealed wall 113, as illustrated by [Fig.2C].

[0034] The first internal channel 111 advantageously forms a coiled tube, in the manner of a serpentine. It then comprises a plurality of annular portions which follow one another and communicate with each other.

[0035] The conductive wire winding 120 is preferably made of a metal, for example copper or aluminum. It comprises several turns and each annular portion of the first internal channel 111 contains a single turn of the winding. Furthermore, the first sealed wall 113 is advantageously arranged so that several portions of the first internal channel 111 are in contact with the cooling fluid, and preferably so that all the annular portions are in contact with the cooling fluid. The cooling of the conductive wire winding 120 is then maximum.

[0036] A first internal channel 111 in the form of a serpentine further guarantees a minimum spacing between two successive turns of the conductive wire winding 120. This minimum spacing is for example equal to twice the thickness of the first sealed wall 113. The winding 100 is then less subject to partial discharges than conventional windings, where the turns are only partially held in place (so-called multi-strand or “wire-in-hand” windings). In conventional windings, partial discharges can destroy the electrical insulation that coats the turns and cause short circuits.

[0037] In order to increase the heat exchanges between the conductive wire winding 120 and the cooling fluid, and thus obtain better cooling of the winding, the conductive wire winding 120 is advantageously in contact with the first sealed wall 113. The first sealed wall 113 is preferably made of an electrically insulating material having a thermal conductivity greater than 5 Wm *.K The electrical conductivity of the electrically insulating material is advantageously less than 10 12 S.cm.

[0038] The coil body 110 is preferably made of a single electrically insulating material. Since it constitutes the first and second sealed walls 113-114, this material is non-porous. In addition to a thermal conductivity greater than 5 Wm *.K1 and / or an electrical conductivity less than 10 12 S.cm, the material of the coil body 110 may have a high mechanical strength, with a Young's modulus greater than 150 GPa.

[0039] The coil body 110 may be made of a ceramic material, for example based on zirconia or alumina. Alternatively, the coil body 110 is made of a polymer material, for example polyethylene terephthalate (PET).

[0040] Still with reference to Figures 2A-2C, the coil body 110 also comprises: • a first inlet orifice 111a and a first outlet orifice 111b, between which the first internal channel 111 extends; and • a second inlet orifice 112a and a second outlet orifice 112b, between which the second internal channel 112 extends.

[0041] The first inlet orifice 111a and the first outlet orifice 111b form the inlets-outlets of an electrical circuit, while the second inlet orifice 112a and the second outlet orifice 112b form the inlets-outlets of a cooling circuit.

[0042] The first inlet orifice 111a and the first outlet orifice 111b are advantageously located at the same end of the coil body 110. This arrangement facilitates the electrical connection of the winding 100 in the electrical machine.

[0043] The second inlet orifice 112a and the second outlet orifice 112b are advantageously located at opposite ends of the coil body 110. The cooling fluid can thus circulate throughout the coil body 110, which has the effect of improving cooling.

[0044] In the first embodiment of the winding 100, represented by 2A to 2C, the first inlet orifice 11a and the first outlet orifice 111b extend parallel to a first plane, while the second inlet orifice 112a and the second outlet orifice 112b extend parallel to a second plane. The first and second planes are intersecting, preferably orthogonal. In the reference of FIGS. 2A to 2C, the first plane is the plane of axes x, y and the second plane is the plane of axes x, z.

[0045] Figures 3A and 3B illustrate a second embodiment of the integrated cooling coil 100. Figure 3A is a complete perspective view, while Figure 2B is a partial perspective view of the coil 100, cut along a plane parallel to the plane of axes x, y.

[0046] This second embodiment differs from the first embodiment essentially in the orientation of the inlets-outlets of the cooling circuit. The first inlet orifice 11a, the first outlet orifice 111b, the second inlet orifice 112a and the second outlet orifice 112b all extend parallel to the same plane. In the reference of FIGS. 3A-3B, this is the plane of axes x, y

[0047] The winding 100 of figures 3A and 3B is furthermore shown in a typical position within an electrical machine, that is to say around a magnetic tooth 18. The coil body 110 is inserted into two notches 19, each notch 19 separating two successive magnetic teeth 18 of the electrical machine. The electrical machine can be an electric motor, an electric generator, an alternator, an electric transformer, an actuator, etc.

[0048] A method of manufacturing the integrated cooling winding 100 will now be described in relation to [Fig.4].

[0049] Generally, the manufacturing method comprises a step S1 of forming the coil body 110 and a step S2 of forming the conductive wire winding 120 inside the coil body 110.

[0050] The coil body 110 is advantageously obtained using an additive manufacturing technique. By way of illustration, mention may be made of spark plasma sintering (SPS), powder injection molding (PIM), fused filament deposition (FFF) or powder bed melting processes, by electron beam (EBM) or laser beam (LBM).

[0051] Additive manufacturing techniques make it possible to manufacture the coil body 110 easily and at low cost. They also offer numerous possibilities for producing and mechanically connecting the first and second internal channels 111-112. As indicated previously, the first internal channel 111 advantageously has the shape of a tube (for example, of round section as in FIGS. 2A-2C or rectangular as in FIGS. 3A-3B) in order to easily accommodate the winding of conductive wire 120. Since it receives the cooling fluid, the second internal channel 112 can adopt a more complex configuration, such as a lattice structure (e.g., honeycomb structure) illustrated in FIGS. 3A-3B.

[0052] The conductive wire winding 120 can be formed in the first internal channel 111 in different ways.

[0053] In a first embodiment of step S2, the formation of the conductive wire winding 120 comprises a sub-step of inserting a metal molten in the first internal channel 111 then a sub-step of solidification of the metal. Beforehand, the coil body 110 can be placed in a furnace and brought to a temperature greater than or equal to the melting temperature of the metal. The molten metal is advantageously introduced under pressure, so that it completely fills the first internal channel 111 (absence of air bubbles). The metal solidifies during cooling of the coil body 110.

[0054] In a second embodiment, the formation of the conductive wire winding 120 comprises a sub-step of inserting a metal powder into the first internal channel 111, a sub-step of melting the metal powder, during which the metal particles agglomerate to form a bead of molten metal, and a sub-step of solidifying the metal. Again, pressure may be exerted so that the molten metal completely fills the first internal channel 111.

[0055] These first two modes of implementation can be envisaged when the first sealed wall 113 (at least) is made of a refractory material. This is the case of the aforementioned ceramic materials.

[0056] In a third embodiment, forming the conductive wire winding 120 comprises inserting a conductive wire into the first internal channel, by pushing or pulling.

[0057] Finally, in a fourth embodiment, the conductive wire winding 120 is formed by additive manufacturing, at the same time as the coil body 120, using a bi-material additive manufacturing technique (for example metal and ceramic).

Claims

Claims

1. Coil (100) comprising: - an electrically insulating coil body (110) comprising: • a sealed internal wall (113); • a first internal channel (111) delimited at least in part by the sealed internal wall (113); • a second internal channel (112) distinct from the first internal channel (111) and intended to receive a cooling fluid; and • an inlet orifice (112a) and an outlet orifice (112b), between which the second internal channel (112) extends; - a conductive wire winding (120) arranged inside the first internal channel (111) and comprising a plurality of turns;winding in which the sealed inner wall (113) is arranged so as to be in contact with the cooling fluid when the cooling fluid circulates in the second inner channel (112) and in which the first inner channel (111) comprises a plurality of annular portions, each annular portion of the first inner channel (111) containing a single turn.;

2. A coil according to claim 1, wherein the sealed inner wall (113) is arranged such that several annular portions of the first inner channel (111) are in contact with the cooling fluid when the cooling fluid flows in the second inner channel (112).

3. Winding according to one of claims 1 and 2, in which the second internal channel (112) is arranged around the first internal channel (111).

4. A winding according to any one of claims 1 to 3, wherein the conductive wire winding (120) is in contact with the sealed inner wall (113).

5. A winding according to any one of claims 1 to 4, wherein the sealed inner wall (113) is made of an electrically insulating material having a thermal conductivity greater than 5 W.m'.K1.

6. A winding according to any one of claims 1 to 5, wherein the sealed inner wall (113) is made of an electrically insulating material having an electrical conductivity of less than 10 12 S.cm.

7. A coil according to any one of claims 1 to 6, wherein the coil body (110) is made of a single material, preferably a ceramic material, for example based on zirconia or alumina.

8. An electrical machine comprising a winding (100) according to any one of claims 1 to 7.

9. A method of manufacturing a winding (100) comprising the following steps: - forming (SI) an electrically insulating coil body (110) comprising: • a sealed inner wall (113); • a first inner channel (111) delimited at least in part by the sealed inner wall (113) and comprising a plurality of annular portions; • a second inner channel (112) distinct from the first inner channel (111) and intended to receive a cooling fluid; and • an inlet orifice (112a) and an outlet orifice (112b), between which the second inner channel (112) extends; the sealed inner wall (113) being arranged so as to be in contact with the cooling fluid when the cooling fluid circulates in the second inner channel (112);and - forming (S2) a conductive wire winding (120) comprising a plurality of turns inside the first internal channel (111), each annular portion of the first internal channel (111) containing a single turn.;

10. The method of claim 9, wherein the coil body (110) is obtained by an additive manufacturing technique.

11. A method according to either of claims 9 and 10, wherein the body of coil (110) is made of a refractory material and wherein the step of forming the conductive wire winding (120) comprises a sub-step of inserting a molten metal into the first internal channel (111) and then a step of solidifying the metal.

12. A method according to one of claims 9 and 10, wherein the coil body (110) is made of a refractory material and wherein the step of forming the conductive wire winding (120) comprises a sub-step of inserting a metal powder into the first internal channel (111), a step of melting the metal powder to form a molten metal bead and then a step of solidifying the metal.

13. A method according to one of claims 9 and 10, wherein the step of forming the conductive wire winding (120) comprises inserting a conductive wire into the first internal channel (111).

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