STATOR OF AN ELECTRIC MOTOR WITH A SYSTEM FOR COOLING THE COILS BY OIL

Description

[0001] The present invention relates to an electric motor stator equipped with coils and comprising a coil cooling system using oil as a heat transfer fluid, as well as an electromagnetic motor or generator equipped with such a stator.

[0002] The present invention finds advantageous, but not limiting, application in an electromagnetic motor delivering high power with a high rotor speed. Such a motor or generator can be used, for example, as an electromagnetic motor or generator in a fully electric or hybrid motor vehicle.

[0003] Advantageously but not limitingly, the electromagnetic motor or generator may comprise at least one rotor framed by two stators, these elements being able to overlap each other while being separated by at least one air gap on the same shaft.

[0004] In high-speed applications, it is necessary not only to have a compact system, made possible by reducing the mass and size of the motor for optimal efficiency, but also very good mechanical strength of the rotating part, i.e., the rotor(s), in order to improve system reliability. Therefore, it is essential to reduce losses for optimal efficiency.

[0005] These losses can occur in the rotor(s) of the electric motor or in the stator(s). Regarding rotors, eddy current losses in magnets have been considerably reduced, notably by developing ironless rotors or magnet poles made up of a plurality of small unit magnets.

[0006] The main losses are therefore now Joule effect losses in the stator coils as well as magnetic losses in the stator iron.

[0007] The overheating therefore occurs mainly in the stators of electric motors and must be reduced as efficiently as possible.

[0008] Several solutions exist, such as circulating a heat transfer fluid in a circuit machined into the electric motor housing or circulating oil at the coil heads. A stator incorporating a coil cooling system using oil as the heat transfer fluid is also known.

[0009] In a conventional manner, the coils are arranged next to each other, leaving a small gap between two adjacent coils and together defining internal and external circumferences in the stator.

[0010] The cooling system includes an oil inlet manifold and an oil outlet manifold, the inlet manifold being drilled with inlet ports to send oil to the coils and the outlet manifold being drilled with outlet ports to collect the oil.

[0011] This is notably documented in US-A-2017 / 012480, which specifies the use of oil as a heat transfer fluid between the stator coils. It is therefore proposed, in order to improve the dissipation of stator losses, to immerse the coils in a heat transfer fluid circuit, as these coils are subject to currents that cause Joule heating or magnetic losses.

[0012] From this document, it is clear that the oil enters the stator through two inlets and circulates around the coils, passing, if necessary, between two adjacent coils. However, for coils located far from the two power inlets, it is oil that has already exchanged heat with the coils at the inlet that cools the distant coils, which does not guarantee uniform cooling of the coils.

[0013] The circulation of the heat transfer fluid, which is oil, can be made difficult by the numerous regular and singular pressure losses, which increase the oil pressure and therefore make it difficult to seal the oil circuit in the electric motor.

[0014] Thus, homogeneous cooling of the coils is not guaranteed by any oil circulation, the coils first cooled by the fluid circulation being more cooled than the following coils, the fluid heating up and losing its heat exchange qualities.

[0015] It is therefore very difficult to achieve uniform oil circulation between each coil head. When the heat transfer fluid arrives through an injection hole, it must circulate throughout the stator, cooling the coils one after the other in a series process, and is thus subject to regular losses.

[0016] Furthermore, the temperature rise is not uniform and this reduces the cooling capacity of the heat transfer fluid circulation cooling device.

[0017] The document JP-A-2006 / 033965 describes an electric motor stator equipped with coils and having a coil cooling system with oil as the heat transfer fluid, the coils being arranged next to each other leaving a gap between two adjacent coils and together defining internal and external circumferences in the stator.

[0018] The cooling system includes an inlet manifold-like element and an outlet manifold-like element, one of the manifolds going around the inner circumference while the other manifold goes around the outer circumference, an oil flow exiting the inlet element circulating predominantly in the gap between an associated coil and at least one of the two coils adjacent to the associated coil and then exiting through the outlet element.

[0019] In this document, oil enters the stator through at least one supply inlet and circulates around the coils, passing, if necessary, between two adjacent coils. However, for coils located further from this at least one supply inlet, it is oil that has already exchanged heat with the coils at the inlet that cools the distant coils, thus preventing uniform cooling of all the coils.

[0020] Furthermore, the inlet and outlet elements are not outside the compartment containing the coils but integrated into this compartment, which does not allow for the same cooling oil temperature to be obtained for all the coils, the coils close to an injection inlet filling the inlet element being cooled more efficiently by colder oil than the other coils through which oil has heated up by contact with the head or the foot of the coils closer to an injection inlet, advantageously the head.

[0021] Document EP-A-3 764 526 is an interfering document, that is to say, it has a date prior to the filing date of this patent application but was not published on that filing date.

[0022] This document describes a stator equipped with coils and input and output collectors but does not describe any means of ensuring uniform cooling for all coils with oil flow specifically directed from the collector to each coil taken individually.

[0023] The problem underlying the present invention is to improve the cooling of the coils of a stator of an electromagnetic motor or generator by a heat transfer fluid in the form of oil while having the lowest possible pressure losses to avoid having oil overpressures in the cooling chambers with respect to the air gap between stator and rotor.

[0024] To this end, the present invention relates to an electric motor stator equipped with coils and comprising a coil cooling system using oil as the heat transfer fluid, the coils being arranged side by side with a gap between two adjacent coils and together defining internal and external circumferences in the stator, the cooling system comprising an oil inlet manifold and an oil outlet manifold, the inlet manifold being perforated with inlet ports to send oil onto the coils and the outlet manifold being perforated with outlet ports to recover the oil, characterized in that each coil is associated with at least one inlet port, one of the manifolds going around the internal circumference while the other manifold goes around the external circumference,an oil flow exiting each inlet orifice circulating predominantly in the gaps between its associated coil and at least one of the two coils adjacent to the associated coil, then exiting through one of the outlet orifices, each coil being associated with at least one inlet orifice, the oil flow exiting an inlet orifice circulating predominantly in the gaps between its associated coil and each of the two coils adjacent to the associated coil, then exiting through one of the outlet orifices, the oil flow from each inlet orifice dividing into two flows with one flow for each gap.

[0025] By associating at least one oil inlet port with each coil, homogeneous cooling of the coils relative to each other is achieved, each coil being cooled by oil at the same temperature because it comes directly from the inlet manifold and without having been previously heated by other coils.

[0026] The main idea behind the present invention is to create a number of injection channels formed by the spacing between adjacent coils that is equal to the number of coils and, advantageously, stator teeth, each carrying a coil, thus creating oil circulations completely surrounding each coil. The numerous oil flows through the spacings are therefore parallel, not series, and almost simultaneous.

[0027] This has the advantage of creating much lower flow resistances, and therefore, lower overpressures needed to circulate the oil between the coil heads.

[0028] "Majorly" means that the injected oil circulates primarily through the gaps between the coils, since the quantities of oil passing from one coil to the other on the surfaces of the coils forming the inner and outer circumferences are small, even negligible, representing less than 20% of the oil circulating in the gaps. According to the invention, there may be several inlet ports dedicated to a single coil, although this is not preferred; however, there is always at least one oil inlet port associated with each coil.

[0029] The fact that the oil flow from each inlet splits into two flows, one for each gap, allows both sides of each coil, each bordering a gap with an adjacent coil, to be cooled simultaneously in this embodiment. It is advantageous for both sides to be traversed by the same flow rate to achieve uniform cooling of both sides of the coil.

[0030] Advantageously, said at least one inlet port associated with a coil is located equidistant from the two spacings between the associated coil and each of the two adjacent coils, the two flows having the same flow rate.

[0031] Advantageously, at least one output port is associated with each coil, the input and output ports being matched by being in equal numbers.

[0032] In this preferred mode, after passing through a gap between two coils, the heated oil is collected and drained individually for each coil. This prevents pressure losses in the cooling circuit and facilitates oil drainage. This results in a similar oil flow rate at the inlet and outlet of the coils, ensuring efficient oil flow into and out of the stator.

[0033] Advantageously, the coils have a trapezoidal cross-section with a smaller base and a larger base, or a triangular cross-section with a base opposite a vertex. The larger bases of trapezoidal coils or the bases of triangular coils define the outer circumference, and the smaller bases of trapezoidal coils or the vertices of triangular coils define the inner circumference. The larger bases form the greater width of a coil, or the coil head, while the smaller bases for a trapezoidal cross-section, or the vertices opposite the base for a triangular cross-section, form the smaller width, or the coil foot.

[0034] Oil, used as a heat transfer fluid, is injected onto each coil on its wider side, directly onto the wider section which requires more cooling than the narrower one. This results in more efficient cooling of each coil. Advantageously, the inlet ports are positioned directly above the outer circumference and the outlet ports are positioned directly above the inner circumference.

[0035] This allows the inlet ports of the inlet manifold to be positioned closer to the coil heads and the outlet ports of the outlet manifold to the coil feet, facilitating oil injection onto each coil and its recovery at the coil outlet. Advantageously, the inlet and outlet manifolds are circular, with diameters corresponding to the outer and inner circumferences, respectively.

[0036] This allows the oil flow in the manifolds to follow the arrangement of the coils and to cool the coils evenly relative to each other.

[0037] Advantageously, the inlet and outlet manifolds are each in the form of a channel having respectively an oil inlet or outlet.

[0038] Since the coils need to be supplied by several inlet ports, at least one of which is dedicated to each coil, it is necessary to provide a large quantity of oil which is significantly greater than the amount of oil leaving the inlet manifold through each port.

[0039] It follows that the inlet channel must have a sufficient cross-section to allow the delivery of enough oil to all the coils so that all the coils are cooled simultaneously and uniformly. The channel cross-section is advantageously related to the number of inlet ports and their cross-section.

[0040] Advantageously, the stator includes at least one temperature probe.

[0041] This allows for monitoring the cooling of the coils in the stator. It is advantageous to install several temperature probes in the stator, preferably near the coils.

[0042] Advantageously, the coils are concentric, each supported by its respective tooth. Such concentric coils have the advantage of being easy to manufacture.

[0043] The invention also relates to an electromagnetic motor or generator comprising a housing surrounding at least one rotor and at least one stator, characterized in that said at least one stator is as described above, the housing being traversed by an oil inlet nozzle and an oil outlet nozzle connected respectively to the inlet manifold or the outlet manifold and a sealed wall separating said at least one stator from said at least one rotor.

[0044] The engine or generator casing is simplified because it only requires one inlet and one outlet nozzle, whereas prior art allowed for multiple inlet and outlet nozzles. The sealed wall protects the rotor(s) from oil leakage from the stator(s).

[0045] Advantageously, said at least one rotor comprises a plurality of magnet poles, each magnet pole consisting of a plurality of unit magnets joined together by glue, resin or composite with or without interposition of a mesh receiving the unit magnets.

[0046] Advantageously, each magnet pole is individually encased in a layer of composite.

[0047] These characteristics contribute to delivering the main preferential advantages of the present invention. It is proposed to replace one or more large magnets with a plurality of small magnets. This results in the creation of magnetic flux by a multitude of small magnets, the number of which can be at least 20 and can even exceed 100 per magnet pole.

[0048] A prior art rotor could comprise from 1 to 10 magnets forming magnet poles, whereas the present invention provides for many more small magnets in each magnet pole.

[0049] It is important not to confuse a magnet pole, a rotor being able to carry for example five to ten or even more, with individual magnets which are significantly more numerous, a rotor being able to carry for example several hundred.

[0050] This results in a rotor that, among other advantages, can rotate at high speeds and contains no iron, thus limiting rotor losses. It has been discovered that a plurality of individual magnets provides a more robust magnet structure in terms of overall rotor deflection, while producing very little heat due to the low losses generated; the heat dissipated by individual magnets is less than the heat dissipated by a larger, single, corresponding magnet.

[0051] The magnet structure forming the magnet pole may include a layer of non-conductive composite coating encapsulating the individual magnets, advantageously arranged in a mesh. Furthermore, its mechanical strength can be high, and the coating can be easily applied, notably by injecting the composite onto an arrangement of individual magnets held in place relative to one another by any means.

[0052] With such a rotor, it is advantageous to combine one or more stators comprising teeth, advantageously made of iron, with concentric coils, which is easy to achieve.

[0053] Therefore, the present invention reverses the approach taken by many manufacturers of electromagnetic motors and generators. It was common practice to focus innovation efforts on stators by designing increasingly complex and difficult-to-engineer coils.

[0054] On the contrary, the inventive approach of the present invention also focused on a rotor containing no iron and encased in a composite material containing magnet poles, each consisting of a plurality of magnets. This made it possible to use concentric coils for the stator(s), whereas such a concentric coil did not provide entirely satisfactory results with single-piece permanent magnets as employed by the prior art. It turned out that using such a combination of a composite rotor with at least one iron stator having iron teeth or studs and concentric coils for the stator provided synergy with regard to the power of the motor or generator used, as well as ease of manufacture and high mechanical strength of the motor or generator.The main inventive contribution of the present invention to the prior art has also been to make this synergy even more significant by eliminating the main disadvantage of such a stator, which is the high heat generation during coil operation. This has been resolved by integrating a cooling system into a stator as previously mentioned.

[0055] Such a motor could be an axial flux motor.

[0056] The attached drawings illustrate the invention: [ Fig 1 ] represents a front view of a stator according to an embodiment of the present invention after removal of a sealing plate intended to separate the stator from the associated rotor to form an electromagnetic motor or generator, [ Fig 2 ] represents an enlarged view of three stator coils according to one embodiment of the present invention, the oil paths between two adjacent coils being identified by arrows in this figure, the oil flow exiting an inlet orifice passing through both lateral sides of the associated coil, [ Fig 3 ] represents a rear view of a stator according to an embodiment of the present invention with visualization of the oil inlet and outlet manifolds and the path of the oil in the manifolds shown by arrows, [ Fig 4 ] represents an axial cross-section of a stator according to an embodiment of the present invention with a view of the oil exchange between the inlet and outlet manifolds respectively with an inlet port or an outlet port, [ Fig 5 ] represents a front view of a rotor that can be associated with a stator as shown in the figures 1 à 4 in order to form an electromagnetic motor or generator according to the present invention.

[0057] In what follows, reference is made to all figures taken in combination. When reference is made to one or more specific figures, these figures are to be taken in combination with the other figures for the recognition of the designated numerical references.

[0058] With particular reference to the figure 1 This figure shows a stator 1 of a motor or electromagnetic generator that may comprise one or more stators and one or more rotors. figure 1 This is a view of the face of the stator 1 facing the rotor, thus limiting an air gap between the stator 1 and the rotor. As can be seen in this figure, the stator 1 of an electric motor, according to a non-limiting embodiment of the present invention, is circular for an axial flux motor, which is not a limitation within the scope of the present invention. Reference numeral 2 indicates the center of the stator 1 or of the housing 1a enclosing the stator 1.

[0059] The stator 1 is equipped with coils 3 arranged circumferentially around the center of the stator 1, advantageously each mounted on a tooth 4. Only one coil 3 is referenced in this figure, but what is stated for this coil is applicable to the other coils. The coils 3, 3a, 3b, at figures 1 et 2 are arranged side by side, leaving a spacing of 15 between two adjacent coils, and together defining internal and external circumferences in the stator 1. Referring more specifically to figures 1 à 3 The stator 1 includes a system for cooling the coils 3, 3a, 3b using oil as the heat transfer fluid. This cooling system includes an oil inlet manifold 8 and an oil outlet manifold 9.

[0060] The inlet manifold 8 has inlet ports 10 to supply oil to the coils 3, 3a, 3b and the outlet manifold 9 has outlet ports 11 to return the oil, only one inlet port 10 and only one outlet port 11 being referenced to the figure 3 With particular reference to figures 2 And 3taken always in combination with the other figures, each coil 3, 3a, 3b is associated with at least one inlet port 10, that is to say there can be one inlet port 10 for a coil 3, 3a, 3b but also several inlet ports 10 for the same coil.

[0061] To the figure 2 , each inlet orifice 10 is placed in the middle part of a coil head 3, 3a, 3b which is the widest base of a coil 3, 3a, 3b, but this is not mandatory.

[0062] In this case, the oil flow exiting an inlet orifice 10 circulates mainly in the gap 15 between its associated coil 3 and each of the two coils 3a, 3b adjacent to the associated coil 3, as illustrated by the arrows in the figure 2 .

[0063] In this case, each flow from a main flow from an inlet orifice 10 which has split into two mixes with a flow from an adjacent coil 3a, 3b which also results from the splitting of a main flow from an inlet orifice 10 associated with the adjacent coil 3a, 3b.

[0064] It follows that the oil flow from each inlet orifice 10 splits into two flows, one for each gap 15 separating a coil 3 from adjacent coils 3a, 3b. Both sides of each coil 3, 3a, 3b, each bordering a gap 15 with an adjacent coil, are thus cooled simultaneously.

[0065] By layering the figures 1 And 3 , one of the collectors, at the figure 3 the output collector 9, goes around the inner circumference while the other collector, at the figure 3 the inlet collector 8, goes around the outer circumference.

[0066] An oil flow, indicated by arrows, exits each inlet port 10 and then circulates primarily within the gap 15 between its associated coil 3 and at least one of the two coils 3a, 3b adjacent to the associated coil 3. This oil flow is then collected in the outlet manifold 9 and exits through one of the outlet ports 11.

[0067] It is possible, however, that there may only be one output port for all coils, but this is not preferred.

[0068] There may be a different number of output ports 11 and input ports 10. For example, although it is preferable, it is possible not to associate an output port 11 with each coil.

[0069] In the non-limiting case of several inlet ports 10 per coil 3, 3a, 3b, one of these inlet ports 10 may be closed under certain operating conditions of the stator 1 for which accelerated cooling is not required.

[0070] The opening of such an inlet orifice 10, advantageously equipped with a valve, can be done by increasing the oil pressure in the inlet manifold 8. This allows the cooling to be regulated as closely as possible to the actual operating conditions of the stator 1 and the heating of the coils 3, 3a, 3b.

[0071] As illustrated in the figure 2 , when the oil flow from each inlet orifice 10 splits into two flows with one flow for each spacing 15, to obtain uniform cooling on both sides of the coil 3, 3a, 3b, it is advantageous that both sides are traversed by the same flow.

[0072] Therefore, the inlet port 10 associated with a coil 3, 3a, 3b can be located at an equal distance from the two spacings 15 between the associated coil 3 and each of the two adjacent coils 3a, 3b, the two flows having the same flow rate.

[0073] Preferably but not exclusively, at least one output port 11 is associated with each coil 3, 3a, 3b, the input ports 10 and output ports 11 being paired in equal numbers, particularly in the case where each coil 3, 3a, 3b is associated with only one input port 10 and one output port 11.

[0074] Without limitation, there may be 18 coils 3, 3a, 3b placed circumferentially on the stator 1 with 18 inlet ports 10 and 18 outlet ports 11.

[0075] Thus, the oil arrives directly from the inlet manifold 8 on each coil 3, 3a, 3b and leaves the magnetic circuit as quickly as possible once it has cooled its associated coil 3 to be recovered in the outlet manifold 9.

[0076] By referring in particular to the figure 2 , coils 3, 3a, 3b may have a trapezoidal cross-section with a small base and a large base, the small base being shown rounded to this figure 2 .

[0077] Alternatively, although not shown in the figures, the coils may have a triangular section with a base opposite a vertex corresponding to a small base reduced substantially to a point.

[0078] In both cases, the large bases of the trapezoidal section coils 3, 3a, 3b or the bases of the triangular section coils can delimit the previously mentioned external circumference.

[0079] The small bases of the trapezoidal section coils 3, 3a, 3b or the vertices of the triangular section coils can then delimit the internal circumference.

[0080] As can be seen by superimposing the figures 1 And 3 When brought to the same scale, the inlet ports 10 can be positioned vertically along the outer circumference and the outlet ports 11 can be positioned vertically along the inner circumference.

[0081] The inlet 8 and outlet 9 collectors can be circular, having a diameter corresponding respectively to the external circumference and the internal circumference delimited by the coils 3, 3a, 3b.

[0082] Thus, in the case of an inlet manifold 8 extending outside an outlet manifold 9, the large bases of the trapezoidal coils 3, 3a, 3b, or the bases of the triangular coils, are cooled first by oil directly from the outlet of the inlet manifold 8, without having yet exchanged heat with the coil in question or any other coil. Since the manifolds must carry sufficient oil for all the coils 3, 3a, 3b, and since the oil flow rates may vary, the inlet manifold 8 and outlet manifold 9 can each be in the form of a channel with an oil inlet or outlet, respectively.

[0083] A ratio can be established between, on the one hand, the cross-section of the channel forming the inlet manifold 8 and, on the other hand, the cross-section of an inlet orifice 10 in order to obtain an optimal and uniform cooling / temperature ratio for all the coils. This ratio depends on the type of motor, for example, its size, geometry, number of teeth, and coil type.

[0084] In the preferred embodiment, the coils 3, 3a, 3b can be concentric, each being supported by a respective tooth 4, as is noticeably visible in the figure 2 , the tooth of the central coil 3 being referenced.

[0085] To control the temperature in the stator 1 advantageously at several different locations near the coils 3, 3a, 3b, the stator 1 may include at least one temperature probe 16.

[0086] By referring in particular to figures 2 à 4 The oil is injected through an inlet nozzle 6 into the inlet manifold 8, advantageously axisymmetric, which supplies all the inlet ports 10 for the magnetic circuit cavity comprising the coils 3, 3a, 3b, advantageously each supported by a tooth. The oil rises to a sealed wall 5, separating the stator 1 from a rotor not shown in these three figures, and passes between the coils 3, 3a, 3b to reach the outlet ports 11, advantageously numbered the same as the number of teeth and the number of inlet ports 10, and is discharged through the outlet manifold 11 and then through the outlet nozzle 7.

[0087] Reference 14 indicates the outer plate intended to be opposed to a rotor, not shown in these figures but referenced as 17 in the figure 5 and references 12 and 13 respectively indicate the cavities under the coil heads opposite the oil inlet manifold 8 and under the coil feet opposite the oil outlet manifold 9.

[0088] By referring in particular to the figure 3 showing stator 1 and at the figure 5 showing a rotor 17, the invention also relates to an electromagnetic motor or generator.

[0089] The motor or generator comprises a casing 1a surrounding at least one rotor 17 and at least one stator 1. The stator(s) 1 are as described previously incorporating a cooling system.

[0090] The crankcase 1a is traversed by the oil inlet nozzle 6 and the oil outlet nozzle 7 connected respectively to the inlet manifold 8 or the outlet manifold 9 and a sealed wall 5, visible in particular at the figure 4 , separates said at least one stator 1 from said at least one rotor 17.

[0091] As can be seen at the figure 5 , the rotor or each rotor 17 may have a plurality of magnet poles 19, only one of which is referenced to the figure 5 .

[0092] The rotor(s) 17 may be made of composite material to reduce iron losses. Each magnet pole 19 may consist of a plurality of individual magnets 18 bonded together with glue or resin, with or without the interposition of a mesh to receive the individual magnets 18.

[0093] To the figure 5 only one unit magnet is referenced 18 and only one magnet pole is referenced 19 but what is stated respectively for the unit magnet 18 and the magnet pole 19 is valid for all unit magnets and magnet poles.

[0094] Furthermore, to reinforce the strength of the magnet pole 19, each magnet pole 19 can be individually encased in a layer of composite.

[0095] With regard to the figures, what has been described previously is essentially an axial flux motor, but the present invention can be applied to any type of motor, in particular a radial flux or mixed flux motor or generator.

Claims

1. Stator (1) of an electric motor equipped with coils (3, 3a, 3b) and comprising a system for cooling the coils (3, 3a, 3b) by oil as heat-transfer fluid, the coils (3, 3a, 3b) being arranged one beside the other so as to leave a spacing (15) between two adjacent coils (3a, 3b) and together delimiting an inner circumference and an outer circumference in the stator (1), the cooling system comprising an oil inlet manifold (8) and an oil outlet manifold (9), one of the manifolds running around the inner circumference while the other manifold runs around the outer circumference, an oil flow leaving the inlet manifold (8) circulating predominantly in the spacings (15) between an associated coil (3) and at least one of the two coils (3a, b) adjacent to the associated coil (3) and then leaving via the outlet manifold (9), characterized in that the inlet manifold (8) is pierced with inlet orifices (10) for delivering oil onto the coils (3, 3a, 3b) and the outlet manifold (9) is pierced with outlet orifices (11) for collecting the oil, each coil (3, 3a, 3b) being associated with at least one inlet orifice (10), the oil flow issuing from an inlet orifice (10) circulating predominantly in the spacings (15) between its associated coil (3) and each of the two coils (3a, 3b) adjacent to the associated coil (3) and then leaving via one of the outlet orifices (11), the oil flow of each inlet orifice (10) dividing into two streams, with one stream for each spacing (15).

2. Stator (1) according to the preceding claim, in which said at least one inlet orifice (10) associated with a coil (3, 3a, 3b) is located at an equal distance from the two spacings (15) between the associated coil (3) and each of the two adjacent coils (3a, 3b), the two streams having a same flow rate.

3. Stator (1) according to either of the two preceding claims, in which at least one outlet orifice (11) is associated with each coil (3, 3a, 3b), the inlet orifices (10) and the outlet orifices (11) being paired by being equal in number.

4. Stator (1) according to any one of the preceding claims, in which the coils (3, 3a, 3b) have a trapezoidal cross-section with a small base and a large base, or a triangular cross-section with a base opposite an apex, the large bases of the coils (3, 3a, 3b) of trapezoidal cross-section or the bases of the coils (3, 3a, 3b) of triangular cross-section delimiting the outer circumference, and the small bases of the coils (3, 3a, 3b) of trapezoidal cross-section or the apices of the coils (3, 3a, 3b) of triangular cross-section delimiting the inner circumference.

5. Stator (1) according to any one of the preceding claims, in which the inlet orifices (10) are positioned vertically in line with the outer circumference and the outlet orifices (11) are positioned vertically in line with the inner circumference.

6. Stator (1) according to the preceding claim, in which the inlet manifold (8) and the outlet manifold (9) are circular, having a diameter corresponding respectively to the outer circumference and to the inner circumference.

7. Stator (1) according to either of the two preceding claims, in which the inlet manifold (8) and the outlet manifold (9) are each in the form of a channel comprising respectively an oil inlet or an oil outlet.

8. Stator (1) according to any one of the preceding claims, which comprises at least one temperature probe (16).

9. Stator (1) according to any one of the preceding claims, in which the coils (3, 3a, 3b) are concentric, each being supported by a respective tooth (4).

10. Electromagnetic motor or generator comprising a casing (1a) surrounding at least one rotor (17) and at least one stator (1), characterized in that said at least one stator (1) is according to any one of the preceding claims, the casing (1a) being passed through by an oil inlet nozzle (6) and an oil outlet nozzle (7) connected respectively to the inlet manifold (8) or to the outlet manifold (9), and a sealed wall (5) separating said at least one stator (1) from said at least one rotor (17).

11. Motor or generator according to the preceding claim, in which said at least one rotor (17) comprises a plurality of magnet poles (19), said at least one rotor (17) being made of composite.

12. Motor or generator according to either of the two preceding claims, in which each magnet pole (19) consists of a plurality of unitary magnets (18) secured to one another by glue, resin or composite, with or without the interposition of a mesh receiving the unitary magnets (18).

13. Motor or generator according to the preceding claim, in which each magnet pole (19) is individually coated in a layer of composite.