Direct cooling of electric motors

Abstract

A direct-cooled electric motor (9) for a traction drive of an electric vehicle configured to be cooled by a refrigerant, the electric motor (9) comprising: a housing (1) containing a stator core (2) having laminated steel plates; a rotor (3) arranged to rotate radially inside the stator core (2); a winding (7) extending axially through the stator core (2) and beyond an axial end (8) of the stator core (2); and at least one end fiber (6), the end fiber (6) extending circumferentially and radially on the axial end (8) of the stator core (2) and comprising a plurality of winding openings (6c) arranged circumferentially around the end fiber (6), the winding (7) extending through the winding openings (6c).

Description

[Technical field]

[0001] SUMMARY OF THE PRESENT EMBODIMENT A primary object of the present invention is directed to a method and apparatus for improving the cooling performance of a directly cooled electric motor. [Background technology]

[0002] Directly cooled electric motors for traction drives of electric vehicles, with power in the range of a few kW to 1 MW, are configured so that at least parts of the windings, in particular in the region of the overhangs, are in direct contact with the coolant, as is well known from the prior art.

[0003] The solution according to JP 2001-103700 discloses a stator with a flange-type plastic coil holder (i.e. end fiber) that abuts against the surface of the stator body. The main purpose of the plastic flange in the case of hairpin windings is to support the conductor during the bending process aimed at forming the coils of the stator winding by bending the wire into a final shape for welding. In its basic form, the end fiber is a disk- or ring-shaped member whose outer shape basically corresponds to that of the stator lamination, in particular with regard to the size and number of slots into which the conductors of the winding are inserted. The manufacture of stators with hairpin windings, I-pin windings or continuous windings is well known in the prior art and will not be described in detail in the present application.

[0004] A disadvantage of the prior art solutions for directly cooled motors is the lack of a solution for controlling the behavior of the coolant flow during the operation of the motor, especially in the region of the air gap between the stator and rotor of the motor, where a significant amount of coolant enters the air gap, where drag forces are created by fluid friction and viscosity effects. Summary of the Invention [Problem to be solved by the invention]

[0005] Directly cooled motors offer superior cooling that can facilitate a high peak to continuous power ratio. However, because the thermal performance of direct cooling is dependent on the coolant level within the motor housing, it is not uncommon for the coolant level to exceed the air gap area between the stator and rotor during motor operation, especially for motors known as wet runners, where the outer surface of the rotor core is in direct contact with the coolant, forcing it to advance and splash into the endwinding area for the purpose of removing heat from the exposed copper wires.

[0006] For purposes of this application, the expression "direct cooling" refers to cooling where heat generated by the motor is removed by a cooling fluid in direct contact with at least a portion of the stator including the winding head, i.e., the individual wires of the winding head are in contact with the cooling fluid at the axial ends of the stator, although the individual wires may have an insulating coating.

[0007] The direct-cooled motor according to the present invention as set forth in claim 1 aims to improve the efficiency or manufacturability of a direct-cooled motor. [Means for solving the problem]

[0008] The proposed solution is to provide a direct-cooled electric motor for traction drives of electric vehicles, configured to be cooled by a cooling fluid, which may be a mixture of a dielectric fluid and air. The direct-cooled electric motor comprises a housing containing a stator core comprising laminated steel sheets, a rotor arranged to rotate radially inside the stator core around an axis of rotation, windings extending axially through the stator core and beyond both axial ends of the stator core, and at least one end fiber, whereby each end fiber extends circumferentially and radially, i.e. along the axial ends of the stator core. The end fibers are ring-like or each form a ring. The end fibers comprise a number of winding openings arranged circumferentially around the end fibers, whereby the windings extend through the winding openings and the inner diameter of the end fibers is smaller than the outer diameter of the rotor. The end fibers therefore extend radially beyond the rotor at their inner ends and radially overlap the rotor. Adjacent to their inner ends, the end fibers comprise contact areas in contact with the respective axial ends of the stator core. The contact areas may preferably be flat. The axial width of the end fibers in the contact areas may thus be smaller, in particular at most one fifth, preferably at most one tenth, than their radial extent. In contrast, the inner ends may extend axially beyond the flat contact areas of the end fibers.

[0009] The axial direction is parallel to the axis of rotation of the rotor, and the radial and circumferential directions are relative to the axis of rotation of the rotor.

[0010] The end fibers therefore have the additional function and advantage of preventing flow into the radial gap between the rotor and the stator. This is particularly advantageous in embodiments whereby a cooling chamber is provided adjacent to the end fibers and the coolant is forced under pressure to pass through the axial cooling channels in the stator core. Alternatively, if the motor is a motor immersed in coolant, the coolant level can be higher than the level of the radial gap between the stator core and the rotor, increasing the coolant's reach to the rotor and / or stator parts and increasing the overall efficiency of the motor, especially at high speeds, due to the reduction in drag losses caused by the rotor, since less coolant enters the gap between the rotor and the stator core from the axial end of the stator. The housing may have a shell and two bearing plates arranged at the axial ends of the shell, on or in which the rotor is rotatably mounted. One of the two bearing plates may be integral with the shell, so that the shell and the integral bearing plate form a recess axially closed by the other bearing plate. The stator core is disposed in the shell and axially spaced from both bearing plates, and the end fibers are disposed at one axial end of the stator core and spaced from an adjacent bearing plate such that the end fibers do not contact the adjacent bearing plate.

[0011] The end fibers are configured to support the wire or winding during the bending process in which the winding head is formed, whereby the support structure also provides at least one flow path for the flow of coolant to the stator core.

[0012] In a preferred embodiment, the axial clearance of the end fibers between the end fibers and the rotor is less than half the difference between the outer diameter of the rotor core and the inner diameter of the end fibers. The axial clearance may, for example, be in the range of 0.3 mm to 15 mm.

[0013] The end fibers may further comprise an air gap flow deflector proximate the air gap between the stator core and the rotor. The air gap flow deflector preferably converges on the inner diameter of the end fibers towards the rotor. The radial clearance of the end fibers between the radially inner ends of the end fibers and the rotor may be equal to or less than the axial clearance of the end fibers between the end fibers and the rotor, preferably in the range of 0.3 mm to 15 mm. The air gap flow deflector has at least one beveled or chamfered, in particular conical, surface. The at least one beveled or conical surface is preferably arranged to direct the flow of the coolant in a generally axial direction. Alternatively or additionally, at least one deflection surface may be provided to direct the coolant away from the rotating parts of the motor, the deflection angle β being in the range of 0° to 90°, more preferably in the range of 10° to 80°, whereby the deflection angle β is defined as the angle between the deflection surface and the radial direction.

[0014] The end fibers may form part of an air gap labyrinth seal located adjacent to the radial gap between the rotor and the stator, whereby the labyrinth seal rotational pair is provided by the rotor core, and the axial clearance of the end fibers and the radial clearance of the end fibers may specifically be in the range of 0.3 mm to 15 mm. By providing a labyrinth seal to seal the gap between the rotor and the stator, the intrusion of the refrigerant into the gap between the stator core and the rotor is more effectively prevented.

[0015] The end fibers may comprise at least one first recess forming a coolant flow passage between the end fibers and the stator core. The width of the coolant flow passage in the axial direction is preferably equal to or preferably smaller than the axial clearance between the end fibers and the rotor, and may in particular be in the range of 0.3 mm to 15 mm. The end fibers thus have the additional function of providing a path for the coolant.

[0016] Advantageously, the stator core may comprise at least two cooling channels extending axially through the stator core, whereby the recess forming the coolant flow path fluidly connects at least two of the at least two cooling channels with each other or at least one of the cooling channels with a coolant outlet or a coolant inlet of the motor. The at least two cooling channels may be fluidly connected in series so that the coolant can flow axially in opposite directions through the stator core, and thus the coolant flow path may fluidly connect the at least two cooling channels. The end fibers therefore have the additional function of conducting the coolant back through the stator.

[0017] In another embodiment, the end fibers further comprise a plurality of second recess grooves extending radially and connecting the coolant flow passages formed by the at least one first recess with cooling channels extending axially through the stator core at the radially inner portion of the stator core, i.e. in the region of the radially inner stator teeth of the yoke portion.

[0018] The end fibers may have at least one radially outer contact surface that contacts and preferably seals with the housing, and may thus function as a partition separating two coolant chambers that communicate with the housing.

[0019] The end fibers may be provided with a connection surface that mates with a contact surface of another component of the motor, specifically an end plate.

[0020] The end fibers may also have a non-bleeding end or an axially extending lip extending circumferentially around the end fibers or extending around the opening to limit the ingress of varnish into the cooling channels during the dripping process for the winding (i.e., when applying an electrically insulating coating over a localized area of ​​a weld or over the entire winding).

[0021] To provide a reference surface location during attachment to the stator core, the end fiber may include at least one locating pin protruding therefrom, preferably axially protruding, for locating the end fiber in a predetermined position relative to the stator core. The slot openings in the stator core may thus be easily aligned with the winding openings in the end fiber.

[0022] In an advantageous embodiment, the rotor comprises an impeller for inducing a flow of coolant past the windings and / or through at least one cooling channel in the stator, whereby the impeller comprises a plurality of blades and edges or grooves which cooperate with the end fibers to form a seal or, in the case of a labyrinth seal, form part of an air gap labyrinth seal.

[0023] The end fibres may advantageously be made from a plastic, preferably a thermosetting material.

[0024] The end fibres may be manufactured as separate elements produced by an injection moulding process, at least the body of said end fibres being preferably made from a PPS material, PPS standing for polyphenylene sulphide.

[0025] The end fibers may alternatively be manufactured by overmolding portions of the stator core, allowing for cost-effective manufacturing.

[0026] The coolant used is preferably a mixture of insulating oil and air. Therefore, no additional electrical insulation or insulation against corrosion of critical parts is required for the motor. The stator core, rotor, windings and end fibers are preferably all exposed to the coolant and are in direct contact with it.

[0027] Subsequently, with reference to the accompanying drawings, the principles of the present invention will be explained in more detail by means of descriptions of preferred and alternative embodiments. [Brief description of the drawings]

[0028] [Figure 1] FIG. 1 shows a cross-sectional view for a preferred embodiment of a directly cooled electric motor according to the present invention. [Diagram 2] FIG. 2 shows a detailed view of A shown in FIG. [Diagram 3] FIG. 3 shows an end fiber according to the invention in a rear view facing the stator core. [Figure 4] FIG. 4 shows the end fiber in cross section BB of FIG. [Diagram 5] FIG. 5 shows the end fibers in detail C in FIG. [Figure 6] FIG. 6 shows an isometric view of an end fiber according to the present invention. [Figure 7] FIG. 7 shows an isometric view of an end fiber according to the present invention, seen from the stator side. [Figure 8] FIG. 8 shows a detailed view of the motor without the housing. [Figure 9] FIG. 9 shows another embodiment of an end fiber according to the present invention. [Figure 10] FIG. 10 shows a detailed view of the embodiment of the end fiber in FIG. [Figure 11] FIG. 11 shows another exemplary embodiment of a directly cooled motor according to the invention in the region of the end fibers. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] With reference to the figure, the directly cooled electric motor 9 comprises a stator core 2 having hairpin windings 7, the solid wires being inserted into slot openings (not shown) in the stator core 2, which extend axially through the stator core 2. The stator core 2 is made from laminated steel sheets. For the purpose of mounting the wires of the windings 7 in the stator slots, the end fibers 6 are provided with a number of winding openings 6C, the number, size and location of which are adapted to and consistent with the configuration of the stator core 2 (i.e. the electromagnetic design of the stator).

[0030] Several types of hairpin techniques exist (i.e. hairpins with welds on one side, hairpin windings with welds on both sides of the stator 2, eye pin windings, wave windings, etc.) with well-known advantages and disadvantages. The windings 7 are not considered to be the subject of the present invention, so the type of windings will not be limited or more broadly described herein. In view of the objectives of the invention, it is important to understand that the main function of the end fibers 6 is to support the conductors of the windings 7 during the installation of the wires (i.e., the individual hairpins) into the slots of the stator core 2, and in particular during the process of bending the weld-side hairpins at the axial end 8 of the stator core 2, where the hairpins are bent into their final position within the winding end overhangs (i.e., winding heads) 7A (see FIG. 2) and the individual hairpins are positioned, connected, and welded according to the desired electromagnetic winding scheme.

[0031] From the viewpoint of the motor cooling system, the stator core 2 designed for direct cooling preferably comprises a number of hole-like cooling channels 2A in the stator core 2 (i.e. laminated sheets of magnetic steel), where the cooling channels 2A are provided in the area of ​​the stator slots between the wires and between the stator teeth and / or in the area of ​​the stator yoke. In an advantageous embodiment, the stator core 2 comprises a number of groove-like cooling channels 2A' on the outer surface of the stator core 2, where the channels required for the utilization of the coolant flow are provided by the cooperation of the stator core 2 and the housing 1 of the motor. As shown in FIG. 1, in an advantageous embodiment of the motor 9, the coolant is discharged from the shaft 4 and is driven through the serial cooling channels 2A, 2A' by the pumping power provided by the impeller 5 arranged on the rotor 3 of the motor 9, where the coolant is injected from one side of the stator core 2 to the other side of the stator core 2 through a system of cooling channels 2A, 2A' operably connected in a combination of parallel and serial connections. To utilize the coolant flow, the end fibers 6 are provided with a recess on the side facing the stator core 2, whereby the recess forms a coolant flow passage 6B together with the stator core 2, the width 6-CH of the coolant flow passage 6B in the axial direction being between 0.3 mm and 15 mm. In another embodiment shown in FIG. 7, the end fibers 6 further comprise an additional recessed groove 6E extending radially and connecting the coolant flow passage 6B with the cooling channel 2A extending axially through the stator core 2 at the radially inner part of the stator core 2, i.e. in the region of the radially inner stator teeth of the yoke part. It is important to note that in an alternative embodiment, the end fibers 6 are provided with one or more contact surfaces 6D (see FIG. 9) for the purpose of dividing the chamber 2-RC (see FIG. 2) on one end 8 of the stator core 2 into two or more chambers, whereby a return chamber and / or a collection chamber are provided by said part of the end fibers 6 in combination with other components of the electric motor 9.

[0032] In order to reduce the effect of viscous resistance of a fully waterproof cooling system for a directly cooled electric motor, the end fibers provide a non-contact flow barrier in the region of the inlet to the radial air gap 10 between the rotor and the stator core 2. This is particularly important in the range of high rotor rotational speeds (i.e., the peripheral speed of the outer surface of the rotor 3 exceeds 100 m / s). As mentioned above, the rotor 3 of the electric motor in an advantageous design comprises an impeller 5 for providing a pumping power for driving the coolant through the cooling system of the electric motor. In a preferred embodiment, the impeller comprises a plurality of backward inclined blades with tangential outlet openings. However, in order to reduce the amount of oil entering the air gap region between the stator core 2 and the rotor 3, the end fibers 6 in an advantageous embodiment comprise an air gap flow deflector 6A, where the inner diameter of the air gap flow deflector 6A is substantially smaller than the outer diameter of the rotor 3 in the region of the radial air gap 10. Thus, the end fibres 6 radially overlap, at their respective axial ends, the rotor 3 which overlaps said radial air gap 10 .

[0033] Therefore, the inner diameter of the air gap flow deflector 6A is matched with the inner diameter Di of the end fibers 6 and is smaller than the outer diameter Do of the impeller 5 on the rotor core 3. Thus, the axial clearance 6-AC (see FIG. 2) between the portion of the end fibers 6 and the axially adjacent portion of the rotor 3 and the radial clearance 6-RC between the portion of the end fibers 6 and the radially adjacent portion of the rotor 3 are provided for the purpose of avoiding friction between the rotating part and the fixed part of the motor, where the axial clearance 6-AC of the end fibers and the radial clearance 6-RC of the end fibers are in the range of 0.3 mm to 15 mm.

[0034] In another embodiment shown in Fig. 11, the air gap flow deflector 6A is modified in the form of an air gap labyrinth seal 6A', where the labyrinth seal's rotational pair is provided by a rotating groove 5A forming part of the impeller 5 or a balancing ring for the rotor core 3, and the axial clearances 6-AC, 6AC' of the end fibers and the radial clearances 6-RC, 6RC' of the end fibers are maintained in all areas between the rotating and stationary parts of the motor. Nevertheless, if the end fibers 6 comprise an air gap flow deflector 6A or an air gap labyrinth seal 6A', the inclination of the intended deflection surface, i.e. the deflection angle β, is in the range of 0°-90°, preferably in the range of 10°-80°, and more preferably in the range of 30°-60°, in these cases the flow deflector 6A comprises a conical or frustoconical surface. The deflection angle β is defined as the angle between the deflection surface and the radial direction, as shown in Fig. 5. In other words, the deflection angle β is measured in an axial plane in which the axis of rotation R of the rotor 3 extends, between the deflection plane and a radial plane extending perpendicular to the axis of rotation R of the rotor 3 .

[0035] 8 shows a detailed view of the motor 9 without the housing, where only one set of wires in a single slot is shown for clarity of illustration. It will be understood that cooling grooves 2A' are provided in the outer surface of the stator core 2 to provide channels for coolant flow on the outside of the stator core 2 in combination with the housing 1 of the motor 9.

[0036] Also shown in FIG. 8 are the shaft 4, the impeller 5 with a number of blade groups 5B, the end fibers 6 with part of the function of an air gap flow deflector 6A, the winding opening 6C, the contact surface 6D, the non-outflow end 6F, the windings 7, and the winding head overhang 7A.

[0037] In an advantageous embodiment, the end fibers 6 are separate elements manufactured by injection molding and made of plastic, preferably polyphenylene sulfide. To provide a reference position during installation on the stator core 2, the end fibers 6 are provided with at least one positioning pin 6G (see FIG. 9), protruding from the end fibers, preferably protruding axially, for positioning the end fibers 6 in a predetermined position relative to the stator core 2. Thus, the slot openings of the stator core 2 can be easily aligned with the winding openings 6C in the end fibers 6. In some embodiments, at least the main features of the end fibers 6, in particular the air gap flow barrier 6A, are manufactured by overmolding the stator with a thermosetting material. Similarly, the windings 7 of the electric motor are coated with a PEEK insulation, where PEEK stands for polyetheretherketone. However, if necessary, the wires of the windings 7 are coated with an additional electrical insulation layer (i.e. varnish), in which case various techniques can be used. If a dripping process is used in which the varnish is poured onto the winding end 7A, the end fibers 6 may be provided with a non-outflowing end or axially extending edge 6F (see Figures 9 and 10) that extends at least partially in the circumferential direction around the cooling channels 2A or around the end fibers 6, in order to prevent some cooling channels 2A from being clogged by the applied substance. Nevertheless, in modern motors it may be considered to not use dripping, but to use only the dipping and spinning processes, if necessary. In this case, only a part of the winding head overhang 7 is immersed in the substance to be applied in order to fix the wire in the area of ​​the winding end overhang 7A. Now, if a suitable insulation, for example polyetheretherketone (PEEK) or a self-bonding wire, is used for the wires of the motor winding 7, even this dipping becomes unnecessary.

Claims

1. A direct-cooling electric motor (9) for a traction drive of an electric vehicle, configured to be cooled by a refrigerant, wherein the electric motor (9) comprises a housing (1) accommodating a stator core (2) having laminated steel sheets, a rotor (3) arranged to rotate radially inside the stator core (2), a winding (7) extending axially through the stator core (2) and extending axially beyond an axial end (8) of the stator core (2), and at least one ring-shaped end fiber (6), and is provided with the end fiber (6) being arranged at one of the respective axial ends (8) of the stator core (2), extending circumferentially and radially across the respective axial ends (8) of the stator core (2), and having a plurality of winding openings (6C) arranged circumferentially around the end fiber (6), the winding (7) extending through the winding openings (6C), the inner diameter (Di) of the end fiber (6) being smaller than the outer diameter (Do) of the rotor (3), a direct-cooling electric motor.

2. The direct-cooling electric motor (9) according to claim 1, characterized in that the end fiber (6) overlaps the rotor (3) radially at its radially inner end. The direct-cooling electric motor (9) according to claim 1.

3. The direct-cooling electric motor (9) according to claim 1, characterized in that the axial clearance (6-AC) of the end fiber between the end fiber (6) and the rotor (3) is smaller than half of the difference between the outer diameter (Do) of the rotor (3) and the inner diameter (Di) of the end fiber (6). The direct-cooling electric motor (9) according to claim 1.

4. The direct-cooling electric motor (9) according to claim 1, characterized in that the axial clearance (6-AC) of the end fiber between the end fiber (6) and the rotor (3) is in the range of 0.3 mm to 15 mm. The direct-cooling electric motor (9) according to claim 1.

5. The direct-cooling electric motor (9) according to claim 1, characterized in that the end fiber (6) further comprises an air-gap flow deflector (6A) having at least one inclined surface in the region of an air gap (10) between the stator core (2) and the rotor (3). The direct-cooling electric motor (9) according to claim 1.

6. The direct-cooling electric motor (9) according to claim 5, characterized in that the air-gap flow deflector (6A) approaches the inner diameter (Di) of the end fiber (6) towards the rotor (3). The direct-cooling electric motor (9) according to claim 5.

7. The radial clearance (6-RC) of the end fiber (6) between the radially inner end thereof and the rotor (3) is not greater than the axial clearance (6-AC) of the end fiber between the end fiber (6) and the rotor (3), characterized in that the direct cooling electric motor (9) according to claim 1. The direct cooling electric motor (9) according to claim 1.

8. The radial clearance (6-RC) of the end fiber between the radially inner end of the end fiber (6) and the rotor (3) is in the range of 0.3 mm to 15 mm, characterized in that the direct cooling electric motor (9) according to claim 1. The direct cooling electric motor (9) according to claim 1.

9. The end fiber (6) forms part of an air gap labyrinth seal (6A'), whereby the rotating pair of the labyrinth seal is provided by the rotor (3), characterized in that the direct cooling electric motor (9) according to claim 1. The direct cooling electric motor (9) according to claim 1.

10. The end fiber (6) comprises at least one sloped or chamfered deflection surface (6A) for deflecting the refrigerant away from the rotating part of the electric motor (9), In an axial plane including the rotation axis (R) of the rotor (3), the deflection angle (β) of the deflection surface (6A) between a plane extending perpendicular to the rotation axis (R) of the rotor (3) and the deflection surface (6A) is in the range of 0° to 90°, characterized in that the direct cooling electric motor (9) according to claim 1. The direct cooling electric motor (9) according to claim 1.

11. The deflection angle (β) of the deflection surface (6A) is in the range of 10° to 80°, characterized in that the direct cooling electric motor (9) according to claim 10. The direct cooling electric motor (9) according to claim 10.

12. The deflection angle (β) of the deflection surface (6A) is in the range of 30° to 60°, characterized in that the direct cooling electric motor (9) according to claim 10. The direct cooling electric motor (9) according to claim 10.

13. The end fiber (6) further comprises a recess for forming a refrigerant flow path (6B) between the end fiber (6) and the stator core (2), whereby the width (6-CH) of the refrigerant flow path (6B) in the axial direction is not greater than the axial clearance (6-AC) of the end fiber between the end fiber (6) and the rotor (3), characterized in that the direct cooling electric motor (9) according to claim 1. The direct cooling electric motor (9) according to claim 1.

14. The width (6-CH) of the refrigerant flow path (6B) in the axial direction is in the range of 0.3 mm to 15 mm, characterized in that The direct-cooling electric motor (9) according to claim 13.

15. The stator core (2) further comprises at least two cooling channels (2A, 2A') extending axially through the stator core (2), whereby the recess of the refrigerant flow path (6B) fluidly connects at least two of the at least two cooling channels (2A, 2A') to each other or fluidly connects at least one of the cooling channels (2A, 2A') to a refrigerant outlet or a refrigerant inlet of the electric motor (9). The direct-cooling electric motor (9) according to claim 13.

16. At least two of the cooling channels (2A, 2A') are fluidly connected in series so that the refrigerant can flow axially in opposite directions through the stator core (2), and the refrigerant flow path (6B) fluidly connects the at least two cooling channels (2A, 2A'). The direct-cooling electric motor (9) according to claim 15.

17. The end fiber (6) further comprises at least one radially outer contact surface (6D) that contacts the housing (1) and preferably seals with the housing (1). The direct-cooling electric motor (9) according to claim 1.

18. The rotor (3) is provided with an impeller (5) for inducing the flow of refrigerant through the winding (7) and / or through at least one cooling channel (2A, 2A') in the stator. Thereby, the impeller (5) comprises a plurality of blade groups (5B) and an edge or groove (5A), and the edge or groove forms part of an air-gap labyrinth seal (6A'). The direct-cooling electric motor (9) according to claim 1.

19. The end fiber (6) is made of plastic. The direct-cooling electric motor (9) according to claim 1.

20. The end fiber (6) is manufactured as an independent element by an injection molding process, and at least the body of the end fiber is made of a polyphenylene sulfide material. The direct-cooling electric motor (9) according to claim 1.

21. The end fiber (6) is manufactured as part of an overmolded structure of the stator core (2) made of a thermosetting material. The direct-cooling electric motor (9) according to claim 1.

22. The stator core (2), the rotor (3), the winding (7), and the end fiber (6) are exposed to the refrigerant and are in direct contact with the refrigerant. The direct-cooling electric motor (9) according to claim 1.

23. The refrigerant is a mixture of a dielectric fluid, particularly insulating oil, and air. The direct-cooling electric motor (9) according to claim 1.

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