stator

Abstract

A stator (10) for an electric motor designed for purely electrically driving a motor vehicle is proposed, comprising a stator body (12) forming stator slots (14); a current-carrying stator winding (18) joined to and extending axially from the stator slots (14) for forming an electromagnetic rotating field; and an insulating paper (20) disposed in the stator slots (14) between the stator windings (18) and the stator body (12) for electrically insulating the stator windings (18) relative to the stator body (12), wherein the insulating paper (20) extends from the stator slots (14) and has an additional layer (26) on its surface for providing a higher leakage current strength than the surface of the insulating paper (20) without the additional layer (26). By achieving a higher leakage current strength with the additional layer (26), the axial extension dimensions of the insulating paper (20) and the stator (10) can be reduced, thereby realizing a space-saving and safe electric motor.

Description

Technical Field

[0001] The present invention relates to a stator by means of which can be assembled into an electric motor for electrically driving a motor vehicle. Background Technology

[0002] A stator slot for an electric motor is known from DE 10 2017 214 195 A1, the stator slot being lined with insulating paper to electrically insulate the windings introduced into the stator slot, wherein the insulating paper extends from the stator slot in an axial direction.

[0003] There is always a need to reduce the structural space of electric machinery without compromising electrical safety. Summary of the Invention

[0004] The purpose of this invention is to demonstrate measures that can achieve a space-saving and safe electric motor.

[0005] According to the present invention, this objective is achieved by the stator of the present invention. Preferred designs of the present invention are given in the preferred embodiments and in the following description, which may constitute an aspect of the present invention, either individually or in combination.

[0006] An aspect of the invention relates to a stator for an electric motor for electrically driving a motor vehicle, the stator having: a stator body forming stator slots; current-carrying stator windings engaged in and extending axially from the respective stator slots for forming an electromagnetic rotating field; and insulating paper disposed in the stator slots between the stator windings and the stator body, the insulating paper for electrically insulating the stator windings relative to the stator body, wherein the insulating paper extends from the stator slots, and wherein an additional layer is disposed on the surface of the insulating paper for providing a higher leakage current strength than the surface of the insulating paper without the additional layer.

[0007] In particular, the stator body designed as a lamination assembly can have radially extending, preferably rib-shaped teeth, with corresponding stator slots formed between these teeth. If the stator is configured for an electric machine designed as an inner rotor, these teeth extend radially inward, while the stator slots can be radially open inward. If the stator is configured for an electric machine designed as an outer rotor, these teeth extend radially outward, while the stator slots can be radially open outward. The stator winding, composed of electrical conductors (especially enameled wire), can be axially guided through the corresponding stator slots, wherein the stator winding can be axially guided out of the corresponding stator slots on one or both axial sides. Under the anticipated electrical boundary conditions, the dielectric strength provided by the insulating paper disposed in the stator slots is sufficient to prevent voltage breakdown between the stator winding and the stator body.

[0008] In electric motors designed for purely electrically driven vehicles, the insulating paper typically protrudes slightly axially from the corresponding stator slots along with the stator windings. This necessitates considering not only the dielectric strength of the insulating paper but also its axial extension outside the stator slots to prevent leakage current. It has been recognized that, particularly in the case of purely electrically driven vehicles, the significantly higher power density leads to higher currents and / or voltages in the electric motor, potentially making the design of the axial extension of the insulating paper outside the stator slots a decisive factor in the axial structural space design. With this additional layer, the resistance to leakage current on the surface of the insulating paper formed by this additional layer can be significantly higher than that of the insulating paper surface without the additional layer in that area. This additional layer improves the material properties of the insulating paper in terms of leakage current resistance, thereby correspondingly reducing the axial extension of the insulating paper outside the stator slots and / or increasing the safety against leakage current within the same dimensions. Similarly, reducing the axial extension of the slot paper reduces the axial structural space requirements of the stator and the material usage required for the stator windings. This can reduce production costs. By adding an additional layer that provides higher leakage current strength, the axial extension dimensions of the insulating paper and stator can be reduced, thereby enabling space-saving and reliable electric motors.

[0009] In particular, due to this additional layer, the insulation paper has a higher leakage current intensity outside the stator slot than inside the stator slot. In principle, the additional layer can be provided along the entire axial extension of the insulation paper, both on the outer side facing the stator body and on the inner side facing the stator windings, so that the additional layer forms most or even the entire surface of the insulation paper. However, it has been recognized that the critical path for potential leakage current lies in the transition region between the windings, the insulation paper, and the stator laminations. Therefore, leakage current preferably travels from the area of ​​the winding not surrounded by the insulation paper, through the surface of the insulation paper, to the stator end. Thus, it is sufficient for the insulation paper to have only the increased leakage current intensity achieved by the additional layer outside the stator slot. The material used for the additional layer and the structural space requirements of the insulation paper inside the stator slot can be kept to a minimum.

[0010] In one embodiment, the additional layer is disposed only on the outside of the stator slot. Thus, the additional layer is applied only to the portion of the insulating paper's axial extension outside the stator slot. This minimizes the material used for the additional layer and the structural space requirements of the insulating paper within the stator slot.

[0011] It can be proposed that the additional layer be disposed only on the outer side of the insulating paper away from the stator winding, or only on the outer side of the insulating paper away from the stator winding and on the end side away from the stator body. Thus, the additional layer is generally disposed only in those areas of the insulating paper where leakage current is most likely to occur.

[0012] In particular, according to IEC 60112, when using solution A, the additional layer belongs to at least insulation group IIIa or insulation group II. In the case of this insulation group, sufficiently high leakage current strength is provided for the stator of an electric motor used in a purely electrically driven trolley. It is also possible, according to IEC 60112, when using solution A, for the additional layer to belong to insulation group I, where such high leakage current strength may not be necessary from a cost perspective. In the IEC 60112 standard, leakage current strength is assessed using the CTI value determined by the droplet method. Here, in a specific electrode arrangement between two platinum electrodes with angled edges as defined in the standard, a predetermined number of droplets of a predetermined liquid (“solution A”) corresponding to a predetermined droplet size are applied to the workpiece under test between the electrodes over a predetermined time period. The CTI value for leakage path formation (based on which the workpiece is classified into insulation group) is a determined value of the highest test voltage (in volts) that the workpiece can withstand under specific conditions without forming a leakage path.

[0013] Preferably, when using solution A according to IEC 60112, the additional layer has a CTI value ≥ 175, especially 175 ≤ CTI ≤ 800 and preferably 400 ≤ CTI < 600. With the leakage current strength defined by this CTI value, a sufficiently high leakage current strength is provided for the stator of an electric motor machine intended for use in a purely electrically driven sports car.

[0014] Particularly preferably, according to IEC 60112, when using solution A, the surface of the insulating paper without the additional layer belongs to insulating material group II or insulating material group IIIa. The insulating paper, different from the additional layer, can be selected based on its dielectric strength rather than its leakage current strength. In this regard, for cost reasons, a correspondingly lower leakage current strength can be provided to the surface of the insulating paper not formed by the additional layer.

[0015] In particular, the additional layer is made of plastics, especially PE, PTFE, and PBT, and / or of resins, especially epoxy resins and polyester resins. Thus, sufficient leakage current strength of the additional layer can be obtained using relatively cost-effective materials.

[0016] Preferably, the insulating paper is abutted against and / or bonded to the stator winding. This prevents the insulating paper from detaching, tearing, and / or folding from the stator winding, which could potentially adversely affect the provided leakage current strength.

[0017] Preferably, the insulating paper is pressed firmly onto the stator body. This allows the volume inside the stator slots to be filled, as much as possible, by the stator windings.

[0018] In particular, the additional layer is applied as a coating onto the insulating paper. As a result, the material usage and production costs for the additional layer can be kept low. Attached Figure Description

[0019] The invention will now be explained by way of example with reference to the accompanying drawings and preferred embodiments, wherein the features shown below, whether individually or in combination, can form an aspect of the invention. In the drawings:

[0020] Figure 1 : A schematic cross-sectional view of a portion of the stator is shown. Detailed Implementation

[0021] exist Figure 1The stator 10 shown in the middle section can be used as an electric motor in a purely electrically driven sports car. The stator 10 has a stator body 12 composed of laminations, which has stator slots 14 open in both the radial and axial directions. Stator windings 18 with multiple electrical conductors 16 are inserted into these slots. The stator windings 18 extend axially from their respective slots 14 and are guided from there to another slot 14. To prevent electrical breakdown between the stator windings 18 and the stator body 12, insulating paper 20 with sufficiently high dielectric strength is provided between the stator windings 18 and the stator body 12.

[0022] The insulating paper 20 extends from the stator slot 14 in the axial direction, particularly in contact with the stator winding 18. The insulating paper 20 has an additional layer 26 on its outer side 22 facing the stator body 12 and, if necessary, on its axial end side 24 facing away from the stator body 12. This additional layer has a significantly higher leakage current strength than the rest of the insulating paper 20. Due to the high leakage current strength of the additional layer 26, the leakage path from the surface of the stator winding 18 facing the insulating paper 20, through the axial end side 24 and the outer side 22 of the additional layer 26, to the end face of the stator body 12 can be shortened. This reduces the axial extension dimension of the portion of the insulating paper 20 located outside the stator slot 14 and thus reduces the axial structural space requirements of the stator 10 without compromising electrical safety.

Claims

1. A stator for an electric motor machine configured to electrically drive a motor vehicle, the stator having: The stator body (12) forms the stator slot (14); A stator winding (18) that is engaged with and extends axially from the corresponding stator slot (14) and through which current can flow, the stator winding being used to form an electromagnetic rotating field; and An insulating paper (20) is disposed in the stator slot (14) between the stator winding (18) and the stator body (12). The insulating paper is used to electrically insulate the stator winding (18) relative to the stator body (12), wherein the insulating paper (20) extends from the stator slot (14). Its features are, The insulating paper (20) has an additional layer (26) on its surface, which provides a higher leakage current strength than the surface of the insulating paper (20) without the additional layer (26), wherein, The additional layer (26) is disposed only outside the stator slot (14) and in a manner that leaves no gap with the stator slot, thereby reducing the axial extension dimension of the portion of the insulating paper (20) disposed outside the stator slot (14), wherein, The additional layer (26) is only provided on the outer side (22) of the insulating paper (20) away from the stator winding (18) and on the end side (24) away from the stator body (12).

2. The stator according to claim 1, characterized in that, Due to the additional layer (26), the insulation paper (20) has a higher leakage current intensity outside the stator slot (14) than it has inside the stator slot (14).

3. The stator according to claim 1 or 2, characterized in that, According to IEC 60112, when using solution A, the additional layer (26) belongs to at least insulation group IIIa or insulation group II.

4. The stator according to claim 1 or 2, characterized in that, According to IEC 60112, when using solution A, the additional layer (26) has a CTI value ≥ 175.

5. The stator according to claim 1 or 2, characterized in that, According to IEC 60112, when using solution A, the surface of the insulating paper (20) without the additional layer (26) belongs to insulating material group II or insulating material group IIIa.

6. The stator according to claim 1 or 2, characterized in that, The additional layer (26) is made of plastic and / or resin.

7. The stator according to claim 1 or 2, characterized in that, The insulating paper (20) is abutted against and / or bonded to the stator winding (18).

8. The stator according to claim 1 or 2, characterized in that, The insulating paper (20) is pressed tightly onto the stator body.

9. The stator according to claim 4, characterized in that, According to IEC 60112, when using solution A, the additional layer (26) has a CTI value of 175 ≤ CTI ≤ 800.

10. The stator according to claim 4, characterized in that, According to IEC 60112, when using solution A, the additional layer (26) has a CTI value of 400 ≤ CTI < 600.

11. The stator according to claim 6, characterized in that, The plastic is PE and / or PTFE and / or PBT.

12. The stator according to claim 6, characterized in that, The resin is an epoxy resin and / or a polyester resin.

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