Stator for an electric machine, electric drive for a vehicle, and vehicle

Abstract

A stator (1) for an electric machine (101), comprising: a stator core (2) comprising a longitudinal axis (3), a first axial face side (4) and a second axial face side (5) opposite the first face side (4), the stator core (2) providing a housing space (6) for a rotor (102) of the electric machine (101); -a plurality of hairpin-type conductors (9, 10) having a first type of legs (12, 15) and a second type of legs (15), said hairpin-type conductors (9, 10) being connected to each other to form a stator winding.

Description

Technical Field

[0001] The present invention relates to a stator for an electric motor, the stator comprising: a stator core comprising a longitudinal axis, an axial first side and an axial second side opposite to the first side, the stator core providing a housing space for a rotor of the electric motor; a plurality of hairpin conductors having a first type of leg and a second type of leg, the hairpin conductors being connected to each other to form a stator winding; and slots formed in the stator core and radially divided into an inner layer closest to the housing space and another layer further away from the housing space than the inner layer; wherein two first type legs extend in the inner layer; one second type leg extends in each other layer, and in a cross section perpendicular to the longitudinal axis, the radial extent of each first type leg is smaller than the radial extent of each second type leg.

[0002] Furthermore, the invention relates to an electric machine, an electric drive for a vehicle and a vehicle. Background Art

[0003] WO 2021 / 074563 A1 discloses a stator assembly for an electric motor, the stator assembly comprising a stator body, a plurality of slots formed in the stator body, and a phase winding comprising a plurality of hairpin windings electrically connected together. Each slot comprises a radial slot position, each radial slot position having an arm of a hairpin winding located therein. The arms at the first radial slot position and the second radial slot position have a larger cross-sectional area than the arms at the third radial slot position and the fourth radial slot position, wherein an outer winding layer occupies the first radial slot position and the second radial slot position, and an inner winding layer occupies the third radial slot position and the fourth radial slot position.

[0004] In a stator having a stator winding formed of a hairpin conductor, higher AC copper losses occur in legs disposed near the accommodation space of the rotor compared to legs further from the accommodation space. Such AC copper losses increase the current density along the first type of legs, which disadvantageously results in a reduction in the performance and efficiency of the motor. Summary of the invention

[0005] The object of the invention is to provide a possibility to operate an electric machine having a stator winding formed by hairpin-type conductors with improved performance and efficiency.

[0006] According to the invention, this object is achieved by a stator as initially described, wherein the first type legs are electrically short-circuited on the first face side.

[0007] A stator for a motor according to the present invention includes a stator core. The stator core includes a longitudinal axis, an axial first face side and an axial second face side. The second face side is opposite to the first face side. The stator core provides a housing space for a rotor of the motor. The stator also includes a plurality of hairpin conductors. The hairpin conductors have a first type leg and a second type leg. The hairpin conductors are connected to each other so as to form a stator winding. The stator also includes a slot. The slot is formed in the stator core. The slot is radially divided into an inner layer and another layer. The inner layer is located closest to the housing space. The other layer is further away from the housing space than the inner layer. Two first type legs extend in the inner layer. One second type leg extends in each of the other layers. In a cross section perpendicular to the longitudinal axis, the radial range of each of the first type legs is smaller than the radial range of each of the second type legs. The first type legs are electrically short-circuited on the first surface side.

[0008] In a conventional stator with a single leg, which extends within the inner layer and has the same radial extent as the other legs in the slot, there will be an uneven current distribution in the leg extending within the inner layer due to the proximity effect, which leads to higher copper losses. This results in unbalanced heating of the legs in the slot. By providing two first type legs that are short-circuited on the first surface side and each have a smaller radial extent or thickness than the second type leg, the resistance of the two short-circuited first type legs can be increased compared to the above-mentioned single leg. The increase in resistance counteracts the proximity effect and allows a balanced distribution of the current density within the slot, which therefore avoids overheating within the inner layer. Advantageously, an electric machine with a stator according to the present invention can operate more efficiently and with higher performance.

[0009] Preferably, the stator core is formed by a plurality of axially stacked and / or mutually insulated metal sheets. Preferably, the accommodation space is circumferentially surrounded by the stator core so as to form an air gap between the rotor and the stator core. The terms "axial", "radial" and "circumferential" refer to the longitudinal axis of the stator core.

[0010] The stator may include further corresponding slots. The slots and further slots may be distributed in the stator core in a circumferential direction. In each further slot, two further first type legs may extend within an inner layer of a corresponding one of the further slots, and one second type leg may extend within each of the further layers. All statements about slots, first type legs and second type legs may apply similarly to further slots, further first type legs and further second type legs.

[0011] The stator winding can be configured to split the current at the second face side so that two local currents flow through the two first type legs and are guided together through the short circuit at the first face side. In a cross section, each leg can have two long sides and two short sides. The smaller radial range of each first type leg can be achieved by having a first type leg with a smaller short side than the other legs. Preferably, the two long sides are parallel and / or the two short sides are parallel. It is further possible that the long sides of the first type leg and the second type leg have the same length. Preferably, the layers of the slot or a corresponding one of the slots have the same radial range, or the inner layer can have a larger range. In addition, the total number of layers, which is the sum of the number of inner layers and the number of other layers, can be an even number, such as two or four or six or eight or ten or twelve.

[0012] The cross-sectional surface of the legs of the first type accommodated in the inner layer may be exactly the cross-sectional surface of the further legs accommodated in the further layers divided by the number of legs of the first type accommodated in the inner layer.

[0013] For any inner layer and the further layer, the total copper cross-sectional surface of any leg may always be the same. This means that, for example, in the case where there are two legs of the first type in the inner layer, their copper cross-sectional surface may be half the size of the copper cross-sectional surface of the legs in the further layer. In another example, when there are three first legs in the inner layer, then their copper cross-sectional surface may be one third the size of the copper cross-sectional surface of the legs in the further layer.

[0014] The cross-sectional surface of the inner layer may be greater than the cross-sectional surface of any additional layer.

[0015] With the stator according to the invention, the first type legs can be short-circuited by a welded connection of connecting portions of the hairpin conductors, each connecting portion extending out of the stator core at the first face side.

[0016] Preferably, the first type leg is formed by a first type hairpin conductor, each first type hairpin conductor having a first type leg and a connection portion on the second surface side, which is electrically and mechanically connected to the connection portion of another first type hairpin conductor of the first type hairpin conductor outside the stator core. The first type hairpin conductor can be considered as an I-pin. Preferably, each first type hairpin conductor is formed by a single bent metal rod. An I-pin can be defined as a metal rod extending on both sides of the stator and connected by a connection process. The connection process can be "welding", "brazing" or "clamping" or any other process that allows current to flow.

[0017] Advantageously, the pairs of second type legs are formed by second type hairpin conductors, each second type hairpin conductor having the pair of second type legs and a bend on the second surface side, each second type hairpin conductor being formed by a single bent metal rod. The second type hairpin conductors may be considered as U-pins.

[0018] With respect to the stator according to the invention, at least one further first type leg extends within the inner layer. In other words, the number of first type legs extending within the inner layer may be three or four or five or more than five. This allows an even higher increase in electrical resistance.

[0019] With regard to the stator according to the present invention, the slots may be further divided into a second inner layer located between the first inner layer and the further layer, and at least two first type legs may extend in the second inner layer. In other words, the number of inner layers may be two. Furthermore, the number of inner layers may be three or four or more than four. The number of first type legs extending in a corresponding one of the inner layers may decrease in a radial direction away from the accommodation space.

[0020] A first leg of a first type hairpin conductor may be connected outside the stator core to all other first legs of first type hairpin conductors housed in the same layer and simultaneously to another hairpin conductor of another layer and slot.

[0021] Preferably, the legs are electrically isolated from each other within the slot. Advantageously, the legs are covered with an insulating material so that they are electrically isolated from each other within the slot. The insulating material may form an enamel coating.

[0022] Preferably, the winding of the stator may include three or more phases. Each phase has an equal number of hairpin conductors, and each phase has a hairpin conductor with a first type of leg and a second type of leg connected in sequence. Each phase may have the same sequence of hairpin conductors, the hairpin conductor having a first type of leg and a second type of leg.

[0023] Two or more hairpin conductors having the first type of legs and accommodated in the same slot may be short-circuited by welding connection of the connection portion at the first face side of the stator and connected to each other at the second face side of the stator.

[0024] The connection portion may be connected to another hairpin conductor having a second type of leg.

[0025] The slot can receive an odd number of legs. This means that the total number of first type legs and second type legs can be an odd number.

[0026] Preferably, the accommodation space is arranged radially inward of the stator core.

[0027] The above objects are further solved by an electric machine comprising a rotor according to the invention and a stator, the rotor being rotatably mounted relative to the stator.

[0028] The electric machine may be a permanently excited or electrically excited synchronous machine. Alternatively, the electric machine may be an induction machine.

[0029] The above object is further solved by an electric drive for a vehicle, which comprises an electric machine according to the present invention, a power converter configured to supply a multi-phase voltage to a stator winding, and a housing accommodating the electric machine and the power converter.

[0030] The above object is further solved by a vehicle comprising an electric machine according to the invention or an electric drive according to the invention; wherein the electric machine is configured to drive the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Further advantages and details of the invention are disclosed in the following examples and schematic drawings, which show:

[0032] Figure 1 is a schematic diagram of a first embodiment of a stator according to the present invention;

[0033] Figure 2 is a schematic diagram of first-type and second-type hairpin conductors according to a first embodiment;

[0034] Figure 3 is a cross section of a slot according to the first embodiment;

[0035] Figure 4 is a longitudinal cross-section of a slot according to the first embodiment;

[0036] Figure 5 is a cross section of a slot of a second embodiment of a stator according to the present invention; and

[0037] Figure 6 is a schematic diagram of an embodiment of a vehicle, an electric drive and an electric machine according to the invention. DETAILED DESCRIPTION

[0038] Figure 1 1 is a schematic diagram of a first embodiment of a stator 1 .

[0039] The stator 1 comprises a stator core 2, which is exemplarily made of a plurality of axially stacked metal sheets electrically isolated from each other. The stator core 2 comprises a longitudinal axis 3, an axial first face side 4 and an axial second face side 5 opposite to the first face side 4. The stator core provides a housing space 6 for a rotor 102 of the electric machine 101 (see Figure 6 ). In the stator core 2, a plurality of slots 7, 8 are formed, which extend from the first face side 4 to the second face side 5 and are distributed in the circumferential direction. For simplicity, Figure 1 Only two slots 7 , 8 are depicted in FIG, but the stator 1 may have, for example, 36, 48, 54, 72 slots or more.

[0040] The stator also includes a plurality of hairpin conductors 9, 10 (see Figure 2 ), which forms the stator winding 11, the stator winding 11 is formed by Figure 1 The winding heads on the two face sides 4 and 5 are depicted.

[0041] Figure 2 is a schematic diagram of a first type hairpin conductor 9 and a second type hairpin conductor 10 according to the first embodiment.

[0042] The first type hairpin conductor 9 comprises a first type leg 12, a first connection 13 arranged at the first type leg 12 on the first face side 4 and a second connection 14 arranged at the first type leg 12 on the second face side 5. The first type hairpin conductor 9 may be considered an I-pin.

[0043] The second type hairpin conductor 10 comprises a pair of second type legs 15, 16 and a connecting portion 16 arranged at each second type leg 15 at the first face side 4. Furthermore, the second type hairpin conductor 10 comprises a bent portion 17 connecting the pair of second type legs 15 at the second face side 5. The second type hairpin conductor 10 may be considered as a U-pin.

[0044] The stator 1 comprises a plurality of first type hairpin conductors 9 and second type hairpin conductors 10 , wherein the connection portions 13 , 16 form a winding head at the first face side 4 , and the bend 17 and the second connection portion 14 form a winding head at the second face side 5 .

[0045] Figure 3 and Figure 4 A slot 7 according to a first embodiment is shown, wherein Figure 3 is the cross section, Figure 4 is a longitudinal section, wherein slot 7 represents all other slots of stator 1 , including slot 8 .

[0046] The slot 7 is radially divided into an inner layer 18 and three other layers 19a, 19b, 19c. The inner layer 18 is closer to the accommodation space 6, while the other layers 19a-c are farther away from the accommodation space 6 than the inner layer 18. The boundaries between adjacent layers 18, 19a-c are depicted by dotted lines. Exemplarily, each layer 18, 19a-c has the same radial extent. In another example, the layer 18 can have a larger extent than the layers 19a-c. Note that the number of layers is selected exemplarily, and the number of layers can be less than or greater than four, but is preferably an even number.

[0047] In the inner layer 18, two first type legs 12 extend. In each of the further layers 19a-c, one second type leg 15 extends. Figure 3 As can be seen in the drawing plane corresponding to a cross section perpendicular to the longitudinal axis 3, the radial extent of each first type leg 12 is smaller than the radial extent of each second type leg 15. In particular, each leg 12, 15 comprises two parallel long sides 20 and two parallel short sides 21, and the short sides 21 of the first type leg 12 are shorter than the short sides 21 of the second type leg 15. Exemplarily, the long sides 20 of all legs 12, 15 have the same length. In the present embodiment, the length of the short sides 21 of the first type leg 12 is half the length of the short sides 21 of the second type leg 15.

[0048] The sum of the lengths of the short sides 21 of the first type of legs is the length of the short sides 21 of the second type of legs 15 .

[0049] The first type legs 12 extending in the inner layer 18 of the slot 7 are electrically short-circuited at the first face side 4. In the present embodiment, the first type legs 12 are short-circuited by the soldered connection 22 of the first connection portion 13, which is Figure 4 In contrast, the connection 16 of the second type leg 15 is connected to the connection 13 , 16 of the other hairpin conductors 9 , 10 , the legs 12 , 15 of which extend in another slot than the slot 7 .

[0050] Furthermore, the legs 12 , 15 are electrically isolated from each other within the slot 7 by an enamel coating (not shown).

[0051] Figure 5 is a cross section of a slot 7 according to a second embodiment of the stator 1. The second embodiment corresponds to the first embodiment, wherein the differences are described hereinafter and identical or equivalent parts are denoted by the same reference numerals.

[0052] In the stator 1 according to the second embodiment, three first type legs 12 extend in the first inner layer 18. Therefore, the short sides 21 of the first type legs 12 in the first inner layer 18 are one third of the length of the short sides 21 of the second type legs 15. The sum of the lengths of the short sides 21 of the first type legs is the length of the short sides 21 of the second type legs 15.

[0053] Furthermore, in the second embodiment, four further layers 19a-d and a second inner layer 18a located between the first inner layer 18 and the further layers 19a-d are provided, so that the total number of layers 18, 18a, 19a-d is equal to six. Two of the first type legs 12a extend within the second inner layer 18a, so that the number of the first type legs 12, 12a decreases in the radial direction away from the accommodation space 6. Therefore, the short side 21 of the first type leg 12a within the second inner layer 18a is half the length of the short side 21 of the second type leg 15.

[0054] With regard to a further embodiment corresponding to the first embodiment, three second type legs 15 extend within the inner layer 18 in contrast to the first inner layer 18 of the second embodiment.

[0055] Regarding another embodiment corresponding to the second embodiment, a third inner layer is provided between the second inner layer 18 and the additional layers 19a-c, and two first-type legs extend in the third inner layer. The number of the first-type legs 12 in the first inner layer 18 may be four, and the number of the first-type legs 12a in the second inner layer 18 may be three. In addition, in this embodiment, the third inner layer replaces one of the additional layers 19a-d, or provides an additional additional layer so that the number of layers is an even number.

[0056] Figure 6 is a schematic diagram of an embodiment of a vehicle 100 , an electric machine 101 , and an electric drive 103 .

[0057] The vehicle 100 comprises an electric machine 101, for example a permanent or electrically excited synchronous motor or an induction motor. The electric machine comprises a stator 1 according to any of the above-described embodiments and a rotor 102. The rotor 102 is rotatably mounted in a receiving space 6 about a longitudinal axis 3 (see Figure 1 The electric drive 103 includes a motor 101 and a power converter 104 configured to supply a multi-phase voltage to a stator winding, and a housing (not shown) accommodating the motor 101 and the power converter 104 .

[0058] Furthermore, the vehicle 100 comprises wheels 105. The electric motor or the electric drive 103 is respectively configured to drive at least one of the wheels 105, for example indirectly via a gearbox (not shown) or directly, for example as a wheel hub motor. The vehicle 100 may also comprise an axle (not shown) coupled to the wheel 105, which is driven directly or indirectly by the electric motor 101.

[0059] The vehicle 100 is a battery electric vehicle (BEV), a vehicle powered via a fuel cell, or a hybrid vehicle, which also includes an internal combustion engine (not shown).

Claims

1. A stator (1) for an electric motor (101), comprising: - a stator core (2), comprising a longitudinal axis (3), a first axial side (4) and a second axial side (5) opposite to the first side (4), the stator core (2) providing a receiving space (6) for a rotor (102) of the electric machine (101); - a plurality of hairpin conductors (9, 12, 15) having a first type of leg (12) and a second type of leg (15) 10), the hairpin conductors (9, 10) are connected to each other to form a stator winding; and - slots (7) formed in the stator core (2) and radially divided into an inner layer (18) located closest to the accommodation space (6) and further layers (19a-d) located further away from the accommodation space (6) than the inner layer (18); in - two first type legs (12) extending inside the inner layer, - one second type leg (15) extends within each of the further layers (19a-d), and - in a cross section perpendicular to the longitudinal axis (3), the radial extent of each of the first type of legs (12) is smaller than the radial extent of each of the second type of legs (15); - It is characterized by The first type legs (12) are electrically short-circuited at the first face side (4).

2. The stator according to claim 1, wherein the first type legs (12) are short-circuited by welded connections (22) of the connecting parts (13) of the hairpin conductors (9), each connecting part (13) extending out of the stator core (2) at the first face side (4).

3. The stator according to claim 1 or 2, wherein The first type leg (12) is formed by the first type hairpin conductor (9), each of the first type hairpin conductors having the first type leg (12) and a connection portion (14) at the second surface side (5), the connection portion (14) being electrically and mechanically connected to the connection portion (14) of another one of the first type hairpin conductors (9) outside the stator core (2).

4. A stator according to any one of the preceding claims, wherein The paired second type legs (15) are formed by second type hairpin conductors (10), each second type hairpin conductor having the paired second type legs (15) and a bend (17) at the second face side (5), each second type hairpin conductor (10) being formed by a single bent metal rod.

5. The stator according to claim 4, wherein each second type leg (15) of each second type hairpin conductor (10) is connected to another second type leg (15) on the first surface side (4) outside the stator core (2) in an electrically conductive and mechanical manner.

6. A stator according to any one of the preceding claims, wherein At least one further first type leg (12) extends within the inner layer (18).

7. A stator according to any of the preceding claims, wherein the slots (7) are further divided into a second inner layer (18a) located between the first inner layer (18) and the further layer (19a-d), wherein at least two first type legs (12a) extend within the second inner layer (18a).

8. The stator according to claim 6 and 7, wherein The number of first type legs (12, 12a) extending within a respective one of the inner layers (18, 18a) decreases in a radial direction away from the accommodation space (6).

9. A stator according to any one of the preceding claims, wherein the legs (12, 12a, 15) are electrically isolated from each other within the slot (7).

10. The stator according to any one of the preceding claims, wherein the accommodation space (6) is arranged radially inside the stator core (2).

11. An electrical machine (101) comprising a rotor (102) and a stator (1) according to any one of the preceding claims, the rotor (102) being rotatably mounted relative to the stator (1).

12. An electric drive (103) for a vehicle (100), comprising an electric machine (101) according to claim 11, a power converter (104) configured to supply a multi-phase voltage to a stator winding, and a housing accommodating the electric machine (101) and the power converter (104).

13. A vehicle (100), comprising - an electric machine (101) according to claim 11 or - An electric drive (103) according to claim 12; The motor (101) is configured to drive the vehicle (100).

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