Stator for an electric machine

Abstract

The invention relates to a stator (1) for an electric machine (2), in particular for an electric machine (2) within a drivetrain (3) of a motor vehicle (4), the stator comprising a stator body (5) having a multiplicity of circumferentially distributed stator teeth (6) and having stator slots (7) formed between the stator teeth (6) and extending through the stator body (5) in the axial direction, wherein electrical conductors (8) of a stator winding that can be supplied with current and is in the form of a wave winding (9) are located in the stator slots (7) and emerge from an end face of the stator body (5) to form at least one winding head (10), wherein at least one of the electrical conductors (8), preferably a plurality of the electrical conductors (8), most preferably all the electrical conductors (8), is / are segmented, wherein the respective conductor segments (11, 12) extend in the wave winding (9) in parallel to each other through a respective stator slot (7) and are arranged next to each other in the circumferential direction in the stator slot (7).

Description

[0001] Stator for an electrical machine

[0002] The present invention relates to a stator for an electrical machine, in particular for an electrical machine within a drive train of a motor vehicle, comprising a stator body with a plurality of stator teeth arranged in a circumferentially distributed manner and stator slots formed between the stator teeth and extending in the axial direction through the stator body, wherein electrical conductors of a stator winding designed as a wave winding which can be energized are arranged in the stator slots and emerge from the front side of the stator body at least to form a winding head.

[0003] Electric motors are increasingly being used to power motor vehicles, creating alternatives to combustion engines that require fossil fuels. Considerable efforts have already been made to improve the everyday suitability of electric drives and also to provide users with the same level of driving comfort they are accustomed to.

[0004] A detailed description of an electric drive can be found in an article in the magazine ATZ, Volume 63, May 2020, pages 360-365, by Erik Schneider, Frank Fickl, Bernd Cebulski, and Jens Liebold, entitled: "Highly Integrative and Flexible Electric Drive Unit for E-Vehicles." This article describes a drive unit for one axle of a vehicle. This drive unit comprises an electric motor arranged concentrically and coaxially with a bevel gear differential. In the power train between the electric motor and the bevel gear differential, a switchable 2-speed planetary gear set is arranged, which is also positioned coaxially with the electric motor or the bevel gear differential or spur gear differential. The drive unit is very compact and, thanks to the switchable 2-speed planetary gear set, allows a good compromise between gradeability, acceleration, and energy consumption. Such drive units are also referred to as e-axles.

[0005] In addition to purely electric drivetrains, hybrid drivetrains are also known. Such drivetrains in hybrid vehicles typically comprise a combination of an internal combustion engine and an electric motor, enabling purely electric operation—for example, in urban areas—while maintaining sufficient range and availability, especially for long-distance journeys. Furthermore, in certain operating situations, it is possible to use both the internal combustion engine and the electric motor simultaneously.

[0006] For the development of electrical machines, in particular electrical machines for the above-mentioned hybrid or fully electric motor vehicles or also for wheel hub drives, basically different winding technologies for a stator of an electrical machine are known.

[0007] Electrical machines with a hollow-cylindrical stator, i.e., internal rotor machines, and configured for use as traction drives in motor vehicles often have a stator winding with a rectangular cross-section to achieve high power density. In electrical machines intended for motor vehicle propulsion, the stator windings are therefore typically designed as wave windings.

[0008] The structure of a stator with a wave winding is a stator design in which winding mats are used to form the phase-specific windings. To form the distributed windings, the individual winding wires or partial mats are braided together, for example using a winding or layering process, and inserted into the stator slots. The wave winding has several, usually three phases, with at least two separate wires or windings usually provided for each phase. Each winding is formed by a first and a second winding mat. In a preferred embodiment, one winding mat carries the current clockwise and the other winding mat carries the current counterclockwise. The first winding mat runs from an axially extending phase input pin, for example counterclockwise, to an axially extending interconnection pin or has these pins.Via the interconnection pin, it is interconnected by means of an interconnection element to a likewise axially extending interconnection pin of the second winding mat, which then runs clockwise to an axially extending phase output pin. This means that each phase-specific winding is formed by two series-connected winding mats and thus by separate windings, which are interconnected via an interconnection element. With three phases and two or one separate winding(s) per phase, six or three windings are provided. The phase output pins, in turn, are connected to one another via a common star interconnection element. The number of windings or wires corresponds to at least the number of phases or is a multiple thereof.

[0009] There is a continuing need to design the stators of such electrical machines in a particularly compact manner while simultaneously achieving a high power density due to the typically limited installation space in motor vehicles.

[0010] This object is achieved by a stator for an electrical machine, in particular for an electrical machine within a drive train of a motor vehicle, comprising a stator body with a plurality of stator teeth arranged in a circumferentially distributed manner and stator slots formed between the stator teeth and extending in the axial direction through the stator body, wherein electrical conductors of a stator winding designed as a wave winding which can be energized are arranged in the stator slots and which emerge from the front side of the stator body at least to form a winding head, wherein and at least one of the electrical conductors, preferably a plurality of the electrical conductors, most preferably all of the electrical conductors, is / are formed in segments, wherein the respective conductor segments in the wave winding extend parallel to one another through a respective stator slot and are arranged next to one another in the circumferential direction in the stator slot.

[0011] This provides the advantage that the stator can realize a winding head with a particularly compact axial dimension thanks to tighter bending radii. This also allows for a reduction in the DC resistance of the electrical conductors due to the correspondingly short conductor length in the winding head. Dividing an electrical conductor into parallel conductor segments also allows for optimized AC resistance behavior of a phase. Processing the conductor segments of an electrical conductor together also does not increase the number of geometries required for the wave winding.

[0012] A further degree of freedom is that, depending on the wiring of the conductors and the appropriate design of the insulation layer between the conductors, a parallel circuit with a minimal insulation layer between the conductors or, in the case of a series circuit, a thicker insulation layer can be provided, whereby the number of turns is scaled as a result.

[0013] First, the individual elements of the claimed subject matter of the invention are explained in the order in which they appear in the set of claims, and subsequently particularly preferred embodiments of the subject matter of the invention are described.

[0014] The stator according to the invention is intended for use in an electrical machine. The electrical machine serves to convert electrical energy into mechanical energy and / or vice versa, and it generally comprises the stationary part referred to as the stator, stand, or armature, and a part referred to as the rotor or runner, which is arranged so as to be movable, in particular rotatable, relative to the stationary part. In particular, the electrical machine is dimensioned such that vehicle speeds greater than 50 km / h, preferably greater than 80 km / h, and in particular greater than 100 km / h, can be achieved. The electric motor particularly preferably has an output greater than 30 kW, preferably greater than 50 kW, and in particular greater than 70 kW. It is further preferred that the electrical machine provides speeds greater than 5,000 rpm, particularly preferably greater than 10,000 rpm, and most particularly preferably greater than 12,500 rpm.

[0015] The stator can, in particular, be powered by power electronics. The power electronics are preferably a combination of various components that control or regulate a current to the stator, preferably including the peripheral components required for this purpose, such as cooling elements or power supplies. In particular, the power electronics contains one or more power electronic components that are designed to control or regulate a current. These are particularly preferably one or more power switches, e.g.

[0016] Power transistors. Particularly preferably, the power electronics comprises more than two, particularly preferably three, separate phases or current paths, each with at least one separate power electronics component.

[0017] The power electronics are preferably designed to control or regulate a power per phase with a peak power, preferably continuous power, of at least 10 W, preferably at least 100 W, particularly preferably at least 1000 W. The power electronics are preferably connected to the stator winding of the stator via an HV terminal (HV = high voltage).

[0018] For the purposes of this application, motor vehicles are defined as land vehicles that are propelled by mechanical power without being tied to railway tracks. A motor vehicle can, for example, be selected from the group of passenger cars (PCs), trucks (HGVs), mopeds, light motor vehicles, motorcycles, buses (KOMs), or tractors.

[0019] The stator according to the invention can preferably be configured for a radial flux machine. The stator of a radial flux machine is usually cylindrical or cylindrically ring-shaped and generally consists of a stator body formed by electrically insulated, layered, and stacked laminations in laminated cores. This structure minimizes the eddy currents in the stator caused by the stator field. Distributed around the circumference, stator slots are recessed into the electrical core, running parallel to the rotor shaft, and accommodate the stator winding or parts of the stator winding. Depending on the design, the slots can be closed with closure elements, such as closure wedges, covers, or the like, to prevent the stator winding from becoming detached.

[0020] The stator body is preferably formed as a single piece. A single-piece stator body is characterized by the fact that the entire stator body is formed as a single piece across its circumference. The stator body is typically formed from a plurality of stacked laminated electrical sheets, each of which is formed into a closed circular ring. The individual sheets can be held together in the stator body, for example, by gluing, welding, or screwing.

[0021] The stator teeth of the stator are preferably formed in the stator body. Stator teeth are components of the stator body that are designed as circumferentially spaced, tooth-like parts of the stator body that are directed radially inward (inner rotor) or radially outward (outer rotor). Between their free ends and a rotor body, an air gap is formed for the magnetic field and for the rotational movement of the rotor. The air gap is the non-magnetic gap existing between the rotor and the stator. In a radial flux machine, for example, this is an essentially circular gap with a radial width that corresponds to the distance between the rotor body and the stator body.

[0022] A stator winding is embedded in the stator slots of the stator according to the invention. A stator winding comprises electrically conductive conductors whose length is significantly greater than their diameter. The stator winding can, in principle, have any cross-sectional shape. Rectangular cross-sectional shapes are preferred, as these allow high packing and, consequently, power densities to be achieved. A stator winding is most preferably made of copper. According to the invention, the stator winding is designed as a continuous wave winding.

[0023] Advantageous embodiments of the invention are specified in the dependent claims. The features listed individually in the dependent claims can be combined with one another in a technologically expedient manner and can define further embodiments of the invention. Furthermore, the features specified in the claims are further specified and explained in the description, where further preferred embodiments of the invention are presented.

[0024] According to an advantageous embodiment of the invention, it can be provided that the at least one segmented electrical conductor, preferably the majority of the segmented electrical conductors, most preferably all segmented electrical conductors are bent by approximately 180° in the region of the winding head and in this case have a V-shaped contour, wherein the electrical conductor is twisted or folded over at the tip of the V-shaped contour. The wires are folded over next to one another in the circumferential direction, which results in installation space advantages compared to a winding head geometry that realizes upright bending without folding over. A layer change from one conductor end to the other is also possible without separate shaping by embossing in the radial direction, as is necessary with conventional axial hairpin conductors or layered wave winding.The combination of the segmented conductor with a winding head geometry that includes a turn in the winding head also enables more compact bending radii by bending around the wire height instead of the wire width, which is based on the slot width, and thus also creates a shorter winding head height.

[0025] According to a further preferred development of the invention, it can also be provided that the conductor segments have a substantially identical conductor cross-section. This can, on the one hand, result in correspondingly cost-effective production of the wave winding due to increased uniformity of parts. The use of conductor segments with a similar cross-section also ensures that the current flows evenly over the entire length of the wave winding. This minimizes unwanted voltage drops and ensures efficient transmission of electrical energy. Uniform current distribution also reduces Joule heat loss caused by the electrical resistance of the conductor. Uniform current distribution also leads to uniform temperature distribution along the wave winding, so that excessive heating at certain points on the wave winding can be avoided.Due to the conductor segmentation in the circumferential direction of the stator slot, equal slot transverse fields are present, which, in contrast to segmentation in the radial direction, does not generate any additional circulating currents and thus no losses.

[0026] Furthermore, according to a similarly advantageous embodiment of the invention, the conductor segments can have a substantially rectangular conductor cross-section. Rectangular conductor cross-sections enable better utilization of the available space within the stator slots compared to other shapes, such as round conductors. Furthermore, rectangular conductor segments also offer better heat dissipation than round conductors, since the larger surface area enables better heat dissipation to the surrounding environment. A further advantage of rectangular conductor segments is the ease of manufacturing and mounting the winding in the stator slots.

[0027] According to another particularly preferred embodiment of the invention, the edge radii of the conductor segments between the conductor segments can be smaller than the remaining edge radii of the conductor segments. This can achieve, in particular, the effect of minimizing the necessary reduction in the total copper area of ​​the parallel partial conductors compared to a solid conductor.

[0028] Furthermore, the invention can also be further developed in such a way that the wire insulation is designed so that it only insulates in the edge regions from other phases or windings of the same phases. The advantage of this design is again that the necessary reduction in the total copper area of ​​the parallel partial conductors is minimized compared to a solid conductor.

[0029] In a likewise preferred embodiment of the invention, it can also be provided that the wire insulation has a layer thickness between the conductor segments that is smaller than the layer thickness of the wire insulation surrounding the electrical conductor. This can achieve electrical insulation between the parallel partial conductors, with a separate design enabling the maximization of the copper surfaces while taking into account the voltage distribution in the conductors.

[0030] In a likewise preferred embodiment of the invention, it can also be provided that there is no insulation between the conductor segments, and insulation is only present on the outer dimensions of the conductor segments that are not in contact with each other. This makes it possible, in particular, to create insulation between adjacent windings of the same or different phases. This ensures that sliding between the wires is achieved during processing, but the final contour does not have a reduced copper surface.

[0031] In a particularly preferred embodiment of the invention, the conductor segments have contours on their surfaces in contact with each other, which are designed so that the conductors support each other in their radial position or maintain their relative position during simultaneous processing. An advantage of such contours can also be a mirrored structure of identical cross-sectional geometries by exploiting the symmetry, thereby simplifying processing.

[0032] According to a further embodiment of the invention, the conductor segments have a ramp-shaped contour on their contacting surfaces, so that they slide along each other in the circumferential direction when a radial force is applied. This allows a larger contour in the circumferential direction than the conductor width permitted for assembly by the slot width to be achieved, and the space in the slot can be better utilized. This configuration can be advantageous for the fill factor, particularly for applications with stator geometries where the slots are significantly wider than the slot width, or with conical slot geometries.

[0033] It may also be advantageous to further develop the invention such that the stator body has a number of stator slots that is less than or equal to 48. The advantage that can be realized in this way is that suitable aspect ratios of the conductor are permitted, which simplify segmentation into conductor segments or in which the aforementioned advantages outweigh the disadvantages.

[0034] The object of the invention can further be achieved by an electric machine comprising a stator according to one of claims 1-8, wherein a rotor is rotatably mounted relative to the cylindrical stator. Finally, the object of the invention can also be achieved by an electrically operable drive train of a motor vehicle comprising an electric machine according to claim 9.

[0035] The invention will be explained in more detail below with reference to figures without limiting the general inventive concept.

[0036] It shows:

[0037] Figure 1 shows an electrical machine in a cross-sectional view,

[0038] Figure 2 shows an electrical machine in a schematic

[0039] Axial section view,

[0040] Figure 3 shows a stator slot with segmented electrical conductors in a cross-sectional view,

[0041] Figure 4 shows a segmented electrical conductor in a cross-sectional view,

[0042] Figure 5 shows an electrical conductor in the area of ​​a winding head,

[0043] Figure 6 shows a motor vehicle with an electric drive train in a schematic representation,

[0044] Figure 7 shows a stator slot with segmented electrical conductors in a cross-sectional view,

[0045] Figure 8 shows a stator slot with segmented electrical conductors in a cross-sectional view. Figures 1-2 show a stator 1 for an electrical machine 2, in particular for an electrical machine 2 within a drive train 3 of a motor vehicle 4, as also sketched in Figure 6. The electrical machine 2, configured as a radial flux machine, comprises a rotor 20 as stator 1, which is rotatably mounted relative to the cylindrical stator 1.

[0046] The stator 1 comprises a stator body 5 with a plurality of stator teeth 6 arranged distributed around the circumference and stator slots 7 formed between the stator teeth 6 and extending in the axial direction through the stator body 5. The stator body 5 has a number of stator slots 7 which is less than or equal to 48. Electrical conductors 8 of a stator winding designed as a wave winding 9 are arranged in the stator slots 7 and emerge from the front side of the stator body 5 to form at least one winding head 10.

[0047] The electrical conductors 8 are segmented, with the respective conductor segments 11, 12 in the wave winding 9 extending parallel to one another through a respective stator slot 7 and being arranged circumferentially adjacent to one another in the stator slot 7, as can be clearly seen in Figure 3. The conductor segments 11, 12 are electrically insulated from one another by wire insulation 13. The conductor segments 11, 12 have a substantially identical, substantially rectangular conductor cross-section.

[0048] Figure 4 shows that the edge radii 18 of the conductor segments 11, 12 between the conductor segments 11, 12 are smaller than the remaining edge radii 19 of the conductor segments 11, 12. Furthermore, the wire insulation 13 is designed such that it only insulates in the edge regions from other phases or windings of the same phases. The wire insulation 13 has a layer thickness 16 between the conductor segments 11, 12 that is smaller than the layer thickness 17 of the wire insulation 13 surrounding the electrical conductor s.

[0049] From Figure 5 it can also be seen that the segmented electrical conductors 8 are bent by approximately 180° in the region of the winding head 10 and in doing so form a V-shaped contour 14, wherein the electrical conductor 8 is twisted at the tip 15 of the V-shaped contour 14. Figures 7 and 8 show further embodiments of the conductor segments 11, 12 in which there is no wire insulation 13 between the conductor segments 11, 12, but rather a wire insulation 13 is present only on the outer dimensions of the conductor segments 11, 12 that are not in contact with one another.

[0050] Figure 8 shows a variant in which the conductor segments 11, 12 have contours 21, 22 on their surfaces in contact with each other, which are designed such that the conductors 8 support each other in their radial position. For this purpose, the contours have an S-shaped profile.

[0051] It would also be conceivable for the conductor segments 11, 12 to have a ramp-shaped contour 21, 22 on their surfaces in contact with one another, so that they slide along one another in the circumferential direction when a radial force is applied, as can be seen in Figure 8. As a result, the conductor segments 11, 12 can be offset from one another in the radial direction, whereby the circumferential extent of the corresponding electrical conductor 8 is reduced, which can be clearly seen from Figure 8. This allows the conductor segments 11, 12 thus radially offset to be guided through a narrowed slot opening of a stator slot 7 and, after insertion in the stator slot 7, to be extended again in the circumferential direction.

[0052] The invention is not limited to the embodiments illustrated in the figures. The above description is therefore not to be considered restrictive, but rather explanatory. The following claims are to be understood as meaning that a stated feature is present in at least one embodiment of the invention. This does not exclude the presence of further features. Where the claims and the above description define 'first' and 'second' features, this designation serves to distinguish between two similar features without establishing a priority. List of reference symbols

[0053] 1 stator

[0054] 2 electric machine

[0055] 3 Drivetrain

[0056] 4 Motor vehicle

[0057] 5 Stator body

[0058] 6 stator teeth

[0059] 7 stator slots

[0060] 8 conductors

[0061] 9 Wave winding

[0062] 10 winding head

[0063] 11 conductor segment

[0064] 12 conductor segments

[0065] 13 Wire insulation

[0066] 14 Contour

[0067] 15 lace

[0068] 16 layer thickness

[0069] 17 Layer thickness

[0070] 18 Edge radius

[0071] 19 Edge radius

[0072] 20 rotors

[0073] 21 Contour

[0074] 22 Contour

Claims

Claims 1. Stator (1) for an electrical machine (2), in particular for an electrical machine (2) within a drive train (3) of a motor vehicle (4), comprising a stator body (5) with a plurality of stator teeth (6) arranged in a circumferentially distributed manner and stator slots (7) formed between the stator teeth (6) and extending in the axial direction through the stator body (5), wherein electrical conductors (8) of a stator winding designed as a wave winding (9) which can be supplied with current are arranged in the stator slots (7), which emerge from the end face of the stator body (5) at least to form a winding head (10), characterized in that at least one of the electrical conductors (8), preferably a plurality of the electrical conductors (8), most preferably all of the electrical conductors (8), is / are formed in a segmented manner, wherein the respective conductor segments (11,12) in the wave winding (9) extend parallel to each other through a respective stator slot (7) and are arranged circumferentially next to each other in the stator slot (7).

2. Stator (1) according to claim 1, characterized in that the at least one segmented electrical conductor (8), preferably the majority of the segmented electrical conductors (8), most preferably all segmented electrical conductors (8) are bent by approximately 180° in the region of the winding head (10) and in this case have a V-shaped contour (14), wherein the electrical conductor (8) is twisted at the tip (15) of the V-shaped contour (14).

3. Stator (1) according to claim 1 or 2, characterized in that the conductor segments (11, 12) have a substantially identical conductor cross-section.

4. Stator (1) according to one of the preceding claims, characterized in that the conductor segments (11, 12) have a substantially rectangular conductor cross-section.

5. Stator (1) according to claim 4, characterized in that the edge radii (18) of the conductor segments (11, 12) between the conductor segments (11, 12) are smaller than the remaining edge radii (19) of the conductor segments (11, 12) 6. Stator (1) according to one of the preceding claims, characterized in that the wire insulation (13) is designed so that it insulates only in the edge regions to other phases or windings of the same phases.

7. Stator (1) according to one of the preceding claims, characterized in that the wire insulation (13) has a layer thickness (16) between the conductor segments (11, 12) which is smaller than the layer thickness (17) of the wire insulation (13) enclosing the electrical conductor (8).

8. Stator (1) according to one of the preceding claims, characterized in that there is no wire insulation (13) between the conductor segments (11, 12) and a wire insulation (13) is only present on the outer dimensions of the conductor segments (11, 12) which are not in contact with one another.

9. Stator (1) according to one of the preceding claims, characterized in that the conductor segments (11, 12) have contours (21, 22) on their surfaces in contact with one another, which are designed such that the conductors (8) support one another in their radial position 10. Stator (1) according to one of the preceding claims, characterized in that the conductor segments (11, 12) have a ramp-shaped contour (21, 22) on their surfaces in contact with one another, so that they slide along one another in the circumferential direction when a radial force is applied.

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