Stator, electrical machine and method for manufacturing a stator

Abstract

Stator (1) for an electric machine (2), in particular within a drive train (3) of a motor vehicle (4), wherein the stator (1) is cylindrical and has a plurality of stator teeth (5) which, in the circumferential direction between adjacent stator teeth (5), each define a stator groove (6) extending radially and axially through the stator (1), into which an energizable hairpin winding (7) comprising a plurality of hairpin conductors (8) is inserted, wherein the hairpin conductors (8) have two conductor sections (9) extending parallel in axial direction and arranged in the stator grooves (6), which exit the stator (1) at an end face (14) of the stator (1) with two free conductor ends (10) each, forming a winding head (11), characterized in thatthat the free conductor ends (10) of the hairpin conductors (8) in the area of ​​the winding head (11) are twisted radially inwards for an inner rotor and radially outwards for an outer rotor, wherein the free conductor ends (10) are twisted radially offset layer by layer, and layers with different diameters and different inclined twist angles are electrically contacted.

Description

[0001] The present invention relates to a stator for an electric machine, particularly within a motor vehicle drivetrain, wherein the stator is cylindrical and ring-shaped and has a plurality of stator teeth which, in the circumferential direction, define a stator groove extending radially and axially through the stator between adjacent stator teeth, into which an energizable hairpin winding comprising a plurality of hairpin conductors is inserted, wherein, in the case of radial flux machines, the hairpin conductors have two axially parallel conductor sections arranged in the stator grooves, which exit the stator at an end face of the stator with two free conductor ends each, forming a winding head. The invention further relates to an electric machine and a method for manufacturing a stator.Such stators, electrical machines and methods for manufacturing stators with such hairpins are known, for example, from WO 2021 / 026576 A1 or DE 10 2019 130 535 A1.

[0002] Electric motors are increasingly being used in motor vehicles to provide alternatives to combustion engines that require fossil fuels. Considerable efforts have already been made to improve the everyday usability of electric drives and to offer users the familiar driving comfort.

[0003] A detailed description of an electric drive system can be found in an article in the journal ATZ, 63rd year, 05 / 2020, pages 360-365, by Erik Schneider, Frank Fickl, Bernd Cebulski, and Jens Liebold, entitled: "Highly Integrated and Flexible Electric Drive Unit for E-Vehicles." This article describes a drive unit for one axle of a vehicle, comprising an electric motor arranged concentrically and coaxially to a bevel gear differential. A switchable two-speed planetary gear set is located in the power train between the electric motor and the bevel gear differential, also positioned coaxially to the electric motor and the bevel or spur gear differential. The drive unit has a very compact design and, thanks to the switchable two-speed planetary gear set, allows for a good compromise between climbing ability, acceleration, and energy consumption. Such drive units are also referred to as e-axles.

[0004] In addition to purely electric powertrains, hybrid powertrains are also known. Such powertrains in hybrid vehicles typically comprise a combination of an internal combustion engine and an electric motor, enabling – for example, in urban areas – purely electric operation while simultaneously providing sufficient range and availability, especially on long-distance journeys. Furthermore, it is possible to use both the internal combustion engine and the electric motor simultaneously in certain operating situations.

[0005] For the development of electric machines, especially electric machines for the aforementioned hybrid or fully electric motor vehicles or for wheel hub drives, various winding technologies for a stator of an electric machine are known.

[0006] In electric machines with a hollow cylindrical stator, i.e., designed as internal rotor machines, and configured for use as a traction drive for a motor vehicle, the stator winding often has a rectangular cross-section to achieve high power density. Therefore, in electric machines intended for motor vehicle propulsion, the stator windings are typically designed as hairpin windings. In this process, essentially U-shaped wire segments are inserted into the stator slots from one end face of the stator and then formed at the opposite end face and joined, for example, by welding.

[0007] There is a continuing need to design such electric machines to be particularly compact while maintaining high power density, due to the typically limited installation space in motor vehicles.

[0008] It is therefore an object of the invention to provide a stator for an electric machine, particularly within a motor vehicle's drivetrain, which has a particularly compact design and high power density. It is further an object to realize a correspondingly compact electric machine. It is also an object of the invention to provide a method for manufacturing a compact stator.

[0009] This problem is solved by a stator for an electric machine, particularly within a motor vehicle's drivetrain, wherein the stator is cylindrical and has a plurality of stator teeth which, in the circumferential direction, define a stator groove extending radially and axially through the stator between adjacent stator teeth, into which a currentable hairpin winding comprising a plurality of hairpin conductors is inserted, wherein the hairpin conductors have two axially parallel conductor sections arranged in the stator grooves, which exit the stator at an end face of the stator with two free conductor ends each, forming a winding head, wherein the hairpin conductors are radially twisted inwards in the region of the winding head for an internal rotor. For an external rotor, the region of the winding head can be twisted outwards.In both variants, the winding head protruding from the stator is twisted in the direction of the rotor. The free conductor ends are twisted radially offset in each layer, and layers with different diameters and different twist angles are electrically contacted or joined by welding.

[0010] The object of the invention can also be achieved by a stator for an electric machine, in particular within a drive train of a motor vehicle, wherein the stator is cylindrical and ring-shaped and has a plurality of stator teeth which, in the circumferential direction between adjacent stator teeth, each define a stator groove extending radially and axially through the stator, into which an energizable I-pin winding comprising a plurality of I-pin conductors is inserted, wherein the I-pin conductors each have a conductor section arranged in the axial extension in the stator grooves, which exits the stator at an end face of the stator with a free conductor end, forming a winding head, wherein the I-pin conductors are angled radially inwards for an internal rotor and radially outwards for an external rotor.The free conductor ends are radially offset in layers, and layers with different diameters and different inclined twisting angles are electrically contacted or connected by welding.

[0011] This achieves the advantage that the stator, thanks to the radially inwardly angled winding head, can have a particularly compact axial design. The winding head shaped in this way utilizes the available space within the stator's inner diameter, thus reducing the required winding head height of the stator.

[0012] Furthermore, the straight conductor sections, which are radially angled inwards, can preferably be used to enable additional torque generation of the rotor in the axial flux direction. The magnet topology on the rotor can be adapted for this purpose. This will be explained in more detail later.

[0013] The axial dimension of the winding head is also independent of the actual coil width due to the chosen topology, which is why windings with a small number of pole pairs can also be implemented without requiring an axial increase of the winding head.

[0014] Furthermore, degrees of freedom in the winding pattern are enabled, independent of the axial installation space. For example, if the winding pattern requires an intersection of adjacent wires, this typically leads to a local axial increase through special pins or special winding angles. Radial outward winding allows for easier integration of cooling channels into the grooves at the tooth head, as the entire groove surface is typically covered by the winding head (fanning).

[0015] First, the individual elements of the claimed invention are explained in the order in which they are mentioned in the claim set, and subsequently, particularly preferred embodiments of the invention are described.

[0016] The stator according to the invention is intended for use in an electric machine. The electric machine serves to convert electrical energy into mechanical energy and / or vice versa, and it generally comprises a stationary part, referred to as the stator, armature, or rotor, and a part, referred to as the rotor or runner, which is arranged to be movable, in particular rotatable, relative to the stationary part. In particular, the electric machine is dimensioned such that vehicle speeds greater than 50 km / h, preferably greater than 80 km / h, and particularly greater than 100 km / h, can be achieved. The electric motor preferably has a power output greater than 30 kW, preferably greater than 50 kW, and particularly greater than 70 kW. It is further preferred that the electric machine provides rotational speeds greater than 5,000 rpm, particularly preferably greater than 10,000 rpm, and most preferably greater than 12,500 rpm.

[0017] The stator can be energized, in particular by power electronics. The power electronics are preferably a combination of various components that control or regulate a current at the stator, preferably including the necessary peripheral components such as cooling elements or power supplies. In particular, the power electronics contain one or more power electronic components configured to control or regulate a current. These are most preferably one or more power switches, e.g., power transistors. The power electronics particularly preferably have more than two, and most preferably three, separate phases or current paths, each with at least one dedicated power electronic component.

[0018] The power electronics are preferably designed to control or regulate a power output per phase with a peak power, preferably continuous power, of at least 10 W, preferably at least 100 W, and 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).

[0019] For the purposes of this application, motor vehicles are defined as land vehicles that are moved by mechanical power and are not bound to railway tracks. A motor vehicle may be selected, for example, from the groups of passenger cars, trucks, mopeds, light vehicles, motorcycles, buses, or tractors.

[0020] The stator according to the invention can preferably be configured for a radial flux machine. The stator of a radial flux machine is typically cylindrical or annular in shape and generally consists of a stator body formed by electrically insulated and layered electrical steel sheets stacked into laminated cores. This design minimizes the eddy currents in the stator caused by the stator field. Stator slots are milled into the electrical steel sheet around its circumference, running parallel to the rotor shaft, to accommodate the stator winding or parts thereof. Depending on the surface design, the slots can be closed with locking elements such as locking wedges or covers to prevent the stator winding from coming loose.

[0021] The stator body is preferably formed in one piece. A one-piece stator body is characterized by the fact that the entire stator body is formed as a single unit. The stator body is generally formed from a multitude of stacked laminated electrical steel sheets, each sheet being formed into a closed ring. The individual sheets can be held together in the stator body, for example, by bonding, welding, or bolting.

[0022] The stator body preferably incorporates the stator teeth. Stator teeth are defined as components of the stator body that are arranged as circumferentially spaced, tooth-like parts of the stator body, directed radially inwards (internal rotor) or radially outwards (external rotor), and between whose 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 essentially an annular gap with a radial width corresponding to the distance between the rotor body and the stator body.

[0023] 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 desired cross-sectional shape. Rectangular cross-sectional shapes are preferred because high packing densities and, consequently, high power densities can be achieved with them. A stator winding made of copper is particularly preferred. According to the invention, the stator winding is configured as a hairpin winding or an I-pin winding.

[0024] A hairpin winding belongs to the group of plug-in coil windings. It typically comprises a number of hairpin conductors, also referred to simply as hairpins, which are formed from U-shaped, preferably lacquered, flat copper wires and whose geometry resembles hairpins.

[0025] An I-pin winding also belongs to the group of plug-in coil windings. It typically comprises a plurality of I-pin conductors, which generally consist of straight flat copper wire elements inserted into the stator slots. Preferably, the I-pin conductors are encased in a current-insulating varnish layer.

[0026] Advantageous embodiments of the invention are specified in the dependent claims. The features listed individually in the dependent claims can be combined in a technologically meaningful manner and can define further embodiments of the invention. Furthermore, the features specified in the claims are specified and explained in more detail in the description, which also presents further preferred embodiments of the invention.

[0027] According to a further preferred embodiment of the invention, the free conductor ends can also be arranged to point radially towards the axis of rotation of a rotor rotatably mounted relative to the stator. This allows for a particularly economical connection of the free wire ends. The smaller radius also reduces the necessary distances for connecting adjacent coils or coil groups, resulting in lower electrical resistance of the connection elements.

[0028] Furthermore, according to another advantageous embodiment of the invention, the free conductor ends can be angled radially inwards by 85°–95° for an inner rotor and radially outwards for an outer rotor relative to the conductor sections arranged in the stator slots. This allows for a particularly high reduction in the installation space required for the wound stator and ensures that the free conductor ends are oriented with particularly low vibration. By varying the angle between the layers, different clearance and creepage distances between the layers can also be achieved without a corresponding increase in the axial installation space.

[0029] According to the invention, the free conductor ends are radially offset in each layer. This makes it possible, in particular, to achieve the effect that the annular layers with their different diameters can be electrically contacted in a particularly advantageous way from a manufacturing perspective. Furthermore, contacting at different inwardly inclined angles also allows for more installation space to be generated for welding fixtures.

[0030] Furthermore, the invention can also be further developed in such a way that the hairpin conductors protrude beyond the radially inner or outer surface of the cylindrical stator. The advantage of this embodiment is that it results in an axially compact structure of the wound stator.

[0031] In a further preferred embodiment of the invention, the rotor may also have a first magnetically active component arrangement at its end face facing the winding head, in particular selected from the group of permanent magnets and / or current-carrying magnetic coils. This allows the straight conductor portions, which are radially angled inwards, to generate additional torque in the axial flux direction of the rotor, which can lead to an improvement in the power density of the stator or the electric machine. The magnet topology on the rotor can be adapted accordingly. This means that the rotor has a first magnetically active component arrangement at at least one end face, namely the one facing the radially angled winding head of the stator, which differs from a second magnetically active component arrangement of the rotor.The first magnetically active component arrangement is optimized for the radially inwardly angled winding head.

[0032] The object of the invention can also be achieved by an electric machine comprising a stator according to any one of claims 1-7. According to a further preferred embodiment of the invention, the electric machine may have a first winding head on a first end face of the stator and a second winding head on a second end face of the stator, wherein the hairpin conductors or the I-pin conductors are angled radially inwards for an internal rotor and radially outwards for an external rotor, both in the region of the first winding head and in the region of the second winding head. This allows for further optimization of an axially compact design of the electric machine.

[0033] Finally, the problem of the invention can also be advantageously solved by a method for manufacturing a stator for an electrical machine, comprising the following steps: • Provision of a stator that is cylindrical in shape and has a plurality of stator teeth which, in the circumferential direction, define a stator groove extending radially and axially through the stator between adjacent stator teeth, • Provision of a plurality of hairpin ladders, each with two free ladder ends, • Inserting the hairpin conductors into the stator slots, so that the hairpin conductors have two axially parallel conductor sections arranged in the stator slots, which exit the stator at one end face of the stator with two free conductor ends each, forming a winding head, • Reshaping the hairpin conductors so that they are twisted radially inwards for an inner runner and radially outwards for an outer runner in the area of ​​the winding head, or • Provision of a stator that is cylindrical in shape and has a plurality of stator teeth which, in the circumferential direction, define a stator groove extending radially and axially through the stator between adjacent stator teeth, • Provision of multiple I-pin conductors, each with one free conductor end, • Inserting the I-pin conductors into the stator slots, so that the I-pin conductors each have a conductor section arranged in the stator slots in axial extension, which exit the stator at one end face of the stator with a free conductor end, forming a winding head. • Reshaping the I-pin conductors so that they are twisted radially inwards for an internal rotor and radially outwards for an external rotor in the area of ​​the winding head.

[0034] In hairpin or I-pin conductors, the free conductor ends are radially offset in layers, and layers with different diameters and different inclined twist angles are electrically contacted or joined by welding.

[0035] The winding head can also be twisted circumferentially to bridge a distance and achieve the desired coil width. This circumferential twisting can be performed before or after the radial twisting.

[0036] The rotor can then be inserted into the wound stator. Most preferably, after inserting the rotor, the second winding head is also twisted radially inwards.

[0037] The invention will now be explained in more detail with reference to figures, without limiting the general concept of the invention.

[0038] It shows: Fig. 1. An electric machine in a cross-sectional view, Fig. 2 a wound stator in a perspective axial section view, Fig. 3 A detailed view of a winding head cutout and a rotor in a top view Fig. 4 A detailed view of a winding head cutout in radially inward unrestricted and restricted states, each in a perspective view. Fig. 5 a motor vehicle with an electric powertrain in a schematic block diagram.

[0039] The Fig. Figure 1 shows a stator 1 for an electric machine 2 designed as an internal radial flux machine, in particular within a drive train 3 of a motor vehicle 4, as is also exemplified in the Fig. 5 is outlined.

[0040] The stator 1 is cylindrical and ring-shaped and has a plurality of stator teeth 5, which define a radially extending stator groove 6 between adjacent stator teeth 5. This groove extends axially through the stator 1, and a currentable hairpin winding 7, comprising a plurality of hairpin conductors 8, is inserted into this groove. The hairpin conductors 8 have two axially parallel conductor sections 9 arranged in the stator grooves 6. These conductor sections 9 exit the stator 1 at an end face 14 with two free conductor ends 10, forming a winding head 11. This is particularly evident from the Fig. 2 emerges. The hairpin ladders 8 are radially angled inwards in the area of ​​the winding head 11.

[0041] The Fig. Figure 2 shows an embodiment with a hairpin winding 7. It is understood that the hairpin winding 7 can also be implemented as an I-pin winding 7. In that case, the I-pin conductors 8 would each have a conductor section 9 arranged axially in the stator slots 6, which exits the stator 1 at an end face 14 with a free conductor end 10, forming a winding head 11, and the I-pin conductors 8 are radially angled inwards in the region of the winding head 11.

[0042] The free conductor ends 10 point radially inwards towards the axis of rotation 12 of a rotor 13 rotatably mounted in the stator 1, which can be clearly seen from the Fig. 3 can be seen. As in the Fig. As shown in Figure 2, the free conductor ends 10 are angled radially inwards by 85°-95° ​​relative to the conductor sections 9 arranged in the stator slots 6.

[0043] As in the Fig. 2 and the Fig. As shown in Figure 4, the free conductor ends 10 are radially offset in layers. The hairpin conductors 8 protrude beyond the radially inner surface 15 of the cylindrical stator 1.

[0044] In the embodiment shown, the Fig. Figure 2 shows a total of three annular layers, axially and radially offset from each other, with their different diameters, the layer closest axially to the end face 14 having the smallest diameter.

[0045] As in the Fig. As shown in Figure 3, the rotor 13 has a first magnetically active component arrangement 17 at its end face 16 facing the winding head 11, in particular selected from the group of permanent magnets and / or current-carrying magnetic coils. This enables the straight conductor portions, which are radially angled inwards, to generate additional torque in the axial flux direction of the rotor 13, which can lead to an improvement in the power density of the stator 1 or the electric machine 2.

[0046] A method for manufacturing the stator 1 for an electric machine 2 is described based on the Fig. 4 is explained in more detail. First, a stator 1 is provided, which is cylindrical and ring-shaped and has a plurality of stator teeth 5. These teeth define a stator groove 6 between adjacent stator teeth 5, extending radially and axially through the stator 1. Next, a plurality of hairpin conductors 8, each with two free conductor ends 10, are provided. The hairpin conductors 8 are then inserted into the stator grooves 6, so that the hairpin conductors 8 have two axially parallel conductor sections 9 arranged in the stator grooves 6. These conductor sections 9 exit the stator 1 at an end face 14 of the stator 1, each with two free conductor ends 10, forming a winding head 11.

[0047] Next, the conductor ends 10 are shaped circumferentially to achieve the desired coil width, so that the winding head 11 is then twisted circumferentially, as shown in the upper figure. Fig. 4 is shown.

[0048] In this state, the reshaping of the hairpin conductor 8 is initiated so that it is radially twisted inwards in the area of ​​the winding head 11, as shown in the lower figure of the Fig. 4 is shown.

[0049] In this manufacturing state, the rotor 13 can then be axially inserted into the stator 1 from the still uncut end face 28 of the winding head 22, which can also be clearly seen from the Fig. 2 can be understood. After the rotor 13 is inserted, the winding head 22 can then also be articulated in a radial direction.

[0050] The terms "radial," "axial," "tangential," and "circumferential direction" used in this application always refer to the rotational axis of the rotor. The terms "left," "right," "above," "below," "above," and "below" serve only to clarify which areas of the figures are currently being described in the text. Later embodiments of the invention may be arranged differently. Furthermore, the invention is not limited to the embodiments shown in the figures. The foregoing description is therefore not to be considered limiting, but rather explanatory. The following claims are to be understood as meaning that a named feature is present in at least one embodiment of the invention. This does not preclude the presence of further features.If the patent claims and the preceding description define 'first' and 'second' feature, this designation serves to distinguish between two similar features without establishing a hierarchy. Reference symbol list 1 Stator 2 electric machine 3 Powertrain 4 Motor vehicle 5 stator teeth 6 Stator slot 7 Hairpin winding 8 Hairpin ladders 9 ladder sections 10 ladder ends 11 winding head 12 Rotation axis 13 Rotors 14 Front 15 lateral surface area 16 End 17 Component Arrangement 22 winding head 28 Front

Claims

[1] Stator (1) for an electric machine (2), in particular within a drive train (3) of a motor vehicle (4), wherein the stator (1) is cylindrical and has a plurality of stator teeth (5) which define a radially extending stator groove (6) between adjacent stator teeth (5) in the circumferential direction and a stator groove (6) extending axially through the stator (1), into which an energizable hairpin winding (7) comprising a plurality of hairpin conductors (8) is inserted, wherein the hairpin conductors (8) have two axially parallel conductor sections (9) arranged in the stator grooves (6), which exit the stator (1) at an end face (14) of the stator (1) with two free conductor ends (10) each, forming a winding head (11), characterized by, that the free conductor ends (10) of the hairpin conductors (8) in the area of ​​the winding head (11) are twisted radially inwards for an inner rotor and radially outwards for an outer rotor, wherein the free conductor ends (10) are twisted radially offset layer by layer and layers with different diameters and different inclined twisting angles are electrically contacted. [2] Stator (1) for an electric machine (2), in particular within a drive train (3) of a motor vehicle (4), wherein the stator (1) is cylindrical and has a plurality of stator teeth (5) which define a radially extending stator groove (6) extending axially through the stator (1) between adjacent stator teeth (5) in the circumferential direction, in which an energizable I-pin winding (7) comprising a plurality of I-pin conductors (8) is inserted, wherein the I-pin conductors (8) each have a conductor section (9) arranged axially in the stator grooves (6), which exits the stator (1) at an end face (14) of the stator (1) with a free conductor end (10) to form a winding head (11), characterized by, that the free conductor ends (10) of the I-pin conductors (8) in the area of ​​the winding head (11) are twisted radially inwards for an inner rotor and radially outwards for an outer rotor, and wherein the free conductor ends (10) are twisted radially offset layer by layer and layers with different diameters and different inclined twisting angles are electrically contacted. [3] Stator (1) according to claim 1 or 2, characterized by , that the free conductor ends (10) point radially to the axis of rotation (12) of a rotor (13) rotatably mounted relative to the stator (1). [4] Stator (1) according to any of the preceding claims, characterized by , that the free conductor ends (10) are angled radially inwards by 85°-95° ​​for an inner rotor and radially outwards for an outer rotor relative to the conductor sections (9) arranged in the stator slots (6). [5] Stator (1) according to any of the preceding claims, characterized by, that the free conductor ends (10) are radially offset in each position. [6] Stator (1) according to any of the preceding claims, characterized by , that the hairpin conductors (8) protrude beyond the radial inner or outer surface (15) of the cylindrical stator (1). [7] Stator (1) according to any of the preceding claims, characterized by , that the rotor (13) has at its end face (16) facing the winding head (11) a first magnetically active component arrangement (17), in particular selected from the group of permanent magnets and / or currentable magnetic coils. [8] Electric machine (2) comprising a stator (1) according to any one of the preceding claims 1-7 [9] Electric machine (2) according to claim 8, characterized by, that the electric machine (2) has a first winding head (11) on a first end face (14) of the stator (1) and a second winding head (22) on a second end face (28) of the stator (1), wherein the hairpin conductors (8) or the I-pin conductors (8) are twisted radially inwards for an internal rotor and radially outwards for an external rotor in both the area of ​​the first winding head (11) and the area of ​​the second winding head (22). [10] Method for manufacturing a stator (1) for an electric machine (2), comprising the following steps: • Provision of a stator (1) which is cylindrical ring-shaped and has a plurality of stator teeth (5) which define a stator groove (6) extending radially and axially through the stator (1) between adjacent stator teeth (5) in the circumferential direction, • Provision of a plurality of hairpin ladders (8) each with two free ladder ends (10), • Inserting the hairpin conductors (8) into the stator slots (6) so that the hairpin conductors (8) have two axially parallel conductor sections (9) arranged in the stator slots (6), which exit the stator (1) at an end face (14) of the stator (1) with two free conductor ends (10) each, forming a winding head (11), • Reshaping the hairpin conductors (8) so that in the area of ​​the winding head (11) they are twisted radially inwards for an inner rotor and radially outwards for an outer rotor, and the free conductor ends (10) are twisted radially offset layer by layer so that layers with different diameters and different inclined twist angles can be electrically contacted, or • Provision of a stator (1) which is cylindrical ring-shaped and has a plurality of stator teeth (5) which define a stator groove (6) extending radially and axially through the stator (1) between adjacent stator teeth (5) in the circumferential direction, • Provision of a plurality of I-pin conductors (8) each with one free conductor end (10), • Inserting the I-pin conductors (8) into the stator slots (6) so that the I-pin conductors (8) each have a conductor section (9) arranged in the stator slots (6) in axial extension, which exit the stator (1) at an end face (14) of the stator (1) with a free conductor end (10) forming a winding head (11), • Reshaping the I-pin conductors (8) so that in the area of ​​the winding head (11) they are twisted radially inwards for an inner rotor and radially outwards for an outer rotor, and the free conductor ends (10) are twisted radially offset layer by layer so that layers with different diameters and different inclined twisting angles can be electrically contacted.

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