CN113258692A

CN113258692A - Stator of electric machine

Info

Publication number: CN113258692A
Application number: CN202110159619.7A
Authority: CN
Inventors: R·赫尔默
Original assignee: Volkswagen AG
Current assignee: Volkswagen AG
Priority date: 2020-02-07
Filing date: 2021-02-05
Publication date: 2021-08-13
Also published as: DE102020201547A1

Abstract

The invention relates to a stator (1) of an electric machine (2) having a rotational axis (4) and being used for a six-phase voltage supply (3). Wherein the six-phase voltage supply (3) comprises: a first three-phase alternating current system (5) with a first set (6) of phases: a first phase (7), a second phase (8), a third phase (9); and a second three-phase alternating current system (10) with a second set (11) of phases: a fourth phase (12), a fifth phase (13), and a sixth phase (14). The stator (1) comprises at least one cylindrical main body (15) having a plurality of grooves (16) which extend in the axial direction (17) and in the radial direction (18) and are arranged next to one another in the circumferential direction (19) and between which teeth (20) are formed in each case. Wherein an electrical conductor (21) is arranged in the slot (16), which is associated with the phases (7,8,9,12,13,14) respectively.

Description

Stator of electric machine

Technical Field

The invention relates to a stator for a six-phase electrical machine.

Background

Electric motor vehicle drives include an electric machine (which is used as a traction drive for the motor vehicle) and power electronics and are usually implemented as three-phase. The power required in future drives with further power increases cannot be supplied in three phases only. It is proposed here to build a six-phase drive from two three-phase half-power electronic systems available and a six-phase electric machine. A six-phase drive offers the advantage of fault tolerance (Fehlertoleranz) in addition to power boosting. If one of the two three-phase power electronics or one of the two three-phase windings in the electric machine fails, the motor vehicle can nevertheless continue to drive at half the power up to the workshop. Increased failure tolerance is expected to be of greater importance in future autonomously driven vehicles than has hitherto been the case for non-autonomously driven vehicles.

In order to provide the required higher power and, if necessary, the required fault tolerance with respect to a failure of the drive system, it is known to provide an all-wheel drive system with a drive, i.e. an electric motor and power electronics, respectively, for each axis. Providing two electric machines with power electronics in each case, however, leads to a higher weight and higher costs of the motor vehicle, wherein the efficiency and the achievable effective distance of the drive are reduced due to additional losses in the second electric machine and the power electronics and the higher weight.

From DE 102016224178 a1, a control of a six-phase, permanently excited synchronous machine is known. The rotational angle and the rotational speed of the rotor of the electric machine are to be determined.

DE 102011016123 a1 discloses an electric machine, the stator of which has slots for arranging the windings. The windings are arranged in a certain manner in the slots.

Disclosure of Invention

It is an object of the present invention to at least partly solve the problems listed in relation to the prior art. In particular, an electric drive is to be proposed which has a high efficiency and a high fault tolerance and in this case makes cost and weight savings possible.

The stator of the electrical machine according to the invention contributes to this object. Advantageous developments are the subject matter of the description. The features listed individually in the invention can be combined with one another in a technically expedient manner and can be supplemented by details in the stated description and/or in the drawings, in which further implementation variants of the invention are listed.

A stator for an electric machine for six-phase voltage supply (Spannungsversorgung) with an axis of rotation is proposed. The six-phase voltage supply includes: a first three-phase alternating current system (Drehstromsystem) with a first set of phases: a first phase, a second phase, a third phase; and a second three-phase ac power system with a second set of phases: a fourth phase, a fifth phase, and a sixth phase. The stator comprises at least one cylindrical base body with a plurality of slots which extend in the axial and radial direction and are arranged next to one another in the circumferential direction and between which teeth are formed in each case. In the slot, electrical conductors are arranged, which are respectively associated with the phases. Each slot has a phase outgoing conductor (hindleiter) or return conductor (Rueckleiter) in the distributed winding. In a tooth coil winding (Zahnspulenwicklung), each tooth is wound with a phase conductor in an adjacent slot. The first set of three phases is arranged in a first annular section of the stator and the second set of three phases is arranged in a second annular section of the stator. The annular segments are alternately arranged along the circumferential direction.

The electric machine is in particular a Synchronous Machine (SM), in particular a permanent magnet excited machine (PSM), a reluctance machine (SRM), a separately excited machine (FSM) or an asynchronous machine (ASM). The motor includes a stationary stator and a rotating rotor. In particular, the rotor is arranged radially outside, but preferably within the stator. The shaft, for example the drive shaft, can be driven via the rotor.

The stator is in particular embodied to be driven by a six-phase voltage supply. Two three-phase ac systems are provided. The individual phases of each phase group are offset by, in particular, a respective 120 degrees from one another.

The stator comprises, in particular, a cylindrical base body which has a plurality of grooves, also referred to as slots, at an outer or inner circumferential surface. The groove extends in the axial direction, in particular parallel to the axis of rotation. The groove has a depth extending in a radial direction, a width extending in a circumferential direction, and a length extending in an axial direction. Between the two corresponding grooves, teeth are formed.

In the groove, electrical conductors are arranged, which are in each case connected to a phase in an electrically conductive manner. The electrical conductor is formed in particular by a cable arranged in a coil on the stator. Each turn is constituted by a lead-to conductor and a return conductor, which represent a respective turn side (Windungsseite) in two different slots, and may be constituted by a cable or a plurality of parallel cables. The coil (Spule) is formed by at least one winding. Similarly to the winding, the coil is also formed by two sides, which are arranged in two different grooves, like the winding sides. The electrical conductor forms a coil. The current-loaded electrical conductor generates in a known manner a rotating field which interacts with a rotor field for driving the rotor.

Different winding types for arranging conductors in slots are known in particular. The coil sides of the coils in the distributed windings are not positioned in slots adjacent to one another but in slots arranged further apart from one another in the circumferential direction. The coil heads of the plurality of coils, which extend outside the slots and connect the coil sides, are then stacked. The distributed winding generates an approximately sinusoidal air gap field (Luftspaltfeld), by means of which the operating behavior of the electric machine is positively influenced.

In a toothed coil winding the coil sides are arranged in slots adjacent to one another and the windings extend around the teeth arranged between them.

In particular, a plurality of electrical conductors, which are associated with only one phase of a group, are arranged in at least one groove, preferably in each groove.

In particular, the stator comprises 2n annular segments, wherein n =1,2,3, …

In particular, each annular section comprises the same number of grooves or teeth. In particular, each annular segment comprises a respective identical angular extent in the circumferential direction.

In particular, the stator comprises at most four annular segments. In particular, each annular segment comprises a respective identical angular extent in the circumferential direction. In the case of four annular segments, each annular segment comprises a 90 degree angle. In particular, the electrical conductors associated with the first group of three phases are arranged, for example, in a first ring segment with an angular range of 0 to 90 degrees and in a third ring segment with an angular range of 180 to 270 degrees. In particular, the electrical conductors associated with the three phases of the second group are arranged, for example, in a second annular section with an angular range of 90 to 180 degrees and in a fourth annular section with an angular range of 270 to 360 or zero degrees.

In particular, the stator comprises exactly two ring segments. In particular, each annular segment comprises a respective identical angular extent in the circumferential direction. In the case of two ring segments, each ring segment comprises 180 degrees. In particular, the electrical conductors associated with the first group of three phases are arranged, for example, in a first ring segment with an angular range of 0 to 180 degrees. In particular, the electrical conductors associated with the three phases of the second group are arranged, for example, in a second annular section with an angular range of 180 to 360 or zero degrees.

If the stator comprises, for example, six ring segments, the conductors associated with the first group of three phases are arranged in a first ring segment (0 to 60 degrees), in a third ring segment (120 to 180 degrees) and in a fifth ring segment (240 to 300 degrees).

The conductor is in particular embodied as a round cable or a profiled cable (formdry) (also referred to as a hairpin).

Furthermore, a drive system for an electric machine with the described stator is proposed. The drive system includes: at least one DC voltage intermediate circuit (Gleichmann backstzwischknekrais) having an intermediate circuit capacitor for providing a voltage and a variable current for driving the electric motor; and a first converter (Umrichter) for the electric machine, which is supplied with voltages of a first group of phases, and a second converter for the electric machine, which is supplied with voltages of a second group of phases. The two converters generate a pulse width modulation signal or PWM signal from the dc voltage intermediate circuit, wherein the first pulse width modulation signal of the first converter and the second pulse width modulation signal of the second converter can be generated offset in time from one another (so-called PWM interleaving).

In particular, each converter generates a sinusoidal voltage for the electric machine by temporally offset (ausschneiden) division of the block-shaped voltage from the dc voltage intermediate circuit by the respective converter. This truncation is known as Pulse Width Modulation (PWM).

In particular, when the dc voltage is cut off from the dc voltage intermediate circuit or the intermediate circuit capacitor, parasitic harmonic voltages (Oberschwingungsspannung) are excited in the intermediate circuit capacitor by the respective three-phase converter. Due to the offset in time of the dc voltage cut off by the two converters, the parasitic harmonics of one converter can be compensated, i.e. balanced, at least to a large extent by the inverted signal of the other converter. Furthermore, the intermediate circuit capacitor can be dimensioned significantly smaller than in the case of a merely three-phase system of the same power (i.e. with only one converter).

The harmonics reduced by PWM interleaving in particular enable a reduction of the electrical losses in the electric machine and in the power electronics.

Furthermore, a method for operating the described drive system is proposed, which comprises at least the following steps:

a) debugging a direct-current voltage intermediate circuit;

b) generating a first pulse width modulated signal by a first converter and

c) generating a second pulse width modulated signal by a second converter;

the first pulse width modulation signal and the second pulse width modulation signal are generated offset in time from one another, so that the current ripple in the intermediate circuit capacitor can be reduced.

Furthermore, a motor vehicle is proposed, which comprises at least one drive train having an electric machine as a traction drive, wherein the electric machine has the described drive train, which can be operated by the described method.

The coupling of the stator to the six-phase voltage supply enables, on the one hand, higher power to be made available, for example for driving a motor vehicle, and also enables higher fault tolerance to be made available. Operating the converters to generate PWM signals that are offset in time from one another, i.e. using PWM interleaving, can result in additional current harmonics (stromoberville) being generated in the windings of the motor. This occurs in particular if the conductors of the first group are arranged next to the conductors of the second group. In order to reduce this effect, it is proposed in particular to separate the conductors of the different groups of phases as far as possible spatially from one another. This is achieved in particular in that the electrical conductors associated with the first group of three phases are arranged in a ring segment and the electrical conductors associated with the second group of three phases are arranged in a further ring segment.

The drive system comprises, inter alia, a controller which is designed, configured or programmed to carry out the described method.

Furthermore, the method may also be implemented by a computer or by means of a processor of a control unit.

Accordingly, a system for data processing is also proposed, the system comprising a processor adapted/configured such that it performs the method or a part of the steps of the proposed method.

A computer-readable storage medium may be provided, which comprises instructions which, when executed by a computer/processor, cause it to carry out at least part of the steps of the method or the proposed method.

Embodiments of the stator are applicable in particular to drive systems, methods performed by a computer (i.e. a computer or processor, a system for data processing, a computer-readable storage medium) and motor vehicles and vice versa.

The use of the indefinite articles "a" and "an" in particular in the context of the present invention should be understood as such and not as a word of numeral. The term or component introduced here accordingly is to be understood as meaning its presence at least once, but in particular also multiply.

It should be noted prophylactically that the terms "first", "second" … … are used herein primarily (solely) to distinguish between a plurality of similar objects, parameters or processes, i.e., without necessarily specifying the relevance and/or order of such objects, parameters or processes with respect to one another, among others. If dependency and/or order is required, this is explicitly stated herein or will be apparent to one of ordinary skill in the art upon study of the specifically stated design. The description of one of these components may equally apply to all or a portion of a plurality of these components, provided that the components may be present in multiple ("at least one"), but this is not mandatory.

Drawings

The invention and the technical field are further elucidated on the basis of the figures. It should be noted that the present invention should not be limited by the illustrated examples. In particular, also partial aspects of the situation illustrated in the figures can be extracted and combined with other constituent parts and realizations in the present description, as long as they are not explicitly indicated otherwise. It should be noted in particular that the figures and the dimensional ratios shown in particular are purely schematic. Wherein:

FIG. 1 shows a motor vehicle with a drive train;

fig. 2 shows a first embodiment variant of the electrical machine in section in a view along the axis of rotation;

fig. 3 shows a stator according to the first embodiment variant according to fig. 2 in a view along the axis of rotation in cross section;

fig. 4 shows a second embodiment variant of the electrical machine in section in a view along the axis of rotation;

fig. 5 shows a motor according to the second embodiment variant according to fig. 4 in a section in a view along the axis of rotation;

fig. 6 shows a stator according to the second embodiment variant according to fig. 4 in a view along the axis of rotation in cross section;

fig. 7 shows a graphical representation of the electrical signals generated by the drive system.

Detailed Description

Fig. 1 shows a motor vehicle 34 with a drive train 35. The drive train 35 comprises the electric motor 2 as a traction drive, wherein the electric motor 2 has a drive system 26 with a controller 33. The drive system 26 comprises a direct voltage intermediate circuit 27 with a voltage supply 3, a resistor 37, an inductance 36 and an intermediate circuit capacitor 28. The dc voltage intermediate circuit 27 is used to provide a voltage and a variable current for driving the motor 2. The dc voltage intermediate circuit 27 furthermore comprises: a first inverter 29 for supplying the motor 2 with a first three-phase alternating current system 5 (which comprises the

phases

7,8,9 of the first group 6) voltage; and a second inverter 30 for supplying the motor 2 with a voltage of a second three-phase alternating current system 10, which comprises the

phases

12,13,14 of the second group 11. The two

converters

29,30 generate pulse width modulation signals 31,32 or PWM signals from the dc voltage intermediate circuit 27, wherein the first pulse width modulation signal 31 of the first converter 29 and the second pulse width modulation signal 32 of the second converter 30 can be generated offset in time from one another (so-called PWM interleaving). The drive system 26 is controlled by a controller 33.

Fig. 2 shows a first embodiment variant of the electric machine 2 in cross section in a view along the axis of rotation 4. The motor 2 comprises a rotor 40 with permanent magnets (not shown) and a stator 1. Alternatively, the rotor 40 can also be embodied as a short-circuit rotor of an ASM in all the exemplary embodiments shown. The stator 1 is arranged radially 18 outside the rotor 40.

The stator 1 is designed for a six-phase voltage supply 3. The six-phase voltage supply 3 includes: a first three-phase alternating current system 5 with a first set 6 of phases: a first phase 7, a second phase 8, a third phase 9; and a second three-phase alternating current system 10 with a second set 11 of phases: a fourth phase 12, a fifth phase 13, and a sixth phase 14. The stator 1 comprises a cylindrical main body 15 with a plurality of grooves 16 which extend in an axial direction 17 and in a radial direction 18 and are arranged next to one another in a circumferential direction 19 and between which teeth 20 are formed in each case. In the slot 16 there are arranged electrical conductors 21, which are associated with the

phases

7,8,9,12,13,14, respectively. The conductor 21 is arranged in a toothed coil winding. In adjacent slots 16, each tooth 20 is wound with a conductor 21 of the

phase

7,8,9,12,13, 14. The three

phases

7,8,9 of the first group 6 are respectively arranged in a first annular section 24 of the stator 1 and the three

phases

12,13,14 of the second group 11 are respectively arranged in a second annular section 25 of the stator 1. The

annular segments

24,25 are arranged alternately and spatially separated from one another along the circumferential direction 19.

The stator 1 includes a columnar base body 15 having a plurality of slots 16 at an inner peripheral surface thereof. The groove 16 has a depth extending in a radial direction 18, a width extending in a circumferential direction 19 and a length extending in an axial direction 17.

In the groove 16, an electrical conductor 21 is arranged, which is electrically conductively connected to the

phases

7,8,9,12,13,14, respectively. The electrical conductor 21 is formed by a cable arranged in a coil on the stator 1. Each turn is constituted by a lead-to conductor 22 and a return conductor 23, which are shown on the side of a respective turn in two different slots 16 and may be constituted by a cable or a plurality of cables connected in parallel. A coil is formed by at least one winding. Similarly to the winding, the coil is also formed by two sides, which are each arranged in two different grooves 16 like the winding sides. The electrical conductor 21 thus forms a coil. The current-loaded electrical conductor 21 generates a rotating field in a known manner, which interacts with a rotor field for driving the rotor 40.

In the toothed coil winding, the coil sides are arranged in slots 16 adjacent to one another and the windings associated with the

phases

7,8,9,12,13,14 extend around teeth 20 arranged therebetween.

In each slot 16, a plurality of electrical conductors 21 is arranged, which are associated with only one

phase

7,8,9,12,13,14 of the

group

6,11 for each slot 16.

Each

annular section

24,25 comprises the same number of grooves 16 or teeth 20. The stator 1 comprises exactly two

ring segments

24, 25. Each

annular segment

24,25 comprises a respective identical angular extent along the circumferential direction 19. In the case of the two

annular sections

24,25, each

annular section

24,25 comprises 180 degrees. The electrical conductors 21 associated with the first three-phase alternating current system 5 or the three

phases

7,8,9 of the first group 6 are arranged in a first ring segment 24 with an angular range of 0 to 180 degrees. The electrical conductors 21 associated with the second three-phase alternating current system 10 or the three

phases

12,13,14 of the second group 11 are arranged in a second annular section 25 with an angular range of 180 to 360 or zero degrees.

The

phases

7,8,9,12,13,14 provided by the two

converters

29,30 according to fig. 1 are offset by a respective 120 degrees from one another for each

group

6,11, as is customary in three-phase ac systems. The respective identical phases of the different sets, i.e. for example the first 7 and fourth 12 phases, the second 8 and fifth 13 phases, the third 9 and sixth 14 phases are in Phase with each other in time (in Phase). Which furthermore have the same phase angle (see the illustration of the phase angle in fig. 4).

In this arrangement of the

phases

7,8,9,12,13,14, a maximum spatial separation of the

phases

7,8,9,12,13,14 of the

different groups

6,11 can be achieved. The electrical losses due to the inductive coupling of the conductors 21 of the

different phases

7,8,9,12,13,14 exactly in the stator 1 can thus be reduced. However, if the

set

6,11 of

phases

7,8,9,12,13,14 fails, there is an increased fluctuation of the torque provided by the electric machine 2.

Fig. 3 shows a stator 1 according to the first embodiment variant (tooth coil winding) according to fig. 2 in a section in a view along the axis of rotation 4. Reference is made to the embodiments for figures 1 and 2.

In contrast to fig. 2, the stator 1 here comprises exactly four

ring segments

24,25,38, 39. Each

annular segment

24,25,38,39 has a corresponding identical angular extent of 90 degrees along the circumferential direction 19. The electrical conductors 21 associated with the first set 6 of three

phases

7,8,9 are arranged in a first ring section 24 with an angular range of 0 to 90 degrees and in a third ring section 38 with an angular range of 180 to 270 degrees. The electrical conductors 21 associated with the three

phases

12,13,14 of the second set 11 are arranged in the second annular section 25 with an angular range of 90 to 180 degrees and in the fourth annular section 39 with an angular range of 270 to 360 or zero degrees.

The

phases

7,8,9,12,13,14 provided by the two

converters

29,30 are offset by a respective 120 degrees from one another for each

group

6,11, as is customary in three-

phase ac systems

5, 10. The respective identical phases of the different groups, i.e. for example the first 7 and fourth 12, second 8 and fifth 13, third 9 and sixth 14 phases are in phase in time. I.e. with the same phase angle (see the illustration of the phase angle in fig. 4).

In this arrangement of the

phases

7,8,9,12,13,14, a smaller spatial separation of the

phases

7,8,9,12,13,14 of the

different groups

6,11 is achieved than in the first embodiment variant. The electrical losses in the stator 1 due to the inductive coupling of the conductors 21 of the

different phases

7,8,9,12,13,14 are thus slightly increased, since the spatial separation with an angle of 90 is smaller compared to the angle of 180 according to fig. 2. If the

group

6,11 of the

phases

7,8,9,12,13,14 fails, there is always a ripple in the torque supplied by the electric machine 2, but this is significantly lower than in the case of the first embodiment variant.

Fig. 4 shows a second embodiment variant of the electric machine 2 in cross section in a view along the axis of rotation 4. The motor 2 comprises a rotor 40 with permanent magnets (not shown) and a stator 1. Reference is made to the embodiments of figures 1 to 3.

The stator 1 comprises exactly two

ring segments

24, 25. Each

annular segment

annular sections

24,25, each

annular section

24,25 comprises exactly 180 degrees. The electrical conductors 21 associated with the three

phases

7,8,9 of the first group 6 are arranged in a first annular section 24 with an angular range of 0 to 180 degrees. The electrical conductors 21 associated with the three

phases

12,13,14 of the second set 11 are arranged in a second annular section 25 with an angular range of 180 to 360 or zero degrees.

The electrical conductors 21 of the second embodiment variant are arranged in windings distributed at the stator 1. In the distributed winding each slot 16 has a lead-to conductor 22 or a return conductor 23 of a

phase

7,8,9,12,13, 14. The coil sides of the coils in the distributed windings are not positioned in the slots 16 adjacent to one another, but rather in the slots 16 arranged further apart from one another along the circumferential direction 19. The coil heads of the plurality of coils, which extend outside the slots 16 and connect the coil sides, overlap. The distributed windings generate an approximately sinusoidal air gap field, by means of which the operating behavior of the electric machine 2 is positively influenced. The outgoing conductors 22 of the

phases

7,8,9,12,13,14 are arranged in the respective slots 16 adjacent to one another. The coil heads extend in the circumferential direction 19 across a plurality of slots 16 and teeth 20 to a further pair of slots 16, in which return conductors 23 of the

respective phases

7,8,9,12,13,14 are arranged.

Fig. 5 shows the electric machine 2 according to the second embodiment variant according to fig. 4 in a section in a view along the axis of rotation 4. Reference is made to the embodiment of figure 4.

Fig. 6 shows a stator 1 according to the second embodiment variant according to fig. 4 in a section in a view along the axis of rotation 4. Reference is made to the embodiment of figure 4.

Unlike the stator 1 according to fig. 4, the stator 1 here comprises a smaller number of slots 16 and teeth 20. However, the construction of the stator 1 and the arrangement of the conductors 21 and the

phases

7,8,9,12,13,14 are otherwise identical.

Fig. 7 shows a diagram of the electrical PWM signals 31,32 generated by the drive system 26. Reference is made to the embodiment of figure 1.

The voltage 42 is plotted on the vertical axis. Time 41 is plotted on the horizontal axis. The voltage 42 of each

phase

7,8,9,12,13,14 is provided as a sinusoidal signal of the motor 2. The first inverter 29 generates a first pulse width modulated signal and the second inverter 30 generates a second pulse width modulated signal 32. The

converters

29,30 are operated here to generate

signals

31,32 with a temporal offset 43 of the

respective phases

7,12 from one another, so-called PWM interleaving.

List of reference numerals

1 stator

2 machine

3 voltage supply

4 axis of rotation

5 first three-phase alternating current system

6 first group

7 first phase

8 second phase

9 third phase

10 second three-phase alternating current system

11 second group

12 fourth phase

13 fifth phase

14 sixth phase

15 base body

16 grooves

17 axial direction

18 radial direction

19 circumferential direction

20 teeth

21 conductor

22 going conductor

23 return conductor

24 first annular segment

25 second annular section

26 drive system

27 DC voltage intermediate circuit

28 intermediate circuit capacitor

29 first converter

30 second converter

31 first pulse width modulation signal

32 second pulse width modulation signal

33 controller

34 motor vehicle

35 drive train

36 inductor

37 resistance

38 third annular segment

39 fourth annular section

40 rotor

41 hours of operation

42 voltage

43 are offset.

Claims

1. Stator (1) of an electric machine (2) for a six-phase voltage supply (3) with a rotation axis (4); wherein the six-phase voltage supply (3) comprises: a first three-phase alternating current system (5) with a first set (6) of phases: a first phase (7), a second phase (8), a third phase (9), and a second three-phase alternating current system (10) with a second set (11) of phases: a fourth phase (12), a fifth phase (13), and a sixth phase (14); wherein the stator (1) comprises at least one cylindrical base body (15) with a plurality of grooves (16) which extend in each case in the axial direction (17) and in the radial direction (18) and are arranged alongside one another in the circumferential direction (19) and between which teeth (20) are formed in each case; wherein in the slot (16) an electrical conductor (21) is arranged, which is associated with the phase (7,8,9,12,13,14) respectively; wherein in the distributed winding each slot (16) has a outgoing conductor (22) or a return conductor (23) of a phase (7,8,9,12,13,14) and in the tooth coil winding each tooth (20) in slots (16) adjacent to each other is wound by a conductor (21) of a phase (7,8,9,12,13, 14); wherein the three phases (7,8,9) of the first group (6) are respectively arranged in a first annular section (24) of the stator (1) and the three phases (12,13,14) of the second group (11) are respectively arranged in a second annular section (25) of the stator (1); wherein the annular segments (24,25) are alternately arranged along the circumferential direction (19).

2. Stator (1) according to claim 1, wherein the stator (1) comprises at most four ring segments (24,25,38, 39).

3. Stator (1) according to claim 2, wherein the stator (1) comprises exactly two ring segments (24, 25).

4. Stator (1) according to any of the preceding claims, wherein the conductor (21) is implemented as a round cable or a profiled cable.

5. Drive system (26) for an electric machine (2) with a stator (1) according to any of the preceding claims, comprising at least: a direct voltage intermediate circuit (27) having an intermediate circuit capacitor (28) for providing a voltage and a variable current for driving the electric machine (2), and a first converter (29) for supplying the electric machine (2) with the voltage of the phases (7,8,9) of the first group (6) and a second converter (30) for supplying the electric machine (2) with the voltage of the phases (12,13,14) of the second group; wherein the converters (29,30) generate pulse width modulation signals (31,32) from the direct voltage intermediate circuit (27), wherein a first pulse width modulation signal (31) of the first converter (29) and a second pulse width modulation signal (32) of the second converter (30) can be generated offset in time from one another.

6. Method for operating a drive system (26) according to claim 5, comprising at least the following steps:

a) debugging the direct-current voltage intermediate circuit (27);

b) generating a first pulse width modulated signal (31) by means of the first converter (29) and

c) generating a second pulse width modulated signal (32) by the second converter (30);

wherein the first pulse width modulation signal (31) and the second pulse width modulation signal (32) are generated offset in time from one another, so that the current ripple in the intermediate circuit capacitor (28) can be reduced.

7. A motor vehicle (34) comprising at least a drive train (35) with an electric machine (2) as traction drive, wherein the electric machine (2) has a drive system (26) according to claim 5, which can be operated by a method according to claim 6.