Drive device

Abstract

The invention relates to a drive device for a motor vehicle, comprising an electric machine and an inverter, the inverter being configured to supply the electric machine with an AC voltage, the electric machine comprising a rotor (12) and a stator (1) surrounding the rotor (12), the stator (1) having a stator core (2), the stator core (2) comprising a stack of stator laminations (3) and comprising windings (4) accommodated by the stack of stator laminations (3), the stator (1) being accommodated in a housing (5), the stator (1) being electrically isolated from the housing (5), a return current path (ICM-C) being formed inside the stator core (2) for returning a current to the inverter, such that a common mode current (ICM- W) flowing in the stator core (2) to the housing, which contributes to a circulating flux (Φcirc) in the stator, is at least partially compensated.

Description

[0001] drive device

[0002] Field of invention

[0003] The present invention relates to a drive device, in particular a drive device for a motor vehicle, comprising an electric machine and an inverter.

[0004] State of the art

[0005] It is known that electric machines can be used as drive motors, particularly as drive motors for motor vehicles. Such an electric machine comprises a rotor and a stator arranged externally around the rotor. The stator can have windings to generate a stator magnetic field. To supply the electric machine with the required alternating voltage, particularly three-phase alternating voltage, it is often connected to a power supply, especially a traction battery, via an inverter.

[0006] It is known that in such an electric machine, common-mode currents and voltages arise due to parasitic capacitances and rapid voltage changes (high du / dt values) caused by the inverter. The common-mode quantities caused by parasitic capacitances do not contribute to the intended function of the electric machine. On the contrary, they cause effects that negatively impact the characteristics of the drive device.

[0007] 2024P00066 WO 24.07.2025 BZ Common-mode currents can be coupled into the electric drive components and wiring through the grounding and housing structure, causing excessive conducted and radiated emissions. This poses, among other things, the risk of EMC (electromagnetic compatibility) interference.

[0008] Furthermore, common-mode quantities negatively affect the service life of rotor bearings through capacitive and inductive coupling mechanisms in the form of bearing voltages and currents.

[0009] Furthermore, common-mode currents generate electrical losses that negatively impact the efficiency of the drive device. If, as is known, a current-compensated choke (AC choke) is used in the AC lines from the inverter to the electric machine, it becomes magnetized by the common-mode currents flowing against the casing. This results in disadvantages regarding the size, available materials, saturation and temperature resistance, and therefore the price of this choke.

[0010] This necessitates expensive measures to avoid and mitigate the impact.

[0011] For example, document DE 10 2010 055 484 C5 discloses an electric drive system with divertable common-mode currents, comprising at least one electric machine, at least one frequency converter, at least one power supply unit, and power supply lines between the power supply unit and the frequency converter unit, wherein the electric machine has a rotor and a stator surrounding it with a plurality of elements arranged around a

[0012] 2024P00066 WO 24.07.2025 BZ Machine axis with distributed magnetic poles and windings received in cavities as well as cooling channels arranged in the cavities through which a cooling medium can flow, wherein the frequency conversion device and the electric machine are arranged within a common, self-contained metal housing and at least the stator is electrically insulated from the housing, wherein the power supply lines and other voltage or signal lines are each arranged within a hydraulically stressable hose with a closed metal or metal mesh sheath and wherein a cooling device is capacitively connected to other components within the housing by means of capacitors.

[0013] Summary of the invention

[0014] It is an object of the invention to provide a drive device comprising an electric machine and an inverter in which there is less risk of EMC interference, bearing currents and efficiency degradation, so that components for damage limitation can be reduced and the electric machine can thus have lower costs, volume and weight.

[0015] The problem is solved by a drive device comprising an electric machine and an inverter, the inverter being configured to supply the electric machine with an alternating voltage, the electric machine comprising a rotor and a stator surrounding the rotor, the stator having a stator core, the stator core comprising a stack of stator laminations and windings received by the stack of stator laminations, the stator being received in a housing

[0016] 2024P00066 WO 24.07.2025 BZ is, wherein the stator is electrically insulated from the housing, wherein a reverse current path is formed inside the stator core for returning a current to the inverter, so that a common-mode current flowing in the stator core to the housing, which contributes to a circulating flux in the stator, is at least partially compensated.

[0017] According to the invention, a return current path is thus created inside the stator core, which enables a current to be returned in a direction that is at least substantially opposite to the common-mode current flowing into the stator core and thus compensates, reduces and at best eliminates the inductively effective common-mode current inside the stator.

[0018] According to the invention, a stator isolated from a surrounding housing with an optimized common-mode current return path to the inverter, in particular to an intermediate circuit of the inverter, is used, i.e. with a DC link bypass, in order to minimize the risk of EMC interference, bearing currents and efficiency degradation.

[0019] An optimized return path for common-mode currents is created that does not use the housing structure, thereby minimizing expensive interference suppression measures by reducing common-mode coupling.

[0020] One cause for the emergence of common-mode currents I C M Hegt's reasoning lies in the fact that the sum of the phase currents in a real stator is greater than zero, which leads to the formation of an axially oriented common-mode current ICM-W inside the stator, particularly via the windings W, and consequently to the formation of

[0021] 2024P00066 WO 24.07.2025 BZ of a circulating flow <f> C This results in an unwanted circulating current (IRC) flowing around the circumference of the stator, inducing a common-mode current in the rotor axis and associated bearings. This common-mode current through the stator windings (ICM-W) is typically returned to the inverter via a return current (ICM-R) through the housing surrounding the stator. Such a return current (ICM-R) through the housing does not compensate for the common-mode currents (ICM) and reduces the unwanted circulating flux. <f> C IRC not.

[0022] According to the invention, electrical insulation of the stator is provided from the stator housing, preferably the housing of the electric machine. This reduces the currents in the housing. Current return no longer occurs through the housing. Insulation features can be provided between the stator and the surrounding housing as well as the mounting elements.

[0023] A low-impedance return current path from the stator to the DC link is preferably created. To reduce the circulating stator flux, a return current path is provided within the stator core, which is effective for the circulating flux and therefore avoids or at least reduces the circulating stator flux.

[0024] The specific design of the current path can vary. Preferably, however, a current path is provided via a collector on the radially inner part of the stator, while the stator is insulated from the surrounding housing.

[0025] This results in a reduction of common-mode currents in the package and thus a possible reduction in the number of components.

[0026] 2024P00066 WO 24.07.2025 BZ for damage limitation, and thus to lower costs, volume and weight of the electric machine.

[0027] The current return preferably occurs via a path that runs axially at least in some areas, but can also run non-axially, for example in some areas, but especially obliquely.

[0028] Preferably, the return current path is formed in the area of ​​the inner circumference of the stator core, particularly near the inner boundary of the windings.

[0029] Preferably, the return current path includes at least one axial return line extending axially along the stator core to an axial end of the stator core.

[0030] Preferably, the return current path comprises several axial return lines extending axially along the stator core to an axial end of the stator core, wherein the several axial return lines are distributed circumferentially around the stator core, preferably around the entire circumference of the stator core, and particularly preferably at equal intervals from each other.

[0031] The axial feedback lines are preferably collected at the axial end of the stator core in a rotating collector, the rotating collector being particularly preferably in a ring shape.

[0032] Preferably, connection terminals for connection to the inverter are provided at the axial end of the return line, preferably at the rotating collector.

[0033] 2024P00066 WO 24.07.2025 BZ Preferably, the rotating collector is electrically insulated from the outermost stator sheet of the stator core, wherein the rotating collector is particularly preferably formed by an additional metal sheet insulated from the stator core.

[0034] The return line or return lines can preferably each be formed by a metal profile or by a weld seam.

[0035] Preferably, the feedback line, preferably the several feedback lines, are formed in areas between two cavities for receiving the windings in the stator laminations.

[0036] Preferably, the inverter comprises at least one intermediate circuit, wherein the return current path is designed to return a current to the intermediate circuit of the inverter.

[0037] If the connection from the inverter to the electric machine includes a current-compensated choke, the return current path to the DC intermediate circuit of the inverter should preferably be included in this choke.

[0038] Brief description of the drawings

[0039] The invention is described below by way of example with reference to the drawings.

[0040] Fig. 1 is a three-dimensional schematic view of an electric machine of a drive device not according to the invention.

[0041] 2024P00066 WO 24.07.2025 BZ Fig. 2 is a representation relating to a circulating magnetic flux <f> C simplified sectional view of the electric machine according to Fig. 1.

[0042] Fig. 3 is a three-dimensional schematic view of an electric machine of a drive device according to the invention.

[0043] Fig. 4 is a representation relating to a circulating magnetic flux. <f> C simplified sectional view of the electric machine according to Fig. 3.

[0044] Fig. 5 is a front view of an electric machine of a drive device according to the invention without a rotating collector.

[0045] Fig. 6 is a detailed view of the electric machine according to

[0046] Fig. 5 in a first embodiment.

[0047] Fig. 7 is a detailed view of the electric machine according to

[0048] Fig. 5 in a second embodiment.

[0049] Fig. 8 is a side view of an electric machine of a drive device according to the invention as shown in Fig. 5.

[0050] Fig. 9 is a view of the axial end region of an electric machine according to the invention.

[0051] 2024P00066 WO 24.07.2025 BZ Drive device according to Fig. 5, with collector and terminals, from the front.

[0052] Fig. 10 is a view according to Fig. 9, with collector and

[0053] Terminals, from the side.

[0054] Detailed description of the invention

[0055] Figures 1 and 2 show an electric machine of a drive device not according to the invention.

[0056] The electric machine comprises a rotor (not shown here) radially within a stator 1 surrounding the rotor. The stator 1 has a stator core 2, wherein the stator core 2 comprises a stack of stator laminations 3 and includes windings 4 received by the stack of stator laminations 3.

[0057] The stator 1 is housed in a casing (not shown). The stator 1 is not electrically insulated from the casing 5.

[0058] Inside the stator core 2, via the windings 4 of the stator 1, a parasitic common-mode current ICM-W flows, which contributes to a circulating flux drc in the stator 1.

[0059] A return current path ICM-R for the common-mode current ICM-W is formed through the stator housing, via which current is returned to the inverter. The common-mode current ICM-W flowing into the stator core 2 is not compensated by the return current ICM-R in the housing, which circulates in the stator core 2.

[0060] 2024P00066 WO 24.07.2025 BZ Circ flow is not reduced. The resulting common-mode current can lead to EMC interference.

[0061] Figs. 3 and 4, in contrast to Figs. 1 and 2, show an electric machine of a drive device according to the invention.

[0062] The drive device comprises an electric machine comprising a rotor and a stator 1 surrounding the rotor, wherein the stator 1 has a stator core 2, wherein the stator core 2 comprises a stack of stator laminations 3 and includes windings 4 received by the stack of stator laminations 3.

[0063] The stator 1 is enclosed in a housing 5, wherein the stator 1 is electrically insulated from the housing 5.

[0064] Inside the stator core 2, a parasitic common-mode current ICM-W flows through the windings 4 of the stator 1. A reverse current path for ICM-C is formed inside the stator core 2 to return current to the inverter, so that the common-mode current ICM-W flowing in the stator core 2, which results in a circulating current <f> C The irc in the stator, which contributes to EMC interference and can lead to electromagnetic disturbances, is compensated. A circulating flux <f> C IRC in the stator does not occur with optimal compensation, as shown in Figs. 3 and 4. The sum of common-mode current ICM-W and reverse current ICM-C, and thus the resulting common-mode magnetizing current, is then zero.

[0065] Fig. 5 shows an electric machine of a drive device according to the invention from the front, wherein a rotating collector as shown in Figs. 8 to 10 may be used, but is not shown in Figs. 5 to 7.

[0066] 2024P00066 WO 24.07.2025 BZ Fig. 5 shows the location of axial return lines 6, which form the return current path ICM-C along the axial extent of the stator 1. The axial return lines 6 are located in the region of the inner circumference of the stator core 2, in particular near the inner boundary of the windings 4.

[0067] The axial feedback lines 6 extend axially along the stator core 2 to an axial end of the stator core 2 and are distributed circumferentially around the entire circumference of the stator core 2 at equal intervals. The axial feedback lines 6 are each arranged in the stator laminations 3 in the areas between two cavities for receiving the windings 4 of the stator 1.

[0068] The axial return lines 6 can be designed, for example, as press-fit metal profiles 10 (Fig. 6) or as welds 11 (Fig. 7).

[0069] As shown in Fig. 8, the axial return lines 6 are collected at the axial end of the stator core 2 in a rotating collector 7, which has a ring shape. The rotating collector 7 is formed by an additional metal sheet that is insulated from the stator core 2. The rotating collector 7 is insulated from the outermost stator sheet 3 of the stator core 2 by means of electrical insulation 9, which can, for example, also be disc-shaped or be formed by a coating of a non-conductive material.

[0070] At the axial end of the axial return line 6, more precisely at the circumferential collector 7, connection terminals 8 are provided for connecting the return current path ICM-C or the collector to the inverter.

[0071] 2024P00066 WO 24.07.2025 BZ The axial return lines 6, the circumferential collector 7 and the connection terminals 8 together form a collector, for the formation of the return flow path ICM-C.

[0072] The return current path ICM-C is designed to return current to the intermediate circuit of the inverter.

[0073] As shown in Fig. 9 and Fig. 10, two connection terminals 8 of the collector can be joined, preferably spot-welded, to the insulated additional metal sheet that forms the circumferential collector 7.

[0074] For example, the three terminals U, V, W of the electric machine can be arranged between the two terminals 8 of the collector.

[0075] 2024P00066 WO 24.07.2025 BZ Reference List

[0076] stator

[0077] Stator core

[0078] Stator laminations

[0079] winding

[0080] Housing axial return line circumferential collector

[0081] Collector connection terminal

[0082] isolation

[0083] Metal profile

[0084] weld

[0085] rotor

[0086] Return flow path collector

[0087] Return current path housing

[0088] Common-mode current circulating flow

[0089] Connection terminals of the electric machine

[0090] 2024P00066 WO 24.07.2025 BZ< / f> < / f> < / f> < / f> < / f> < / f>

Claims

Patent claims 1. Drive device comprising an electric machine and an inverter, wherein the inverter is configured to supply the electric machine with an alternating voltage, wherein the electric machine comprises a rotor (12) and a stator (1) surrounding the rotor (12), wherein the stator (1) has a stator core (2), wherein the stator core (2) comprises a stack of stator laminations (3) and includes windings (4) received by the stack of stator laminations (3), wherein the stator (1) is received in a housing (5), wherein the stator (1) is electrically insulated from the housing (5), characterized in that a reverse current path (ICM-C) is formed inside the stator core (2) for returning a current to the inverter, so that a common-mode current (ICM-W) flowing in the stator core (2) to the housing, which contributes to a circulating flux (dGic) in the stator, is at least partially compensated.

2. Drive device according to claim 1, characterized in that the reverse current path (ICM-C) is formed in the area of ​​the inner circumference of the stator core (2), in particular near the inner boundary of the windings (4).

3. Drive device according to at least one of the preceding claims, 2024P00066 WO 24.07.2025 BZ characterized by the fact that the return current path (ICM-C) includes at least one axial return line (6) which extends axially along the stator core (2) to an axial end of the stator core (2).

4. Drive device according to claim 3, characterized in that the return current path (ICM-C) comprises several axial return lines (6) extending axially along the stator core (2) to an axial end of the stator core (2), wherein the several axial return lines (6) are distributed circumferentially around the stator core (2), preferably around the entire circumference of the stator core (2), particularly preferably at equal intervals from each other.

5. Drive device according to claim 4, characterized in that the axial return lines (6) are collected at the axial end of the stator core in a rotating collector (7), wherein the rotating collector (7) preferably has a ring shape.

6. Drive device according to claim 5, characterized in that the rotating collector (7) is electrically insulated (9) from the outermost stator lamination (3) of the stator core (2), wherein the rotating collector (7) is preferably formed by an additional metal lamination insulated from the stator core (2).

7. Drive device according to at least one of the preceding claims, 2024P00066 WO 24.07.2025 BZ 16 characterized in that connection terminals (8) for connection to the inverter are provided at the axial end of the axial return line (6), preferably at the rotating collector (7).

8. Drive device according to at least one of the preceding claims, characterized in that the axial return line (6) or the axial return lines (6) are formed by a metal profile (10) or a weld seam (11).

9. Drive device according to at least one of the preceding claims, characterized in that the axial return line (6) or axial return lines (6) are each formed in areas between two cavities for receiving the windings (4) in the stator laminations (3).

10. Drive device according to at least one of the preceding claims, characterized in that the inverter comprises at least one intermediate circuit, wherein the return current path (ICM-C) is designed to return a current to the intermediate circuit of the inverter.

11. Drive device according to at least one of the preceding claims, characterized in that the return current path (ICM-C) is designed to return a current to the 2024P00066 WO 24.07.2025 BZ The intermediate circuit of the inverter, if a current-compensated choke is present between the AC voltage outputs of the inverter and the electric machine, is included in this choke. 2024P00066 WO 24.07.2025 BZ

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