Electric motor

Abstract

The invention relates to an electric motor comprising a stator which has at least three stator windings (31, 32, 33), a rotor which is rotatable about an axis of rotation (D) relative to the stator, and a power part for actuating the stator windings (31, 32, 33), which power part comprises an upper busbar (Uz+) to which a positive voltage is applied, a lower busbar (Uz-) to which a negative voltage is applied, at least three busbars (51, 52, 53), which are each electrically connected to one of the stator windings (31, 32, 33), at least three upper switches (11, 12, 13), which are electrically connected between the upper busbar (Uz+) and in each case one of the busbars (51, 52, 53), and at least three lower switches (21, 22, 23), which are electrically connected between the lower busbar (Uz-) and in each case one of the busbars (51, 52, 53). The electric motor comprises a hollow-cylindrical holding element (7) which coaxially surrounds the axis of rotation (D), and the switches (11, 12, 13, 21, 22, 23) are arranged offset to one another in the circumferential direction on an inner surface of the holding element (7) facing the axis of rotation (D).

Description

[0001] electric motor

[0002] Description:

[0003] The invention relates to an electric motor comprising a stator having at least three stator windings, a rotor rotatable about an axis of rotation relative to the stator, and a power unit for controlling the stator windings.

[0004] Document DE 102009 051 979 A1 discloses a generic electric motor comprising a rotor and a stator. The stator comprises stator windings and is arranged in a motor housing. The rotor is rotatable relative to the stator.

[0005] A generic electric motor also includes a converter for supplying the stator with electrical energy. The converter is supplied with a DC voltage, for example, and provides a three-phase output voltage for the stator. The converter includes a power section and a control module. The power section includes several switches controlled by the control module.

[0006] Document DE 103 06 227 B4 discloses a power section for a converter that includes a heat sink. Heat-generating components, such as semiconductor switches, are arranged at regular intervals on the outside of the heat sink.

[0007] DE 102010 017 519 B4 discloses a motor device with an integrated electronic circuit. The motor device comprises a motor, a heat sink, and an electronic circuit mounted on the motor housing.

[0008] DE 102017213395 A1 discloses a three-phase inverter system for a motor. The three-phase inverter system includes first, second, and third output units and first, second, and third capacitors arranged radially to form a hexagonal shape.

[0009] DE 11 2015 004 112 T5 discloses an electronics module that includes a cooling tower with first and second axial ends. The cooling tower extends around a central module axis.

[0010] ISI \ EIDOPAT 08.05.2024 An electronic drive device is known from WO 2019 / 223882 A1. The drive device comprises a stator and a rotor. Drive windings are interconnected via a connection element.

[0011] Drive systems with electric motors are known from the document by Robert Abebe et al. "Integrated motor drives: state of the art and future trends" in: IET Electr. Power Appl., Vol. 10, 2016, Iss. 8, pp. 757-771. - ISSN 1751-8660.

[0012] The converter is usually designed as a separate component and located near the electric motor. The converter therefore requires space. It is also common to locate the converter away from the stator, for example, in a control cabinet. In this case, ohmic losses occur in the supply lines from the converter to the stator.

[0013] The invention is based on the object of developing an electric motor.

[0014] The object is achieved according to the invention by an electric motor having the features specified in claim 1. Advantageous embodiments and further developments are the subject of the subclaims.

[0015] An electric motor according to the invention comprises a stator having at least three stator windings, a rotor rotatable about a rotational axis relative to the stator, and a power section for controlling the stator windings. The power section has an upper busbar to which a positive voltage is applied, a lower busbar to which a negative voltage is applied, at least three busbars, each electrically connected to one of the stator windings, at least three upper switches electrically connected between the upper busbar and each of the busbars, and at least three lower switches electrically connected between the lower busbar and each of the busbars. The electric motor comprises a hollow cylindrical holding element coaxially surrounding the rotational axis.The switches are arranged offset from one another in the circumferential direction on an inner surface of the holding element facing the rotational axis. The power section of the converter is thus located in the immediate vicinity of the stator or integrated into the stator. The inventive arrangement of the switches significantly reduces the space required for the power section. A control module for controlling the switches of the power section can be arranged away from the stator, since no significant ohmic losses occur in the control lines connecting the control module to the switches.

[0016] According to an advantageous embodiment of the invention, the stator has a hollow cylindrical stator housing in which the stator windings are arranged, and the retaining element is axially connected to the stator housing. Thus, the upper busbar, the lower busbar, and the busbars are also axially connected to the stator housing. This further reduces the space required for the power section.

[0017] According to an advantageous embodiment of the invention, the holding element consists of an electrically insulating material or has an electrically insulating coating at least on the inner surface facing the rotational axis. This makes it possible to arrange busbars and busbars of the power section directly on the inner surface of the holding element. The electrically insulating coating allows the holding element to be manufactured from a metallic material. In particular, it is conceivable for the holding element to be formed integrally with the stator housing.

[0018] According to an advantageous embodiment of the invention, the busbars, the upper busbar, and the lower busbar are arranged on the inner surface of the holding element facing the rotation axis and each have an insulating coating facing the holding element. This embodiment also allows the holding element to be manufactured from a metallic material. In particular, it is conceivable for the holding element to be formed integrally with the stator housing.

[0019] According to an advantageous embodiment of the invention, the upper busbar is arranged offset in the circumferential direction from the lower busbar on the inner surface of the holding element facing the axis of rotation. The upper busbar and the lower busbar together preferably extend approximately over the entire circumference of the inner surface of the holding element. This reduces the axial expansion of the busbars and the holding element. Furthermore, the waste heat generated in the switches is dissipated relatively quickly. According to another advantageous embodiment of the invention, the upper busbar is arranged offset in the axial direction from the lower busbar on the inner surface of the holding element facing the axis of rotation. This makes the internal interconnection between the busbars, the switches, and the busbars easy to implement.

[0020] According to an advantageous embodiment of the invention, the busbars are arranged offset from one another in the circumferential direction on the inner surface of the holding element facing the rotation axis. The busbars preferably extend together approximately over the entire circumference of the inner surface of the holding element. This reduces the axial dimensions of the busbars and the holding element.

[0021] According to an advantageous embodiment of the invention, the busbars are arranged axially offset from the upper busbar and the lower busbar on the inner surface of the holding element facing the rotation axis. This allows for easy internal interconnection between the busbars, the switches, and the busbars.

[0022] According to an advantageous embodiment of the invention, the busbars are arranged axially between the upper busbar and the lower busbar on the inner surface of the holding element facing the rotation axis. This makes the internal interconnection between the busbars, the switches, and the busbars particularly easy to implement.

[0023] According to a preferred embodiment of the invention, the switches are each designed as field-effect transistors and each have a gate terminal, a source terminal, and a drain terminal. Field-effect transistors can be controlled at relatively high frequencies and cause relatively low switching losses with relatively low ohmic losses in the switched-on state. In particular, the drain terminal of a field-effect transistor can be connected to a busbar or a busbar in a material-to-material manner. Material-to-material connections include, in particular, laser welding and soldering. According to an advantageous embodiment of the invention, the drain terminals of the upper switches are materially connected to the upper busbar. The upper busbar is arranged in the radial direction between the holding element and the upper switches.Heat generated in the upper switches is dissipated radially outwards through the upper busbar and the holding element.

[0024] According to an advantageous embodiment of the invention, the drain terminals of the lower switches are integrally connected to the lower busbar. The lower busbar is arranged radially between the retaining element and the lower switches. Heat generated in the lower switches is dissipated radially outward through the lower busbar and the retaining element.

[0025] According to an advantageous embodiment of the invention, the drain terminals of the upper switches are each integrally connected to one of the busbars. The busbars are arranged radially between the holding element and one of the upper switches. Heat generated in the upper switches is dissipated radially outward through the respective busbar and the holding element, and partially into the windings.

[0026] According to an advantageous embodiment of the invention, the drain terminals of the lower switches are each integrally connected to one of the busbars. The busbars are arranged radially between the holding element and one of the lower switches. Heat generated in the lower switches is dissipated radially outward through the respective busbar and the holding element, and partially into the windings.

[0027] According to an advantageous development of the invention, the power section has at least one intermediate circuit capacitor, which is connected between the upper busbar and the lower busbar and is arranged on the inner surface of the holding element facing the rotation axis, and / or the power section has at least one interference suppression capacitor, which is arranged on the inner surface of the holding element facing the rotation axis. According to an advantageous development of the invention, the power section has at least three current sensors, which are arranged on the inner surface of the holding element facing the rotation axis. The invention is not limited to the combination of features of the claims.For the person skilled in the art, further reasonable combination possibilities of claims and / or individual claim features and / or features of the description and / or the figures will arise, in particular from the task and / or the task arising from a comparison with the prior art.

[0028] The invention will now be explained in more detail with reference to the accompanying drawings. The invention is not limited to the exemplary embodiments shown in the drawings. The drawings only represent the subject matter of the invention schematically. They show:

[0029] Figure 1 : a schematic circuit diagram of a power unit with a stator of an electric motor,

[0030] Figure 2: a perspective view of a part of an electric motor according to a first embodiment,

[0031] Figure 3: another perspective view of the part of the electric motor according to the first embodiment,

[0032] Figure 4: a schematic representation of a development of a power part of the electric motor according to the first embodiment,

[0033] Figure 5: a schematic representation of a development of a power section of an electric motor according to a second embodiment,

[0034] Figure 6: a schematic representation of a development of a power section of an electric motor according to a third embodiment and

[0035] Figure 7: a schematic representation of a development of a power part of an electric motor according to a fourth embodiment.

[0036] Figure 1 shows a schematic circuit diagram of a power section with a stator of an electric motor. The electric motor is an electrical machine and comprises the stator and a rotor (not shown here). The stator has a first stator winding 31, a second stator winding 32, and a third stator winding 33. The stator windings 31, 32, 33 are connected in a star configuration and electrically connected to a common star point 35.

[0037] The stator has a first phase conductor U, a second phase conductor V, and a third phase conductor W. The first phase conductor U is electrically connected to the first stator winding 31. The second phase conductor V is electrically connected to the second stator winding 32. The third phase conductor W is electrically connected to the third stator winding 33.

[0038] The electric motor also includes the power section for controlling the stator windings 31, 32, 33. The power section has an upper busbar Uz+, to which a positive voltage is applied, and a lower busbar Uz-, to which a negative voltage is applied. A DC voltage is thus applied between the upper busbar Uz+ and the lower busbar Uz-.

[0039] The power unit further comprises a first busbar 51, a second busbar 52 and a third busbar 53. The first busbar 51 is electrically connected to the first phase conductor U via a first current sensor 41. The second busbar 52 is electrically connected to the second phase conductor V via a second current sensor 42. The third busbar 53 is electrically connected to the third phase conductor W via a third current sensor 43. The busbars 51, 52, 53 are thus electrically connected to one of the stator windings 31, 32, 33 via the current sensors 41, 42, 43 and the phase conductors U, V, W. The current sensors 41, 42, 43 are designed, for example, as measuring resistors.

[0040] The power section has a first upper switch 11, a second upper switch 12, and a third upper switch 13. The first upper switch 11 is electrically connected between the upper busbar Uz+ and the first busbar 51. The second upper switch 12 is electrically connected between the upper busbar Uz+ and the second busbar 52. The third upper switch 13 is electrically connected between the upper busbar Uz+ and the third busbar 53.

[0041] The power section has a first lower switch 21, a second lower switch 22, and a third lower switch 23. The first lower switch 21 is electrically connected between the lower busbar Uz- and the first busbar 51. The second lower switch 22 is electrically connected between the lower busbar Uz- and the second busbar 52. The third lower switch 23 is electrically connected between the lower busbar Uz- and the third busbar 53.

[0042] The power section is part of a converter. The converter also has a control module, which is not shown here. The upper switches n, 12, 13 and the lower switches 21, 22, 23 are controlled by the control module in such a way that a three-phase alternating voltage is applied to the stator windings 31, 32, 33. The converter thus supplies a three-phase output voltage for the stator.

[0043] The upper switches 11, 12, 13 and the lower switches 21, 22, 23 are each implemented as field-effect transistors. Switches 11, 12, 13, 21, 22, 23 each have a gate terminal, a source terminal, and a drain terminal. The gate terminals of switches 11, 12, 13, 21, 22, 23 are connected to the control module (not shown here).

[0044] The power section has a DC link capacitor 05. The DC link capacitor 05 is connected between the upper busbar Uz+ and the lower busbar Uz. A single DC link capacitor 05 is shown here.

[0045] Alternatively, a parallel connection of several intermediate circuit capacitors 05 is also conceivable.

[0046] Changing potentials on the phase conductors U, V, and W lead to unwanted parasitic currents that can travel along undefined paths and thus cause conducted interference. Uncontrolled conducted interference that travels through loops also leads to radiated interference fields. To minimize the effect of these unwanted but unavoidable parasitic currents and improve the EMC of the power section, a low-inductance path is provided for the return of these parasitic currents to a protective earth (PE).

[0047] For this purpose, the power section has an upper interference suppression capacitor O1 and a lower interference suppression capacitor O2. The upper interference suppression capacitor O1 is electrically connected between the upper busbar Uz+ and a node 55. The lower interference suppression capacitor O2 is electrically connected between the lower busbar Uz- and node 55. Node 55 is electrically connected to the protective earth PE. Alternatively, node 55 is electrically connected to the protective earth PE via another capacitor.

[0048] Figure 2 shows a perspective view of part of an electric motor according to a first embodiment. The stator has a hollow cylindrical stator housing 4, which is made of an electrically conductive material. The stator housing 4 coaxially surrounds a rotational axis D. The rotor, not shown here, is rotatable about the rotational axis D relative to the stator. The stator windings 31, 32, 33 are arranged in the hollow cylindrical stator housing 4.

[0049] The electric motor comprises a hollow cylindrical holding element 7. The holding element 7 adjoins the stator housing 4 in the axial direction and coaxially surrounds the rotational axis D. In this case, the holding element 7 is made of an electrically insulating material. Alternatively, the holding element 7 has an electrically insulating coating on at least one inner surface facing the rotational axis D.

[0050] The power section has a parallel circuit of two intermediate circuit capacitors C5. The power section does not have a suppression capacitor in this case. The upper switches 11, 12, 13 are arranged offset from one another in the circumferential direction on the inner surface of the holding element 7 facing the rotation axis D.

[0051] Figure 3 shows a further perspective view of the part of the electric motor according to the first embodiment from a different viewing direction than in Figure 2. The lower switches 21, 22, 23 are arranged offset from one another in the circumferential direction on the inner surface of the holding element 7 facing the rotation axis D. Thus, all switches 11, 12, 13, 21, 22, 23 are arranged offset from one another in the circumferential direction on the inner surface of the holding element 7 facing the rotation axis D.

[0052] The upper busbar Uz+, the lower busbar Uz- and the busbars 51, 52, 53 are connected to the stator housing 4 in the axial direction.

[0053] Figure 4 shows a schematic representation of a developed power section of the electric motor according to the first embodiment. As already mentioned, the power section has a parallel circuit of two intermediate circuit capacitors C5, but no interference suppression capacitor.

[0054] The upper busbar Uz+ is arranged offset in the circumferential direction to the lower busbar Uz- on the inner surface of the holding element 7 facing the rotation axis D. The busbars 51, 52, 53 are arranged offset in the axial direction to the upper busbar Uz+ and to the lower busbar Uz- on the inner surface of the holding element 7 facing the rotation axis D. The drain connections of the upper switches 11, 12, 13 are materially connected to the upper busbar Uz+. The upper switches 11, 12, 13 are each designed as N-channel MOSFETs. Alternatively, the drain connections of the upper switches 11, 12, 13 are positively and / or non-positively connected to the upper busbar Uz+, for example by means of a spring element, optionally with the addition of a silver paste.

[0055] The drain terminals of the lower switches 21, 22, and 23 are connected to the lower power rail Uz- by a material fit. The lower switches 21, 22, and 23 are each designed as P-channel MOSFETs. Alternatively, the drain terminals of the lower switches 21, 22, and 23 are connected to the lower power rail Uz- by a form-fitting and / or force-fitting connection, for example, using a spring element, optionally with the addition of a silver paste.

[0056] Figure 5 shows a schematic representation of a developed power section of an electric motor according to a second embodiment. The power section has a parallel circuit of two intermediate circuit capacitors C5.

[0057] The power section has an upper interference suppression capacitor C1, which is electrically connected between the upper busbar Uz+ and a node 55, and a lower interference suppression capacitor C2, which is electrically connected between the lower busbar Uz- and node 55. Node 55 is electrically connected to the protective earth PE. The protective earth PE is electrically connected to the stator housing 4, which is made of an electrically conductive material.

[0058] The upper busbar Uz+ is arranged offset in the circumferential direction from the lower busbar Uz- on the inner surface of the holding element 7 facing the rotation axis D. The busbars 51, 52, 53 are arranged offset in the axial direction from the upper busbar Uz+ and from the lower busbar Uz- on the inner surface of the holding element 7 facing the rotation axis D.

[0059] The drain terminals of the upper switches 11, 12, 13 are materially connected to the upper power rail Uz+. The upper switches 11, 12, 13 are each designed as N-channel MOSFETs. Alternatively, the drain terminals of the upper switches 11, 12, 13 are connected to the upper power rail Uz+ in a form-fitting and / or force-fitting manner, for example by means of a spring element, optionally with the addition of a silver paste. The drain terminals of the lower switches 21, 22, 23 are materially connected to the lower power rail Uz-. The lower switches 21, 22, 23 are each designed as P-channel MOSFETs. Alternatively, the drain terminals of the lower switches 21, 22, 23 are connected to the lower power rail Uz- in a form-fitting and / or force-fitting manner, for example by means of a spring element, optionally with the addition of a silver paste.

[0060] Figure 6 shows a schematic representation of a developed power section of an electric motor according to a third embodiment. The power section has a parallel circuit of two intermediate circuit capacitors C5, but no interference suppression capacitor.

[0061] The upper busbar Uz+ is arranged offset in the axial direction from the lower busbar Uz- on the inner surface of the holding element 7 facing the rotation axis D. The busbars 51, 52, 53 are arranged offset from one another in the circumferential direction on the inner surface of the holding element 7 facing the rotation axis D. The busbars 51, 52, 53 are arranged offset in the axial direction from the upper busbar Uz+ and from the lower busbar Uz- on the inner surface of the holding element 7 facing the rotation axis D.

[0062] The drain terminals of the upper switches 11, 12, 13 are each connected to one of the busbars 51, 52, 53 by a material fit. The upper switches 11, 12, 13 are each designed as a P-channel MOSFET. Alternatively, the drain terminals of the upper switches 11, 12, 13 are each connected to one of the busbars 51, 52, 53 by a form-fitting and / or force-fitting connection, for example, by means of a spring element, optionally with the addition of a silver paste.

[0063] The drain terminals of the lower switches 21, 22, 23 are each connected to one of the busbars 51, 52, 53 by a material fit. The lower switches 21, 22, 23 are each designed as an N-channel MOSFET. Alternatively, the drain terminals of the lower switches 21, 22, 23 are each connected to one of the busbars 51, 52, 53 by a form-fitting and / or force-fitting connection, for example, by means of a spring element, optionally with the addition of a silver paste.

[0064] Figure 7 shows a schematic representation of a developed power section of an electric motor according to a fourth embodiment. The power section has a parallel circuit of two intermediate circuit capacitors C5, but no interference suppression capacitor.

[0065] The upper busbar Uz+ is arranged offset in the axial direction to the lower busbar Uz- on the inner surface of the holding element 7 facing the axis of rotation D. The busbars 51, 52, 53 are arranged offset from one another in the circumferential direction on the inner surface of the holding element 7 facing the axis of rotation D. The busbars 51, 52, 53 are arranged offset in the axial direction to the upper busbar Uz+ and to the lower busbar Uz- on the inner surface of the holding element 7 facing the axis of rotation D. The busbars 51, 52, 53 are arranged in the axial direction between the upper busbar Uz+ and the lower busbar Uz-.

[0066] The drain terminals of the upper switches 11, 12, and 13 are connected to the upper power rail Uz+ by a material fit. The upper switches 11, 12, and 13 are each designed as N-channel MOSFETs. Alternatively, the drain terminals of the upper switches 11, 12, and 13 are connected to the upper power rail Uz+ by a form-fitting and / or force-fitting connection, for example, using a spring element, optionally with the addition of a silver paste.

[0067] The drain terminals of the lower switches 21, 22, 23 are each connected to one of the busbars 51, 52, 53 by a material fit. The lower switches 21, 22, 23 are each designed as an N-channel MOSFET. Alternatively, the drain terminals of the lower switches 21, 22, 23 are each connected to one of the busbars 51, 52, 53 by a form-fitting and / or force-fitting connection, for example, by means of a spring element, optionally with the addition of a silver paste.

[0068] List of reference symbols

[0069] 4 Stator housing

[0070] 7 Holding element

[0071] 11 first upper switch

[0072] 12 second upper switch

[0073] 13 third upper switch

[0074] 21 first lower switch

[0075] 22 second lower switch

[0076] 23 third lower switch

[0077] 31 first stator winding

[0078] 32 second stator winding

[0079] 33 third stator winding

[0080] 35 star point

[0081] 41 first current sensor

[0082] 42 second current sensor

[0083] 43 third current sensor

[0084] 51 first busbar

[0085] 52 second busbar

[0086] 53 third busbar

[0087] 55 Junction

[0088] D axis of rotation

[0089] Uz+ upper busbar

[0090] Uz- lower busbar

[0091] C1 upper interference suppression capacitor

[0092] C2 lower interference suppression capacitor

[0093] C5 DC link capacitor

[0094] U first phase conductor

[0095] V second phase conductor

[0096] W third phase conductor

[0097] PE protective earthing

Claims

Patent claims:

1. An electric motor comprising a stator having at least three stator windings (31, 32, 33), a rotor which is rotatable about a rotational axis (D) relative to the stator, and a power section for controlling the stator windings (31, 32, 33), which power section comprises an upper busbar (Uz+) to which a positive voltage is applied, a lower busbar (Uz-) to which a negative voltage is applied, at least three busbars (51, 52, 53), which are each electrically connected to one of the stator windings (31, 32, 33), at least three upper switches (11, 12, 13), which are electrically connected between the upper busbar (Uz+) and one of the busbars (51, 52, 53), and at least three lower switches (21, 22, 23), which are electrically connected between the lower busbar (Uz-) and one of the busbars (51, 52, 53) are connected, characterized in that the electric motor comprises a hollow cylindrical holding element (7),which coaxially surrounds the rotational axis (D), and that the switches (11, 12, 13, 21, 22, 23) are arranged offset from one another in the circumferential direction on an inner surface of the holding element (7) facing the rotational axis (D).

2. Electric motor according to claim 1, characterized in that the stator has a hollow cylindrical stator housing (4) in which the stator windings (31, 32, 33) are arranged, and that the holding element (7) adjoins the stator housing (4) in the axial direction.

3. Electric motor according to one of the preceding claims, characterized in that the holding element (7) consists of an electrically insulating material or has an electrically insulating coating at least on the inner surface facing the axis of rotation (D).

4. Electric motor according to one of the preceding claims, characterized in that the busbars (51, 52, 53), the upper busbar (Uz+) and the lower busbar (Uz-) are arranged on the inner surface of the holding element (7) facing the axis of rotation (D) and each have an insulating coating facing the holding element (7).

5. Electric motor according to one of the preceding claims, characterized in that the upper busbar (Uz+) is arranged offset in the circumferential direction to the lower busbar (Uz-) on the inner surface of the holding element (7) facing the axis of rotation (D).

6. Electric motor according to one of the preceding claims, characterized in that the upper busbar (Uz+) is arranged offset in the axial direction to the lower busbar (Uz-) on the inner surface of the holding element (7) facing the axis of rotation (D).

7. Electric motor according to one of the preceding claims, characterized in that the busbars (51, 52, 53) are arranged offset from one another in the circumferential direction on the inner surface of the holding element (7) facing the axis of rotation (D).

8. Electric motor according to one of the preceding claims, characterized in that the busbars (51, 52, 53) are arranged offset in the axial direction to the upper busbar (Uz+) and to the lower busbar (Uz-) on the inner surface of the holding element (7) facing the axis of rotation (D).

9. Electric motor according to one of the preceding claims, characterized in that the busbars (51, 52, 53) are arranged in the axial direction between the upper busbar (Uz+) and the lower busbar (Uz-) on the inner surface of the holding element (7) facing the axis of rotation (D).

10. Electric motor according to one of the preceding claims, characterized in that the switches (11, 12, 13, 21, 22, 23) are each designed as field-effect transistors and each have a gate terminal, a source terminal and a drain terminal.

11. Electric motor according to claim 10, characterized in that the drain terminals of the upper switches (11, 12, 13) are integrally connected to the upper busbar (Uz+).

12. Electric motor according to one of claims 10 to 11, characterized in that the drain terminals of the lower switches (21, 22, 23) are integrally connected to the lower busbar (Uz-).

13. Electric motor according to one of claims 10 to 12, characterized in that the drain terminals of the upper switches (11, 12, 13) are integrally connected to one of the busbars (51, 52, 53).

14. Electric motor according to one of claims 10 to 13, characterized in that the drain terminals of the lower switches (21, 22, 23) are integrally connected to one of the busbars (51, 52, 53).

15. Electric motor according to one of the preceding claims, characterized in that the power section has at least one intermediate circuit capacitor (C5) which is connected between the upper busbar (Uz+) and the lower busbar (Uz-) and is arranged on the inner surface of the holding element (7) facing the axis of rotation (D), and / or that the power section has at least one interference suppression capacitor (C1, O2) which is arranged on the inner surface of the holding element (7) facing the axis of rotation (D).

16. Electric motor according to one of the preceding claims, characterized in that the power unit has at least three current sensors (41, 42, 43) which are arranged on the inner surface of the holding element (7) facing the axis of rotation (D).

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