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 upper busbar (Uz+) and the lower busbar (Uz-) are arranged offset relative each other in the circumferential direction, and the busbars (Uz+, Uz-) coaxially surround the axis of rotation (D) and the switches (11, 12, 13, 21, 22, 23).

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 103 062 27 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] 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.

[0008] DE 102014205957 A1 discloses a driver assembly for an electric motor. The driver assembly comprises a predetermined number of semiconductor switches, with one of the semiconductor switches being arranged within a circular line and the remaining semiconductor switches being arranged on the circular line.

[0009] The invention is based on the object of developing an electric motor. This 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.

[0010] 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 upper busbar and the lower busbar are arranged offset from one another in the circumferential direction, and the busbars coaxially surround the rotational axis and the switches.

[0011] The converter's power section is thus located in close proximity to the stator or integrated into the stator. The space required for the power section, especially in the axial direction, is significantly reduced. A control module for controlling the power section's switches can be located away from the stator, since no significant ohmic losses occur in the control lines connecting the control module to the switches. The outer contour of a stator housing can remain unchanged.

[0012] According to a preferred embodiment of the invention, the upper busbar and the lower busbar are each designed in the form of a half-shell. The upper busbar and the lower busbar extend together, preferably almost completely around the axis of rotation. Only relatively small gaps remain between the upper busbar and the lower busbar, ensuring electrical insulation between the upper and lower busbars.

[0013] According to an advantageous embodiment of the invention, the busbars coaxially surround the busbars. This further reduces the space required for the power section in the axial direction. According to an advantageous embodiment of the invention, the switches are arranged radially between the busbars and the busbars. This further reduces the space required for the power section in the axial direction.

[0014] 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 driven at relatively high frequencies and cause relatively low switching losses with relatively low ohmic losses in the switched-on state.

[0015] According to a preferred embodiment of the invention, the drain terminals of the upper switches are frictionally connected to the upper busbar. The upper switches are each designed, for example, as N-channel MOSFETs. Heat generated in the upper switches is dissipated radially outward through the upper busbar and the holding element.

[0016] According to a preferred embodiment of the invention, the drain terminals of the lower switches are frictionally connected to the lower busbar. The lower switches are each designed, for example, as P-channel MOSFETs. Heat generated in the lower switches is dissipated radially outward through the lower busbar and the holding element.

[0017] According to an advantageous development of the invention, the power section has a clamping unit that presses the busbars radially outward against the switches. The clamping unit presses the switches outward against the busbars via the busbars.

[0018] According to an advantageous embodiment of the invention, the clamping unit comprises a spring element and a plurality of cams. The cams rest against the busbars, and the spring element presses the cams radially outward against the busbars. According to an advantageous embodiment of the invention, the clamping unit presses the busbars against the switches in such a way that a force-locking connection between the source terminals of the switches and the busbars is created.

[0019] According to an advantageous development of the invention, the power section has at least three current sensors, and the busbars coaxially surround the current sensors. This enables current measurement without significantly increasing the space required for the power section in the axial direction.

[0020] According to an advantageous embodiment of the invention, the stator has a hollow cylindrical stator housing in which the stator windings are arranged. The busbars are arranged axially offset from the stator windings. This further reduces the space required for the power section.

[0021] According to an advantageous development of the invention, the electric motor comprises a hollow cylindrical support element that coaxially surrounds the rotational axis. The support element is axially connected to the stator housing, and the support element coaxially surrounds the busbars. 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.

[0022] According to an advantageous embodiment of the invention, the busbars rest against an inner surface of the holding element facing the rotation axis. The holding element is made of an electrically insulating material or has an electrically insulating coating at least on its inner surface. This makes it possible to arrange the busbars directly on the inner surface of the holding element. The electrically insulating coating allows the holding element to be manufactured from a metallic material.

[0023] The invention is not limited to the combination of features in the claims. Further possible combinations of claims and / or individual claim features and / or features of the description and / or the figures will become apparent to those skilled in the art, particularly from the task and / or the problem posed by comparison with the prior art. The invention will now be explained in more detail with reference to figures. The invention is not limited to the exemplary embodiments shown in the figures. The figures represent the subject matter of the invention only schematically. They show:

[0024] Figure 1 : a schematic circuit diagram of a power unit with a stator of an electric motor,

[0025] Figure 2: a perspective view of part of an electric motor,

[0026] Figure 3: a schematic representation of a development of a radially inner region of a power unit,

[0027] Figure 4: a schematic representation of a development of a radially outer region of a power unit and

[0028] Figure 5: a schematic representation of a development of a radially outer region of a power unit according to an alternative embodiment.

[0029] 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. Stator windings 31, 32, 33 are connected in a star configuration and electrically connected to a common star point 35.

[0030] 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.

[0031] 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 direct voltage is therefore applied between the upper busbar Uz+ and the lower busbar Uz-. The power section further includes 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 II, V, W. The current sensors 41, 42, 43 are designed, for example, as measuring resistors.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] The upper switches 11, 12, 13 and the lower switches 21, 22, 23 are each implemented as field-effect transistors. The switches 11, 12, 13, 21, 22, 23 each have a gate terminal, a source terminal, and a drain terminal. The gate terminals of the switches 11, 12, 13, 21, 22, 23 are connected to the control module (not shown here).

[0036] The power section features a DC link capacitor C5. The DC link capacitor C5 is connected between the upper busbar Uz+ and the lower busbar Uz. A single DC link capacitor C5 is shown here. Alternatively, a parallel connection of several DC link capacitors C5 is also conceivable.

[0037] 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).

[0038] For this purpose, the power section has an upper interference suppression capacitor C1 and a lower interference suppression capacitor C2. The upper interference suppression capacitor C1 is electrically connected between the upper busbar Uz+ and a node 55. The lower interference suppression capacitor C2 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. The interference suppression capacitors are not absolutely necessary and can therefore be omitted.

[0039] Figure 2 shows a perspective view of part of an electric motor. 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.

[0040] The electric motor comprises a hollow cylindrical retaining element (not shown here). The retaining element adjoins the stator housing 4 in the axial direction and coaxially surrounds the rotational axis D. In this case, the retaining element is made of an electrically insulating material. Alternatively, the retaining element has an electrically insulating coating on at least one inner surface facing the rotational axis D.

[0041] The retaining element serves in particular to accommodate components of the electric motor's power section. The retaining element is not mandatory. Alternatively, the stator housing 4 is extended in the axial direction, and the aforementioned components of the power section are accommodated in the stator housing 4.

[0042] The upper busbar Uz+ and the lower busbar Uz- are each designed in the form of a half-shell. The upper busbar Uz+ and the lower busbar Uz- are arranged offset from one another in the circumferential direction. The upper busbar Uz+ and the lower busbar Uz- extend almost completely around the rotation axis D. Only relatively small gaps remain between the upper busbar Uz+ and the lower busbar Uz-, which ensure electrical insulation between the upper busbar Uz+ and the lower busbar Uz-.

[0043] The power section features a parallel circuit of two DC link capacitors C5. The power section does not have a suppression capacitor. The DC link capacitors C5 are each arranged in the gaps between the upper busbar Uz+ and the lower busbar Uz-.

[0044] The busbars Uz+, Uz- rest on an inner surface of the holding element facing the rotational axis D. The holding element thus coaxially surrounds the busbars Uz+, Uz-. The busbars Uz+, Uz- coaxially surround the rotational axis D. The busbars Uz+, Uz- are arranged offset in the axial direction from the stator windings 31, 32, 33.

[0045] The busbars Uz+, Uz- coaxially surround the busbars 51, 52, 53. The switches 11, 12, 13, 21, 22, 23 are arranged radially between the busbars Uz+, Uz- and the busbars 51, 52, 53. The busbars Uz+, Uz- thus also coaxially surround the switches n, 12, 13, 21, 22, 23.

[0046] The upper switches 11, 12, and 13 are arranged offset from one another in the circumferential direction. The lower switches 21, 22, and 23 are also arranged offset from one another in the circumferential direction. All switches 11, 12, 13, 21, 22, and 23 are arranged offset from one another in the circumferential direction. The upper switches 11, 12, and 13 are each designed as N-channel MOSFETs. The drain terminals of the upper switches 11, 12, and 13 are located on the upper power rail Uz+ and are electrically connected to the upper power rail Uz+.

[0047] The lower switches 21, 22, and 23 are each implemented as P-channel MOSFETs. The drain terminals of the lower switches 21, 22, and 23 are located on the lower power rail Uz- and are electrically connected to the lower power rail Uz-.

[0048] The power section has a clamping unit. The clamping unit presses the first busbar 51 radially outward against the first upper switch 11 and the first lower switch 21. The clamping unit presses the second busbar 52 radially outward against the second upper switch 12 and the second lower switch 22. The clamping unit presses the third busbar 53 radially outward against the third upper switch 13 and the third lower switch 23.

[0049] The clamping unit comprises a spring element 60 and a spring plate 61. The clamping unit further comprises a plurality of cams 65 arranged on the spring plate 61. The spring plate 61 has two partial regions which are pivotable relative to one another about a pivot axis running parallel to the rotation axis D. The spring element

[0050] 60 is clamped between the two sections and presses the two sections of the spring plate 61 apart.

[0051] The cams 65 rest on the busbars 51, 52, 53 as well as on the phase conductors U, V, W. The spring element 60 presses, as already mentioned, the two sections of the spring plate

[0052] 61, whereby the cams 65 are pressed radially outward. The spring element 60 thus presses the cams 65 radially outward against the busbars 51, 52, 53 and against the phase conductors U, V, W via the spring plate 61.

[0053] The busbars 51, 52, 53 press the switches 11, 12, 13, 21, 22, 23 radially outward against the busbars Uz+, Uz-. The drain terminals of the upper switches 11, 12, 13 are thus frictionally connected to the upper busbar Uz+, and the drain terminals of the lower switches 21, 22, 23 are frictionally connected to the lower busbar Uz-. Figure 3 shows a schematic representation of a developed view of a radially inner region of a power section. The radially inner region of the power section comprises the busbars 51, 52, 53, the current sensors 41, 42, 43, and the phase conductors U, V, W. The busbars

[0054] 51, 52, 53 are connected to switches 11, 12, 13, 21, 22, 23, which are not shown here.

[0055] Figure 4 shows a schematic representation of a developed section of a radially outer region of a power section. The radially outer region of the power section includes the busbars Uz+, Uz- and the switches n, 12, 13, 21, 22, 23. The switches n, 12, 13, 21, 22, 23 are connected to the busbars 51, 52, 53 (not shown here).

[0056] The radially outer region of the power section also includes two intermediate circuit capacitors C5, which are connected between the upper busbar Uz+ and the lower busbar Uz. The power section does not have a suppression capacitor.

[0057] Figure 5 shows a schematic representation of a developed section of a radially outer region of a power section according to an alternative embodiment. The radially outer region of the power section comprises the busbars Uz+, Uz- and the switches 11, 12, 13, 21, 22, 23. The switches 11, 12, 13, 21, 22, 23 are located on the busbars 51, not shown here.

[0058] 52, 53.

[0059] The radially outer region of the power section also includes two intermediate circuit capacitors C5, which are connected between the upper busbar Uz+ and the lower busbar Uz. The power section also has an upper interference suppression capacitor C1 and a lower interference suppression capacitor C2.

[0060] List of reference symbols

[0061] 4 Stator housing

[0062] 11 first upper switch

[0063] 12 second upper switch

[0064] 13 third upper switch

[0065] 21 first lower switch

[0066] 22 second lower switch

[0067] 23 third lower switch

[0068] 31 first stator winding

[0069] 32 second stator winding

[0070] 33 third stator winding

[0071] 35 star point

[0072] 41 first current sensor

[0073] 42 second current sensor

[0074] 43 third current sensor

[0075] 51 first busbar

[0076] 52 second busbar

[0077] 53 third busbar

[0078] 55 Junction

[0079] 60 spring element

[0080] 61 spring plate

[0081] 65 cams

[0082] D axis of rotation

[0083] Uz+ upper busbar

[0084] Uz- lower busbar

[0085] C1 upper interference suppression capacitor

[0086] C2 lower interference suppression capacitor

[0087] C5 DC link capacitor

[0088] U first phase conductor

[0089] V second phase conductor

[0090] W third phase conductor

[0091] 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 thatthat the upper busbar (Uz+) and the lower busbar (Uz-) are arranged offset from one another in the circumferential direction, and that the busbars (Uz+, Uz-) coaxially surround the axis of rotation (D) and the switches (11, 12, 13, 21, 22, 23).

2. Electric motor according to claim 1, characterized in that the upper busbar (Uz+) and the lower busbar (Uz-) are each designed in the form of a half-shell.

3. Electric motor according to one of the preceding claims, characterized in that the busbars (Uz+, Uz-) coaxially surround the busbars (51, 52, 53).

4. Electric motor according to one of the preceding claims, characterized in that the switches (11, 12, 13, 21, 22, 23) are arranged in the radial direction between the busbars (Uz+, Uz-) and the busbars (51, 52, 53).

5. 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.

6. Electric motor according to claim 5, characterized in that the drain terminals of the upper switches (11, 12, 13) are non-positively connected to the upper busbar (Uz+).

7. Electric motor according to one of claims 5 to 6, characterized in that the drain terminals of the lower switches (21, 22, 23) are non-positively connected to the lower busbar (Uz-).

8. Electric motor according to one of the preceding claims, characterized in that the power section has a clamping unit which presses the busbars (51, 52, 53) radially outwards against the switches (11, 12, 13, 21, 22, 23).

9. Electric motor according to claim 8, characterized in that the tensioning unit comprises a spring element (60) and a plurality of cams (65), and that the cams (65) bear against the busbars (51, 52, 53), and that the spring element (60) presses the cams (65) radially outwards against the busbars (51, 52, 53).

10. Electric motor according to one of claims 8 to 9, characterized in that the clamping unit presses the busbars (51, 52, 53) against the switches (11, 12, 13, 21, 22, 23) in such a way that a force-fitting connection of the source terminals of the switches (11, 12, 13, 21, 22, 23) with the busbars (51, 52, 52) is created.

11. Electric motor according to one of the preceding claims, characterized in that the power section has at least three current sensors (41, 42, 43), and that the busbars (Uz+, Uz-) coaxially surround the current sensors (41, 42, 43).

12. Electric motor according to one of the preceding claims, characterized in that the stator has a hollow cylindrical stator housing (4) in which the stator windings (31, 32, 33) are arranged, and in that the busbars (Uz+, Uz-) are arranged offset in the axial direction from the stator windings (31, 32, 33).

13. Electric motor according to claim 12, characterized in that the electric motor comprises a hollow cylindrical holding element which coaxially surrounds the axis of rotation (D), and in that the holding element adjoins the stator housing (4) in the axial direction, and in that the holding element coaxially surrounds the busbars (Uz+, Uz-).

14. Electric motor according to claim 13, characterized in that the busbars (Uz+, Uz-) bear against an inner surface of the holding element facing the axis of rotation (D), and in that the holding element consists of an electrically insulating material or has an electrically insulating coating at least on the inner surface.

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