Electric motor

Abstract

The invention relates to an electric motor comprising a stator having at least three stator windings (31, 32, 33), a rotor rotatable about an axis of rotation (D) relative to the stator, and a power section for controlling the stator windings (31, 32, 33), comprising 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) electrically connected to each of the stator windings (31, 32, 33), at least three upper switches (11, 12, 13) electrically connected between the upper busbar (Uz+) and each of the busbars (51, 52, 53), and at least three lower switches (21, 22, 23) electrically connected between the lower busbar (Uz-) and each of the busbars (51, 52, 53). 52, 53) are switched, has, includes.The switches (11, 12, 13, 21, 22, 23) are arranged on a plurality of main circuit boards (61, 62, 63), and the main circuit boards (61, 62, 63) are arranged circumferentially offset from each other around the axis of rotation (D).

Description

[0001] 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 section for controlling the stator windings.

[0002] Document DE 10 2009 051 979 A1 discloses a generic electric motor comprising a rotor and a stator. The stator includes stator windings and is arranged in a motor housing. The rotor is rotatable relative to the stator.

[0003] A typical electric motor also includes a converter for supplying the stator with electrical energy. The converter is supplied, for example, with a DC voltage and provides a three-phase output voltage for the stator. The converter comprises a power section and a control module. The power section includes several switches that are controlled by the control module.

[0004] Document DE 103 062 27 B4 discloses a power section for a converter which includes a heat sink. Heat-generating components, for example semiconductor switches, are arranged at regular intervals on the outside of the heat sink.

[0005] The inverter is usually a separate component located near the electric motor. Therefore, the inverter requires installation space. It is also known to position the inverter remotely from the stator, for example, in a control cabinet. In this case, ohmic losses occur in the leads from the inverter to the stator.

[0006] The invention is based on the objective of further developing an electric motor.

[0007] The problem is solved 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 dependent claims.

[0008] An electric motor according to the invention comprises a stator having at least three stator windings, a rotor rotatable about an axis of rotation relative to the stator, and a power section for driving 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 electrically connected to each 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 switches are arranged on a plurality of main circuit boards, and the main circuit boards are arranged circumferentially offset from one another around the axis of rotation.

[0009] The power section of the inverter is thus arranged in the immediate vicinity of the stator or integrated into the stator. The arrangement of the main circuit boards according to the invention significantly reduces the space required for the power section. A control module for controlling the switches of the power section can be arranged remotely from the stator, since there are no significant ohmic losses in the control lines connecting the control module to the switches.

[0010] The main circuit boards are preferably designed as IMS circuit boards. IMS circuit boards can carry relatively high currents and have relatively high thermal conductivity.

[0011] According to a preferred embodiment of the invention, the stator has a hollow cylindrical stator housing in which the stator windings are arranged, and the main circuit boards are each arranged on an inner surface of the stator housing facing the axis of rotation. This further reduces the space required for the power section.

[0012] According to an advantageous embodiment of the invention, the main circuit boards are arranged axially offset from the stator windings. This further reduces the space required in the radial direction for the power section.

[0013] According to a preferred embodiment of the invention, the inner surface of the stator housing has a plurality of flat sub-surfaces facing the axis of rotation, which are arranged circumferentially offset from one another around the axis of rotation. Each of the main circuit boards is arranged on one of these sub-surfaces. This results in relatively good thermal coupling between the main circuit boards and the stator housing. Consequently, waste heat generated by switching losses in the switches is dissipated relatively efficiently through the main circuit boards into the stator housing.

[0014] According to an advantageous embodiment of the invention, each of the main circuit boards is positively attached to the stator housing, in particular by means of a screw. The screws allow the main circuit boards to be fastened to the stator housing with the necessary contact pressure.

[0015] According to an advantageous embodiment of the invention, the stator has a spring element which presses the main circuit boards against the inner surface of the stator housing. The main circuit boards can also be attached to the stator housing with the necessary contact pressure by means of the spring element.

[0016] According to an advantageous embodiment of the invention, the power section comprises at least one auxiliary circuit board. Furthermore, the power section comprises at least one intermediate circuit capacitor, which is connected between the upper and lower busbars and is arranged on the auxiliary circuit board, and / or the power section comprises at least one interference suppression capacitor, which is arranged on the auxiliary circuit board.

[0017] The auxiliary circuit board is preferably designed as an IMS circuit board. IMS circuit boards can carry relatively high currents and have relatively high thermal conductivity. However, other circuit board technologies can also be used.

[0018] According to an advantageous embodiment of the invention, the auxiliary circuit board is arranged offset in the circumferential direction to the main circuit boards.

[0019] According to an advantageous embodiment of the invention, the power section has at least three current sensors which are arranged on the main circuit boards.

[0020] According to an advantageous embodiment of the invention, the upper busbar is arranged axially offset from the lower busbar on each of the main circuit boards. This simplifies the internal interconnection between the busbars, the switches, and the busbars.

[0021] According to an advantageous embodiment of the invention, the busbars are arranged axially between the upper and lower busbars on each of the main circuit boards. This makes the internal interconnection between the busbars, the switches, and the busbars particularly easy to implement.

[0022] According to an advantageous embodiment of the invention, the main circuit boards surround the rotor.

[0023] According to an advantageous embodiment of the invention, the main circuit boards are arranged in the axial direction between one end of the rotor and the stator windings.

[0024] According to an advantageous embodiment of the invention, the switches are each arranged on a surface of the main circuit boards facing the axis of rotation.

[0025] The invention is not limited to the combination of features stated in the claims. For a person skilled in the art, further meaningful combinations of claims and / or individual claim features and / or features of the description and / or the figures will become apparent, in particular from the problem statement and / or the problem arising from a comparison with the prior art.

[0026] The invention will now be explained in more detail with reference to the illustrations. The invention is not limited to the embodiments shown in the illustrations. The illustrations only depict the subject matter of the invention schematically. They show: Fig. 1: A schematic circuit diagram of a power section with a stator of an electric motor, Fig. 2: a perspective view of part of an electric motor, Fig. 3: another perspective view of part of an electric motor and Fig. 4: a schematic representation of the development of a power section of an electric motor.

[0027] Fig. Figure 1 shows a schematic circuit diagram of a power section with a stator of an electric motor. The electric motor is an electric machine and comprises the stator and a rotor (not shown). The stator has a first stator winding 31, a second stator winding 32, and a third stator winding 33. The stator windings 31, 32, and 33 are connected in a star configuration and electrically connected to a common star point 35.

[0028] 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.

[0029] The electric motor also includes the power section for driving 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 therefore present between the upper busbar Uz+ and the lower busbar Uz-.

[0030] The power section 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. Thus, the busbars 51, 52, and 53 are electrically connected to each of the stator windings 31, 32, and 33 via the current sensors 41, 42, and 43, and the phase conductors U, V, and W, respectively. The current sensors 41, 42, and 43 are, for example, implemented as measuring resistors.

[0031] 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.

[0032] 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.

[0033] The power section is part of an inverter. The inverter also includes a control module, which is not shown here. The upper switches 11, 12, 13 and the lower switches 21, 22, 23 are controlled by the control module such that a three-phase AC voltage is applied to the stator windings 31, 32, 33. The inverter thus provides a three-phase output voltage for the stator.

[0034] 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, which is not shown here.

[0035] The power section includes a DC link capacitor C5. This capacitor is connected between the upper busbar Uz+ and the lower busbar Uzan. A single DC link capacitor C5 is shown here. Alternatively, multiple DC link capacitors C5 can be connected in parallel.

[0036] Fluctuating potentials on the phase conductors U, V, W lead to unwanted parasitic currents that can close via undefined paths and thus cause conducted interference. Similarly, uncontrolled conducted interference that closes via loops 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).

[0037] The power section includes an upper interference suppression capacitor C1, a lower interference suppression capacitor C2, and a middle capacitor C3. The upper interference suppression capacitor C1 is electrically connected between the upper busbar Uz+ and junction 55. The lower interference suppression capacitor C2 is electrically connected between the lower busbar Uz- and junction 55. Junction 55 is electrically connected to the protective earth (PE) via the middle capacitor C3. Alternatively, the middle capacitor C3 can be omitted, and junction 55 can be electrically connected directly to the protective earth (PE).

[0038] Fig. Figure 2 shows a perspective view of part of an electric motor. The stator of the electric motor 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 a part of the hollow cylindrical stator housing 4, which is not shown here.

[0039] The part of the stator housing 4 shown here has an inner surface facing the axis of rotation D. This inner surface comprises a plurality of flat sub-surfaces, also facing the axis of rotation D. These sub-surfaces are arranged circumferentially offset from one another around the axis of rotation D. In this case, the inner surface of the stator housing 4 has eight flat sub-surfaces. Adjacent sub-surfaces are arranged circumferentially offset from one another by 45°.

[0040] The power section comprises a first main circuit board 61, a second main circuit board 62, and a third main circuit board 63. The first upper switch 11, the first lower switch 21, and the first current sensor 41 are arranged on the first main circuit board 61. The second upper switch 12, the second lower switch 22, and the second current sensor 42 are arranged on the second main circuit board 62. The third upper switch 13, the third lower switch 23, and the third current sensor 43 are arranged on the third main circuit board 63.

[0041] Each of the main circuit boards 61, 62, 63 is arranged on one of the partial surfaces of the inner surface of the stator housing 4. The main circuit boards 61, 62, 63 are thus each arranged on the inner surface of the stator housing 4. The main circuit boards 61, 62, 63 are therefore arranged circumferentially offset from each other around the axis of rotation D. The main circuit boards 61, 62, 63 are also arranged axially offset from the stator windings 31, 32, 33.

[0042] Each of the main circuit boards 61, 62, 63 has a connection point 70. The connection points 70 are bores that penetrate the main circuit boards 61, 62, 63. Screws (not shown) protrude through the connection points 70 and are screwed into the stator housing 4. The main circuit boards 61, 62, 63 are thus positively locked to the stator housing 4 by means of screws. Metallic rings are placed over the bores. The rings are electrically connected to the protective earth (PE).

[0043] The power section comprises a first auxiliary circuit board 67 and a second auxiliary circuit board 68. Each of the auxiliary circuit boards 67, 68 is arranged on one of the partial surfaces of the inner surface of the stator housing 4. The auxiliary circuit boards 67, 68 are thus each arranged on the inner surface of the stator housing 4. The main circuit boards 61, 62, 63 and the auxiliary circuit boards 67, 68 are arranged circumferentially offset from each other around the axis of rotation D. The auxiliary circuit boards 67, 68 are also arranged axially offset from the stator windings 31, 32, 33.

[0044] The upper busbar Uz+ comprises one or more conductor tracks on the main circuit boards 61, 62, 63 and on the auxiliary circuit boards 67, 68, as well as connecting elements that link the conductor tracks on the main circuit boards 61, 62, 63 and on the auxiliary circuit boards 67, 68 together. The lower busbar Uz- also comprises one or more conductor tracks on the main circuit boards 61, 62, 63 and on the auxiliary circuit boards 67, 68, as well as connecting elements that link the conductor tracks on the main circuit boards 61, 62, 63 and on the auxiliary circuit boards 67, 68 together.

[0045] The electric motor includes a connector 72. The connector 72 is located on the stator housing 4. A supply voltage can be supplied to the electric motor via the connector 72. Furthermore, it is conceivable that the connector 72 has connections for a data bus.

[0046] Fig. Figure 3 shows another perspective view of part of an electric motor from a different viewpoint than in Figure 3. Fig. 2. The first auxiliary circuit board 67 and the second auxiliary circuit board 68 are arranged on diametrically opposed partial surfaces of the inner surface of the stator housing 4. The stator housing 4 has an opening into which the first auxiliary circuit board 67 is inserted.

[0047] The first auxiliary circuit board 67 has two connection points 70. The second auxiliary circuit board 68 has one connection point 70. The connection points 70 are bores that penetrate the auxiliary circuit boards 67 and 68. Screws (not shown) protrude through the connection points 70 and are screwed into the stator housing 4. The auxiliary circuit boards 67 and 68 are thus positively locked to the stator housing 4 by means of screws. Metallic rings are placed over the bores. The rings are electrically connected to the protective earth (PE).

[0048] The first auxiliary circuit board 67 contains an intermediate circuit capacitor C5, an upper interference suppression capacitor C1, a lower interference suppression capacitor C2, and a center capacitor C3. The second auxiliary circuit board 68 also contains an intermediate circuit capacitor C5, an upper interference suppression capacitor C1, a lower interference suppression capacitor C2, and a center capacitor C3. The first auxiliary circuit board 67 is also connected to the connector 72.

[0049] Fig. Figure 4 shows a schematic representation of the development of a power section of an electric motor. As already mentioned, the power section comprises a first main circuit board 61, a second main circuit board 62, a third main circuit board 63, a first auxiliary circuit board 67, and a second auxiliary circuit board 68.

[0050] The upper busbar Uz+ extends approximately circumferentially over the main circuit boards 61, 62, 63 and the auxiliary circuit boards 67, 68. The lower busbar Uzer also extends approximately circumferentially over the main circuit boards 61, 62, 63 and the auxiliary circuit boards 67, 68. The upper busbar Uz+ is axially offset from the lower busbar Uz- on each of the main circuit boards 61, 62, 63 and on each of the auxiliary circuit boards 67, 68.

[0051] The first busbar 51 is located on the first main circuit board 61. The second busbar 52 is located on the second main circuit board 62. The third busbar 53 is located on the third main circuit board 63. The busbars 51, 52, and 53 are thus arranged offset from each other in the circumferential direction.

[0052] The busbars 51, 52, 53 are arranged axially offset from the upper busbar Uz+ and the lower busbar Uz-. The busbars 51, 52, 53 are arranged axially between the upper busbar Uz+ and the lower busbar Uz- on each of the main circuit boards 61, 62, 63.

[0053] The drain terminals of the upper switches 11, 12, 13 are electrically connected to the upper busbar Uz+. The source terminals of the upper switches 11, 12, 13 are each electrically connected to one of the busbars 51, 52, 53. The upper switches 11, 12, 13 are each implemented as an N-channel MOSFET.

[0054] The drain terminals of the lower switches 21, 22, 23 are electrically connected to each of the busbars 51, 52, 53. The source terminals of the lower switches 21, 22, 23 are electrically connected to the lower busbar Uz-. The lower switches 21, 22, 23 are each implemented as an N-channel MOSFET. Reference symbol list 4 Stator housings 11 first upper switch 12 second upper switch 13 third upper switch 21 first lower switch 22 second lower switch 23 third lower switch 31 first stator winding 32 second stator winding 33 third stator winding 35 Star point 41 first current sensor 42 second current sensor 43 third current sensor 51 first busbar 52 second busbar 53 third busbar 55 Junction D axis of rotation Uz+ upper busbar Uz- lower busbar C1 upper interference suppression capacitor C2 lower interference suppression capacitor C3 center capacitor C5 intermediate circuit capacitor U first phase conductor V second phase conductor W third phase conductor PE protective earthing 61 first main circuit board 62 second main circuit board 63 third main circuit board 67 first auxiliary circuit board 68 second auxiliary circuit board 70 Connection point 72 plugs QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2009 051 979 A1

[0002] DE 103 062 27 B4

[0004]

Claims

[1] Electric motor, comprising a stator having 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 section for controlling the stator windings (31, 32, 33), which has 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), each of which is 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), characterized by , that the switches (11, 12, 13, 21, 22, 23) are arranged on a plurality of main circuit boards (61, 62, 63), and that the main circuit boards (61, 62, 63) are arranged offset from one another in the circumferential direction around the axis of rotation (D). [2] Electric motor according to claim 1, characterized by , that the stator has a hollow cylindrical stator housing (4) in which the stator windings (31, 32, 33) are arranged, and that the main circuit boards (61, 62, 63) are each arranged on an inner surface of the stator housing (4) facing the axis of rotation (D). [3] Electric motor according to claim 2, characterized by that the main circuit boards (61, 62, 63) are arranged offset in the axial direction to the stator windings (31, 32, 33). [4] Electric motor according to one of claims 2 to 3, characterized by , that the inner surface of the stator housing (4) has a plurality of flat partial surfaces facing the axis of rotation (D), which are arranged offset from one another in the circumferential direction around the axis of rotation (D), and that each of the main circuit boards (61, 62, 63) is arranged on one of the partial surfaces. [5] Electric motor according to one of claims 2 to 4, characterized by that each of the main circuit boards (61, 62, 63) is positively secured to the stator housing (4), in particular by means of a screw. [6] Electric motor according to one of claims 2 to 5, characterized by , that the stator has a spring element which presses the main circuit boards (61, 62, 63) against the inner surface of the stator housing (4). [7] Electric motor according to one of the preceding claims, characterized by that the power section has at least one auxiliary circuit board (67, 68), and 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 auxiliary circuit board (67, 68), and / or that the power section has at least one interference suppression capacitor (C1, C2) which is arranged on the auxiliary circuit board (67, 68). [8] Electric motor according to claim 7, characterized by that the auxiliary circuit board (67, 68) is arranged offset in the circumferential direction to the main circuit boards (61, 62, 63). [9] Electric motor according to one of the preceding claims, characterized by that the power unit has at least three current sensors (41, 42, 43) which are arranged on the main circuit boards (61, 62, 63). [10] Electric motor according to one of the preceding claims, characterized bythat the upper busbar (Uz+) is arranged offset in the axial direction to the lower busbar (Uz-) on each of the main circuit boards (61, 62, 63). [11] Electric motor according to one of the preceding claims, characterized by that the busbars (51, 52, 53) are arranged in the axial direction between the upper busbar (Uz+) and the lower busbar (Uz-) on each of the main circuit boards (61, 62, 63). [12] Electric motor according to one of the preceding claims, characterized by that the main circuit boards (61, 62, 63) surround the rotor. [13] Electric motor according to one of the preceding claims, characterized by that the main circuit boards (61, 62, 63) are arranged in the axial direction between one end of the rotor and the stator windings (31, 32, 33). [14] Electric motor according to one of the preceding claims, characterized bythat the switches (11, 12, 13, 21, 22, 23) are each arranged on a surface of the main circuit boards (61, 62, 63) facing the axis of rotation (D).

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