ELECTRIC MOTOR

Description

[0001] The invention relates to an electric motor with a stator-side rod winding.

[0002] Electric motors can have a bar winding on the stator side. In this case, the stator has a series of bars instead of wound wire conductors as field conductors. Compared to conventional windings, the bars have a low inductance. Therefore, a comparatively high current flow is required to generate a given magnetic field.

[0003] This high current flow requires only a comparatively low voltage, for example, 12 V. This low voltage allows the inverter components, which control the rods, to be positioned close to each other. For instance, the power electronics components can be arranged on one or more circuit boards located near the electric motor. A particular advantage is that such an electric motor can be designed compactly so that each field conductor is driven by its own power components, and thus each field conductor can be driven by its own phase. In this way, electric motors with 48, 72, or even 120 field conductors and phases can be built compactly.

[0004] The problem is that the large number of power components must be connected to a central control unit. Cable connections between a central control unit and a large number of power components result in a very complex setup, which is a disadvantage.

[0005] Document DE 10 2005 032965 A1 shows a motor in which individual rod conductors are controlled by a corresponding circuit board.

[0006] Document US 2021 / 288555 A1 shows a power electronics unit for an electric motor, on whose circuit boards several connectors are arranged.

[0007] The object of the invention is to provide an electric motor that eliminates the aforementioned disadvantage, in particular by having an efficient connection between the control unit and the power components.

[0008] This problem is solved by an electric motor having the features specified in claim 1.

[0009] The electric motor according to the invention comprises a stator with a plurality of field conductors configured as rods. Furthermore, the electric motor comprises an inverter with one or more parallel power sections for each of the field conductors for their control, wherein the inverter includes a control unit for generating control signals for the power sections.

[0010] The inverter's output stages are arranged on multiple printed circuit boards. These boards are arranged to form at least two circular or ring-shaped structures. These structures are parallel to each other and axially offset, so that their centers lie on a common central axis.

[0011] Each circuit board has one or more connectors for contacting the output stages. A connecting board is plugged into connectors on circuit boards of various circular or ring-shaped structures that are azimuthally aligned with respect to the central axis.

[0012] In relation to circular or ring-shaped structures, "parallel" means that their circular or ring planes are parallel, or, expressed mathematically differently, that their surface normals have the same direction.

[0013] In relation to circular or ring-shaped structures, axial displacement means that these are (exclusively) shifted relative to each other along a corresponding axis, where this axis corresponds to the central axis, i.e., the surface normal through the center of the circle or ring.

[0014] Since the circular or ring-shaped structures are built from multiple printed circuit boards, it is understood that they are not geometrically exact and the circular or ring area does not have to be completely filled. Rather, gaps remain between the printed circuit boards.

[0015] If polar coordinates are assigned to each of the circular or ring-shaped structures, then azimuthal denotes the angle in these polar coordinates. Connectors with the same azimuthal orientation are therefore located in the same direction from the central axis. Such connectors of different circular or ring-shaped structures thus form a line that lies parallel to the central axis.

[0016] The connectors can be, for example, spring contacts or direct PCB connectors. They can be a socket or a (panel-mount) plug, with the corresponding mating side located on the connecting board.

[0017] In this text, the term "power stage" essentially refers to the power semiconductor switches belonging to an AC voltage output of a power section. Since the gate driver circuits associated with the power semiconductor switches are physically separated from the switches in some embodiments of the invention, they are not considered part of the power stage. The term "power section" refers to the power semiconductor switches together with their respective gate driver circuits. The entire assembly of power sections and control circuitry is referred to as an inverter.

[0018] The invention advantageously achieves a particularly simple method of contacting the electronic components on the printed circuit boards, in which a multitude of cables between the controller and the printed circuit boards (at least one per azimuthally aligned printed circuit board) are replaced by a single connecting board per phase or even a single connecting board for multiple phases. For example, if six printed circuit boards are connected in parallel for one phase in this type of electric motor, then a single connecting board with a single cable to the controller is sufficient to contact all six printed circuit boards.

[0019] It is advantageous to have a connecting board for all connectors. For example, the connectors can be distributed azimuthally around the outer or inner edge of any ring-shaped structure. Then, a connecting board is provided for each azimuth position. These then form a shape resembling a gapped cylindrical shell.

[0020] Furthermore, it is advantageous if each connecting board is connected to all connectors at the same azimuthal position. Therefore, if four circular or ring-shaped structures are present, then preferably all of the circular or ring-shaped structures have a connector at the same azimuthal positions, and each connecting board contacts all connectors that are at an azimuthal position, i.e., form a line parallel to the central axis.

[0021] The interconnect boards advantageously establish an indirect connection between the control unit on the one hand and the output stages, i.e., the power semiconductor switches, on the printed circuit boards on the other. "Indirect" in this context means that the gate driver circuits for the power semiconductor switches are located within this connection, regardless of their physical location. These gate driver circuits can be arranged in various ways.

[0022] Advantageous embodiments of the electric motor according to the invention are described in the dependent claims. The embodiment of the independent claims can be combined with the features of one of the dependent claims or with those of several dependent claims. Accordingly, the following additional features can be provided: The central axis of the circular or ring-shaped structures can correspond to the motor axis. In other words, this means that the center of each circular or ring-shaped structure lies on the motor axis and that each of the circular or ring-shaped structures is arranged perpendicular to the motor axis.

[0023] In this arrangement of circular or ring-shaped structures, the field conductors or the current conductors extending them penetrate the circular or ring-shaped structures in a rotationally symmetrical manner when continuing in a straight line. This results in a highly modular design in which identical circuit boards can be used and in which the contacting of each field conductor is particularly simple.

[0024] Furthermore, the field conductors or the current conductors extending from them can even serve as a mechanical support for the circuit boards, thus further simplifying the construction.

[0025] The circular or ring-shaped structures can have the same diameter. This design is advantageous because it allows the spring contacts to form an axially oriented line when mounted identically on the circuit boards. This facilitates easy installation of the connecting boards.

[0026] The connecting plates preferably extend axially parallel to the motor axis. This extension refers to the orientation of the longest edge of the preferably rectangular connecting plates.

[0027] The number of connection boards can correspond to the number of field conductors. In this configuration, one connection board is used per phase of the electric motor. This simplifies the design of the connection board and reduces the wiring effort on the board.

[0028] In alternative configurations, a smaller number of connection boards than the number of field conductors can also be used. For example, the power components for two, three, or more of the phases (i.e., the field conductors) can be arranged on a single board, and the board can be designed such that a connection between the power components and the control system is achieved via a single connection board. In this case, the number of connection boards corresponds to the number of field conductors or phases divided by the number of power components per board.

[0029] This design of the electric motor is particularly advantageous when a large number of field conductors, for example 48, 72, or even 120, are used. With such electric motors, it is advantageous to reduce the number of circuit boards and connecting boards compared to the simpler variant with one connecting board per phase.

[0030] The interconnect board can include gate driver circuits for the power components. This eliminates the need for dedicated board space for the gate driver circuits. Consequently, more space remains for the power components, simplifying the board design. Furthermore, the heat generated by the gate driver circuits is dissipated from the boards, thus simplifying heat dissipation.

[0031] Furthermore, the interconnect board can also include one or more local control chips that perform control tasks, such as current measurement for a respective output stage. Each local control chip is assigned to and connected to one or more gate driver circuits.

[0032] Alternatively, the gate driver circuits can be arranged directly on the circuit boards themselves, along with the respective power semiconductor switches. This simplifies the design of the interconnect boards, as they only need to establish a connection between the controller and the boards, and thus the gate driver circuits, while still allowing for additional circuitry such as monitoring, control, amplifier / buffer circuits, or communication interfaces. For this purpose, the interconnect boards can advantageously include a multiplexer.

[0033] Alternatively, the gate driver circuits can also be arranged on separate driver boards. These are preferably plugged onto the boards containing the power semiconductor switches, with the arrangement of the boards being sandwich-like, i.e., the driver boards at least partially covering the boards. In this case, the interconnect boards can be connected to the driver boards, the output stage boards, or both, i.e., they can have a connection to one or both of these board types through which signals are transmitted.

[0034] Each phase controlled on a circuit board has a half-bridge consisting of two logic switches. A logic switch can comprise exactly one single power semiconductor switch. However, to allow switching higher currents, a logic switch can also comprise multiple power semiconductor switches, for example, two, three, five, or even more power semiconductor switches connected in parallel.

[0035] A gate driver circuit is preferably designed to control the control terminals (e.g., gate terminals) of the two logic switches of the half-bridge, i.e., to supply current / voltage in such a way that the switching operations required by the control system take place and the switches are turned on and off in a manner required by the control system.

[0036] If the logic switches of the half-bridge each contain more than one parallel power semiconductor switch, the gate driver circuit can be designed to control all of the power semiconductor switches. However, it is also possible to use more than one gate driver circuit. For example, the number of gate driver circuits can exactly match the number of parallel power semiconductor switches. Thus, if the half-bridge contains five high-side MOSFETs and five low-side MOSFETs, up to ten gate driver circuits can be used. In this case, it is advantageous for space reasons to place the gate driver circuits on the driver board or the interconnect board.

[0037] The connecting board can include a multiplexer and be designed such that a control signal received from the controller on a first signal line for a first power section is routed by the multiplexer to one of several second signal lines, which is connected to the first power section via a spring contact.

[0038] The multiplexer on the interconnect board allows the controller to be connected to the board with only a single signal line, simplifying the design. This is particularly advantageous when the interconnect board connects multiple power components on a single board, as well as multiple power components connected in parallel, to the controller. Without the multiplexer, a large number of parallel control lines would be required from the controller to the interconnect board. The single signal line can be a direct electrical connection or a connection operating according to a communication standard, such as an optical connection, a USB connection, or a LAN connection.

[0039] The connecting plate can include one or more screw connections to one or more of the circular or ring-shaped structures. The screw connections prevent the connecting plate from loosening due to vibrations and other external factors.

[0040] The interconnect board can be bent, for example, in a tangential direction. In this case, the interconnect board has the shape of a shallow pitched roof whose ridge extends axially. A more complex shape results when the interconnect board has several, preferably parallel, bend lines. Such an interconnect board is suitable for contacting the connectors of several adjacent printed circuit boards of multiple circular or ring-shaped structures, even if these connectors no longer lie in the same plane and are radially oriented, i.e., not parallel to each other, but inclined relative to each other. While the unbent interconnect boards result in a shape that approximately forms a gapped cylindrical shell, such bent interconnect boards represent a combination of several of the unbent interconnect boards and thus reduce the gaps in the cylindrical shell.A connecting board with one bend is suitable for connecting two adjacent circuit boards. A connecting board with two bends is suitable for connecting three adjacent circuit boards.

[0041] The interconnect board can be a flexible printed circuit board (PCB). Flexible PCBs can deform under mechanical stress. Traces and other electronic components on such PCBs retain their electrical function. Using a flexible PCB as an interconnect board simplifies assembly and installation, as the circular or ring-shaped structures no longer need to have fixed distances from each other and can be moved relative to each other even after installation.

[0042] The electric motor can include two connection boards. Each of these two connection boards is then connected to a plurality of other connection boards. Each of these connection boards, in turn, is connected to a single second connection board. Each of these second connection boards includes a cable connection to the controller. This advantageously eliminates the need for a separate cable connection from each of the connection boards to the controller, thus reducing the number of cable connections.

[0043] The second connecting boards can, for example, be designed in a ring sector or circular sector shape. The central angle is chosen so that at least two of the connecting boards can be contacted. It is also possible for them to be designed as essentially rectangular, but bent, boards.

[0044] The current conductors can be designed to axially extend the field conductors. The current conductors are similar in design to the field conductors of the electric motor, but can, for example, have a different cross-sectional shape. For instance, the current conductors can have a circular cross-section, while the field conductors have an elongated rectangular cross-section. It is advantageous if the current conductors can carry at least the same current as the field conductors. Current conductors and field conductors can be connected via specially designed connectors that ensure a mechanical and electrical connection.

[0045] The printed circuit boards (PCBs) can be arranged on at least one cooling plate. The cooling plate can be covered with PCBs on both sides to achieve a high density of electrical components. The cooling plate is preferably a metallic, essentially circular or ring-shaped plate. For heat dissipation, the cooling plate can have heat pipes or cooling channels for air or fluid flow. The cooling plate can also be constructed from two parallel, ring-shaped plates screwed together, leaving a gap between them. Active ventilation can then be arranged to draw air between the plates.

[0046] The cooling plate can be arranged such that the field conductors or electrically connected conductors are in mechanical contact with the cooling plate. For example, the conductors or field conductors can be designed as a mechanical support for the cooling plate. For this purpose, the cooling plate is preferably arranged perpendicular to the axis of the electrical machine. In this way, the cooling plate and the circuit boards can be arranged in a space-saving manner at one axial end of the electrical machine.

[0047] The printed circuit boards can be designed in a circular or ring sector shape. Printed circuit boards of this shape are particularly easy to assemble into a circle or ring and thus optimally adapted to the shape of the electrical machine, allowing them to be positioned at one axial end of the machine while simultaneously achieving a high degree of modularity.

[0048] The power components are preferably designed to generate an alternating voltage with an amplitude of 200 V or less, particularly 100 V or less, and especially 50 V or less. This makes it possible to arrange the power electronics components, especially the power semiconductor switches, at close intervals of millimeters, thus enabling a significant number of power semiconductor switches to be arranged in a relatively small space. This makes it possible to provide high currents while requiring minimal space and simultaneously generating a large number of phases, for example, 6, 12, 24, 48, 72, or even 120 phases.

[0049] The invention will now be described and explained in more detail with reference to the exemplary embodiments shown in the figures. The figures schematically show: Figure 1an electric motor with power components arranged on circuit boards supported by cooling plates in oblique view, Figure 2 Circuit boards arranged on a cooling plate in front view, Figure 3 a section of the electric motor in oblique view with cooling plates and circuit boards, Figure 4 a section of the electric motor with cooling plates with circuit boards and connecting boards attached via spring contacts in side view, Figure 5 a front view of the electric motor with cooling plates, circuit boards and connecting boards, Figure 6 a second scheme for the spring contacts as a connection between connecting boards and circuit boards, Figure 7 a setup with gate driver circuits on driver boards, Figure 8 a first embodiment for the connecting boards, Figure 9 a second embodiment for the connecting boards, Figure 10 a third embodiment for the interconnect boards with gate driver circuits, Figure 11a setup with additional second connecting boards.

[0050] Figure 1 Figure 10 is an isometric view of an electric motor 10, which is an embodiment of the invention. The electric motor 10 comprises a stator 11 and a rotor arranged substantially within the stator 11, which is Figure 1 The rotor is not visible. It is non-rotatably connected to a shaft, which is also in Figure 1 (Not shown.) Through electromagnetic interaction of the rotor with a current-energized stator 11, the rotor is set into rotation about an axis 9. The rotor is separated from the stator 11 by an air gap. In other embodiments, the electric motor 10 can also be an external rotor motor or a coreless motor.

[0051] The stator 11, acting as a field conductor, comprises a plurality of rigid and straight conductor bars 12. These conductor bars 12 are located on the in Figure 1The conductor bars 12 on the opposite end face 13 are connected to each other via a short-circuit ring. On the rear side 14 of the electric motor 10, the conductor bars 12 are individually supplied by their respective inverter modules. Since the electric motor 10 operates at low voltages due to the conductor bars 12, the inverter modules, along with other electronic components (DC converter, rectifier), can be arranged relatively close together on circuit boards 15. In this example, the circuit boards 15 are sector-shaped, and many individual circuit boards 15 together form a ring-shaped circuit board structure.

[0052] While the examples assume that the circuit boards 15 carry at least the power components of inverters, it is also possible that some of the circuit boards 15 carry rectifiers and DC / DC converters.

[0053] Figure 2shows a top view of such a circuit board structure. The number in Figure 2 The circuit boards shown are presented in a different format for better clarity compared to the representation in Figure 1 The diagram is reduced and greatly simplified. The specific number of such printed circuit boards 15 depends on the specific design of the electric motor 10, in particular the number of conductor bars 12. Each of the printed circuit boards 15 comprises several semiconductor switches 422. The semiconductor switches 422 together form power sections of inverters that provide an alternating voltage for the conductor bars 12.

[0054] Furthermore, some or all of the printed circuit boards 15 may include driver circuits and other electronic components such as capacitors, which are not shown in the figures. The semiconductor switches 422 are power semiconductors such as IGBTs, MOSFETs, or JFETs and, depending on the circuit configuration, may also include diodes not shown. The semiconductor switches 422 are connected, for example, as half-bridges. A capacitor not shown may, for example, represent an intermediate circuit capacitor of the half-bridges. The semiconductor switches 422 of a printed circuit board 15 may be assigned to a single phase. In an electric motor 10 with a large number of field conductors 12 and a corresponding number of phases, it is advantageous if one printed circuit board 15 carries the power components for several phases.

[0055] The printed circuit boards 15 also include contact points 421 to which the conductor bars 12 are connected. The printed circuit boards 15 are supported by disc-shaped cooling plates 16, which, for better space utilization, can be covered with printed circuit boards 15 on both sides.

[0056] Since relatively high currents are required in the conductor bars of the electric motor 10, several power components are preferably connected in parallel to supply them with current. This can be achieved, for example, by connecting the in Figure 1 The six circuit board structures shown on three cooling plates 16 are all connected to the conductor bars 12 in the same way and are thus electrically connected in parallel. This takes advantage of the fact that the conductor bars 12 or connecting elements 18 to the conductor bars 12 penetrate the cooling plates 16 and thus also the circuit boards 15 in the same way at the contact points, or at least make contact in the case of the outermost cooling plate 16.

[0057] Figure 3 Figure 1 shows a cross-sectional view of the electric motor 10 in oblique view. It can be seen that the connecting elements 18 mechanically support and penetrate the three cooling plates 16. The connecting elements 18 are connected to the conductor bars 12 via shoes 17. The output stages, located on the circuit boards 15 in the areas where one of the connecting elements 18 penetrates a cooling plate 16, are connected in parallel and together supply the current to the conductor bar 12. In the Figure 3 The illustrated structure shows that two of the connecting elements 18 each pass through a circuit board 15. Thus, each of the circuit boards carries the output stages for two phases of the electric motor 10. In other variants for the electric motor 10, a single circuit board 15 can also carry only one phase or three or more phases, with the same number of connecting elements 18 passing through the circuit board 15.

[0058] Figure 4shows a side view of a section of the electric motor 10. The following are shown in Figure 4 eight circuit boards 15 arranged on two cooling plates 16. Furthermore, it shows Figure 4 Two connecting boards 32, each connecting four of the printed circuit boards 15. The connecting boards 32 extend axially and are connected to sockets 34 of a respective printed circuit board 15 by means of spring contacts 33. Each connecting board 32 also has a socket 35 for a cable connection to a control board 31.

[0059] The arrangement in Figure 4 corresponds to those of Figures 1 to 3 . Of the four ring structures that form the circuit boards 15, the cross-sectional view of the Figure 4 Therefore, eight of the circuit boards 15. Likewise, the sectional view only captures the two connecting boards 32 that are plugged into these eight circuit boards 15. In addition to the in Figure 4The electric motor 10 comprises the two connecting boards 32 shown, but also further connecting boards 32 not shown. These are plugged into the circuit boards 15 not shown and thus surround the assembly shown and form - geometrically greatly simplified - the shape of a loose cylindrical shell.

[0060] Figure 5 shows the same structure in a highly simplified front view. Figure 5 It can be seen that the circuit boards 15 form a ring structure. For each of the circuit boards 15, there is a connecting board 32, which is connected to the respective circuit board 15 via a spring contact 33 and a socket 34. According to Figure 5 Eight circuit boards 15 are arranged on the front of the cooling plate 16, with both sides of the cooling plates 16 being covered and two cooling plates being used as in Figure 4As shown, the electric motor 10 comprises 32 circuit boards 15, which are connected to a control board 31 by means of eight connecting boards 32.

[0061] The number of phases and thus current bars 12 does not necessarily play a role in the number of connecting boards 32. Figure 5 The diagram does not show how many phases, and therefore current bars 12, the electric motor 10 has. One, two, three, or more phases can be controlled per circuit board 15. The same number of current bars 12 or connecting conductors 18 then terminates in each of the circuit boards 15. However, the connection boards 32 are adapted to the number of phases to be controlled, as a corresponding number of signal lines must be present.

[0062] The figures show, for simplicity, individual spring contacts 33 and sockets 34. However, each can also represent several actual signal lines. The sockets 34 could therefore actually be socket strips, and the spring contacts 33 corresponding plug strips.

[0063] Figure 6 Figure 1 shows an alternative design of the spring contacts 33 and sockets 34, which is suitable for an electric motor 10 in which the cooling plates 16 are only covered on one side with circuit boards 15. For the sake of clarity, Figure 6 greatly simplified. In this case, the sockets 34 can have an axial orientation instead of a radial one. The insertion of the connecting boards 32 is achieved in this example by movement in the axial direction instead of the radial direction.

[0064] Other connector orientations are also possible, for example a tangential orientation.

[0065] In another variant for the construction of the electric motor 10, which is not shown in the figures, the control board 31 is arranged concentrically with the cooling plates and axially offset from them, and has the same outer radius as the circuit boards 15. In this embodiment, the connecting boards 32 are also plugged onto the control board 31, establishing signal connections via these boards. A cable connection between the connecting boards 32 and the control board 31 is therefore unnecessary.

[0066] In another variant for the construction of the electric motor 10, which is in Figure 11As shown, several of the connection boards 32 are connected to a second connection board 110. The second connection board 110 can, for example, be shaped like a ring sector. It is advantageous if the connection boards 32 are designed so that they extend beyond the cooling plate 16 furthest from the stator / rotor block 8 and have an additional connector 111 at their end. This additional connector 111 can be axially or radially oriented. Accordingly, the second connection boards 110 are then connected to the end face, the inside, or the outside of the connection boards 32.

[0067] The second connection boards 110 are designed to be plugged into several of the connection boards 32. In the example of the Figure 11The second connection boards 110 have a central angle of approximately 90°, thus forming roughly quarter rings. For large electric motors 10 with, for example, 72 or 120 phases, the radius of the rings can be in the meter range, and it may be advantageous to connect only two, three, or four of the connection boards 32. In this case, the central angle for each of the second connection boards 110 is then, for example, only 9°, and three connection boards 32 are connected to each of the second connection boards 110. In this case, the electric motor 10 then comprises 40 of the second connection boards 110.

[0068] The second connection boards 110 provide a connection to the controller, for example, via a LAN connection, USB connection, or optical connection using a socket 112 on the second connection boards. This eliminates the need for the connection from the connection boards 32 to the controller, i.e., socket 35 on the connection boards 32. Electrically speaking, the second connection boards 110 thus combine the connections of the connection boards 32 and reduce the number of cable connections required to the controller.

[0069] An electric motor 10, for example, can have three double-sided cooling plates 16 with twelve printed circuit boards 15 per side, i.e., 72 printed circuit boards 15. The printed circuit boards 15 are axially connected by twelve connecting boards 32, each of which is plugged into six azimuthally aligned printed circuit boards 15. Four ring-sector-shaped secondary connecting boards 110 are then plugged into three of the connecting boards 32 each. Each of the secondary connecting boards 110 is thus directly, i.e., cable-free, connected to 18 printed circuit boards 15, and the number of cable connections to the control system is reduced to four, one per secondary connecting board 110.

[0070] In addition to the in Figure 11 The elements shown include the second connecting boards 110, at least one multiplexer 93 for distributing the signals, and suitable line connections between the socket 35, the multiplexer 93, and the connectors 111.

[0071] In all the given examples, it was assumed that the connecting boards 32 are plugged radially outwards onto the printed circuit boards 15. However, it is also possible, alternatively or additionally, to plug the connecting boards 32 inwards. In other words, the connecting boards 32 are arranged on the inner edge of the ring-shaped structures formed by the printed circuit boards 15, i.e., the edge belonging to the inner radius of the ring.

[0072] In addition to the option of directly connecting the connecting boards 32 to the circuit boards 15 that carry the output stages, there is another embodiment, shown in Figure 7. The circuit board 15, mounted on a cooling plate 16, carries an output stage of the inverter, simplified as a power semiconductor switch 71. A driver board 70 carries the gate driver circuit 72 and a local control chip 73. Connectors 74 transmit the signals between the circuit board 15 and the driver board 70. In this embodiment, the spring contact 33 is located on the driver board 70. The connecting board 32 is therefore plugged into the driver board 70 in this embodiment.

[0073] The above-described design options for the arrangement of the connecting boards 32 on the printed circuit boards 15 can be combined with various embodiments for the connecting boards 32 themselves, which are illustrated below by means of examples.

[0074] A first exemplary connection board 81 is in Figure 8 A more detailed illustration follows. The connecting board 81 is rectangular, with its long side extending axially in the installed state, as shown in the figures described above. In this first variant, the connecting board 81 comprises only four signal lines 82.

[0075] These terminate at one end in socket 35. Socket 35 is intended for connection to the control board 31. It can route the signal lines in parallel, for example as a socket strip for a direct board connector or as a socket for a parallel interface cable. Alternatively, socket 35 could be a USB or LAN (RJ45) socket. In this case, the connection board 81 also includes... Figure 8 Electronic components not shown for controlling socket 35.

[0076] In this embodiment, the interconnection board 81 is responsible for signal transmission. This requires that the gate driver circuits for the power semiconductor switches are arranged together with the switches on the circuit boards 15 or on separate driver boards, which are, for example, plugged onto the circuit boards 15 in such a way that they partially cover them (sandwich-like stacked boards). The control signals for the gate driver circuits are passed through by the interconnection board 81. Furthermore, it is assumed that four circuit boards 15, which are axially aligned at the same position but arranged on the front and back of the two cooling plates 16, each control only one phase and require only one control signal for gate driver circuits.

[0077] The connecting board 81, as well as the other embodiments shown, can also include additional circuits besides the elements shown, such as monitoring, control, amplifier / buffer circuits or communication interfaces.

[0078] A more complex connection board 91 is in Figure 9 shown. In this example, socket 35 is a LAN connection with a control chip 36. The incoming control signals are split by a multiplexer 93 into a plurality of signal lines 92. In the Figure 9 Three signal lines 92 are shown per spring contact 33, but in real designs there may be significantly more, for example 10 or even 30 signal lines 92, leading to each of the attached circuit boards 15.

[0079] In this embodiment of the interconnection board 91, the gate driver circuits for the power semiconductor switches are also located together with the switches on the circuit boards 15 or on separate driver boards. The control signals for the gate driver circuits are passed through by the interconnection board 91.

[0080] It is also possible to arrange the gate driver circuits for the power semiconductor switches on the interconnect boards. An example interconnect board 101, as shown in Figure 10, with gate driver circuits is described in Figure 10shown. Socket 35 is again a LAN connection with a control chip 36. The incoming control signals are split by a multiplexer 93 into a number of signal lines. The signal lines lead to one gate driver circuit 1031...1034 and one local control chip 1041...1044 each. The gate driver circuits 1031...1034 and the local control chips 1041...1044 are each assigned to a spring contact 33 and connected via this contact to a circuit board 15.

[0081] In principle, the interconnection board 101 allows the connected circuit boards 15 to be controlled completely independently. Therefore, there is no need for any connection between azimuthally aligned circuit boards 15. However, in the electric motor 10 shown here, azimuthally aligned circuit boards 15 always control the same phase or phases. For the electric motor 10 shown here, it is therefore advantageous to use the interconnection board 101 to control a single phase of the electric motor 10, which comprises several parallel-connected output stages on those circuit boards 15 that are connected via the interconnection board 101.

[0082] In cases where a circuit board 15 carries the output stages for several phases of the electric motor 10, it is advantageous to use a connecting board of the type described in Figure 10The connecting board 101 shown carries a corresponding number of gate driver circuits 1031...1034 and local control chips 1041...1044 and transmits their signals to the circuit board 15 via the spring contact 33.

[0083] Since the connecting board 101 according to Figure 10 already incorporates gate driver circuits, a combination with a design according to the Figure 7 not practical. However, it is possible to connect the required number of gate driver circuits between the connection board 101 and a driver board 70 according to Figure 7 to divide. Compared to the driver boards 70, which are arranged in parallel to the circuit boards 15, the connection board 101 has the advantage that it enables the connection to the control with a single cable connection for all azimuthally aligned circuit boards 15. Reference sign

[0084] 9 Motor shaft 10 Electric motor 11 Stator 12 Conductor bars 13 Front 14 Back 15 Circuit board 16 Cooling plate 17 Shoe 18 Connecting element 32, 81, 91, 101 Connection board 33 Spring contact 34, 35 Socket 36 Control chip 70 Driver board 71 Power semiconductor chip 72 Gate driver circuit 73 Local control chip 82, 92 Signal line 93 Multiplexer 1031...1034 Gate driver circuit 1041...1044 Local control chip 110 Second connection board 421 Contact points 422 Semiconductor switch

Claims

1. Electric motor (10) comprising: - a stator (11) having a plurality of field conductors (12) configured as bars, - an inverter having one or more parallel power components for each of the field conductors (12) for controlling them, wherein the inverter comprises a controller for generating control signals for the power components, wherein - the output stages of the inverter are arranged on a plurality of printed circuit boards (15), - the printed circuit boards (15) are arranged such that they form at least two circular or annular structures, - the circular or annular structures are arranged parallel to each other and axially offset from each other, so that their centre points lie on a common central axis, - one or more plug-in connectors (33) are arranged on each of the printed circuit boards (15) for contacting the output stages, - a connection board (32, 81, 91, 101) is connected to plug-in connectors (33) of printed circuit boards (15) of various circular or annular structures, the plug-in connectors being azimuthally equal with respect to the central axis.

2. Electric motor (10) according to Claim 1, in which the axis of the circular or annular structures corresponds to the motor axis (9).

3. Electric motor (10) according to Claim 1, in which the circular or annular structures have the same diameter.

4. Electric motor (10) according to Claim 1, in which the connection boards (32, 81, 91, 101) extend parallel to the motor axis (9) in the axial direction.

5. Electric motor (10) according to Claim 1, in which the number of connection boards (32, 81, 91, 101) corresponds to the number of field conductors (12).

6. Electric motor (10) according to Claim 1, in which the connection board (32, 81, 91, 101) comprises gate driver circuits (72) for the power components.

7. Electric motor (10) according to Claim 1, in which the connection board (32, 81, 91, 101) comprises a multiplexer (93) and is configured to conduct control signals received from the controller to one of several signal lines such that they are supplied to the power components to which they are addressed.

8. Electric motor (10) according to Claim 1, in which the connection board (32, 81, 91, 101) comprises one or more screw connections to one or more of the circular or annular structures.

9. Electric motor (10) according to Claim 1, in which the connection board (32, 81, 91, 101) is a flexible printed circuit board.

10. Electric motor (10) according to Claim 1, in which current conductors (18) axially extend the field conductors (12).

11. Electric motor (10) according to Claim 1, in which the printed circuit boards (15) are arranged on at least one cooling plate (16).

12. Electric motor (10) according to Claim 1, in which the cooling plate (16) is arranged such that the field conductors (12) or current conductors (18) electrically connected to the field conductors (12) are mechanically operatively connected to the cooling plate (16), in particular are designed as mechanical carriers for the cooling plate (16).

13. Electric motor (10) according to Claim 1, in which the printed circuit boards (15) are configured in the form of sectors of a circle or sectors of a ring.

14. Electric motor (10) according to Claim 1, configured to control the field conductors (12) with at least 6 phases.

15. Electric motor (10) according to Claim 1, in which the inverters are configured for generating an AC voltage with an amplitude of 200 V or less, in particular 100 V or less, in particular 50 V or less.