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. A motor of this type is described in EP19167289 A1.

[0003] This high current flow, however, requires only a comparatively low voltage of, for example, 12 V due to the low resistance of the rods. This low voltage allows the inverter components that 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 (printed circuit boards) located near the electric motor. The rods can be used directly as the mechanical support for the circuit boards, either directly or via electrically conductive rod-like connecting elements.

[0004] The printed circuit boards (PCBs) are mounted on cooling plates and individually connected via busbars. These busbars rest on the PCBs and are connected to them via screw connections. However, these screw connections are also secured to the cooling plates (mechanically decoupled from them) to ensure reliable contact. This presents the challenge of insulating the connection between the screw and the cooling plate, which must be addressed for each individual screw connection by using a suitable sleeve. Particularly when a PCB needs to be replaced due to defective components, the two busbars, which typically clamp and power up to 150 PCBs, must be unscrewed, then fully insulated, and screwed back on.

[0005] The documents EP3719975 A1, DE102019113237 A1, DE102017112993 A1, DE102020113555 A1, disclose electric motors which have a rod winding on the stator side and a plurality of power electronic components for controlling the field conductors.

[0006] The invention is based on the objective of providing an electric motor with a stator-side rod winding and integrated power electronics, which requires less repair effort when replacing printed circuit boards of the power electronics compared to the prior art.

[0007] The solution to the problem consists of an electric motor with the features of claim 1.

[0008] This electric motor includes A stator with a plurality of field conductors configured as rods, a plurality of power electronic components for controlling the field conductors, wherein the power electronic components are arranged on one or more printed circuit boards, and at least one printed circuit board arranged on at least one cooling plate, wherein the cooling plate is arranged such that the field conductors are in mechanical contact with the cooling plate via current conductors that are electrically connected to the field conductors. The current conductors thus form conductive connecting elements between the field conductors and the printed circuit boards and ultimately to the power electronic components (also semiconductor switches). Due to the mechanical connection, these components also have a load-bearing function for the cooling plate, while being electrically insulated from it.wherein at least one groove-like recess is recessed in the cooling plate, in which at least one busbar is arranged that is electrically insulated from the cooling plate, and is at least partially covered by the circuit boards, and the circuit boards are electrically contacted with the at least one busbar.

[0009] The described electric motor differs from conventional electric motors in that the stator has a series of bars instead of wound wire conductors as field conductors. Compared to conventional windings, these bars have a low inductance. Therefore, a comparatively high current flow is required to generate a given magnetic field.

[0010] The design of the bar winding offers fundamental advantages in machine operation: The segment-wise controllability of the magnetic flux between each pair of field conductors allows for far more flexible magnetic field configurations to be applied to the machine than would be possible with a distributed winding and its inherent superposition effects. This results in numerous (control-related) advantages regarding the machine's running characteristics. Furthermore, the failure of one phase (the control signal of a field conductor) has significantly less of an impact than, for example, in a double-three-phase or even a standard three-phase machine. Since these effects can be very effectively compensated by the adjacent phases, with appropriate control, each phase failure results in a decrease of almost exclusively in the drive power, by only a small fraction, without significantly affecting the other characteristics.

[0011] The advantage of this electric motor over the prior art of motors of this type lies in the fact that the busbars are not mounted on the circuit boards, but are recessed into the cooling plate. This allows each circuit board to be easily removed and replaced by simply loosening the screws that typically also connect to the busbars. Therefore, repairs do not require disassembling large sections or even the entire assembly of circuit boards, resulting in significant labor savings and cost savings during power electronics repairs. Repair costs are considerably reduced.

[0012] Furthermore, this design simplifies the insulation between the cooling plate and the busbar, as contact is only made between the circuit board and the busbar. The busbar itself can be insulated from the cooling plate using conventional insulating material. The previously required screw connection to the cooling plate can potentially be eliminated, further reducing assembly effort.

[0013] It is advantageous to arrange two busbars in the recess. This reduces the surface area of ​​the groove-shaped recess, which is not available for heat dissipation from the circuit board. Two busbars can be arranged side-by-side radially to a motor axis within the recess. This allows for the routing of two busbars in a single recess with minimal insulation required between the cooling plate and the busbars.

[0014] In a further embodiment, two busbars are arranged one above the other in the recess along the motor axis, which requires more effort in terms of contacting, but is suitable for keeping the width of the recess small and thus providing a larger area for heat dissipation.

[0015] On the other hand, it can be advantageous to provide at least two recesses, each containing at least one busbar. This allows for targeted contact with specific areas of the circuit boards.

[0016] Furthermore, it can also be advantageous for the cooling plate to be designed as a busbar. This means that the recess occupies as little of the cooling plate's surface as possible and that at least one busbar runs within it. If the cooling plate is made of metal, it can also function as the second busbar. This further reduces the effort required for assembly and disassembly.

[0017] It should be noted that, generally speaking, exactly two busbars are not strictly necessary for the described motor. It is also advantageous to use duplicated potentials, or, for example, three potentials with a DC link center point, or double (redundant) DC links, which require more than two busbars. By using the cooling plate as a busbar, one busbar is therefore eliminated.

[0018] In an advantageous embodiment of the invention, the cooling plate is designed in an annular shape. This allows it to be integrated into the electric motor in a space-saving manner. In this context, it is also advantageous for the busbar to be designed in an annular or ring-sector shape. It then runs along the contour of the cooling plate and the circuit boards adapted to it.

[0019] Furthermore, it can be advantageous to clamp the busbar in the recess using an insulating, flexible material. Such a flexible and insulating material could be, for example, a profiled silicone ring or a thermally resistant and electrically insulating fiberglass fabric.

[0020] Furthermore, it is also advisable if the circuit boards are electrically contacted with at least one busbar by means of a screw connection.

[0021] The printed circuit boards can be designed in a circular or ring sector shape. Printed circuit boards of this shape can be assembled into a circle or ring and thus optimally adapted to the shape of the electrical machine, arranged at one axial end of the machine, while simultaneously achieving a high degree of modularity.

[0022] The terms "axial," "radial," and "tangential" refer to the axis of the rotor and thus to the corresponding axis of symmetry of the stator. "Axial" describes a direction parallel to this axis, "radial" describes a direction orthogonal to the axis, either towards or away from it, and "tangential" is a direction that rotates circularly around the axis at a constant radial distance and with a constant axial position. The expression "circumferential" is synonymous with "tangential."

[0023] When the terms "axial", "radial" and "tangential" are used in relation to a surface, e.g. a cross-sectional area, the terms describe the orientation of the normal vector of the surface, i.e. the vector that is perpendicular to the surface in question.

[0024] Further embodiments of the invention and additional features are explained in more detail with reference to the following figures. These are purely schematic embodiments and do not represent a limitation of the scope of protection.

[0025] This shows: Figure 1 shows an electric motor with cooling plates for dissipating heat from printed circuit boards in a side view, Figure 2 shows the electric motor in a front view, Figure 3 shows an enlarged view of the Figure 1 In the section of the cooling plates in side view with busbars according to the state of the art, Figure 4, the same section as in Figure 3 with a modified arrangement of the busbars, Figure 5 shows a cross-section through a cooling plate with circuit boards and busbars recessed in two groove-like depressions, Figure 6, a cross-section as in Figure 5 with superimposed busbars in a recess, figure 7, a cross-section as in Figure 5 and in Figure 6with a single recess and two busbars arranged therein, and Figure 8 a partial cross-section through a cooling plate, which schematically shows a screw connection between busbar and circuit board.

[0026] 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.

[0027] In other embodiments, the electric motor 10 can also be an external rotor motor or a bell-shaped armature motor.

[0028] 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 1 The conductor bars 12 are connected to each other via a short-circuit ring on the opposite end face 13. 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 printed circuit boards 15. In this example, the printed circuit boards 15 are sector-shaped, and many individual boards 15 together form a ring-shaped board structure. The rigid conductor bars can be made of a metallic rod, for example, a copper rod, or of a solid multifilament conductor.

[0029] While the examples assume that the circuit boards carry 15 inverter modules, it is also possible that some of the circuit boards carry 15 rectifiers and DC / DC converters.

[0030] Figure 2 shows 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 circuit boards 15 depends on the specific design of the electric motor 10, in particular the number of conductor bars 12. Each of the circuit boards 15 comprises several power electronic components, in particular semiconductor switches 26.

[0031] Furthermore, some or all of the circuit boards 15 may include driver circuits and other electronic components such as capacitors not shown in the figures. The semiconductor switches 26 are power semiconductors such as IGBTs, MOSFETs, or JFETs and, depending on the circuit configuration, may also include diodes not shown. The semiconductor switches 26 are, for example, connected as half-bridges. A capacitor not shown may, for example, represent an intermediate circuit capacitor of the half-bridges. The semiconductor switches 26 of a circuit board 15 may be assigned to a single phase or to several phases.

[0032] The circuit boards 15 also include contact points 24 to which the conductor bars 12 are connected. The circuit boards 15 are supported by disc-shaped cooling plates 16, which, for better space utilization, can be covered with circuit boards 15 on both sides.

[0033] Since the electric motor 10 requires relatively high currents in the conductor bars compared to conventional motors with windings, several inverters are preferably connected in parallel to supply them with current. This can be achieved, for example, by having 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.

[0034] Figure 3Figure 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 inverters, 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.

[0035] In Figure 3Busbars 22' are also shown in the state-of-the-art configuration. These are screwed onto the circuit boards 15, thus securing them to the cooling plate 16. If a circuit board 15 is defective and needs to be replaced, the busbars 22, along with all their individual screw connections to the circuit boards 15, must be removed. This means that, for example, with one hundred circuit boards 15, each with three screw connections 28, three hundred screw connections 28 must be loosened. This effort is reduced by the design according to Figure 4 , and further shown schematically and enlarged in the Figures 5 to 8 , reduced.

[0036] In Figure 4 is the same arrangement as in Figure 3 The busbars 22 are designed such that they are arranged below the circuit boards 15 in recesses 20 of the cooling plate 16. The overview diagram according to Figure 4illustrates the basic position of the busbars 22, which are located in the Figures 5-8 They are shown schematically but enlarged.

[0037] Figure 5 Figure 1 schematically shows a cross-section through a cooling plate 16 with printed circuit boards 15 mounted on it and recesses 20 in which the busbars 22 are arranged. The contacts are made in the Figure 5 as indicated by point 24. In Figure 5 Accordingly, two recesses 20 are provided in which the busbars 22 run separately from each other. One recess 20 is arranged in a radially outer region of the cooling plate 16, and a second busbar 22 is arranged in a radially inner region of the cooling plate 16. The busbars 22 run far apart from each other, and contact is made at the respective outer ends of the circuit boards 15.

[0038] In Figure 5The busbar is completely covered by the circuit board 15. In some embodiments of the invention, which are not shown graphically here, the busbar 22 can, however, project beyond the cooling plate 16 at its edges and only be partially covered by the circuit board 15. In this case, the recess would be open at one outer edge of the cooling plate and flanked by the cooling plate only on one side. However, it is important to note, as in all considerations of the Figures 4 - 8The busbar 22 is located in a recess 20 between the circuit board 15 and the cooling plate 16, and can therefore be removed and replaced by simply loosening the screw 28 of one circuit board 15. It is not necessary to unscrew the entire ring of the busbar 22 from all circuit boards 15 if only one circuit board 15 needs to be replaced. It should be noted that the term "screw 28" can refer to any detachable connection with an electrical contact. A suitably designed bolt can also be included under the term "screw connection." However, a particularly advantageous design for such a contact is the insertion of a metal screw.

[0039] In contrast, according to Figure 6Only one recess 20 is provided in the cooling plate 16, in which two busbars 22 are mounted one above the other, but electrically insulated from each other. Contact is also provided here via the contact point 24, with the contact being insulated from each other by each busbar 22. The advantage of the design according to Figure 6 compared to the Figure 5 The difference lies in the fact that only one recess 20 is provided, thus offering more contact area between the circuit board 15 and the surface of the cooling plate 16 for heat dissipation. However, in this design, according to Figure 6 This requires a greater effort to insulate the contacts and the two busbars 22 from each other. The screw connection 28 is located in the Figures 5-7 merely indicated very schematically by a dashed line.

[0040] In another alternative design form according to Figure 7Only one recess 20 is provided, which extends radially around a center point of the cooling plate 16. However, two busbars 22 are arranged side by side in this recess. Only one recess 20 is necessary here; however, to accommodate the two busbars 22 side by side, it will be wider than the comparable recess 20 in [reference missing]. Figure 6 .

[0041] In Figure 8 The contact between the busbar 22 and the circuit board 15 is also sketched very schematically. The screw connection 28 is guided through an at least partially electrically conductive contact point 24, whereby this screw connection 28 is screwed into the busbar 22, so that an electric current can flow from the busbar 22 to the contact point 24 via the screw connection 28. Furthermore, in Figure 8An additional insulation 30 is shown, which electrically insulates the busbar 22 from the cooling plate 16. This can be a flexible material, for example a silicone mat, which can also help to confine the busbars 22 within the recess 20 and fix them there. The design according to Figure 8 It can also be used to employ only one busbar 22 and the electrically conductive cooling plate 16 as a second current-carrying unit. The cooling plate 16 thus takes over the function of a second busbar 22. This simplifies the contacting and saves one busbar 22. Reference sign

[0042] 8 Stator / Rotor Block 9 Motor Shaft 10 Electric Motor 11 Stator 12 Conductor Bars 13 Front 14 Back 15 Circuit Boards 16 Cooling Plate 17 Shoe 18 Connecting Element 20 Recess 22 Busbar 24 Contact Points 26 Semiconductor Switch 28 Screw Connection 30 Insulation

Claims

1. Electric motor (10) having: - a stator (11) having a plurality of field conductors (12) in the form of rods, - a plurality of power electronics components for controlling the field conductors (12), wherein - the power electronics components are arranged on one or more printed circuit boards (15) located at an axial end of the machine, - at least one printed circuit board (15) is arranged on at least one cooling plate (16), - the cooling plate (16) is arranged in such a way that the field conductors (12) are mechanically operatively connected to the cooling plate via current conductors (18) that are electrically connected to the field conductors (12); and - wherein at least one groove-like depression (20) is recessed in the cooling plate (16), in which depression at least one busbar (22) is arranged so as to be electrically insulated from the cooling plate (16) - and is least partially covered by the printed circuit boards (15), and - the printed circuit boards (15) are electrically contact-connected to the at least one busbar (22).

2. Electric motor according to Claim 1, characterized in that at least two busbars (22) are arranged in the depression (20).

3. Electric motor according to Claim 1 or 2, characterized in that two busbars (22) in the depression are arranged next to one another radially to a motor axis (9).

4. Electric motor according to Claim 1 or 2, characterized in that two busbars (22) in the depression are arranged above one another along the motor axis (9).

5. Electric motor according to Claim 1, characterized in that at least two depressions are provided, in each of which at least one busbar runs.

6. Electric motor according to Claim 1, characterized in that the cooling plate is in the form of a second busbar.

7. Electric motor according to any one of the preceding claims, characterized in that the cooling plate is ring-shaped.

8. Electric motor according to any one of the preceding claims, characterized in that the busbar is ring-shaped.

9. Electric motor according to any one of the preceding claims, characterized in that the busbar is clamped in the depression by means of an insulating flexible material.

10. Electric motor according to any one of the preceding claims, characterized in that the printed circuit boards (15) are electrically contact-connected to the at least one busbar (22) by means of a screw connection.

11. Electric motor (10) according to any one of the preceding claims, in which the printed circuit boards (15) are in the shape of a circle or a ring sector.

12. Electric motor (10) according to any one of the preceding claims, in which the cooling plate (16) is arranged perpendicular to the axis (9) of the electric motor (10).

13. Electric motor (10) according to any one of the preceding claims, designed to control each of the field conductors (12) with its own phase.

14. Electric motor (10) according to any one of the preceding claims, in which the inverters are designed to generate an AC voltage with an amplitude of 200 V or less, in particular 150 V or less, in particular 50 V or less.