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. Motors of this type are known from EP 3719975 A1 and DE 10 2018 131 971 A1. 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, 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 components of the inverters that control the rods to be positioned close to each other. For example, the power electronics components can be arranged on one or more 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] In addition to the high heat loss from the electrical and electronic components caused by the high currents, such a motor design also features a high packing density of these components. Their direct connection to the stator / rotor block via the rods results in further heat input from the stator / rotor block. This, in turn, leads to a significant increase in the cooling requirements for the electrical and electronic components on the circuit boards.

[0005] The object of the invention is to provide an electric motor that reduces the aforementioned disadvantage.

[0006] This problem is solved by an electric motor having the features specified in claim 1.

[0007] The electric motor according to the invention comprises a stator with a plurality of field conductors designed as rods, as well as a plurality of inverters for controlling the field conductors.

[0008] The inverters are arranged on one or more circuit boards. Furthermore, the circuit boards are arranged on at least one cooling plate, and the cooling plate is arranged such that the field conductors or current conductors electrically connected to the field conductors are in mechanical contact with the cooling plate, in particular, penetrate it.

[0009] Finally, at least one cooling device is present, which includes a fluid line that is routed externally along one or more of the field conductors and / or current conductors.

[0010] The electric motor according to the invention advantageously features improved heat dissipation for the field conductors due to fluid cooling. This results in a lower heat flow reaching the cooling plates and the electronics arranged on the cooling plates, in particular the inverters. This, in turn, reduces the cooling requirements in the area of ​​the cooling plates and the electronics.

[0011] The field conductors or current conductors primarily act as mechanical supports for the cooling plates and are therefore in mechanical contact with them. It is possible that the field conductors or current conductors penetrate the cooling plate and the circuit board.

[0012] Field conductors designed as rods can be either solid rods or composed of several sub-conductors. These sub-conductors can be connected in parallel, for example, if the field conductors are Roebel conductors. Alternatively, the sub-conductors can be connected in series, with the field conductors consisting of several sub-elements joined together, for example, by welding.

[0013] The current conductors can be mechanically fixed to and connected with the field conductors, with exactly one field conductor always being connected to exactly one current conductor, the current conductors extending the field conductors axially. In this case, the field conductors, current conductors, and cooling plate can form a mechanically rigid unit.

[0014] 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, preferably, with those of several dependent claims. Accordingly, the following additional features can be provided: The fluid lines can be water lines. Water is a standard coolant and can, for example, be supplied from outside the electric motor in a factory, so lines suitable for water are advantageous.

[0015] The electric motor may have a pump for a cooling fluid. If the cooling fluid is not supplied externally, it is advantageous for the electric motor to be designed in such a way that fluid circulation can be generated, ensuring heat dissipation through material movement. If the motor has a large number of field conductors, for example, more than 50 or even more than 100, several pumps may be present.

[0016] In a first alternative according to the invention, the electric motor is designed such that a fluid line is routed along each of the field conductors and / or current conductors. It is advantageous to provide heat dissipation for each of the field conductors or current conductors, since during operation of the electric motor the field conductors or current conductors are uniformly exposed to heat and thus each of the field conductors or current conductors contributes approximately equally to the heat transfer to the cooling plates.

[0017] In this first alternative according to the invention, a region is located in which the fluid line is guided axially between a cooling plate and an axial starting point of the rotor, in contact with the field conductor and / or current conductor on the outside. In this region, the field conductors and / or current conductors are exposed, and the fluid line can be easily attached. Furthermore, it is advantageous to dissipate heat in this region in order to reduce the heat input from the rotor area, i.e., the drive system, into the electronics, i.e., the area of ​​the cooling plates and circuit boards.

[0018] If electrical conductors are present, they are conveniently connected to the field conductors by means of a connector, with the fluid line running along the connector. The connector provides a secure connection between the field conductors and the electrical conductors. The field conductors belong to the drive side of the electric motor, while the electrical conductors connect the electronics on the circuit boards and support the cooling plates and circuit boards. Advantageously, the connector can be geometrically adapted to the fluid line without altering the shape or cross-section of the field conductors. This simplifies the manufacturing of the field conductors. Alternatively, the fluid line can be routed externally along a field conductor.

[0019] The fluid lines for at least two of the field conductors or current conductors can be connected in series. In other words, a single fluid line leads to one field conductor or current conductor and then subsequently to at least one other field conductor or current conductor. Only then does the fluid line lead away from the field conductors, for example, to a reservoir. In this way, several of the field conductors or current conductors are cooled by a single fluid line, which reduces the connection effort.

[0020] In a second alternative according to the invention, the fluid line surrounds the ring formed by the field conductors or current conductors, either at its outer edge or on its inner edge. In other words, the fluid line extends azimuthally over at least two of the field conductors or current conductors. The fluid line can form a complete ring, i.e., contact all field conductors or current conductors, or it can form only a sector of the ring, in which the fluid line sweeps over a portion of the field conductors or current conductors and thus dissipates their heat. In the latter case, it is advantageous to use several such fluid lines that together sweep over all field conductors or current conductors and thus dissipate heat. Furthermore, it is advantageous to use one fluid line for an angular segment or a portion of the field conductors or current conductors that corresponds to a fraction of the full circle with an integer denominator, i.e., 1 / 3, 1 / 4, or 1 / 8 of the full circle.For example, with 72 field conductors, 1 / 6 of them, i.e., 12, could be cooled by a fluid line, and six such fluid lines would be present. Each of the fluid lines would thus cover an angle of 60° of the full circle.

[0021] In this second alternative according to the invention, the fluid line is guided along a radially outward or inward-facing side of the field conductor or current conductor and has surface elements in contact with an azimuthal side of the field conductor or current conductor. The surface elements increase the contact area between the fluid line and the field conductor or current conductor, thus ensuring better heat transfer from the field conductor or current conductor to the fluid. If the fluid lines are guided along a radially outward-facing side of the field conductor or current conductor, the surface element advantageously points radially inward, and vice versa. The surface element can be U-shaped and thus, in addition to improved thermal contact, also provide mechanical support for the fluid line.

[0022] In the first alternative according to the invention, the fluid line runs at least section by section parallel to the field conductor or current conductor. In other words, it is arranged section by section on the field conductor or current conductor such that the fluid channel runs parallel to the field conductor or current conductor.

[0023] The fluid line can be made of a ceramic material, or in particular, consist entirely of a ceramic material. Ceramic materials are heat-resistant, chemically resistant, and electrically insulating, and therefore allow installation in the electric motor without requiring additional measures such as electrical insulation.

[0024] The fluid line can be electrically insulated from the field conductor or current conductor by an electrically insulating material layer. Insulating pads are suitable for this purpose. A particular advantage here is that the electric motor, due to its design, operates at relatively low voltages, thus keeping the effort required for electrical insulation comparatively low. The thickness of the material layer and any additional lateral insulation only need to be adapted to voltage differences in the range of, for example, 12 V.

[0025] The electric motor can have multiple printed circuit boards (PCBs). In particular, multiple separate PCBs can be mounted on a single cooling plate. By distributing the components across multiple PCBs, the power electronics can be modularized. This allows for the production of a large number of inverters using a variety of identical PCBs, thereby improving manufacturing processes and reducing scrap.

[0026] The printed circuit boards (PCBs) can be designed in a circular or ring sector shape. This allows the PCBs to be arranged in a circle or ring that encircles the axis of the electric motor. PCBs of this shape can be assembled into a circle or ring and thus optimally adapted to the shape of the electric machine, positioned at one axial end of the machine while simultaneously achieving a high degree of modularity. The PCBs can therefore be arranged axially offset from the stator and rotor, saving space and forming an integral part of the electric motor. In this way, it is also possible to arrange several cooling plates with PCBs axially offset from one another, thus enabling, for example, the parallel connection of inverters located at the same azimuthal position.

[0027] Preferably, the cooling plate is arranged perpendicular to the axis of the electric motor. This allows the cooling plate and the circuit boards to be positioned compactly at one axial end of the electric machine. Multiple cooling plates can also be arranged axially offset and close to one another. Furthermore, this arrangement ensures a uniform distance between the cooling plate and the power electronics and the rods forming the field conductors, thus simplifying the contacting of the rods.

[0028] It is particularly advantageous if each field conductor is driven by its own phase. A phase is defined as an AC voltage supply that is phase-shifted by a non-zero angle relative to all other phases used in the electric motor. In this case, it is advisable to have a separate inverter for each field conductor, which drives only that specific field conductor.

[0029] The inverters can be designed to generate an alternating voltage with an amplitude of 200 V or less, in particular 150 V or less, and especially 50 V or less. The voltage thus generated is the voltage applied to the field conductors, i.e., the stator bars. This comparatively low voltage makes it possible to arrange the inverter components very close to each other. Spacings of approximately 2 mm between components such as the power semiconductor switches can be used, resulting in a high packing density of the electronic components and the possibility of arranging a large number of inverters in a relatively small space. This, in turn, makes it possible to use a large number of phases in a small space, in particular a number of phases corresponding to the number of stator bars.With a sufficiently high number of stator bars, 48, 72 or even 120 phases can be used.

[0030] The terms "axial", "radial", and "azimuthal" refer to the axis of the rotor and thus to the corresponding axis of symmetry of the stator. "Aximal" describes a direction parallel to this axis, "radial" describes a direction orthogonal to the axis, either towards or away from it, and "azimuthal" is a direction that rotates circularly around the axis at a constant radial distance and with a constant axial position.

[0031] 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.

[0032] 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 1 an electric motor with three cooling plates for cooling printed circuit boards in oblique view, Figure 2 Circuit boards arranged on a cooling plate, front view Figure 3 a cross-sectional view of the cooling plates with conductor rods and connecting elements, Figure 4 A side view of conductor bars and cooling plates with one embodiment of fluid channels, Figure 5 a non-perspective scheme for a serial circuit of the fluid channels, Figure 6 another embodiment for a fluid channel with azimuthal guidance.

[0033] 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 1The 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.

[0034] In other embodiments, the electric motor 10 can also be an external rotor motor or a bell-shaped armature motor.

[0035] 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 are sector-shaped, and many individual circuit boards 15 together form a ring-shaped circuit board structure.

[0036] 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.

[0037] Figure 2 shows a top view of such a circuit board structure. The number in Figure 2The 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 semiconductor switches 422.

[0038] 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 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 circuit board 15 may be assigned to a single phase or to several phases.

[0039] The circuit boards 15 also include contact points 421 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.

[0040] Since relatively high currents are required in the conductor bars of the electric motor 10, several inverters 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.

[0041] 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.

[0042] The stator / rotor block 8 of the electric motor 10 and the electronics on the circuit boards 15 generate heat. The conductor bars 12 and the connecting elements 18, in addition to their electrical conductivity, also form a thermal bridge between the two components. It is particularly important on the electronics side that the additional heat input is not too high, as the electronic components must not exceed a temperature of approximately 80°C for extended periods. However, enhanced cooling in the circuit board area is complex.

[0043] Therefore, it is advantageous to provide cooling in the area 19 between the cooling plates 16 and the stator / rotor block 8. Figure 4 Such cooling is shown on a conductor rod 12. In the case of the Figure 4For the intended cooling, a fluid channel 20 is attached to the conductor rod 12 such that the water, which is used here as the cooling fluid, is guided along the conductor rod 12 over a distance of a few centimeters. The amount of heat that can be transferred from the conductor rod 12 to the fluid channel 20 and thus to the water can be adjusted by the length of this path, since a longer path results in a larger contact area and thus a greater energy flow.

[0044] The fluid channel 20 can, for example, be made of ceramic. In this case, it is rigid, as is typical of ceramic materials. A hose connection 23 can therefore be provided at both ends, into which a hose for conveying the water opens. This creates an inlet 21 and an outlet 22 for the fluid channel. These hoses can be joined elsewhere to form a cooling circuit. At this point, the heat can be dissipated to the environment via a heat exchanger or cooling element. It is possible that the aforementioned elements are integrated as part of the electric motor 10. Alternatively, it is also possible that the cooling circuit already exists independently of the electric motor 10 at its installation location, and that the electric motor 10 is connected to it along with other devices.

[0045] In alternative configurations, the fluid channel can also be made of other materials, including, for example, metallic materials. In this case, electrical conduction from the conductor rod 12 to other elements must be prevented, for example by using plastic tubing for water conveyance.

[0046] Since all conductor bars 12 are heated equally from the side of the stator / rotor block 8 and are connected equally to the circuit boards 15, it is advantageous to provide a fluid channel 20 for each of the conductor bars 12. However, in certain configurations of the electric motor 10, the number of conductor bars 12 is high, for example 48, 72, or even 120. In the latter case, there are thus 120 outlets 22 and 120 inlets 21, which must be connected or combined elsewhere and supplied with water, for example by a pump system.

[0047] Therefore, for certain embodiments of the electric motor 10, it is advantageous to group closely spaced fluid channels 20 together and connect them in series. Such a configuration is shown schematically in Figure 5 depicted. It is further assumed that the fluid channels 20 are arranged directly on the conductor bars 12. Figure 5 To simplify the representation, however, neither the conductor rods 12 nor the actually three-dimensional ring-shaped arrangement of the fluid channels 20 is shown, but the fluid channels 20 are shown side by side in a simplified manner.

[0048] According to Figure 5Three fluid channels 20 are grouped together and connected in series with respect to the water flow. If this grouping is applied to an electric motor 10 with 120 conductor bars 12, this results in 40 such groups and therefore 40 inlets 21 and 40 outlets 22, which is significantly fewer than before. By forming larger groups, the effort required for guiding the cooling fluid can be further reduced, as long as the cooling capacity for the last conductor bars 12 in the series of fluid channels remains sufficiently high.

[0049] In the design according to Figure 5The water flow still runs section by section parallel to the orientation of the conductor rods 12. In an alternative embodiment, shown in Figure 6, the orientation of the water flow is rotated by 90° and the water is guided azimuthally around the ring formed by the conductor rods 12. Figure 6 shows the fluid channel 60 thus formed. The fluid channel 60 rests on four of the conductor rods 12 along its course. Figure 6 This does not correspond to all conductor bars 12, but only to a portion of the conductor bars 12. A similar assessment can be made here as in the grouping of the Figure 5The more conductor bars 12 the fluid channel 60 spans, the simpler the installation and connection, as the number of inlets 21 and outlets 22 decreases. However, the potential cooling capacity also decreases. Furthermore, in this case, with a rigid fluid channel 60, it may be easier to install if it does not form a complete ring, i.e., if it only spans a portion of the conductor bars 12.

[0050] Since the water flow in the fluid channel 60 in the embodiment according to Figure 6 Since the heat transfer does not take place along the longitudinal extent of the conductor rods 12, the distance available for heat dissipation, and thus also the area, is shorter than in the embodiments of the Figures 4 and 5 To ensure sufficient heat transfer, the fluid channel 60 can have additional surface-expanding elements 61. These appear in Figure 6They are tooth-shaped and made of solid material to ensure good heat conduction. In other words, they do not represent an additional volume for the cooling fluid, but rather extend the surrounding material in such a way that an increased surface area in contact with the conductor rods 12 is created.

[0051] When plastic tubing is used for the cross-connection between the fluid channels, electrical insulation is automatically provided. The fluid channel 60, however, can also be designed as a single component. If it is then made of an insulating material, such as a ceramic, insulation between the conductor bars 12 is still ensured. If, on the other hand, the fluid channel 60 is metallic, then insulation is necessary to prevent a short circuit between the conductor bars 12. For this purpose, insulating pads can be placed between the fluid channel 60 and, if applicable, the additional surface elements 61 and the conductor bar 12.

[0052] In the preceding embodiments, the fluid channel 20, 60 is always routed along the surface of the conductor bars 12. However, in all embodiments, the fluid channel 20, 60 can equally well be routed along the connecting elements 18, thus enabling heat dissipation from the connecting elements 18.

[0053] Another option, which can be substituted in all embodiments, is to route the fluid channel 20, 60 along the shoes 17, which connect the connecting elements 18 and the conductor bars 12. This is advantageous because the shoes are typically designed to connect the conductor bars 12 and connecting elements 18, which have different cross-sectional shapes, and are therefore themselves more complex in shape than the conductor bars 12 or the connecting elements 18. Therefore, it is easily possible to accommodate and compensate for any reduction in the current-conducting cross-section resulting from bores in the design of the shoes 17. Both the conductor bars 12 and the connecting elements 18 can thus be uniformly constructed and therefore easier to manufacture. Reference sign

[0054] 8 Stator / Rotor Block 9 Motor Shaft 10 Electric Motor 11 Stator 12 Conductor Bars 13 Front 14 Rear 15 Circuit Board 16 Cooling Plate 17 Shoe 18 Connecting Element 19 Area 20, 60 Fluid Channel 21 Inlet 22 Outlet 23 Hose Connections 61 Additional Surface Element 421 Contact Points 422 Semiconductor Switch

Claims

1. Electric motor (10) comprising: - a stator (11) having a plurality of field conductors (12) designed as bars, - a plurality of inverters for controlling the field conductors (12), wherein - the inverters are arranged on one or more printed circuit boards (15), - the printed circuit boards (15) are arranged on at least one cooling plate (16), - 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, - at least one cooling device is provided, characterized in that the cooling device either comprises a fluid line (20, 60) for each of the field conductors (12) and / or current conductors (18), the fluid line being guided in a manner bearing against the outside of the field conductor (12) and / or current conductor (18) such that the fluid flow runs axially, i.e. parallel to the orientation of the conductor bars (12), in sections, wherein a region (19), in which the fluid line (20, 60) is guided in a manner bearing against the outside of the field conductor (12) and / or current conductor (18), lies axially between a cooling plate (16) and an axial start of the stator / rotor block (8), or comprises a fluid line (20, 60) which encircles the ring, which is formed by the field conductors (12) or the current conductors (18), at its outer edge or on the inside at its inner edge and is guided along a radially outwardly or inwardly facing side of the field conductors (12) or current conductors (18) and has surface elements (61) bearing against an azimuthal side of the field conductors (12) or current conductors (18).

2. Electric motor (10) according to Claim 1, in which the fluid lines (20, 60) are water lines.

3. Electric motor (10) according to Claim 1 or 2, in which a pump for a cooling fluid is provided.

4. Electric motor (10) according to any one of the preceding claims, in which field conductors (12) and current conductors (18) are connected by means of a shoe (17) and in which the fluid line (20, 60) is guided along the shoe (17).

5. Electric motor (10) according to any one of the preceding claims, in which the fluid lines (20, 60) for at least two of the field conductors (12) or current conductors (18) are connected to each other in series.

6. Electric motor (10) according to any one of the preceding claims, in which the fluid line (20, 60) comprises a ceramic material, in particular consists of a ceramic material.

7. Electric motor (10) according to any one of the preceding claims, in which the fluid line (20, 60) is electrically insulated from the field conductor (12) or current conductor (18) by an electrically insulating material layer.

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

9. 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).

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

11. 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.