Electric motor having circuit board carrying power electronics and cooling plate

Abstract

The invention relates to an electric motor comprising a stator (11) having a plurality of field conductors (12) in the form of rods, a plurality of power electronics for controlling the field conductors (12). The power electronic components are arranged on a plurality of printed circuit boards (15). The at least one printed circuit board (15) is arranged on the at least one cooling plate (16) and the cooling plate (16) is arranged in such a way that the field conductor (12) is mechanically and electrically operatively connected to the cooling plate (16) via a current conductor (18) electrically connected to the field conductor (12). Furthermore, the cooling plate (16) is divided into at least two sub-sections (16-1), (16-2) which are electrically insulated from one another, and a separating surface (20) formed by the insulating body (30) comprises at least two sub-sections (16-1, 16-2), the separating surface being less than 20% of the cooling surface (22). In this case, the printed circuit board (15) is in electrical contact with the subsections (16-1, 16-2) of the cooling plate (16) in order to supply power.

Description

Technical Field

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

[0002] Electric motors can have a rod-shaped winding on the stator side. Here, the stator has a series of rods as field conductors instead of wound wires. Rods have a lower inductance than conventional windings. Therefore, a relatively high current is required to generate a predetermined magnetic field. An electric motor of this design is described in EP19167289 A1.

[0003] However, due to the low resistance of the rod, this high current requires only a relatively low voltage, for example 12 V. The low voltage allows the components required for the inverter's control rod to be arranged at a relatively close distance from one another. Therefore, the components of the power electronics can be mounted, for example, on one or more circuit boards (printed circuit boards) located near the electric motor (preferably within the motor housing). The rod can serve as a mechanical support for the circuit board, either directly or via electrically conductive, rod-shaped connecting elements.

[0004] Here, the printed circuit boards are mounted on the cooling plate and contacted individually via electrical busbars. Here, the busbars are on the printed circuit boards and in contact with them via screw fasteners. However, the screw fasteners are also fastened in the cooling plate (mechanically decoupled from the cooling plate) in order to establish a secure contact. This leads to insulation problems between the screw fasteners and the cooling plate in each case, which must be loosened using a corresponding sleeve for each individual screw fastener. Especially when a printed circuit board needs to be replaced due to a damaged individual component, typically two busbars (which span up to 150 printed circuit boards and supply them with power) must be unscrewed, then completely insulated and screwed back on. Summary of the Invention

[0005] The object of the present invention is to provide an electric motor with a stator-side rod winding and an integrated power electronics component which, compared to the prior art, allows for lower maintenance expenditure when replacing a printed circuit board of the power electronics component.

[0006] This object is achieved by an electric motor having the features of claim 1 .

[0007] The electric motor includes

[0008] a stator having a plurality of field conductors in the form of rods,

[0009] - a plurality of power electronic components for controlling the field conductors, wherein:

[0010] - the power electronics are arranged on one or more printed circuit boards, and

[0011] at least one printed circuit board is arranged on at least one cooling plate,

[0012] The cooling plate is arranged such that the field conductors are mechanically connected to the cooling plate via current conductors electrically connected to the field conductors. (This can be achieved by means of through-holes through the cooling plate. However, the mechanical connection can also be achieved indirectly to the cooling plate, for example, via holes in a printed circuit board, where the printed circuit board partially protrudes beyond the edge of the cooling plate at these holes.) Accordingly, the current conductors form current-conducting connecting elements between the field conductors and the printed circuit board, and ultimately to the power electronics (also called semiconductor switches). Due to the mechanical connection, they also have load-bearing properties for the cooling plate and are electrically insulated relative to the cooling plate.

[0013] - The present invention is characterized in that

[0014] The cooling plate is divided into at least two mutually electrically insulated subsections 16 - 1 , 16 - 2 ,

[0015] wherein the dividing surface 20 between the sub-segments 16 - 1 , 16 - 2 represents less than 20% of the cooling surface 22 , and

[0016] The printed circuit board 15 is in electrical contact with the subsections 16 - 1 , 16 - 2 of the cooling plate 16 for power supply.

[0017] Accordingly, the power supply for the electric motor is firstly supplied by a subsection of the cooling plate to the printed circuit board and the power electronics arranged thereon, and the power electronics are then supplied via the current conductors to the field conductors of the stator.

[0018] The electric motor described here differs from conventional electric motors in that the stator has a series of rods instead of wound conductors as field conductors. These rods have a lower inductance than conventional windings. Therefore, a relatively high current is required to generate a predetermined magnetic field.

[0019] The rod winding design offers fundamental advantages in machine operation: the segmented control of the magnetic flux between each two field conductors allows for a much more flexible magnetic field pattern in the motor than with distributed windings and their inherent superposition effects. This results in numerous (control-related) advantages in the machine's operating characteristics. Furthermore, the consequences of a phase failure (of a (controlled) field conductor) are significantly less severe than, for example, in dual three-phase or even conventional three-phase machines. Since these effects can also be very effectively compensated by adjacent phases, the drive power only decreases slightly for each phase failure with appropriate stabilization, without significantly affecting the remaining characteristics.

[0020] The described electric motor has the advantage over prior art electric motors of this type that the busbars are not located on the printed circuit board. Instead, the cooling plate itself provides the printed circuit board with power. This allows each printed circuit board to be easily removed and replaced individually by simply loosening the screw fasteners that typically also serve as contact points for the busbars. This eliminates the need to disassemble most components, or even all printed circuit boards, for repairs. This significantly reduces effort and therefore costs when repairing power electronics.

[0021] Furthermore, this design, which divides the cooling plate into at least two segments and uses them for electrical contact and thus power supply, offers the advantage that, on the one hand, it does not hinder the installation of the printed circuit board, while at the same time allowing the entire contact surface of the printed circuit board on the cooling plate to be used as a cooling surface. Also advantageous is a larger electrical contact surface for the DC (direct current) supply (instead of a smaller contact surface to the corresponding DC busbars). Furthermore, the metal busbars lowered into the cooling plate are also thermally conductive in principle, but they do not contribute to cooling because they are electrically and, therefore, largely thermally insulated from the cooling plate (this insulation is often omitted, which is also advantageous). Therefore, after the busbars heat up, they do not provide significant heat dissipation and, therefore, do not function as a cooling plate.

[0022] Here, the term "cooling surface" is defined as a surface against which a printed circuit board rests at least indirectly and in a planar manner. For technical reasons (e.g., to achieve additional electrical insulation or mechanical damping), it may be expedient to provide an intermediate layer or film between the printed circuit board and the cooling plate. This also refers to a planar placement of the printed circuit board on the cooling surface, as the cooling surface serves to absorb heat from the printed circuit board. Separating surfaces are surfaces that, when viewed vertically, are arranged between the subsections of the cooling plate and serve to provide electrical insulation between the subsections.

[0023] It should be noted that, in general, for the described electric motor, it is not usually necessary to use exactly two current-carrying potentials. It is also advantageous to use a double potential or, for example, a triple potential or a double (redundant) intermediate circuit with an intermediate circuit center point, wherein more than two current conductors are required.

[0024] In one embodiment of the present invention, contacting of the printed circuit board at the contact point is achieved by means of a fastening device on the cooling plate. Preferably, the fastening device can be a screw fastener. Contacting by means of the fastening device achieves both the necessary requirements of contacting and fastening between the cooling plate and the printed circuit board by means of the device, thus saving additional technical effort. In addition to screw fasteners for contacting, snap-on or clamping connections are also suitable.

[0025] It is also advantageous if the cooling plate 16 is thermally connected to a heat sink 38. This allows heat introduced into the cooling plate by the components via the printed circuit board to be effectively dissipated again. The heat sink is particularly preferably designed in the form of a cooling channel, which, on the other hand, preferably passes through the cooling plate in a horizontal plane relative to the cooling surface.

[0026] Furthermore, the subsections of the cooling plate are preferably annular or designed in the form of ring segments. This allows for a combination of good contact with the printed circuit board and good heat dissipation. Furthermore, it is advantageous if the cooling plate is made of aluminum or copper or an alloy of these metals.

[0027] The printed circuit board can be designed in the form of a circle or ring segment. Printed circuit boards with this shape can be combined into a circle or ring and thus arranged on the shaft end of the machine in an optimally matched manner to the shape of the electric motor, wherein a high modularity is simultaneously achieved.

[0028] The terms "axial," "radial," and "tangential" are used here with reference to the rotor axis and, therefore, the axis of symmetry of the stator. "Axial" describes a direction parallel to the axis, "radial" a direction perpendicular to the axis, toward or away from the axis, and "tangential" a direction oriented annularly around the axis at a constant radial distance from the axis and at a constant axial position. The expression "in the circumferential direction" is equivalent to "radial."

[0029] If the concepts "axial", "radial" and "tangential" are used in relation to surfaces, such as cross sections, then these concepts describe the surface normals, i.e. the vectors perpendicular to the surface in question. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Further embodiments and features of the present invention will be described in detail with reference to the following figures, which are purely schematic and do not represent a limitation of the scope of protection.

[0031] Here it is shown:

[0032] Figure 1 is a side view of an electric motor with heat dissipation for a printed circuit board,

[0033] Figure 2 This is the front view of the electric motor.

[0034] Figure 3 is Figure 1 A partial enlarged side view of a cooling plate with a busbar in the prior art,

[0035] Figure 4 is the same partial view as FIG3 with a modified arrangement of the power supply,

[0036] Figure 5 is a three-dimensional cross-sectional view of a cooling plate with the described printed circuit board,

[0037] Figure 6 is a top view of a cooling plate with the described printed circuit board,

[0038] Figure 7 is the cross section through the cooling plate through the threaded fixing,

[0039] Figure 8 is the cross section through the cooling plate having the cooling channels of the surface,

[0040] Figure 9 is a cross section through a cooling plate with centrally arranged cooling channels,

[0041] Figure 10 is a three-dimensional illustration of a cooling plate having subsegments designed in the form of ring segments. DETAILED DESCRIPTION

[0042] Figure 1 An isometric view of an electric motor 10 is shown, which is an exemplary embodiment for use with the present invention. The electric motor 10 includes a stator 11 and a rotor substantially disposed within the stator 11. Figure 1 The rotor is connected to the shaft in a rotationally fixed manner, which is also Figure 1 The rotor rotates around the shaft 9 by electromagnetic interaction between the rotor and the energized stator 11. The rotor and the stator 11 are separated by an air gap.

[0043] In other embodiments, the electric motor 10 can also be an external rotor electric motor or a bell armature electric motor.

[0044] The stator 11 comprises a plurality of rigid and straight conductor rods 12 as field conductors. Figure 1 The conductor bars 12 are connected to each other on the rearward-facing end face 13 via shorting rings. On the rear side 14 of the electric motor 10, conductor bars 12 are each individually powered by a corresponding inverter module. Because the conductor bars 12 allow the electric motor 10 to operate at low voltage, the inverter module can be arranged relatively closely together with other components of the electronic device (DC converter, rectifier) ​​on a printed circuit board 15. In this example, the printed circuit board 15 is in the form of ring segments, with multiple individual circuit boards 15 forming a ring-shaped circuit board structure. The rigidly formed conductor bars can be made of metal bars, such as copper, or formed from solid multi-filament conductors.

[0045] In this example, it is assumed that the printed circuit board (PCB) 15 carries the inverter module, and a portion of the PCB 15 can also carry a rectifier and a DC / DC (Direct Current / Direct Current) converter.

[0046] Figure 2 Here, for the sake of clarity, Figure 2 The number of printed circuit boards 15 shown is greater than Figure 1 The illustration is reduced and highly simplified. The actual number of such printed circuit boards 15 depends on the specific design of the electric motor 10 , in particular on the number of conductor bars 12 . Each of the printed circuit boards 15 includes a plurality of power electronic components, in particular semiconductor switches 26 .

[0047] Furthermore, some or all of the printed 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 may also include diodes (not shown), depending on the connection method. The semiconductor switches 26 are connected, for example, to form a half-bridge. The capacitors (not shown) can, for example, represent the intermediate circuit capacitors of the half-bridge. The semiconductor switches 26 of the printed circuit board 15 can be assigned to a single phase or to multiple phases.

[0048] Since, compared to conventional electric motors with windings, relatively high currents are required in the conductor bars of the electric motor 10, a plurality of inverters are preferably connected in parallel to supply it. This can be achieved, for example, by Figure 1 The six printed circuit board structures shown are all connected to the conductor bars 12 in the same manner on three cooling plates 16 and are therefore electrically connected in parallel. This is because the conductor bars 12 or the connecting elements 18 thereto pass through the cooling plates 16 and thus also the printed circuit boards 15 in the same manner at the contact points, or in the case of the outermost cooling plate 16, at least make contact with the same contact points.

[0049] Figure 3 shows an oblique partial view of electric motor 10. It can be seen here that connecting element 18 is mechanically supported and extends through three cooling plates 16. This can also be achieved by having printed circuit board 15 protrude radially beyond cooling plates 16, with the connecting element extending through the printed circuit board in the protruding region. Connecting element 18 is connected to conductor bar 12 via guide shoe 17. On printed circuit board 15, the inverters located in the region where one of connecting element 18 passes through cooling plate 16 are connected in parallel and jointly supply current to conductor bar 12.

[0050] FIG3 also shows busbars 32 in an embodiment according to the prior art. These busbars are screwed onto the printed circuit board 15, thereby fastening the printed circuit board to the cooling plate 16. If the printed circuit board 15 is damaged and needs to be replaced, the busbars 32 together with all the screw fasteners to the printed circuit board 15 must be removed. This means that, for example, out of one hundred printed circuit boards 15 each having three screw fasteners, three hundred screw fasteners must be removed. Figure 4 and subsequent Figures 5 to 10 The schematic and enlarged configuration shown in FIG. 1 reduces this expenditure.

[0051] Figure 4 The same arrangement of the cooling plate 16 relative to the electric motor 10 and the electric motor shaft 9 as in FIG. 3 is shown, wherein however the printed circuit board 15 is contacted via the subsections 16 - 1 and 16 - 2 of the cooling plate 16 .

[0052] Figure 5 A detailed cross-sectional view of a cooling plate 16 is now shown, which is for example Figure 4 The cooling plate 16 is arranged in a manner. The cooling plate 16 is divided into two subsections, namely a first subsection 16-1 and a second subsection 16-2. The two subsections 16-1 and 16-2 are electrically insulated from each other by an insulator 30. When viewing the cooling plate 16 perpendicular to the electric motor shaft 9, the subsections 16-1 and 16-2 and the insulator 30 form a plane. The surfaces of the subsections 16-1 and 16-2 form a cooling surface 22. In a top view, the cooling surface 22 is separated by a partition surface 20 formed by the insulator 30. To dissipate the heat input from the printed circuit board 15, it is advantageous if the area of ​​the partition surface 20 is as small as possible; the partition surface should account for a maximum of 20% of the area of ​​the cooling surface 22. Particularly advantageously, the partition surface 20 should account for less than 10% of the cooling surface 22, and particularly advantageously, less than 5%.

[0053] exist Figure 5 and 6 The positioning of the printed circuit board 15 is indicated by dashed lines in FIG. Furthermore, contact points 24 are marked, via which electrical contact is made between the electrically conductive cooling plate 16 and the printed circuit board 15 and the power electronics arranged thereon.

[0054] exist Figure 5 and 6 The neutron segments 16-1 and 16-2 are designed in the form of two concentric rings. It should be noted that other possible segmentations on the cooling plate 6 are also suitable, such as Figure 10 As shown. Figure 10In the embodiment, the sub-segments 16-1, 16-2, 16-3 are divided into units in the form of ring segments. Here, the sub-segments have a geometrical design similar to the printed circuit board 15 which is generally advantageously designed. In this case, it can be expedient for the printed circuit board 15 to cover two sub-segments 16-1 to 16-2, such as Figure 10 As shown, contacting with different potentials is achieved with the individual subsections. It should be noted that, depending on the electrical connection, even in the case of a DC supply of the printed circuit board, multiple electrically conductive contacts with different potentials may be suitable and / or necessary.

[0055] The cooling plate 16, divided into subsegments 16-1, 16-2, and / or 16-3, is preferably made of aluminum or an aluminum alloy or copper or a copper alloy. These metals are easy to manufacture, conduct electricity very well, and have high thermal conductivity. Therefore, the cooling plate functions not only as a current conductor but also as a cooler. Meanwhile, the insulator 30 is preferably constructed of an insulating plastic. The insulator 30 can also be configured at least partially as a cavity, in which air serves as the insulating medium.

[0056] exist Figures 7 to 9 Shown in the Figure 6 and Figure 5 The cross-sectional view of the cooling plate 16 is shown in FIG, and is marked there with sections VII, VIII and IX. Figure 7 In addition to a cross-section through subsections 16-1 and 16-2, which are separated from each other by an insulator 30 and together form the cooling plate 16, the diagram schematically illustrates how the printed circuit board 15 is fastened to the cooling plate 16. A fastening device 34, designed as a screw fastener 36, is provided at the contact point 24. The screw fastener 36 is a fastening device 34 that ensures good contact between the electrically conductive cooling plate 16 and the printed circuit board 15. In principle, riveting is also suitable, but this makes removal less feasible in the event of damage to the printed circuit board 15. However, a snap-on connection, similar to a quick-release clip on a bicycle seat, also allows for equally good contact of the printed circuit board to the cooling plate.

[0057] exist Figures 7 to 9 1 and 16 - 2 are shown for the subsections 16 - 1 and 16 - 2 in each case with the same large cross-sectional area. However, this is not absolutely necessary. It is advantageous if both subsections 16 - 1 and 16 - 2 are connected to the heat sink 38 . Figure 8 and 9 In the embodiment shown, the heat sink 38 is designed in the form of a cooling channel 40. However, the heat sink can also be in physical contact with another good heat conductor that conducts heat away from the cooling plates 16 and away from the electric motor 10. The heat sink 38 can also be a sufficient distance between the cooling plates 16 through which a fluid, in particular air, flows.

[0058] exist Figure 8 and 9 A possible configuration for arranging cooling channels 40 through the cooling plate 16 is shown in FIG. Figure 8 The cooling channel 40 is embedded in the groove in the cooling surface 22. The cooling channel 40 is Figure 8 In the example, it has a rectangular cross section.

[0059] exist Figure 9 In the embodiment, a cooling channel 40 is also introduced into the cooling plate 16, but is located in the center of the cooling plate 16. Such a cooling channel 40 can be produced either by lost-core sand casting, in particular as aluminum sand casting. Alternatively, the cooling plate can also be divided by horizontal planes 42, where the cooling channels are also removed in the form of grooves. When the horizontally divided cooling plates 16 are joined together, these grooves form closed cooling channels 40. The horizontally divided cooling plates can then be joined together during production using a welding process or sealed by a circumferential seal. A second option allows the creation of additional subsections (not shown) that can provide additional independent conductive potentials.

[0060] The described arrangement of electric motor 10 and power electronics on cooling plate 16 and printed circuit board 15 has the advantage that cooling plate 16, which in the prior art was originally used only to dissipate heat from the power electronics, is now also used to dissipate electrical contact with the power electronics. This has the advantage, firstly, that no additional components in the form of conductive busbars are required, and secondly, that elaborate electrical insulation from the cooling channels is unnecessary. Furthermore, these conductive busbars are not located above printed circuit board 15 (as viewed from cooling plate 16), so that in the event of damage to one printed circuit board 15, all contacts on the other printed circuit board 15 do not need to be removed. Consequently, the described arrangement requires less effort and fewer parts both during initial assembly of electric motor 10 and in the event of any repairs.

[0061] Reference Signs List

[0062] 8 stator / rotor blocks

[0063] 9 Electric motor shaft

[0064] 10 electric motors

[0065] 11 stator

[0066] 12 conductor rods

[0067] 13 End side

[0068] 14 rear side

[0069] 15 printed circuit boards

[0070] 16 cooling plates

[0071] 16-1 First subsection of cooling plate

[0072] 16-2 Second subsection of cooling plate

[0073] 17 Guide Shoes

[0074] 18 Connecting elements

[0075] 20 Dividing surface

[0076] 22 Cooling surface

[0077] 24 contact positions

[0078] 26 semiconductor switches

[0079] 28 threaded fasteners

[0080] 30 Insulator

[0081] 32 Busbars in the Prior Art

[0082] 34 Fastening device

[0083] 36 threaded fixings

[0084] 38 Radiator

[0085] 40 cooling channels

[0086] 42 horizontal plane.

Claims

1. An electric motor (10) comprising: a stator (11) having a plurality of field conductors (12) in the form of rods, - a plurality of power electronic components for controlling the field conductors (12), wherein - the power electronics are arranged on one or more printed circuit boards (15), - at least one of the printed circuit boards (15) is arranged on at least one cooling plate (16), The cooling plate (16) is arranged such that the field conductor (12) is mechanically effectively connected to the cooling plate (16) via a current conductor (18) electrically connected to the field conductor (12), characterized in that - the cooling plate (16) is divided into at least two mutually electrically insulated subsections (16-1), (16-2), - wherein the dividing surface (20) between the sub-segments (16-1), (16-2) represents less than 20% of the cooling surface (22), and The printed circuit board (15) is in electrical contact with the subsections (16-1), (16-2) of the cooling plate (16) for power supply.

2. The electric motor according to claim 1, wherein Contacting of the printed circuit board (15) at a contact point (24) is achieved by means of a fastening device (34) on the cooling plate (16).

3. The electric motor according to claim 2, wherein: The fastening device (34) is designed in the form of a screw fastener (36).

4. An electric motor according to any one of the preceding claims, characterized in that The cooling plate (16) is thermally connected to the heat sink (38).

5. The electric motor according to claim 4, wherein: The heat sink (38) is configured in the form of a cooling channel (40).

6. The electric motor according to claim 5, characterized in that The cooling channel (40) extends through the cooling plate (16) in a horizontal plane (42).

7. An electric motor according to any one of the preceding claims, characterized in that The subsections ( 16 - 1 ), ( 16 - 2 ) are annular or designed in the form of ring segments.

8. An electric motor according to any one of the preceding claims, characterized in that The cooling plate (16) is made of aluminum or copper or an alloy of these metals.

9. An electric motor according to any one of the preceding claims, characterized in that The printed circuit board (15) is designed in the form of a circle or ring segment.

10. An electric motor according to any one of the preceding claims, characterized in that The cooling plate (16) is arranged perpendicular to the shaft (9) of the electric motor (10).

11. An electric motor according to any one of the preceding claims, characterized in that The electric motor is configured to control each of the field conductors (12) with its own phase.

12. An electric motor according to any one of the preceding claims, characterized in that in, The inverter is designed to generate an AC voltage having an amplitude of 200 V or less, in particular 150 V or less, in particular 50 V or less.

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