A structure for cooling a lead frame and a winding coil and a generator or motor

Abstract

The present invention relates to the field of electric machines and discloses a structure for cooling a lead frame and winding coils of an electric generator or motor and an electric generator or motor. The stator core comprises a plurality of circumferentially distributed stator teeth. The lead frame electrically connects a first inverter to a first set of coil windings mounted on the stator core of the electric motor or generator. The lead frame comprises a printed circuit board having a plurality of layers of circuit board, wherein each layer of circuit board comprises an insulating substrate and an electrically conductive layer disposed on the insulating substrate. The lead frame is positioned between a cooling channel and the stator teeth. A potting material is positioned between the cooling channel and the lead frame, wherein the potting material acts as a heat transfer between the cooling channel and the lead frame. The cooling channel is formed in the stator housing. The present invention increases the cooling of the lead frame mounted on the stator. The arrangement of the lead frame provides a large current between the inverter and the coil windings of the electric motor or generator, thereby producing a large torque and power value.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electric machines, and in particular to a structure for cooling lead frame and winding coil and a generator or motor. BACKGROUND

[0002] Motor systems typically include a motor whose control unit is arranged to control the power of the motor. Known motor types include induction motors, synchronous brushless permanent magnet motors, switched reluctance motors and linear motors. As high torque is required for driving a vehicle, the most commonly used motor is a three-phase motor. A three-phase motor typically includes three coil windings, where each coil winding is arranged to generate a magnetic field associated with one of the three phases of an alternating voltage. To increase the number of magnetic poles formed within the motor, each coil winding will typically have a number of coil sub-groups distributed around the motor, which are driven to generate a rotating magnetic field. Chinese patent CN201710715959.7 provides a three-phase permanent magnet brushless DC hub motor.

[0003] As shown in Figure 1 A typical three-phase motor has three coil groups 14, 16, 18. Each coil group is made up of four coil sub-groups in series, where for a given coil group, the magnetic field generated by each coil sub-group will have a common phase. The three coil groups of a three-phase motor are typically configured in a delta or star configuration. The control unit of a three-phase motor with a direct current power supply typically includes an inverter drive motor that generates a three-phase power supply from a three-phase bridge. Each respective voltage phase is applied to a respective coil group of the motor. A three-phase bridge inverter includes a number of switching devices, such as power electronic switches, such as insulated gate bipolar transistor (IGBT) switches, for generating an alternating voltage from a direct current power supply. In the context of electric vehicle motors, an increasingly popular drive design is one in which the motor and its associated control system are integrated within the vehicle wheel. However, due to the space constraints within the vehicle wheel in which the electric motor and its associated control system are integrated, this can have an impact on the power generation capability of the motor. The present application provides a motor lead frame that can provide a large current. SUMMARY

[0004] The present application provides a structure for cooling lead frame and winding coil according to the defect that the existing hub motor cannot provide large torque.

[0005] In order to solve the above technical problems, the present application is solved by the following technical scheme:

[0006] A structure for cooling a lead frame and winding coils, the stator comprising a circumferential bracket, a cooling channel and a lead frame, the circumferential bracket comprising a plurality of stator teeth circumferentially distributed around the circumferential bracket, a first set of coil windings mounted on the stator teeth, a second set of coil windings and a third set of coil windings, the lead frame for electrically connecting a first inverter to the first set of coil windings of a motor or generator mounted on the circumferential bracket, wherein the lead frame comprises a printed circuit board having a plurality of layers of circuit board, wherein each layer of circuit board comprises an insulating substrate and a conductive layer disposed on the insulating substrate, the lead frame is located between the cooling channel and the stator teeth, and a potting material is located between the cooling channel and the lead frame, wherein the potting material is configured to provide a thermal path between the cooling channel and the lead frame, the cooling channel is formed in the circumferential bracket.

[0007] As a preference, the lead frame is in a whole circumferential shape, or two half circumferential lead frames are spliced into a whole circumferential lead frame.

[0008] As a preference, the inner edge and the outer edge of the printed circuit board are each provided with a recess for receiving a corresponding coil winding, and the coil winding is electrically coupled to the printed circuit board through the recess.

[0009] As a preference, the lead frame is mounted on the circumferential bracket close to the coil windings.

[0010] As a preference, the cooling channel is arranged to have a first portion and a second portion, the first portion being perpendicular to the second portion.

[0011] As a preference, the first portion of the cooling channel is disposed on the inner side of the stator core and along the axial direction of the stator core.

[0012] As a preference, the second portion of the cooling channel is disposed on the side of the lead frame away from the stator core and along the radial direction of the lead frame.

[0013] As a preference, the end face of the stator core at both ends is provided with a sink groove distributed along the axial direction of the stator core, and the potting material is filled in the sink groove.

[0014] As a preference, the printed circuit board has at least a first circuit board layer, a second circuit board layer, a third circuit board layer and a fourth circuit board layer; the first circuit board layer comprises a first conductive layer arranged to be electrically coupled to a first coil winding of the first set of coil windings and a first leg of the first inverter; the second circuit board layer comprises a second conductive layer arranged to be electrically coupled to a second coil winding of the first set of coil windings and a second leg of the first inverter; the third circuit board layer comprises a third conductive layer arranged to be electrically coupled to a third coil winding of the first set of coil windings and a third leg of the first inverter; the fourth circuit board layer comprises a fourth conductive layer arranged to be coupled to the first coil winding, the second coil winding and the third coil winding of the first set of coil windings to form a neutral point between the first coil winding, the second coil winding and the third coil winding.

[0015] The present application also provides an electric machine comprising the above described stator.

[0016] The present application has remarkable technical effects due to the above technical solutions:

[0017] The present application increases the cooling of the lead frame mounted on the stator, the arrangement of the lead frame provides a large current between the inverter and the coil winding of the electric motor or generator, thereby generating a large torque and power value, while allowing to reduce the space envelope of the coil winding and the inverter of the electric motor / generator. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 A three-phase electric motor of the prior art is illustrated;

[0019] Figure 2 An exploded view of an electric machine comprising the present application is illustrated;

[0020] Figure 3 is a schematic view of a control device;

[0021] Figure 4 An electrical connection provided by the lead frame according to an embodiment of the present application is illustrated;

[0022] Figure 5 A lead frame according to an embodiment of the present application is illustrated;

[0023] Figure 6 A lead frame arrangement according to an embodiment of the present application is illustrated;

[0024] Figure 7 A lead frame according to an embodiment of the present application is illustrated;

[0025] Figure 8 A lead frame arrangement according to an embodiment of the present application is illustrated;

[0026] Figure 9An electrically conductive layer on a circuit board layer of a lead frame according to an embodiment of the present application is described;

[0027] Figure 10 A lead frame according to an embodiment of the present application is described;

[0028] Figure 11 An electrically conductive layer on a circuit board layer of a lead frame according to an embodiment of the present application is shown;

[0029] Figure 12 An electrically conductive layer on a circuit board layer of a lead frame according to an embodiment of the present application is described;

[0030] Figure 13 An electrically conductive layer on a circuit board layer of a lead frame according to an embodiment of the present application is described.

[0031] Figure 14 An electrically conductive layer on a circuit board layer of a lead frame according to an embodiment of the present application is described;

[0032] Figure 15 A lead frame according to an embodiment of the present application is shown;

[0033] Figure 16 A schematic diagram of a coil end cooperating with a lead frame according to an embodiment of the present application is shown;

[0034] Figure 17 A stator core, a coil winding and a lead frame according to an embodiment of the present application are described;

[0035] Figure 18 A schematic diagram of a cooling structure according to the present application is described;

[0036] Figure 19 A schematic diagram of a stator coil winding and a stator core is shown;

[0037] Figure 20 An exploded schematic diagram of a stator coil winding unit and a stator core is shown. DETAILED DESCRIPTION

[0038] Embodiment 1

[0039] This embodiment provides a structure for cooling a lead frame and a coil, such as Figure 18As shown, the lead frame 255 is mounted on the stator core 600, and the ends of the coil are connected to the lead frame 255. The stator core 600 is configured to be mounted to the stator radiator 253. Preferably, the stator core 600 is mounted on the stator radiator 253 via a heat dissipation mechanism. To cool the stator core 600, the coil 400, and the lead frame 255, the lead frame has a cooling channel having a first section 1810 extending along the inner axial edge of the stator teeth 800 and the stator core 600, and a second section 1820 extending in a radially outward direction parallel to the axial mounting surface of the stator core 600 on which the lead frame is mounted.

[0040] like Figure 18 The stator cross-sectional view is shown. To improve thermal conductivity between the stator heat sink 253 and the lead frame 255, potting material 1830 is placed between the heat sink 253 and the lead frame 255, and between the lead frame 255 and the stator coil 400. The potting material 1830 is typically arranged to provide good thermal conductivity. An example of a suitable potting material is ceramic-filled epoxy resin; however, other types of potting materials can be used.

[0041] This embodiment provides a lead frame 255 for coupling the inverter of a motor or generator to a DC power supply; the motor in this embodiment is a hub motor for automobile wheels. Figure 2 As shown, the hub motor includes a stator 252 comprising a circumferential bracket serving as a radiator 253, multiple coils 254, and two control devices 300 (not shown) mounted on the circumferential bracket 253 at the rear of the stator for driving the coils. A capacitor and lead frame 255 are mounted between the axial edge of the coils 254 and an axial flange formed on the circumferential bracket 253 for connecting the control devices to the coils 254. The coils 254 are engaged in stator teeth 800 to form coil windings; a stator cover is mounted at the rear of the stator 252, surrounding the control devices and the annular capacitor to form the stator 252, which is then secured to the vehicle and does not rotate relative to the vehicle during use.

[0042] Specifically, the stator core assembly includes a central stator core 600 and a circumferential support 550 installed on the outer circumference of the stator core 600, with stator teeth 800 formed on the annular outer surface of the circumferential support 550.

[0043] like Figure 3 As shown, each control device 300 includes an inverter 310, and one control device 300 includes a controller regulator 320. In this embodiment, the control device 300 includes a processor for controlling the operation of the two inverters 310. Figure 3As shown, each control device 300 includes an inverter 310, and one of the control devices includes control logic 320, which in this embodiment includes a processor, for controlling the operation of both inverters 310. As described below, each inverter is coupled to three sets of coil windings, which are electrically connected in parallel, forming a set of three sub-machines.

[0044] A ring capacitor is coupled between the inverter 310 and the DC power supply for the motor, also referred to as the DC bus, to reduce voltage ripple on the motor power supply line and to reduce voltage overshoot during motor operation. To reduce inductance, the capacitor is mounted in close proximity to the control device 300.

[0045] The magnets are positioned in close proximity to the coil windings on the stator 252, so that the magnetic field generated by the coils interacts with the magnets 242 positioned inside the cylindrical portion 221 of the rotor 240, thereby causing the rotor 240 to rotate. Since the permanent magnets 242 are used to generate the drive torque that drives the motor, the permanent magnets are often referred to as drive magnets. In this embodiment, the motor includes six coil sets, each coil set having three coil subsets, which are also referred to as coil phase windings in this embodiment; the three coil subsets are coupled in a Y-configuration to form a three-phase sub-machine, so that the motor has six three-phase sub-machines. The stator includes a circumferential support, which is a stator core 600, and stator winding units 550 mounted on the circumferential support, which are teeth with coils wound thereon, each tooth having a tooth slot 801 formed therein, and the outer circumference of the circumferential support has stator teeth 800, with the tooth slots 801 being interference fit into the stator teeth 800. In this embodiment, there are 54 stator winding units 550, since there are two coil sets, each coil set including three coil sets, each coil set including three coil phase windings (subsets), and each coil phase winding including three coils. As described above, the coils of the six coil sets are wound on the stator teeth 800 as part of the stator. As described below, the operation of the sub-machines is controlled by one of the two control devices 300. Although this embodiment describes a motor having six coil sets (i.e., six sub-machines), the motor can also have one or more coil sets with associated control devices. Likewise, each coil set can have any number of coil subsets, thereby allowing each sub-machine to have two or more phases.

[0046] Figure 3The connection between each coil set 60 and the control device 300 is illustrated, wherein three coil sets 60 are connected to a respective three-phase inverter 310 on the control device 300. As is well known to those skilled in the art, a three-phase inverter comprises six switches, wherein a three-phase alternating voltage can be generated by controlled operation of the six switches. However, the number of switches will depend on the number of voltage phases applied to the respective sub-machines, which can be built with any number of phases. Each control device 300 communicates with other control devices 300 via a communication bus.

[0047] One of the control devices 300 comprises a processor 320 for controlling the operation of the inverter switches in both control devices 300, and is further electrically connected to a temperature sensor 503 for receiving a signal from the temperature sensor 503 to determine whether the electric motor is operating within an acceptable temperature range. Furthermore, each control device 300 comprises an interface arrangement allowing communication between the control devices 300 via the communication bus 330, wherein one of the control devices 300 is arranged to communicate with a vehicle controller mounted externally to the electric motor.

[0048] The processor 320 is arranged to control the operation of the inverter switches mounted within each control device 300 to allow each electric motor coil set 60 to be supplied with a three-phase voltage supply, thereby allowing each coil sub-set to generate a rotating magnetic field. As mentioned above, although the present embodiment describes each coil set 60 as having three coil sub-sets, the present application is not limited as such, and it will be appreciated that each coil set 60 can have one or more coil sub-sets.

[0049] Each three-phase bridge inverter 310 is arranged to provide pulse width modulated voltage control in the respective coil sub-set under the control of the processor, thereby generating a current in the respective coil sub-set to provide the required torque for the respective sub-machine. The principle of PWM control is to use the motor inductance to average the applied pulse voltage, thereby driving the required current into the motor coil. Using pulse width modulation control, the applied voltage is switched between the motor windings. During the voltage switching through the motor coil, the current in the motor coil rises at a rate determined by its inductance and the applied voltage. The PWM voltage control is switched off before the current rises above the required value, thereby achieving accurate control of the current. For a given coil set, the three-phase bridge inverter 310 switches are arranged to apply a single voltage phase on each coil sub-set. Using PWM switching, multiple switches are arranged to apply an alternating voltage on the respective coil sub-set. The voltage envelope and phase angle of the electrical signal is determined by the modulated voltage pulses.

[0050] The inverter formed on one control device is coupled to three coil sets, forming a first set of three sub-machines, and the inverter formed on the other control device is coupled to the other coil sets, forming a second set of three sub-machines.

[0051] The two inverters 310 are coupled to the respective coil sets by the leadframe 255, with each leg of the respective inverter 310 being coupled to the leadframe 255 by a respective phase busbar. For the present embodiment, the different voltage phases generated by the three legs of the inverter are designated as W, V and U. The coil windings are coupled to the leadframe 255 to allow current to flow from the DC power supply through the respective inverters 310 in the control device to the coil windings, thereby allowing the motor to generate drive torque.

[0052] Figure 4 The leadframe 255 is shown providing the electrical connection between the phase busbars of one of the control devices and the coil windings mounted on the stator, with the leadframe 255 being arranged in a Y-configuration for coupling the phase windings of the respective coil subsets. However, the leadframe 255 can be configured to couple the phase windings of the respective coil subsets in different configurations. As mentioned above, each coil winding comprises three coil subsets (i.e. phase windings) to form a three-phase sub-motor. Figure 4 The leadframe 255 is shown providing the electrical connection between the phase busbars of one of the control devices and the coil windings mounted on the stator, with the leadframe 255 being arranged in a Y-configuration for coupling the phase windings of the respective coil subsets. However, the leadframe 255 can be configured to couple the phase windings of the respective coil subsets in different configurations. As mentioned above, each coil winding comprises three coil subsets (i.e. phase windings) to form a three-phase sub-motor. The first, second and third coil windings of the first set of coil windings in the present embodiment correspond one-to-one with the first, second and third sub-motors hereinafter.

[0053] For the present embodiment, each coil set forming a coil subset is formed from three individual coils, which are coupled by the circuit board layers of the leadframe 255.

[0054] Reference is made to Figure 4 For the first sub-motor 411, coil 401 forms a first phase winding of the first sub-motor 411, coil 402 forms a second phase winding of the first sub-motor 411, and coil 403 forms a third phase winding of the first sub-motor 411. For the second sub-motor 412, coil 404 forms a first phase winding of the second sub-motor 412, coil 405 forms a second phase winding of the second sub-motor 412, and coil 406 forms a third phase winding of the second sub-motor 412. For the third sub-motor 413, coil 407 forms a first phase winding of the third sub-motor 413, coil 408 forms a second phase winding of the third sub-motor 413, and coil 409 forms a third phase winding of the third sub-motor 413. Figure 4 Each coil 400 shown in Figure 8 corresponds to a coil on a single stator tooth 800, with the end portions of each coil being arranged to couple to the leadframe 255 to enable the coils to be connected in series as described above. Figure 4The illustrated configuration is coupled.

[0055] The lead frame 255 is used to connect the W-phase inverter bus to the first coils 400 of the first phase winding 401 of the first sub-motor 411, the first phase winding 404 of the second sub-motor 412 and the first phase winding 407 of the third sub-motor 413. The lead frame 255 also connects the V-phase inverter bus to the first coils 400 of the second phase winding 402 of the first sub-motor 411, the second phase winding 405 of the second sub-motor 412 and the second phase winding 408 of the third sub-motor 413, and the U-phase inverter to the first coils 400 of the third phase winding 403 of the first sub-motor 411, the third phase winding 406 of the second sub-motor 412 and the third phase winding 409 of the third sub-motor 413.

[0056] As Figure 4 illustrated, the lead frame 255 connects the last coil 400 of the first phase winding 401 of the first sub-motor 411 to the last coils 400 of the second and third phase windings 402, 403 of the first sub-motor 411. Likewise, the lead frame 255 also connects the last coil 400 of the first phase winding 404 of the second sub-motor 412 to the last coils 400 of the second and third phase windings 405, 406 of the second sub-motor 412, and the last coil 400 of the first phase winding 407 of the third sub-motor 413 to the last coils 400 of the second and third phase windings 408, 409 of the third sub-motor 413. These connections serve as the star point for each sub-motor.

[0057] Furthermore, the lead frame 255 is arranged to electrically connect the individual coils 400 of each phase winding to form a series connection between the individual coils 400 of each phase winding. Accordingly, the lead frame 255 provides electrical connections between the W, V, U phase inverter buses and the individual coils 400 to form a three sub-motor driven by a single inverter 310, wherein the coil windings of each sub-motor are coupled in a Y-shaped configuration. Likewise, the lead frame 255 also connects the phase winding buses of the inverters 310 of the other control device 300 and the coils mounted on the stator in the same manner to form a three sub-motor driven by the inverters 310 in the second control device 300. The structure of the lead frame 255 will now be described, wherein in the first embodiment, as Figure 5 illustrated, a substantially circumferential lead frame 255 is used to provide current from both control devices to the respective coil sets.

[0058] The lead frame 255 includes a first set of three holes 660 for receiving corresponding bus lead frame pins for coupling the lead frame 255 to the inverter 310 in the first control device 300, and a second set of three holes 660 for receiving corresponding bus lead frame pins for coupling the lead frame 255 to the inverter 310 in the second set.

[0059] The lead frame 255 has fixing holes at predetermined positions, and hot posts 630 are inserted into the fixing holes. In this embodiment, the hot posts 630 are arranged at the ends of the teeth of the stator winding unit 550, close to the lead frame 255. The hot posts 630 are designed on the inner and outer sides of the stator winding unit 550 and are arranged to extend through the holes formed in the lead frame 255. Once the lead frame 255 is mounted on the stator core 600 and the respective hot posts 630 pass through the corresponding fixing holes formed in the lead frame 255, the hot posts 630 melt, thereby fixing the lead frame 255 to the stator core 600. However, any suitable method can be used to connect the lead frame 255 to the stator core.

[0060] like Figure 6 As shown, the lead frame 255 includes a plurality of grooves 640 formed on the inner and outer radial edges of the lead frame 255 for receiving the ends of the coil wound on the stator teeth 800 and for coupling the coil 400 to the lead frame 255, as described below, wherein for each coil wound on the stator teeth 800, a portion is installed in the groove 640 formed on the inner radial edge of the lead frame 255 and another portion is installed in the groove 640 formed on the outer radial edge of the lead frame 255.

[0061] A single circumferential lead frame 255 serves as a current path from each inverter 310 within the control device 300 to each coil winding, wherein the lead frame 255 is a basic circumferential printed circuit board having multiple circuit board layers. Each layer has a conductive layer printed on it. Each circuit board layer includes an insulating substrate on which the conductive layer is formed. In this embodiment, there are two inverters; in other words, half a circumference of the lead frame printed circuit board is allocated for coupling the first control device 300 to a set of coil windings to form a three-sub-motor formed by the first set of coil windings, and the other half a circumference of the lead frame printed circuit board is allocated for coupling the second control device 300 to a three-sub-motor formed by the second set of coil windings. The multiple circuit board layers are separated by their respective insulating substrates.

[0062] To allow large currents to flow from the inverters 310 to the coil windings, allowing the electric motor to produce sufficient torque to drive the vehicle, the conductive layers on each circuit board layer are arranged to extend across a substantial portion of each circuit board, with each conductive layer arranged to correspond to a particular circuit path between each inverter 310 and coil winding, and between different subsets of coils making up each sub-motor, so that each circuit board layer optimizes current flow.

[0063] To achieve Figure 4 The configuration of the printed circuit board layers and the conductive layers printed on the circuit board layers will now be described, with reference to the circuit configuration shown. Each circuit board layer includes two sets of electrical connections for coupling a first set of three coil windings to one inverter, and a second set of three coil windings to another inverter, although each circuit board layer can include any number of conductive layers based on the number of inverters. For example, if one inverter is used to drive all of the coil windings mounted on the stator, the conductive layers printed on each circuit board layer would be arranged to form a particular circuit path between the inverter and the coil windings, and between different subsets of coils making up each respective sub-motor.

[0064] The lead frame 255 in this embodiment includes a first lead frame 701 and a second lead frame 702, where both the first lead frame 701 and the second lead frame 702 are semi-circumferential, forming a substantially circumferential lead frame 255 when mounted on the stator 252. As shown in Figure 8 Each lead frame 255 is mounted on an axial mounting surface of the stator core 600, which forms part of the stator 252, with the coil windings being wound around stator teeth 800 formed on the stator core 600.

[0065] Both the first lead frame 701 and the second lead frame 702 include a set of three holes 660 for receiving respective busbar lead frame pins for coupling the first lead frame 701 and the second lead frame 702 to the inverters 310 in the first control device 300 and the second control device 300, respectively.

[0066] The first lead frame 701 and the second lead frame 702 are mounted to the stator core 600 by connecting to hot posts 630 at predetermined positions. The hot posts 630 are arranged to extend through holes formed in the first lead frame 701 and the second lead frame 702. Once the first lead frame 701 and the second lead frame 702 are mounted on the stator core 600, and the respective hot posts 630 pass through their respective holes formed in the first lead frame 701 and the second lead frame 702, the hot posts 630 melt, thereby holding the first lead frame 701 and the second lead frame 702 fixed to the stator core 600. However, any suitable method can be used to connect the first lead frame 701 and the second lead frame 702 to the stator core 600.

[0067] like Figure 8 As shown, the first lead frame 701 and the second lead frame 702 include a plurality of grooves 640 formed on the inner and outer radial edges of the first lead frame 701 and the second lead frame 702, for receiving end portions of coils 400 wound on stator teeth 800 for coupling, the coils 400 being connected to the first lead frame 701 and the second lead frame 702 respectively. For each coil wound on the stator teeth 800, one end is mounted in the groove 640 formed on the inner radial edge of the first lead frame 701 or the second lead frame 702, and the other end is mounted in the groove 640 formed on the outer radial edge of the corresponding lead frame 255 portion 701.

[0068] The circuit board layer of the first printed circuit board on the first lead frame 701 is a mirror image of the circuit board layer of the second printed circuit board on the second lead frame 702. The first printed circuit board is responsible for the three sub-motors formed by the first group of coil windings (named first sub-motor, second sub-motor, and third sub-motor, or sub-motor 1 / 2 / 3), and the second printed circuit board is responsible for the three sub-motors formed by the second coil windings (named fourth sub-motor, fifth sub-motor, and sixth sub-motor, or sub-motor 4 / 5 / 6).

[0069] The following description uses the circuit board layer and circuit connection of the first lead frame as an example.

[0070] The first printed circuit board includes a first circuit board layer, the first circuit board layer having, as shown in the figure Figure 9The first conductive layer is shown extending substantially to a first half circumferential portion of the circumferential circuit board, the first half circumferential portion is arranged to be electrically coupled to the W-phase inverter 310 bus bar and the first coils of the first phase windings 401 of the first sub-motor 411, the first coils of the first phase windings 404 of the second sub-motor 412 and the first coils of the first phase windings 407 of the third sub-motor 413. As mentioned above, the printed circuit board on the second lead frame 702 has circuit board layers corresponding to the first circuit board layers, on which the conductive layers are arranged to be electrically coupled to the W-phase inverter bus bar of the second inverter and to the corresponding coil windings of the second set of coil windings mounted on the stator.

[0071] As Figure 10 shown, the W-phase inverter 310 bus bar is coupled to the first circuit board layer by bus bar lead frame pins 1010, which are cylindrical conductive elements coupled to the W-phase inverter 310 bus bar, the bus bar lead frame pins 1010 extend through the associated lead frame pin holes 660 formed in the printed circuit board. The W bus bar lead frame pins 1010 are electrically coupled to the first conductive layer 900 at locations 910. In order for the first coils of the first phase windings 401 of the first sub-motor 411, the first coils of the first phase windings 404 of the second sub-motor 412 and the first coils of the first phase windings 405 of the third sub-motor 413 to be coupled to the first conductive layer 900 at locations 920, 930, 940, the ends of the associated coil windings are mounted in the grooves 640 formed in the inner and outer radial edges of the lead frame 255 as described above, wherein the ends of the coil windings are mounted in the grooves 640 formed in the inner radial edge of the lead frame 255 at locations 920, 930, 940 and are electrically coupled to the first conductive layer 900. The other ends of the first coils of the first phase windings of the first, second and third sub-motors and the ends of the remaining coil windings are mounted in respective grooves formed in the inner and outer radial edges of the lead frame 255 and are electrically isolated from the first conductive layer 900.

[0072] The first printed circuit board includes a second circuit board layer having a second conductive layer as Figure 11The second conductive layer 1100 shown extends substantially into the first half-circumferential portion of the circumferential circuit board, which is arranged to be electrically coupled to the busbar of the U-phase inverter 310 and the first coil of the second phase winding 402 of the first sub-motor 411, the first coil of the second phase winding 405 of the second sub-motor 412, and the first coil of the second phase winding 408 of the third sub-motor 413. The printed circuit board on the second lead frame 702 has a circuit board layer corresponding to the second circuit board layer, on which conductive layers are arranged to be electrically coupled to the U-phase inverter busbar of the second inverter and to the corresponding coil windings of the second set of coil windings mounted on the stator.

[0073] like Figure 10 As shown, the U-phase inverter 310 busbar is coupled to the second circuit board layer via busbar lead frame pins 1010. These busbar lead frame pins 1010 are cylindrical conductive elements coupled to the U-phase inverter 310 busbar, extending through the corresponding lead frame 255 pinholes 660 formed in the printed circuit board. The U-shaped busbar lead frame pins 1010 are electrically coupled to the second conductive layer 1100 at position 1110. To couple the first coil of the second phase winding 402 of the first sub-motor 411, the first coil of the second phase winding 405 of the second sub-motor 412, and the first coil of the second phase winding 408 of the third sub-motor 413 to positions 1120, 1130, and 1140 of the second conductive layer, respectively, and as described above, the relevant coils are installed in grooves 640 formed within the inner and outer radial edges of the lead frame 255. The ends of the coil windings installed in the grooves formed within the inner radial edge of the lead frame 255 are electrically coupled to the second conductive layer at positions 1120, 1130, and 1140. The other ends of the first coils of the second phase windings of the first, second, and third sub-motors, and the ends of the remaining coil windings, are installed in their respective grooves formed within the inner and outer radial edges of the lead frame 255, electrically isolated from the second conductive layer.

[0074] The printed circuit board includes a third circuit board layer 1200, the third circuit board layer having, as shown in... Figure 12 The third conductive layer shown extends substantially to a first half-circumferential portion of the circumferential circuit board, which is arranged to be electrically coupled to the V-phase inverter 310 bus and the first coil of the first phase winding 403 of the first sub-motor 411, the first coil of the third phase winding 406 of the second sub-motor 412, and the first coil of the third phase winding 409 of the third sub-motor 413. As described above, the printed circuit board on the second lead frame 702 has a circuit board layer corresponding to the third circuit board layer, on which the conductive layer is arranged to be electrically coupled to the V-phase inverter bus of the second inverter and to the corresponding coil windings of the second set of coil windings mounted on the stator.Figure 10 As shown, the V-phase inverter 310 bus is coupled to the third circuit board layer by bus lead frame pins 1010, which are cylindrical conductive elements coupled to the V-phase inverter 310 bus that extend through the associated lead frame 255 pin holes 660 formed in the printed circuit board. The V-bus lead frame pins 1010 are arranged to electrically couple to the third conductive layer 1200 of the printed circuit board at locations 1210. To couple the first coils of the third phase windings 403 of the first sub-motor 411, the first coils of the third phase windings 406 of the second sub-motor 412, and the first coils of the third phase windings 409 of the third sub-motor 413 to the third conductive layer, the ends of the associated coils are arranged as described above in the grooves 640 formed in the inner and outer radial edges of the lead frame 255, the ends of the coil windings mounted in the grooves formed in the lead frame 255 at 1220, 1230, 1240 are electrically coupled to the third conductive layer. The other ends of the first coils of the first, second, and third sub-motor third phase windings, as well as the ends of the remaining coil windings, are mounted in the respective grooves formed in the inner and outer radial edges of the lead frame 255 are electrically isolated from the third conductive layer.

[0075] The printed circuit board includes a fourth circuit board layer having a fourth conductive layer 1310, a fifth conductive layer 1320, and a sixth conductive layer 1330, as shown in Figure 13 wherein the fourth conductive layer 1310, the fifth conductive layer 1320, and the sixth conductive layer 1330 together extend over the first semicircumferential portion of the annular printed circuit board. The fourth conductive layer 1310, the fifth conductive layer 1320, and the sixth conductive layer 1330 are electrically isolated from one another.

[0076] The fourth conductive layer 1310 is arranged to electrically couple the last coil of the first phase winding 401, the last coil of the second phase winding 402 and the last coil of the third phase winding 403 of the first sub-motor 411. The first coil winding 401, the second coil winding 402 and the third coil winding 403 of the first sub-motor 411 form a neutral point (i.e. star point) therebetween. To electrically couple the last coil of the first phase winding 401, the last coil of the second phase winding 402 and the last coil of the third phase winding 403 of the first sub-motor 411, the ends of the relevant coil are mounted at the inner and outer radial edges of the leadframe 255 as described above, wherein the ends of the coil winding mounted within the groove formed in the outer radial edge of the leadframe 255 are electrically coupled to the fourth conductive layer 1310 at 1311, 1312, 1313. The other ends of the last coil of the first phase winding 401, the last coil of the second phase winding 402 and the last coil of the third phase winding 403 of the first sub-motor 411 and the ends of the remaining coil windings are mounted in the respective grooves formed therein. The inner and outer radial edges of the leadframe 255 are electrically isolated from the fourth conductive layer 1310.

[0077] The fifth conductive layer 1320 is arranged to electrically couple the last coil of the first phase winding 404 of the second sub-motor 412, the last coil of the second phase winding 405 of the second sub-motor 412 and the last coil of the third phase winding 406 of the second sub-motor 412. The first coil winding 404 of the second sub-motor 412, the second coil winding 405 and the third coil winding 406 of the second sub-motor 412 form a neutral point (i.e. star point) between them. To electrically couple the last coil of the first phase winding 404 of the second sub-motor 412, the last coil of the second phase winding 405 of the second sub-motor 412 and the last coil of the third phase winding 406 of the second sub-motor 412, the ends of the relevant coil are arranged to be mounted in the inner and outer radial edges of the lead frame 255 as described above, wherein the ends of the coil winding mounted in the grooves formed in the outer radial edge of the lead frame 255 are electrically coupled to the fifth conductive layer 1320 at 1321, 1322, 1323. The other ends of the last coil of the first phase winding 404 of the second sub-motor 412, the last coil of the second phase winding 405 of the second sub-motor 412 and the last coil of the third phase winding 406 of the second sub-motor 412 and the ends of the remaining coil windings, which are mounted in the respective grooves 640 formed in the inner and outer radial edges of the lead frame 255, are electrically isolated from the fifth conductive layer 1320. The sixth conductive layer 1330 is arranged to electrically couple the last coil of the first phase winding 407 of the third sub-motor 413, the last coil of the second phase winding 408 of the third sub-motor 413 and the last coil of the third phase winding 409 of the third sub-motor 413. The first coil winding 407 of the third sub-motor 413, the second coil winding 408 and the third coil winding 409 of the third sub-motor 413 form a neutral point (i.e. star point) between them. The printed circuit board of the second lead frame 702 has the same layers of the printed circuit board of the fifth layer structure of the circuit board for connecting the respective coils of the second set of coil windings, thereby forming the second set of sub-motors.

[0078] To couple the last coil of the first phase winding 401 of the first sub-motor 411, the last coil of the second phase winding 402 of the first sub-motor 411 and the last coil of the third phase winding 403 of the first sub-motor 411, the end of the relevant coil is mounted at the inner and outer radial edges of the leadframe 255 as described above, specifically the end of the coil winding mounted within the groove formed in the outer radial edge of the leadframe 255 is electrically coupled with the fourth conductive layer 1310 at 1311, 1312, 1313. The other end of the last coil of the first phase winding 407 of the third sub-motor 413, the last coil of the second phase winding 408 of the third sub-motor 413 and the last coil of the third phase winding 409 of the third sub-motor 413 and the end of the remaining coil winding is mounted in the corresponding groove 640 formed in the inner radial edge of the leadframe 255 and the outer radial edge of the leadframe 255 is electrically isolated from the sixth conductive layer 1330.

[0079] The printed circuit board comprises a fifth circuit board layer having Figure 14 The plurality of conductive layers shown are arranged for electrically coupling the coils 400 forming the first phase winding 401 of the first sub-motor 411, for forming the coils 400 of the second phase winding 402 of the first sub-motor 411 and for forming the coils 400 of the third phase winding 402 of the first sub-motor 411. With respect to the second sub-motor, the plurality of conductive layers are arranged for electrically coupling the coils 400 forming the first phase winding 404 of the second sub-motor 412, for forming the coils 400 of the second phase winding 405 of the second sub-motor 412 and for forming the coils 400 of the third phase winding 406 of the second sub-motor 412. With respect to the third sub-motor, the plurality of conductive layers are arranged for electrically coupling the coils 400 forming the first phase winding 407 of the third sub-motor 413, for forming the coils 400 of the second phase winding 408 of the third sub-motor 413 and for forming the coils 400 of the third phase winding 409 of the third sub-motor 413. The plurality of conductive layers on the fifth circuit board layer are arranged to allow the plurality of coils of each respective coil subgroup to be coupled such that each coil within a coil winding generates a magnetic field that is anti-parallel to its adjacent coils in a given current direction while having a common phase.

[0080] The second printed circuit board includes a circuit board layer corresponding to the fifth circuit board layer having a plurality of conductive layers arranged to electrically couple a first coil winding, a second coil winding, a first phase winding, a second phase winding, and a third phase winding of a third coil winding of the second set of coil windings; the first phase winding, the second phase winding, and the third phase winding each include a plurality of coils, the plurality of conductive layers arranged to allow the plurality of coils of each respective phase winding to couple relative to one another so that each coil sub-group of coils produces a magnetic field that is anti-parallel to an adjacent coil in a given current direction while having a common phase. The connection of the second printed circuit board to the circuit board layer corresponding to the fifth circuit board layer to the second set of coil windings is a mirror image of the connection of the fifth circuit board to the first coil winding.

[0081] Among the plurality of conductive layers formed on the fifth printed circuit board layer, two conductive layers 1501, 1502 are used to form coupled coils 400 of a first phase winding 401 of a first sub-motor 411, two conductive layers 1503, 1504 are used to form coupled coils 400 of a second phase winding 402 of the first sub-motor 411, and two conductive layers 1505, 1506 are used to couple coils 400 forming a third phase winding 403 of the first sub-motor 411. In the second sub-motor, two conductive layers 1507, 1508 are used to form coupled coils 400 of a first phase winding 404 of a second sub-motor 412, two conductive layers 1509, 1510 are used to couple coils 400 forming a second phase winding 405 of the second sub-motor 412, and two conductive layers 1511, 1512 are used to couple coils 400 forming a third phase winding 406 of the second sub-motor 412. For the third sub-motor, two conductive layers 1513, 1514 are used to form coupled coils 400 of a first phase winding 407 of a third sub-motor 413, two conductive layers 1515, 1516 are used to couple coils 400 forming a second phase winding 408 of the third sub-motor 413, and two conductive layers 1517, 1518 are used to couple coils 400 forming a third phase winding 409 of the third sub-motor 413. As described above, one end of a first coil forming a coil group of the first phase winding 401 of the first sub-motor 411 is mounted in a groove 640 formed at a location 920 on an inner radial edge of the leadframe 255. The first coil is electrically coupled to a first conductive layer 900 formed on the first circuit board layer while being electrically isolated from any other conductive layer on other circuit board layers. The other end of the first coil is mounted in an opposing groove formed at a location 950 on an outer radial edge of the leadframe 255 and is electrically coupled to a conductive layer 1502 on the fifth circuit board layer.

[0082] One end of a second coil of the coil set forming the first phase winding 401 of the first sub motor 411 is mounted in a recess formed at a location 951 at the outer radial edge of the leadframe 255 and is electrically coupled to a layer 1502 on the fifth conductive circuit board layer, thereby electrically connecting the second coil to the W-phase bus leg pin through the first coil. The other end of the second coil is mounted in an opposing recess formed at a location 952 on the inner radial edge of the leadframe 255 and is electrically coupled to a conductive layer 1501 on the fifth circuit board layer, which is electrically isolated from the conductive layer 1502. One end of a third coil of the coil set forming the first phase winding 401 of the first sub motor 411 is mounted in a recess formed at a location 953 at the inner radial edge of the leadframe 255 and is electrically coupled to a layer 1501 on the fifth conductive circuit board layer, thereby electrically connecting the third coil to the W-phase bus leg pin through the first and second coils. The other end of the third coil is mounted in an opposing recess formed at a location 954 on the outer radial edge of the leadframe 255 and is electrically connected to a fourth conductive layer 1310 on the fourth circuit board layer for coupling the third coil to the corresponding coils forming the second phase winding 402 and the third phase winding 403 of the first sub motor 411.

[0083] The next set of two conductive layers 1503, 1504 on the fifth circuit board layer are used to couple the coils 400 forming the second phase winding 402 of the first sub motor 411 to the V-phase bus leg pin, and the next set of two conductive layers 1505, 1506 on the fifth circuit board layer are used to couple the coils 400 forming the third phase winding 403 of the first sub motor 411 to the U-phase bus leg pin. The next set of two conductive 1507, 1508 on the fifth circuit board layer are used to couple the coils 400 forming the first phase winding 404 of the second sub motor 412 to the next set of two conductive layers 1509 of the W-phase bus leg pin, 1510 on the fifth circuit board layer are used to couple the coils 400 forming the second phase winding 405 of the second sub motor 412 to the V-phase bus leg pin, and the next set of two conductive layers 1511, 1512 on the fifth circuit board layer are coupled to be used to couple the coils 400 forming the third phase winding 406 of the second sub motor 412 to the U-phase bus leg pin. The next set of two conductive layers 1513, 1514 on the fifth circuit board layer are used to couple the coils 400 forming the first phase winding 407 of the third sub motor 413 to the next set of two conductive layers 1515 of the W-phase bus leg pin, 1516 on the fifth circuit board layer are used to couple the coils 400 forming the second phase winding 408 of the third sub motor 413 to the V-phase bus leg pin, and the next set of two conductive layers 1517, 1518 on the fifth circuit board layer are coupled to be used to couple the coils 400 forming the third phase winding 409 of the third sub motor 413 to the U-phase bus leg pin.

[0084] The electrical connections for coupling the W, U, V phase bus pins and corresponding coils to the lead frame 255 will now be described. For the electrical connections for coupling the phase bus pins 1010 to the corresponding conductive layers printed on the circuit board layers of the lead frame 255, conductive sleeves 1600 are inserted into corresponding holes formed in the lead frame 255 for the W, U, V phase bus pins 1010 as shown in Figure 15 When the W, U, V phase bus pins are inserted into the corresponding conductive sleeves 1600, the phase bus pins 1010 are arranged to be in electrical contact with the sleeves 1600. To improve the electrical contact between the pins 1010 and the sleeves 1600, solder or other conductive material can be used.

[0085] For any conductive layers formed on the corresponding circuit board layers that need to be electrically connected to the phase bus pins 1010, the corresponding conductive layers are arranged to extend and be in electrical contact with the conductive sleeves 1600. For any conductive layers formed on the various circuit board layers that are electrically isolated from the phase bus pins 1010, the various conductive layers are arranged to be electrically isolated from the conductive sleeves 1600. For example, referring to Figure 15 , the lead frame 255 includes ten circuit board layers of which the first two circuit board layers 1611, 1612 correspond to the first circuit board layers described above for coupling the W bus lead frame pins to the lead frame 255, the next two circuit board layers 1613, 1614 correspond to the second circuit board layers for coupling the U bus lead frame pins to the lead frame 255, the next two circuit board layers 1615, 1616 or alternatively correspond to the third circuit board layers for coupling the V bus lead frame pins to the lead frame 255, the next two circuit board layers 1617, 1618 correspond to the fourth circuit board layers for coupling the first phase windings, the second phase windings and the third phase windings of the various sub-motors, the next two circuit board layers 1619, 1620 correspond to the fifth circuit board layers for coupling the coils of the various phase windings. As shown in Figure 15 , the first conductive layers on the first two circuit board layers 1611, 1612 are in contact with the conductive sleeves for coupling the W bus lead frame pins to these two conductive layers. In contrast, the conductive layers printed on the other circuit board layers are electrically isolated from the conductive sleeves.

[0086] Although this embodiment uses conductive sleeves 1600 to electrically couple the busbar lead frame pins 1010 to the lead frame 255, any mechanism can be used to couple the respective inverter leg to the lead frame 255. With respect to the respective end portions of the coils, a similar arrangement as used to electrically couple the busbar pins 1010 can be used to electrically couple the respective end portions of the coils 400 to the desired conductive layer printed on one or more layers of the circuit board, where a semicircular conductive sleeve is placed within the respective groove formed in the inner and outer radial edges of the lead frame 255. Alternatively, the ends of the respective coils 400 can be placed directly within the grooves 640 formed in the inner and outer radial edges of the lead frame 255, with a conductive material placed between the ends of the coils and the associated conductive layer to improve the electrical conductivity between the ends of the respective coils and the conductive layer, which are electrically connected to the conductive layer. The preferred process for mounting the ends of the coils 400 in the inner and outer radial grooves 640 of the lead frame 255 will now be described.

[0087] Prior to mounting the lead frame 255 to the stator core 600, the ends of the coils are arranged to extend radially away from the stator core 600 and in the same plane as the axial mounting face of the stator core 600. In this configuration, the ends of the coils on the outer radial edge of the stator core 600 are arranged to extend in the radial direction away from the center of the stator core 600. The inner radial edge of the stator core 600 is arranged to extend in the radial direction toward the center of the stator core 600. Preferably, a hot stake 310 is used, where the grooves formed in the inner and outer radial edges of the lead frame 255 are arranged to align with the ends of the coils, such that the respective grooves 640 formed in the inner and outer radial edges are positioned over the respective end sections of the coils of the lead frame 255. Where Figure 16 One of the coil ends 1610 is shown extending in the radial direction, and then the ends of the coils are rotated 90 degrees to extend into the printed circuit board grooves and the lead frame 255 grooves 640 located over the respective ends of the coils, resulting in the coil ends 1620 extending in the axial direction. Any means can be used to rotate the ends into the respective grooves formed on the inner and outer radial edges of the lead frame 255. As shown in the cross-sectional view of the lead frame 255 in FIG. 16, the ends of the coils 400 are shown extending into the grooves 640 formed in the inner and outer radial edges of the lead frame 255. Figure 17 A portion of the stator core is shown with six coils 400, each of which has its respective coil end extending into the inner and outer radial grooves 640 formed in the lead frame 255 for coupling the respective coil to the lead frame 255. To improve the electrical contact between the ends of the respective coils and the lead frame 255, solder or some other conductive material can be used between the ends of the coils and the lead frame 255. For this embodiment, since each lead frame 255 portion forms only a semicircular portion, this has the advantage of reducing the manufacturing cost of the overall lead frame 255 arrangement compared to the manufacturing cost of a single circumferential lead frame 255.

[0088] Example 2

[0089] The difference between this embodiment and Example 1 is that a sink 5501 extending axially along the stator core 600 is provided on the end face of each end of the stator core assembly, and the potting material layer is filled in the sink 5501. Specifically, the sink 5501 is provided on the end face of each end of the circumferential support 550.

[0090] Example 3

[0091] The difference between this embodiment and Example 1 is that, in order to improve current flow, if there are portions of the conductive layer on one or more printed circuit board layers that do not require current flow, these portions of the conductive layer can be electrically isolated from the rest of the conductive layer and used as an additional current path for the conductive layer on other printed circuit board layers. For example, because the right portion of the conductive layer 900 on the first printed circuit board does not need to be used for current flow between the W-phase bus pin and the first phase windings of the first, second, and third sub-motors, this portion of the conductive layer can be used to support current flow for other conductive layers. In the case of this embodiment, this portion of the first conductive layer is electrically isolated from the rest of the first conductive layer and used to support current flow in the sixth conductive layer on the fourth printed circuit board layer.

[0092] Example 4

[0093] This embodiment provides a generator or motor comprising the stator described in Example 1.

[0094] In summary, the above description is only the preferred embodiment of the present application, and any equivalent changes and modifications made within the scope of the patent application of the present application shall be covered by the scope of the patent of the present application.

Claims

1. An electric motor characterized by: The stator comprises a circumferential support as a heat sink, a plurality of coils (254), and two control devices not shown, which are mounted on the circumferential support at the rear of the stator and are used to drive the coils; the stator comprises two sets of coil windings, namely a first set of coil windings and a second set of coil windings, the first set of coil windings is connected with the lead frame to form three sub-motors, and the second set of coil windings is connected with the lead frame to form the second set of coil windings; the cooling structure further comprises a cooling structure; The cooling structure comprises a lead frame and a circumferential support for supporting the stator core, the winding coils of the stator are mounted on the stator teeth formed on the outer circumferential side of the stator core, the circumferential support is fixedly inserted in the middle of the stator core, the circumferential support is provided with a cooling channel, the winding coils at least comprise a first set of coil windings, the lead frame is used to electrically connect the first inverter to the first set of coil windings, wherein the lead frame comprises a printed circuit board having a plurality of layers of circuit board, wherein each layer of circuit board comprises an insulating substrate and a conductive layer disposed on the insulating substrate, the lead frame is located between the cooling channel and the stator teeth, and a layer of potting material is located between the cooling channel and the lead frame, wherein the layer of potting material is arranged to provide a thermal path between the cooling channel and the lead frame; the potting material is a ceramic-filled epoxy resin; a ring capacitor is coupled between the inverter and the DC power supply of the motor; The stator comprises a circumferential support and a stator winding mounted on the circumferential support, the circumferential support is a stator core, the stator winding is composed of a stator winding unit, the stator winding unit is a tooth wound with a coil, each tooth is provided with a tooth slot, and the outer circumference of the circumferential support is provided with a stator tooth, and the tooth slot is inserted into the stator tooth in an interference fit. The control device comprises a processor for controlling the operation of the inverter switch in the two control devices, and the control device is electrically connected with a temperature sensor for receiving the signal of the temperature sensor.

2. An electric motor as claimed in claim 1, characterised in that: The lead frame is in the shape of a whole circle, or two half-circular lead frames are spliced into a whole circular lead frame.

3. An electric motor as claimed in claim 1, characterised in that: The inner edge and the outer edge of the printed circuit board are provided with grooves for receiving the corresponding coil windings, and the coil windings are electrically coupled to the printed circuit board through the grooves.

4. An electric motor as claimed in claim 1, characterized in that: The lead frame is mounted on the circumferential support close to the coil winding.

5. An electric motor as claimed in claim 1, characterized in that: The cooling channel is arranged to have a first part and a second part, and the first part is perpendicular to the second part.

6. An electric motor as claimed in claim 5, characterised in that: The first part of the cooling channel is arranged on the inner side of the stator core and along the axial direction of the stator core.

7. An electric motor as claimed in claim 5, wherein: The second part of the cooling channel is arranged on the side of the lead frame away from the stator core and distributed along the radial direction of the lead frame.

8. An electric motor as claimed in claim 1, characterized in that: The end faces of the stator core assembly are provided with a sink groove distributed along the axial direction of the stator core, and the potting material layer is filled in the sink groove.

9. An electric motor as claimed in claim 1, characterized in that: The printed circuit board has at least a first circuit board layer, a second circuit board layer, a third circuit board layer, and a fourth circuit board layer; the first circuit board layer includes a first conductive layer arranged to be electrically coupled to a first coil winding of a first set of coil windings and a first leg of a first inverter; the second circuit board layer includes a second conductive layer arranged to be electrically coupled to a second coil winding of the first set of coil windings and a second leg of the first inverter; the third circuit board layer includes a third conductive layer arranged to be electrically coupled to a third coil winding of the first set of coil windings and a third leg of the first inverter; the fourth circuit board layer includes a fourth conductive layer arranged to be coupled to the first coil winding, the second coil winding, and the third coil winding of the first set of coil windings to form a neutral point therebetween; the first coil winding, the second coil winding, and the third coil winding each include three subgroups of coils, respectively a first phase winding, a second phase winding, and a third phase winding; the printed circuit board further includes a fifth circuit board layer having a plurality of conductive layers arranged to be electrically coupled to the first phase winding, the second phase winding, and the third phase winding of the first coil winding, the second coil winding, and the third coil winding; the first phase winding, the second phase winding, and the third phase winding each include a plurality of coils, the plurality of conductive layers on the fifth circuit board arranged to allow the plurality of coils for each respective phase winding to be coupled relative to one another such that each subgroup of coils produces a magnetic field that is anti-parallel to an adjacent coil in a given current direction while having a common phase.

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