System and method for cooling switching devices in an integrated motor drive

Abstract

Systems and methods for cooling switching devices in an integrated motor drive are provided. Power semiconductor switching devices in an integrated motor drive are directly mounted to a circuit board substrate via a "pick and place" assembly process. The circuit board substrate is then mounted within a housing of the integrated motor drive, and preferably, the circuit board substrate is then mounted in a generally centered orientation within the housing. Encapsulation material is disposed within the housing of the integrated motor drive and around the circuit board. The encapsulation material substantially surrounds the circuit board and fills a volume within the integrated motor drive. The encapsulation material is selected to provide good thermal conductivity between the circuit board and the housing of the integrated motor drive. The encapsulation material is also selected to provide flexibility such that expansion and contraction of the encapsulation material due to heating and cooling of the encapsulation material does not damage the circuit board or electronic components mounted to the circuit board.

Description

Technical Field

[0001] The subject matter disclosed herein relates to systems and methods for cooling power semiconductor devices in integrated motor drivers. More specifically, the power semiconductor devices are mounted to a circuit board and housed within a housing of the integrated motor driver. The interior of the housing is filled with a potting material that provides a thermal conduction path for heat transfer from the power semiconductor devices to the housing and then through the housing to the surrounding environment. Background Technology

[0002] Electric rotating machines, such as electric motors or generators, have become commonplace and are found in many applications and configurations. An electric motor comprises a stationary component (i.e., a stator) and a rotating component (i.e., a rotor). In an electric motor, a magnetic field is established in the rotor, for example, via magnets mounted to the rotor or via current applied to or induced in coils wound around the rotor. A second rotating magnetic field is established due to a stator current generated by a controlled voltage applied to the stator. Rotation of the magnetic field in the stator causes the magnetic field in the rotor to follow the stator magnetic field, thus causing the rotor to rotate. A shaft or other drive component is mounted to the rotor and extends outside the rotor housing, providing a mechanical connection to a device such as a gearbox, pump, or fan, which will be driven as the rotor rotates. The amplitude and frequency of the controlled voltage applied to the stator are varied to achieve the desired operation of the motor.

[0003] As is known to those skilled in the art, a motor controller, also referred to herein as a motor driver, is used to change the amplitude and frequency of the voltage applied to the motor to achieve the desired operation of the motor. The motor controller is configured to receive power at an input, which can be supplied from an alternating current (AC) source or a direct current (DC) source. If the input power is supplied from an AC source, a rectifier section converts the AC power to DC power. A DC bus from the output of the rectifier section or directly supplied from a DC source is provided to the DC bus within the motor controller. An inverter section is controlled using current regulators and modulation techniques, which in turn supplies the required current and voltage to the motor from the DC bus to achieve the desired operation of the motor.

[0004] The inverter section includes power semiconductor switching devices, such as bipolar junction transistors (BJTs), insulated-gate bipolar transistors (IGBTs), or metal-oxide-semiconductor field-effect transistors (MOSFETs). These switching devices are rapidly switched on and off to alternately connect the positive DC voltage, negative DC voltage, or common voltage from the DC bus to the output of the inverter section. Using known switching algorithms, the voltage at the output of the inverter section will have a fundamental AC component at the desired amplitude and frequency, which will provide the desired operation of the motor.

[0005] However, power semiconductor switching devices experience power losses within the device during operation. Some power is dissipated in each device due to the current flowing through it; this is also known as conduction loss. Additional power is dissipated in each device when it switches between the off and on states; this is known as switching loss. Other power is also dissipated in each device for other reasons; this is known as parasitic loss. The power dissipated in each device is often converted into heat within the device, causing the device temperature to rise. It is important to remove heat from power switching devices to avoid catastrophic failure.

[0006] Historically, motor drives were mounted within control cabinets. These cabinets typically include air conditioning units for removing heat from the cabinet. In some applications, the cabinet itself could be located in an environmentally controlled space, making it easy to remove heat generated within the motor drive. However, recent improvements to motor drives have led to their integration onto the motor itself. Motor drives mounted on the motor are called integrated motor drives. Because the motor drive is mounted on the motor, it is no longer located within a control cabinet, but rather in the manufacturing environment or other environment where the controlled machine or process is located. The ambient temperature of the controlled machine or process may be higher than the temperature inside the control cabinet or the control room housing the cabinet. Therefore, thermal management of integrated motor drives is more challenging than that of cabinet-mounted motor drives.

[0007] To help dissipate heat generated in integrated motor drivers, a direct copper bonding (DBC) process is typically used to mount power semiconductor switching devices to a copper base plate. The copper base plate acts as a heat sink for the DBC-mounted power semiconductor devices and is also mounted to the housing of the integrated motor driver. The integrated motor driver is typically mounted to the side of the motor housing, with the outer surface of the motor driver housing wall having a copper base plate mounted to its inner surface. This mounting arrangement provides a heat conduction path from the switching devices, through the copper base plate, through the integrated motor driver housing, and then into the motor housing. Heat is then radiated from the motor housing to the surrounding environment.

[0008] However, mounting the integrated motor driver to the side of the motor housing is not without its drawbacks. The motor also generates heat during normal operation, which is dissipated through the motor housing. The heat generated in the motor is a result of the current flowing through it, and the amount of current flowing through the motor corresponds to the torque the motor can produce. If additional heat is transferred from the integrated motor driver to the motor housing, the total heat generated by the motor and the integrated motor driver must be limited.

[0009] Heat generated by the motor, integrated motor driver, or both can be limited by derating the device. Derating a motor requires limiting the maximum current that can be conducted by the motor, and thus the amount of torque produced by the motor. Derating an integrated motor driver requires limiting the amount of current conducted through the power switching devices compared to a similarly sized cabinet-mounted motor driver. Limiting the current in the motor driver, in turn, limits the heat generated in the power switching devices. Alternatively, both the motor and the motor driver can have some degree of derating, allowing the heat generated by these two components to be successfully dissipated from the motor housing.

[0010] However, derating a motor or motor drive requires a larger motor or motor drive to handle the same power and provide the same workload as a motor controlled by a cabinet-mounted motor drive. The larger unit increases the size and cost of the system.

[0011] Therefore, there is a need for improved systems and methods for cooling switching devices in integrated motor drives. Summary of the Invention

[0012] According to one embodiment of the invention, a system for cooling switching devices in a motor driver includes a motor driver housing, wherein the motor driver housing is configured to be mounted to a motor housing. A volume is defined within the inner periphery of the housing, and at least one switching device is mounted within the motor driver. The at least one switching device is operatively controlled to convert a first voltage appearing on a DC bus within the motor driver into a second voltage appearing at an output terminal of the motor driver, and the second voltage is configured to control the operation of a motor to which the motor driver is mounted. A circuit board on which each of the at least one switching device is mounted is mounted within the volume of the motor driver housing. After the circuit board is mounted, potting material is inserted into the volume of the motor driver housing, and the potting material covers each switching device mounted on the circuit board and extends from the circuit board to the inner periphery of the motor driver housing.

[0013] According to another embodiment of the present invention, a method for cooling switching devices in a motor driver includes: mounting at least one switching device to a circuit board, and mounting the circuit board having each switching device in a housing of the motor driver. The housing of the motor driver is configured to be mounted to a motor housing. A volume within the housing is filled with a potting material. The potting material covers each switching device mounted on the circuit board and extends from the circuit board to the inner periphery of the housing of the motor driver. The switching devices are operably controlled to convert a first voltage appearing on a DC bus within the motor driver into a second voltage appearing at the output terminal of the motor driver. Heat generated by controlling the at least one switching device is conducted to the housing of the motor driver via the potting material.

[0014] These and other advantages and features of the present invention will become apparent to those skilled in the art from the specific embodiments and accompanying drawings. However, it should be understood that the specific embodiments and accompanying drawings are given by way of illustration rather than limitation when indicating preferred embodiments of the invention. Many changes and modifications can be made within the scope of the invention without departing from its spirit, and the invention includes all such modifications. Attached Figure Description

[0015] Various exemplary embodiments of the subject matter disclosed herein are illustrated in the accompanying drawings, throughout which the same reference numerals denote the same parts, and in the drawings:

[0016] Figure 1 This is a perspective view of an integrated motor driver mounted to the end of a motor according to an embodiment of the present invention;

[0017] Figure 2 yes Figure 1 An exemplary schematic representation of an integrated motor driver;

[0018] Figure 3 yes Figure 2 A schematic representation of the inverter section of an integrated motor driver;

[0019] Figure 4 This is a perspective view of an integrated motor driver with a portion of the housing removed according to another embodiment of the present invention;

[0020] Figure 5 yes Figure 4 A partial perspective view of the integrated motor driver, showing the potting material and the mounting of the circuit board within the integrated motor driver;

[0021] Figure 6 This is a top plan view of an exemplary integrated motor driver, showing the potting material within the integrated motor driver; and

[0022] Figure 7 This is a partial cross-sectional view of an exemplary power switching device mounted to a circuit board, used in one embodiment of the present invention.

[0023] In describing the various embodiments of the invention illustrated in the accompanying drawings, specific terminology will be used for clarity. However, the invention is not intended to be limited to the specific terminology chosen so far, and it should be understood that each specific term includes all technical equivalents that operate in a similar manner to achieve similar purposes. For example, the terms "connection," "attachment," or similar terms are frequently used. They are not limited to direct connections but include connections via other elements, where such connections are considered equivalent by those skilled in the art. Detailed Implementation

[0024] The various features and advantageous details of the subject matter disclosed herein will be explained more fully with reference to the non-limiting embodiments described in detail below.

[0025] This document describes improved systems and methods for cooling switching devices in integrated motor drivers. As previously mentioned, mounting an integrated motor driver to a motor previously required derating the motor, motor driver, or a combination of both. Furthermore, the DBC mounting process required a complex assembly procedure. After mounting the power semiconductor switching device to a copper substrate, the terminals of the switching device must be connected to the circuit board to receive control signals. The terminals of the power semiconductor device require a wire bonding process that requires specialized knowledge to connect bonding wires between the terminals and the circuit board substrate.

[0026] In contrast, this invention allows power semiconductor switching devices to be directly mounted onto a circuit board substrate. Each switching device can be mounted onto the circuit board substrate via a "pick-and-place" assembly process. The terminals of the switching devices are soldered to pads on the circuit board. Mounting the switching devices via the pick-and-place process eliminates the wire bonding process, thereby simplifying the construction and reducing the cost of integrated motor drivers.

[0027] As previously mentioned, the construction of the previous integrated motor driver resulted in heat transfer from the motor driver to the motor housing. This heat transfer primarily occurred due to the mounting of a copper base plate to the surface of the integrated motor driver housing, which in turn was mounted to the surface of the motor housing. The main heat conduction path of the integrated motor driver was through the motor housing.

[0028] In contrast, the present invention envisions mounting the housing of the integrated motor driver to the end of the motor housing. The integrated motor driver according to the invention is configured to conduct heat to the sides of the motor driver housing and dissipate heat to the surrounding environment. Mounting the integrated motor driver to the end of the motor housing significantly reduces or eliminates heat transfer to the motor housing, which in turn significantly reduces or eliminates the need for derating the motor and / or the integrated motor driver.

[0029] The conduction of heat to the sides of the integrated motor driver depends on the mounting method of the power semiconductor devices within the integrated motor driver. After the power semiconductor switching devices are mounted to a circuit board substrate, the circuit board substrate is then mounted within the housing of the integrated motor driver, and preferably, the circuit board substrate is then mounted in a generally centrally located position within the housing. However, the circuit board substrate typically provides better thermal insulation compared to heat conduction. Similarly, the air surrounding the switching devices acts as a poor thermal conductor. Therefore, a potting material is disposed within the housing of the integrated motor driver and around the circuit board. The potting material substantially surrounds the circuit board and fills the volume within the integrated motor driver. The potting material is selected to provide good thermal conductivity between the circuit board and the housing of the integrated motor driver. The potting material is also selected to provide flexibility such that expansion and contraction of the potting material due to heating and cooling will not damage the circuit board or the electronic components mounted to the circuit board. Therefore, the present invention provides a simplified construction process and reduces or potentially eliminates the need for derating the motor or integrated motor driver.

[0030] First go to Figure 1 and Figure 2 An exemplary integrated motor driver 20 is shown mounted to a motor 10. The integrated motor driver 20 includes a power section 21 and a control section 23. The power section 21 includes components that typically handle, for example, 200VAC to 528VAC or 200VDC to 800VDC, and the power section 21 receives power in a controlled manner and utilizes power switching devices to regulate the power output to the motor 10 to achieve desired operation of the motor 10. The control section 23 includes components that typically handle, for example, 110VAC or 3.3VDC to 58VDC, and the control section 23 includes processing means, feedback circuitry, and supporting logic circuitry to receive feedback signals and generate control signals within the motor driver 20.

[0031] The power section 21 is configured to receive a first voltage at input 25 and provide a second voltage at output 53. According to the illustrated embodiment, input 25 receives a DC voltage, which is provided to the positive rail 42 and negative rail 44 of the DC bus 41 within the integrated motor driver 20. It is conceivable that the rectifier unit or active front-end (AFE) can be located within the control cabinet away from the integrated motor driver 20. The rectifier unit or AFE receives, for example, AC voltage from a utility power grid and converts it into DC voltage for delivery to the integrated motor driver 20. The rectifier unit or AFE can be sized such that it can supply DC voltage to multiple integrated motor drivers 20 distributed around the controlled machine or controlled process. The rectifier section will typically include electronics such as diodes suitable for passively rectifying AC voltage to DC voltage. The AFE will typically include other solid-state devices, including but not limited to thyristors, silicon controlled rectifiers (SCRs), or transistors, which receive control signals to convert AC voltage into DC voltage for the DC bus 41. According to another aspect of the invention, the rectifier unit or AFE may be included within the integrated motor driver 20, and the integrated motor driver 20 may receive AC voltage and convert the AC voltage into DC voltage within the integrated motor driver.

[0032] DC bus 41 supplies the DC voltage appearing on the bus as input to inverter section 30. See also... Figure 3 The inverter section 30 comprises switching elements known in the art, such as transistors, thyristors, or SCRs. The illustrated inverter section 30 includes MOSFETs 35 and freewheeling diodes 40 connected in pairs between the positive rail 42 and each phase of the output voltage, and between the negative rail 44 and each phase of the output voltage. Each of the MOSFETs 35 receives a gating signal 57 to selectively enable the transistor and convert the DC voltage from the DC bus 41 into a controlled three-phase output voltage for the motor 10. According to the illustrated embodiment, the processor 55 in the motor driver 20 can be configured to generate the gating signal 57. Optionally, as discussed further below, the processor 55 can execute a control module and provide a voltage reference signal to a gate drive module. The gate drive module converts the voltage reference signal into the gating signal 57 to control the operation of each transistor 35. When enabled, each transistor 35 connects the corresponding rails 42, 44 of the DC bus 41 to the inverter output 50. The inverter output 50 shown supplies three-phase AC voltage to the motor, with the first phase at 50U, the second phase at 50V, and the third phase at 50W. The inverter output 50 is connected to the motor driver output 53, and then to the motor 10.

[0033] The processor 55 in the motor driver 20 receives a reference signal 65 that identifies the desired operation of the motor 10 connected to the motor driver. The reference signal 65 may be, for example, a position reference (θ*), a speed reference (ω*), or a torque reference (T*). The processor 55 also receives a feedback signal indicating the current operation of the motor driver 20. A position feedback device 15 is operatively connected to the motor 10 to provide a position feedback signal to the motor driver 20. The position feedback signal may be a single or orthogonally provided analog signal such as a sine wave, a series of pulses, or it may be a digital data packet according to a serial communication protocol of the position feedback device 15. The position feedback signal provides the angular position of the motor 10 to the motor driver 20 for controlling the operation of the motor 10.

[0034] As shown, the feedback signal is provided directly to the processor 55. This is for ease of illustration. As will be understood in the art, the feedback signal will typically include additional logic circuitry, including but not limited to analog-to-digital (A / D) converters, buffers, amplifiers, and any other components required to convert the first format feedback signal into a second format suitable for use by the processor 55. The motor driver 20 may include a voltage sensor 70 and / or a current sensor 72 on the DC bus 41, which generates a feedback signal corresponding to the magnitude of the voltage and / or current appearing on the DC bus 41. The motor driver 20 may also include one or more voltage sensors 74 and / or current sensors 76 on the output phase of the inverter section 30, which generate a feedback signal corresponding to the magnitude of the voltage and / or current appearing at the output terminal 53 of the motor driver 20. The processor 55 uses the feedback signal and a reference signal 65 to control the operation of the inverter section 30 to generate an output voltage with a desired amplitude and frequency for the motor 10.

[0035] Next, turn to Figure 4 An embodiment of an integrated motor driver 20 prior to the insertion of potting material 100 is shown. The motor driver 20 includes a housing 80, with sides 86 shown as transparent to observe the arrangement of circuit boards 90 within the motor driver. The housing 80 includes a first end 82 and a second end 84 opposite to the first end, the first end 82 being configured to be mounted to an end of the housing of the motor 10. Four sides 86 extend between the first end 82 and the second end 84 to define a box-like structure of the housing 80. Also see... Figure 5 The volume 85 is defined within the housing 80. The volume 85 extends from the inner surface of the first end 82 to the inner surface of the second end 84, and is within the inner periphery of each side 86.

[0036] according to Figure 4In the illustrated embodiment, three circuit boards 90 are inserted into the volume 85 of the housing 80. An end cap 87 on the first end 82 of the housing can be removed to allow insertion into the housing 80. It is contemplated that the inner surface of the second end 84 may include a mounting bracket in which each circuit board 90 is inserted. It is contemplated that the first circuit board 90A and the third circuit board 90C typically include a processor 55, a memory 60, and all additional logic components for the control section 23 of the motor driver 20. The second circuit board 90B typically includes a power switching device 35 from the power section 21 of the motor driver and each of other components. The illustrated embodiment is not intended to be limiting, and it is contemplated that fewer or more than three circuit boards 90 may be included within the integrated motor driver 20. It is also contemplated that components from the control section 23 or the power section 21 may be distributed among the circuit boards 90 in any combination according to application requirements. After the circuit boards 90 are inserted into the volume 85 of the housing 80 and any required electrical connections are made to the circuit boards, the remaining portion of the volume is filled with potting material 100 to at least a sufficient height to cover the circuit boards 90.

[0037] Reference Figure 7 The integrated circuit package 110 may include one or more MOSFETs 35. The integrated circuit package 110 is mounted to one of the circuit boards 90. Each circuit board 90 is a multilayer board. According to the illustrated embodiment, the circuit board 90 includes four layers 92A to 92D. The number of layers shown is not intended to be limiting, and it is conceivable that the circuit board 90 may have fewer or more than four layers 92A to 92D. The integrated circuit package 110 is mounted to pads 95 on the first layer 92A of the circuit board. The first pad 95A and the second pad 95B are shown as each of two terminals for the integrated circuit package 110. Each terminal will be mounted to a separate pad. Depending on the circuit board layout and design, the pads 95 are connected to other electronic devices via traces on the circuit board.

[0038] Each layer 92 of the circuit board 90 is typically made of a dielectric material. Each dielectric material is electrically insulating and generally a poor thermal conductor. To improve thermal conduction from the first layer 92A to the fourth layer 92D of the circuit board 90, a series of thermal vias 115 are located beneath the footprint of the integrated circuit package 110. Furthermore, copper material 120, which can form traces, is left beneath the integrated circuit package 110 and between each layer 92. The vias 115 are also made of copper and can be filled, thus providing a solid copper path between the layers 92 of the circuit board 90. The integrated circuit package 110 can be electrically mounted to pads 95, and the body of the integrated circuit package 110 can contact or be located near the top layer of the copper material 120. The body of the integrated circuit package 110 is non-conductive, but heat is radiated from or conducted from the body of the integrated circuit package 110 to the copper layer 120 and then conducted through the vias 115 to the lower surface of the circuit board 90.

[0039] During operation of the motor driver 20, the potting material 100 is configured to provide a thermal conduction path for heat generated within each integrated circuit package 110 to the housing 80 of the motor driver. As previously described, the MOSFETs 35 in the inverter section 30 of the integrated motor driver 20 generate heat during operation. Switching losses, conduction losses, and parasitic losses cause heat to accumulate within each of the integrated circuit packages 110. Because the potting material 100 encapsulates the circuit board 90, the potting material 100 is in contact with the top surface of the integrated circuit package 110 and the outer layer 92 of the circuit board 90. A portion of the heat generated in each integrated circuit package 110 is transferred through the circuit board 90 via thermal vias 115 and copper material 120. Another portion of the heat generated in each integrated circuit package 110 is transferred directly to the potting material 100. Some of the heat initially transferred through the circuit board 90 may radiate outward within the circuit board 90. The potting material 100 is in contact with the circuit board 90 and the thermal vias 115 and copper material 120 on the lower layer 92D of the circuit board. Therefore, the heat generated by the MOSFET 35 within the integrated circuit package 110 is conducted directly from the integrated circuit package to the potting material 100 or indirectly via the circuit board 90 to the potting material 100.

[0040] Historically, potting materials have typically been used sparingly on circuit boards to help secure circuit components to the board. For example, lead-mounted capacitors allow leads to be inserted through the circuit board and then soldered to it. The capacitor body extends away from the circuit board. However, vibrations on the device with the circuit board mounted can cause the capacitor body to vibrate similarly. Over time, this vibration can cause the leads to move back and forth and eventually detach from the circuit board. Potting material can be applied to the bottom of the capacitor, and it hardens as it dries. The potting material holds the lead-mounted capacitor to the circuit board and helps prevent vibrations between the component and the circuit board, which in turn helps prevent connection failures. However, this type of potting material is not suitable for large-scale filling of the volume 85 within the housing 80 of the motor drive 20.

[0041] The inventors have determined that a potting material 100 with good thermal conductivity and a certain degree of elasticity is desirable for filling the volume 85 of the housing 80. Many potting materials are thermally insulating materials. The present invention envisions using the potting material 100 to establish a heat conduction path between the circuit board 90 of the motor driver 20 and the housing 80. According to one aspect of the invention, the potting material 100 has a thermal conductivity of at least 0.75 W / (m·K). According to a preferred embodiment of the invention, the potting material 100 has a thermal conductivity of at least 1 W / (m·K).

[0042] Furthermore, the potting material 100 conducts heat away from the switching devices 35 in the inverter section 30 of the motor driver 20. In some applications, the motor 10 can operate in a near-continuous state, causing the switching devices 35 to generate a constant amount of heat. In other applications, the motor 10 can be started and stopped for different durations. During the operating period, heat is generated by the switching devices 35, which is then transferred to and heats the potting material 100. During the inactive period, the switching devices 35 do not generate heat, allowing heat within the potting material 100 to dissipate through the housing 80, thereby cooling the potting material 100. The heating and cooling of the potting material 100 will cause it to expand and contract. As mentioned above, when a rigid potting material is selected, the expansion and contraction of the potting material will exert forces on the electronic components mounted to the circuit board 90. The expansion and contraction of a rigid material can damage the components on the circuit board 90. Therefore, a potting material 100 with a certain degree of elasticity is desirable.

[0043] To allow for the expansion and contraction of the potting material 100 within the volume 85 of the housing 80 and to avoid damaging components on the circuit board 90, a soft potting material 100 is selected. The soft potting material 100 allows pressure against electronic components without pushing them away from the circuit board 90. The soft potting material also allows the potting material to expand upwards within the upper void 89 within the housing 80. The potting material 100 fills the housing 80 with sufficient volume 85 to cover the circuit board 90. The potting material encapsulates the circuit board and fills the volume 85 around the circuit board 90 to the inner periphery of the housing 80 of the motor driver 20. However, with the end cap 87 secured to the housing 80, some volume is reserved above the potting material 100 to define the upper void 89. According to one aspect of the invention, the hardness of the potting material 100 is less than or equal to 70 on the Shore A hardness scale. According to a preferred embodiment of the invention, the hardness of the potting material 100 is less than or equal to 30 on the Shore A hardness scale. According to one embodiment of the present invention, select SI 5633 TM 100 is used as a potting material.

[0044] Compared to cabinet-mounted motor drives, using potting material 100 within the integrated motor drive 20 and mounting the housing 80 of the motor drive 20 to the end of the motor housing allows the integrated motor drive 20 to operate with minimal or no dederating. Previous integrated motor drives using DBC and mounted to the side surface of the motor required approximately 30% to 40% (30% to 40%) dederating. Eliminating the previous dederating allows for the mounting of smaller, lower-cost motor drives to the motor 10 for use in the integrated motor drive package.

[0045] It should be understood that the invention is not limited in its application to the details of the construction and arrangement of the components described herein. The invention can have other embodiments and can be practiced or performed in various ways. Variations and modifications to the foregoing are within the scope of the invention. It should also be understood that the invention disclosed and defined herein extends to all alternative combinations of two or more features mentioned or apparent from the text and / or drawings. All these different combinations constitute various alternative aspects of the invention. The embodiments described herein illustrate the known best mode for practicing the invention and will enable those skilled in the art to utilize the invention.

[0046] Various embodiments have been described in the foregoing specification with reference to the accompanying drawings. However, it will be apparent that various modifications and alterations can be made to the invention, and other embodiments can be implemented, without departing from the broader scope of the invention as set forth in the appended claims. Therefore, the specification and drawings should be considered illustrative rather than restrictive.

Claims

1. A system for cooling switching devices in a motor driver, the system comprising: The housing of the motor driver, wherein: The housing of the motor driver is configured to be mounted to the motor housing, and A volume is defined within the inner periphery of the housing; At least one switching device is mounted within the motor driver, wherein: The at least one switching device is operable to controllably convert a first voltage appearing on the DC bus within the motor driver into a second voltage appearing at the output of the motor driver, and The second voltage is configured to control the operation of the motor on which the motor driver is mounted; A circuit board, on which each of the at least one switching device is mounted, wherein the circuit board is mounted within the volume of the housing of the motor driver; and Potting materials, including: After the circuit board is installed, the potting material is inserted into the volume of the motor driver housing. The potting material covers at least one switching device mounted on the circuit board, and the potting material extends from the circuit board to the inner periphery of the motor driver housing. The circuit board includes at least one thermal via that extends through a layer of the circuit board and is located at the position where each of the at least one switching device is mounted.

2. The system according to claim 1, wherein, The housing of the motor driver is also configured to be mounted to the end of the motor housing.

3. The system according to claim 1, wherein, The potting material has a Shore hardness rating of 70A or less.

4. The system according to claim 3, wherein, The Shore hardness grade is less than or equal to 30A.

5. The system according to claim 1, wherein, The potting material has a density greater than or equal to 0.

75. Thermal conductivity.

6. The system according to claim 5, wherein, The thermal conductivity is greater than or equal to 1 .

7. The system according to claim 1, wherein, Each of the at least one switching device is mounted onto the circuit board using a pick-and-place machine.

8. The system according to claim 1, wherein: The volume of the shell includes the first end, the second end, and the inner periphery. The first end is opposite to the second end. The inner periphery includes at least one sidewall extending between the first end and the second end. The circuit board is mounted at the first end of the volume, and The potting material fills the volume between the inner peripheries, and the potting material extends from the first end for a length of at least the same volume as the length of the circuit board.

9. The system according to claim 1, wherein, The second voltage is greater than or equal to 200 VAC.

10. A method for cooling a switching device in a motor driver, the method comprising: At least one switching device is mounted to a circuit board, the circuit board including a first side on which the at least one switching device is mounted, a second side opposite to the first side, and at least one heat-perforated hole extending through a layer of the circuit board and extending between the first side and the second side of the circuit board, and located at the position where the at least one switching device is mounted; A circuit board having at least one switching device is mounted in the housing of the motor driver, wherein the housing of the motor driver is configured to be mounted to the motor housing; The volume inside the housing is filled with potting material, wherein the potting material covers at least one switching device mounted on the circuit board, and the potting material extends from the circuit board to the inner periphery of the housing of the motor driver; Operable to control the at least one switching device to convert a first voltage appearing on the DC bus within the motor driver into a second voltage appearing at the output of the motor driver; and The heat generated by controlling the at least one switching device is conducted to the housing of the motor driver via the potting material. The heat conduction process also includes: A first portion of the heat is conducted from the at least one switching device through the circuit board via the at least one thermal via. The heat is conducted from the second side of the circuit board to the inner periphery of the motor driver housing via the potting material, and A second portion of the heat is conducted from the at least one switching device to the inner periphery of the housing of the motor driver via the potting material.

11. The method of claim 10, further comprising the step of mounting the housing of the motor driver to an end of the motor housing.

12. The method according to claim 10, wherein, The potting material has a Shore hardness rating of 70A or less.

13. The method according to claim 12, wherein, The Shore hardness grade is less than or equal to 30A.

14. The method of claim 10, wherein, The potting material has a density greater than or equal to 0.

75. Thermal conductivity.

15. The method according to claim 14, wherein, The thermal conductivity is greater than or equal to 1 .

16. The method of claim 10, wherein, The step of mounting the at least one switching device to the circuit board uses a pick-and-place machine.

17. The method of claim 10, wherein: The volume of the shell includes the first end, the second end, and the inner periphery. The first end is opposite to the second end. The inner periphery includes at least one sidewall extending between the first end and the second end. The circuit board is mounted at the first end of the volume, and The potting material fills the volume between the inner peripheries, and the potting material extends from the first end for a length of at least the same volume as the length of the circuit board.

18. The method according to claim 10, wherein, The second voltage is greater than or equal to 200 VAC.

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