Inverter bus with integrated bleeder resistor

Abstract

The invention provides an inverter bus with an integrated bleeder resistor. An electric drive system includes a power electronics module having a prefabricated DC bus bar assembly. In one embodiment, the prefabricated DC bus bar assembly includes a shaped bleeder resistor that provides two different functions. First, it dissipates energy from the capacitor when the battery is disconnected. Next, it physically supports the positive electrode bus bar and the negative electrode bus bar relative to each other.

Description

Technical Field

[0001] The present disclosure relates to an inverter for an electrified vehicle, and more particularly to an inverter having a bleeder resistor. Background Art

[0002] Electrified vehicles utilize batteries that provide electrical energy in the form of direct current (DC). The powertrain utilizes a motor to convert electrical energy into mechanical torque to propel the vehicle. Several types of motors, such as permanent magnet synchronous motors, require electrical energy in the form of alternating current (AC). An inverter is used to convert DC power from the battery into AC power of the frequency and phase required by the motor. A contactor switch may be provided between the battery and the inverter to disconnect the inverter when the vehicle is not in use, in order to protect maintenance personnel, etc. However, the inverter may include a capacitor that also stores electrical energy and is not disabled by the contactor switch. A bleeder resistor may be used to gradually dissipate the energy from the capacitor. Summary of the invention

[0003] An electric drive system includes two rigid busbars, a power electronics module, and a molded bleeder resistor. The power electronics module is configured to convert DC power carried by the busbars into AC power. The power electronics module includes a capacitor connected between the two busbars. The molded bleeder resistor is directly bonded to the busbar so that the molded bleeder resistor rigidly fastens the two busbars to each other. The bleeder resistor is configured to dissipate energy from the capacitor. The electric drive system may include a variable voltage converter and an inverter. If present, the variable voltage converter is configured to deliver DC power at a second voltage different from the battery voltage. The inverter is then configured to convert the power at the second voltage into AC power. The busbar may connect the variable voltage converter to the inverter. The bleeder resistor may surround both of the two busbars. The bleeder resistor may be formed of a polymer or ceramic and fine carbon particles. The electric drive system may further include: a contactor switch electrically connected to one of the two bus bars; and a battery electrically connected to the contactor switch and to the other bus bar.

[0004] A method for manufacturing a busbar assembly includes holding two rigid conductive busbars in a predetermined position relative to each other and injecting a substance between the busbars. For example, the busbars can be held in a predetermined position by placing the busbars into a mold. The busbars do not contact each other in the predetermined position. The substance is bonded to the busbars and hardened, thereby rigidly attaching the two busbars together in a predetermined relative position. The substance contains fine carbon particles so that it forms a bleeder resistor. The substance may also contain a polymer or a ceramic. The mold may be shaped so that the bleeder resistor surrounds both of the two busbars.

[0005] A method for assembling an electric drive system includes connecting a DC bus bar assembly to a power electronics module. The power electronics module includes a capacitor and an inverter. The DC bus bar assembly includes a positive bus bar and a negative bus bar rigidly fastened to each other by a molded bleeder resistor. The molded bleeder resistor is joined to the positive bus bar and the negative bus bar before the positive bus bar and the negative bus bar are connected to the power electronics module. The bleeder resistor may surround both the positive bus bar and the negative bus bar. The bleeder resistor may include a polymer or ceramic and fine carbon particles. The method may also include: electrically connecting a contactor switch to one of the bus bars; and electrically connecting a battery to the contactor switch and electrically connected to another bus bar. Alternatively, the method may include electrically connecting the positive bus bar to the output of a variable voltage converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 A block diagram of an electric vehicle is shown.

[0007] Figure 2 yes Figure 1 Circuit diagram of a variable voltage converter of a power electronics module of an electric vehicle.

[0008] Figure 3 yes Figure 1 Circuit diagram of an inverter of a power electronics module of an electric vehicle.

[0009] Figure 4 Yes Figure 2 Variable voltage converter, Figure 3 Schematic diagram of the power electronics system with inverter and battery.

[0010] Figure 5 is a perspective view of a first embodiment of a DC bus with a shaped bleeder resistor.

[0011] Figure 6 is a cross-sectional view of a bleeder resistor and a DC bus bar according to a second embodiment.

[0012] Figure 7 is used for Figure 4 Flowchart of the manufacturing process of a power electronic system. DETAILED DESCRIPTION

[0013] Detailed embodiments of the present invention are disclosed herein; however, it should be understood that the disclosed embodiments are merely examples of the present invention that may be embodied in various forms and alternative forms. The drawings are not necessarily drawn to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, the specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching those skilled in the art to employ the present invention in various ways.

[0014] Reference now Figure 1 , a block diagram of an exemplary electric vehicle ("EV") 12 is shown. In this example, the EV 12 is a plug-in hybrid electric vehicle (PHEV). The EV 12 includes one or more electric machines 14 that are mechanically connected to a transmission 16. The electric machine 14 is capable of operating as a motor and a generator. The transmission 16 is mechanically connected to an engine 18 and a drive shaft 20 that is mechanically connected to wheels 22. The electric machine 14 can provide propulsion and retarding capabilities when the engine 18 is turned on or off. The electric machine 14 acting as a generator can recover energy that might normally be lost as heat in a friction braking system. The electric machine 14 can reduce vehicle emissions by allowing the engine 18 to operate at a more efficient speed and allowing the EV 12 to operate in an electric mode with the engine 18 turned off under certain conditions.

[0015] The traction battery 24 ("battery") stores energy that can be used by the motor 14 to propel the EV 12. The battery 24 generally provides a high voltage (HV) direct current (DC) output. The battery 24 is electrically connected to a power electronics module 26. The power electronics module 26 is electrically connected to the motor 14 and provides the ability to transfer energy bidirectionally between the battery 24 and the motor 14. For example, the battery 24 may provide a DC voltage, while the motor 14 may require a three-phase alternating current (AC) voltage to operate. The power electronics module 26 may convert the DC voltage to a three-phase AC voltage to operate the motor 14. In a regenerative mode, the power electronics module 26 may convert the three-phase AC voltage from the motor 14 acting as a generator to a DC voltage that is compatible with the battery 24.

[0016] The battery 24 can be recharged by an external power source 36 (e.g., an electrical grid). An electric vehicle supply equipment (EVSE) 38 is connected to the external power source 36. The EVSE 38 provides circuits and controls to control and manage the energy transfer between the external power source 36 and the EV 12. The external power source 36 can provide DC or AC power to the EVSE 38. The EVSE 38 can have a charging connector 40 for plugging into a charging port 34 of the EV 12. The charging port 34 can be any type of port configured to transfer power from the EVSE 38 to the EV 12. The power conversion module 32 of the EV 12 can condition the power supplied from the EVSE 38 to provide the appropriate voltage and current levels to the battery 24. The power conversion module 32 can interface with the EVSE 38 to coordinate the power delivery to the battery 24. Alternatively, the various components described as being electrically connected can use wireless inductive coupling to transfer power.

[0017] Wheel brakes 44 are provided to slow and prevent movement of the EV 12. The wheel brakes 44 are part of a braking system 50. The braking system 50 may include a controller to monitor and control the wheel brakes 44 to achieve desired operation.

[0018] The various components discussed may have one or more associated controllers to control and monitor the operation of the components. The controllers may be microprocessor-based devices. The controllers may communicate via a serial bus (e.g., a controller area network (CAN)) or via discrete conductors. For example, there is a system controller 48 (i.e., a vehicle controller) to coordinate the operation of the various components.

[0019] As depicted, the EV 12 in this example is a PHEV having an engine 18 and a battery 24. In other embodiments, the EV 12 is a battery electric vehicle (BEV). In a BEV configuration, the EV 12 does not include an engine.

[0020] Reference now Figure 2 and Figure 3 , a schematic diagram of components of a power electronics module 26 in the electric drive system of the EV 12 is shown. As described above, the power electronics module 26 is coupled between the battery 24 and the motor 14. The power electronics module 26 converts DC power provided from the battery 24 to AC power to provide to the motor 14. In this manner, the power electronics module 26 utilizes power from the battery 24 to drive the motor 14 for the motor to propel the EV 12. During regenerative braking, the power electronics module 26 converts AC power induced within the motor 14 to DC power to charge the battery 24.

[0021] The power electronics module 26 includes a DC-DC converter 51 and an inverter 52. As known to those of ordinary skill, the inverter converts DC power into multi-phase AC power (three-phase is the most common). The DC-DC converter can step up (increase) or step down (reduce) the DC voltage available to the inverter from the DC voltage available from the battery. The DC power from the battery is delivered on the negative bus 54 and the positive bus 56. Buses 54 and 56 form a first DC bus. The DC power from the converter 51 is delivered to the inverter 52 by the negative bus 54 and the positive bus 58. Buses 54 and 58 form a second DC bus. The inverter 52 delivers AC power to the motor via AC terminals 60. Some embodiments may omit the DC-DC converter 51.

[0022] The converter 51 and the inverter 52 include a plurality of power switch units. Each power switch unit includes a power switch 62 arranged in reverse parallel with a diode 64. The converter 51 also includes an inductor 66 and a capacitor 67. The inverter 52 also includes a capacitor 68. The switch 62 may be, for example, silicon carbide (SiC) or an insulated gate bipolar transistor (IGBT).

[0023] Figure 4 Additional components of the electric drive system are schematically shown. Negative bus bar 54 is electrically connected to the negative terminal of battery 24. Contactor switch 70 is electrically connected between the positive battery terminal and positive bus bar 56. Opening contactor switch 70 disconnects the DC power stored in the battery from the power electronics module 26. In an alternative embodiment, the contactor switch can be connected between the battery and the negative bus bar.

[0024] Although opening the contactor switch disconnects the battery, a large amount of power can remain in capacitors 67 and 68. To dissipate this energy, bleeder resistors 72 and 74 are installed between the negative bus 54 and the positive bus of the respective first and second DC bus bars. The resistance of the bleeder resistors is selected to be high enough so that it does not dissipate excessive energy during normal operation, but low enough so that when the contactor switch 70 is opened, the energy stored in capacitors 67 and 68 is dissipated at a sufficient rate.

[0025] Figure 5is a perspective view indicating the physical arrangement of a DC bus with a bleeder resistor and a capacitor. The first DC bus includes a negative bus bar 54, a positive bus bar 56 and a bleeder resistor 72, and is connected to a capacitor 67. The second DC bus includes a negative bus bar 54, a positive bus bar 58 and a bleeder resistor 74, and is connected to a capacitor 68. Terminals 76 are provided to connect to other components of a corresponding converter or inverter. The bus bar is a rigid metal component. The bleeder resistor is bonded to the opposite surface of the bus bar. The bleeder resistor can be made of, for example, a polymer or ceramic injected with fine carbon particles to provide a desired level of resistance. In addition to providing the desired resistance, the bleeder resistor also fastens the bus bars to each other and rigidly positions them relative to each other. This reduces the chance that one of the two bus bars is accidentally bent and contacts the other bus bar. As discussed below, it also facilitates assembly. The bleeder resistor is separated from the capacitor and other power electronic components so that the heat generated at the bleeder resistor does not heat other components.

[0026] Figure 6 is a cross section through a bleeder resistor in one possible embodiment. In this embodiment, the bleeder resistor 72 or 74 surrounds both the negative bus bar 54 and the positive bus bar 56 or 58. This embodiment provides an additional bonding area to increase the fastening capability of the bleeder resistor. The bleeder resistor can be formed of a polymer or ceramic substrate infused with fine carbon particles. The amount of fine carbon particles is set to establish the desired resistance value.

[0027] Figure 68 is a flow chart of a manufacturing process for manufacturing and installing a power electronic module with a molded bleeder resistor. At 80, a positive bus bar 56 or 58 and a negative bus bar 54 are manufactured. The bus bars are each made of a conductive material. The bus bars can be manufactured, for example, using a stamping process. At 82, a bleeder resistor 72 or 74 is molded together with the bus bar to form a bus bar assembly. An overmolding process can be used, in which the positive bus bar and the negative bus bar are placed in a mold before a plastic or ceramic material infused with fine carbon particles is injected into the mold. After molding, the bleeder resistor rigidly supports the positive bus bar and the negative bus bar in position relative to each other. Thus, the bus bar assembly can be easily handled or transported between assembly locations. At 84, the DC bus bar assembly is mechanically and electrically attached to the capacitor. The bus bar is also attached to other components depending on whether it is a first DC bus or a second DC bus. At 86, the negative bus bar is connected to the negative terminal of the battery. At 88, the capacitor is electrically connected in series between the positive terminal of the battery and the positive bus bar. In an alternative embodiment, instead of or in addition to the contactor switch between the positive battery terminal and the positive bus bar, a contactor switch may be installed between the negative terminal of the battery and the negative bus bar. In the case of a second DC bus, the positive bus bar would instead be electrically connected to the output of the variable voltage converter.

[0028] Although exemplary embodiments are described above, these embodiments are not intended to describe all possible forms of the present invention. Rather, the words used in the specification are descriptive rather than restrictive terms, and it should be understood that various changes can be made without departing from the spirit and scope of the present invention. In addition, the features of the various embodiments of implementation can be combined to form other embodiments of the present invention.

[0029] According to the present invention, there is provided an electric drive system having: two rigid busbars; a power electronics module configured to convert DC power carried by the busbars into AC power, the power electronics module comprising a capacitor connected between the two rigid busbars; and a formed bleeder resistor directly bonded to the busbars so that the formed bleeder resistor rigidly fastens the two busbars to each other, the bleeder resistor being configured to dissipate energy from the capacitor.

[0030] According to one embodiment, the power electronics module comprises: a variable voltage converter configured to deliver the DC power at a second voltage different from a battery voltage; and an inverter configured to convert the power at the second voltage into AC power.

[0031] According to one embodiment, the busbar connects the variable voltage converter to the inverter.

[0032] According to one embodiment, the bleeder resistor surrounds both of the two bus bars.

[0033] According to one embodiment, the invention also features a contactor switch electrically connected to one of the two bus bars.

[0034] According to one embodiment, the invention also features a battery electrically connected to the contactor switch and to the other of the two bus bars.

[0035] According to one embodiment, the bleeder resistor includes: a polymer; and fine carbon particles.

[0036] According to one embodiment, the bleeder resistor includes: ceramic; and fine carbon particles.

[0037] According to the present invention, a method for manufacturing a busbar assembly for an electric drive system includes: holding two rigid conductive busbars in a predetermined position relative to each other but not in contact with each other; and injecting a substance between the two busbars, the substance bonding to the busbars and hardening, thereby rigidly attaching the two busbars together in the predetermined relative position; wherein the substance contains fine carbon particles so that it forms a bleeder resistor.

[0038] In one aspect of the invention, holding the two bus bars in the predetermined position includes placing the two bus bars into a mold.

[0039] In one aspect of the invention, the mold is shaped so that the bleeder resistor surrounds both of the two bus bars.

[0040] In one aspect of the invention, the substance comprises a polymer.

[0041] In one aspect of the invention, the substance comprises a ceramic.

[0042] According to the present invention, a method of assembling an electric drive system comprises: connecting a DC bus bar assembly to a power electronic module, wherein the power electronic module comprises a capacitor and an inverter, and wherein the DC bus bar assembly comprises a positive bus bar and a negative bus bar, wherein the positive bus bar and the negative bus bar are rigidly fastened to each other by a formed bleeder resistor, wherein the formed bleeder resistor is joined to the positive bus bar and the negative bus bar before the positive bus bar and the negative bus bar are connected to the power electronic module.

[0043] In one aspect of the present invention, the bleeder resistor surrounds both the positive bus bar and the negative bus bar.

[0044] In one aspect of the present invention, the bleeder resistor includes: a polymer; and fine carbon particles.

[0045] In one aspect of the present invention, the bleeder resistor includes: ceramic; and fine carbon particles.

[0046] In one aspect of the invention, the method includes electrically connecting a contactor switch to one of the positive bus bar and the negative bus bar.

[0047] In one aspect of the invention, the method includes electrically connecting a battery to the contactor switch and to the other of the positive bus bar and the negative bus bar.

[0048] In one aspect of the invention, the method includes electrically connecting the positive bus bar to an output of a variable voltage converter.

Claims

1. An electric drive system, comprising: two rigid bus bars; a power electronics module configured to convert DC power carried by the busbars into AC power, the power electronics module comprising a capacitor connected between the two rigid busbars; as well as A formed bleeder resistor is directly bonded to the bus bar such that the formed bleeder resistor rigidly secures the two bus bars to each other, the bleeder resistor being configured to dissipate energy from the capacitor.

2. The electric drive system according to claim 1, wherein the power electronics module comprises: a variable voltage converter configured to deliver the DC power at a second voltage different from a battery voltage; as well as An inverter is configured to convert the electric power at the second voltage into AC electric power. 3 . The electric drive system of claim 2 , wherein the bus bar connects the variable voltage converter to the inverter. 4 . The electric drive system of claim 1 , wherein the bleeder resistor surrounds both of the two bus bars. 5 . The electric drive system of claim 1 , further comprising a contactor switch electrically connected to one of the two bus bars. 6 . The electric drive system of claim 5 , further comprising a battery electrically connected to the contactor switch and to the other of the two bus bars.

7. The electric drive system according to claim 1, wherein the bleeder resistor comprises: polymer; as well as Fine carbon particles.

8. The electric drive system according to claim 1, wherein the bleeder resistor comprises: ceramics; as well as Fine carbon particles.

9. A method for manufacturing a busbar assembly for an electric drive system, the method comprising: holding two rigid electrically conductive bus bars in a predetermined position relative to each other but not in contact with each other; as well as injecting a substance between the two bus bars, the substance bonding to the bus bars and hardening, thereby rigidly attaching the two bus bars together in the predetermined relative position; The substance comprises fine carbon particles, so that it forms a bleeder resistor. 10 . The method of claim 9 , wherein maintaining the two bus bars in the predetermined position comprises placing the two bus bars into a mold. 11 . The method of claim 10 , wherein the mold is shaped so that the bleeder resistor surrounds both of the two bus bars.

12. The method of claim 9, wherein the substance comprises a polymer.

13. The method of claim 9, wherein the substance comprises a ceramic.

14. A method of assembling an electric drive system, comprising: A DC bus bar assembly is connected to a power electronics module, wherein the power electronics module includes a capacitor and an inverter, and wherein the DC bus bar assembly includes a positive bus bar and a negative bus bar, the positive bus bar and the negative bus bar are rigidly fastened to each other by a formed bleeder resistor, the formed bleeder resistor being bonded to the positive bus bar and the negative bus bar before the positive bus bar and the negative bus bar are connected to the power electronics module. 15 . The method of claim 14 , wherein the bleeder resistor surrounds both the positive bus bar and the negative bus bar.

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