A bstmct -This paper describes some of the design considerations and tradeoffs that are involved in developing the power electronics for an electric vehicle propulsion inverter. A review of topology, voltage, current and switching frequency requirements is presented. Guidelines for the design oE gate driven, current loops, snubbers, auxiliary power supplies and protection circuits are given. Finally, loss calculations and thermal design methods are sugges ted.
I. Introductionile there are many opportunities for the use of power m l e c t r o n i c s devices in an electric vehicle, this paper will limit itself to a description of the propulsion inverter. A discussion of battery chargers, heat pumps, electronic suspension, anti-locking brakes, servos for mirrors and seat belts, DC to D C converters, light switches and numerous other areas will be deferred. This paper is not intended to be a comprehensive study of electric vehicle applications; rather, it is an effort to make an educated best guess as to the most likely power electronics structure of a typical EV used for domestic transport at ion.The EV's speed, torque, motor type and performance will ultimately dictate the switching device required by the propulsion inverter. The generic types of switching devices to select from include: SCRs, BJTs, MCTs, GTOs, SITS, SITHs, MOSFETs and IGBTs. New devices are constantly being added to this list. The latest new devices are the VSDMOSFETI'] and the DGMOSFET[*]. Both were developed by Fuji Electric Company of Japan.The VSDMOSFET (Vertical Schottky Drain MOS-FET) is a cross between an IGBT and a MOSFET. It switches at a specd approaching that of a MOSFET, but has a saturation voltage similar to an IGBT. This device would be idcallysuitcd for use in a batterycharger, but has limited advantage at the lower frequencies of thc invcrtcr.The DGMOSFET (Double Gate MOSFET) is a cross betwen an IGUT and a MCT. It is projectcd to have the high current dcrisityofa MCT(IOWVCE(SAT)) and thc speed and short circuit cap;ibilityofan IGBT. Although thistlevicc would be a future candidate for use in the inverter, it is not presently available.
A. Typical Switch RequirementsThe topology, switching frequency, voltage and current must first be specified in order to select the proper switch.A typicalEV might require a 3$ bridge inverter that switches at 20 Khz, operates off of a 300VDC bus and produces 140A RMS continuously per phase. This would be equivalent to a 50 kW controller.Other considerationswould include: ease ofassembly, size, ruggedness, cost; and because of present battery limitations, efficiency.Topolom-Modules which include antiparalleldiodes would simplify the bus structure, optimize ruggedness and reduce assembly time. O n the surface, the cost of many paralleled discrete devices would seem to be less than that of a module. At high power levels, however, when assembly, test and repair costs are included, modules are the best choice.-The industrial market is moving toward 20 kHz switching. This eliminates audible noise probl...
