The recent introduction of high power Silicon Carbide (SiC) switching devices has enabled electric vehicle (EV) traction inverters to achieve >99% efficiency. The consequentially low heat loss is horrific to vehicle heating-systems designers, since ~200W of power is available, at highway speeds, to heat a liquid coolant -- an order of magnitude less than that necessary to thermally condition High Voltage (HV) battery packs, and is ~40x lower than the peak heating levels needed to warm a passenger cabin.
Rather than resort to convention by adding expensive and unreliable immersion heaters, including their inherently leak-prone plumbing and high power electronics; or adding exotic heat pumps to scavenge heat, this paper discusses the benefits and implementation of a traction inverter, that eliminates resistive heaters altogether, through novel modalities of either maintaining SiC’s high efficiency or, using a logic signal, to turn on a heating mechanism inherent in switching devices’ physics to provide multi-kilowatt coolant heating intended for HV battery pack and passenger cabin heating.
A review of traditional traction inverter architecture and a brief overview of switching device characteristics is performed at a thermal engineer’s level, along with introducing the heating physics being exploited and the low cost circuit implementation in the novel inverter.
Simulations showing circuit performance at several kilowatts of coolant heating power, independent of vehicle speed, are presented in the context of applicability to the imminent need for extremely cost-competitive EVs that do not provision any expensive heating devices, yet necessarily incorporate this traction inverter for EV propulsion.
