Possibilities and Limitations of Wide Bandgap Transistors in High-Speed Electric Drives

In this paper, an inverter with wide bandgap transistors was designed, experimentally evaluated and compared to a conventional IGBT-based inverter in a three-phase slotless PM motor drive. Using the developed inverter, GaN and SiC transistors (650 V) were experimentally tested using switching frequencies up to 48 kHz. Despite operation at significantly higher switching frequencies, the inverter efficiency was increased from approximately 90 to 95 % by using wide band-gap transistors. Furthermore, a system weight reduction of up to 50 % was enabled due to the elimination of the inductive filter and use of a smaller heatsink (due to lower losses). By combining the wide band-gap technology with a new slotless 4-pole motor type, the total system losses can be reduced by more than 30 %.