Efficiency Evaluation of Six-Phase VSI and NSI for 400V and 800V Electric Vehicle Powertrains

This paper presents an efficiency evaluation of two six-phase inverter topologies for automotive applications: voltage source inverter (VSI) and nine-switch inverter (NSI). Their efficiency is studied for electric powertrains rated at 400 V and 800 V, and using silicon carbide (SiC) MOSFETs rated at 650 V and 1200 V operating at a switching frequency of 30 kHz. Prior to efficiency evaluation, a thorough analysis on the total device count required for 100 kW design is investigated for both topologies. It is found that NSI enjoys a superior efficiency when compared to six-phase VSI, at the expense of increased total device count.