HV SiC MOSFETs can improve the efficiency and power density of MV motor drives by enabling higher fundamental frequencies. Series connection of devices with RC snubber-based voltage balancing is often employed to realize higher converter voltages. RC snubbers decrease the device turn-off loss but result in high turn-on loss due to snubber capacitor discharge. This paper proposes to overcome this limitation by leveraging the existing voltage balancing snubber capacitors to realize ZVS turn-on through auxiliary resonant commutation. This results in soft turn-on and turn-off along with controllable output dv/dt eliminating the need for an external dv/dt filter. The operating principle and design criteria for the soft switching inverter have been discussed. A 3-phase 2-level 100kVA inverter with three series connected 3.3kV SiC MOSFETs has been designed for a 3.3kV 25000 rpm motor drive. The inverter has been tested in hard switching conditions and its losses have been evaluated. The auxiliary components needed to realize ZVS turn-on have been designed. The converter will be operated under soft switching and its losses will be evaluated and baselined against the hard switching losses.
