Resonant snubber-based soft-switching inverters for electric propulsion drives

This paper summarizes recently developed soft-switching inverters and proposes two possible options for electric propulsion drives, The newly developed soft-switching inverter employs an auxiliary switch and a resonant inductor per phase to produce a zero voltage across the main switch, so that the main switch can turn on at the zero-voltage condition, Both the auxiliary switch and the resonant inductor are operating at a fractional duty and, thus, are small in size as compared to the main inverter circuit components, Operation modes in a complete zero-voltage switching cycle for the single-phase soft-switching inverter are described in detail, with graphical explanations. The circuit operation was first verified by a computer simulation, and then further tested with a l-kW single-phase and a 100-kW three-phase inverter, Both simulation and experimental results are presented to show the superior performance in efficiency improvement, EMI reduction, and dv/dt reduction of the proposed soft-switching inverters.