Efficiency modeling and evaluation of a resonant snubber based soft- switching inverter for motor drive applications

This paper establishes an analytical model for a resonant snubber based soft-switching inverter. The model adopts loss separation method to evaluate losses in individual components. Because of symmetry of the inverter circuit, the developed model is suitable for both single-phase and three-phase inverters. A single-phase inverter was built and tested with a single-phase induction motor driving a fan load to verify the developed model. The equivalent single-phase induction motor model was curve-fitted from experiment. Analytical results showed reasonable agreement with experiment. The same efficiency evaluation method was then applied to the conventional hard-switching inverter, and the results were compared with that of the soft-switching inverter. The resonant snubber base soft-switching inverter shows substantial efficiency improvement over the hard switching PWM (pulse-width-modulation) inverter, especially in low speed operation