Three-phase soft-switching inverter for induction motor drives

A zero-voltage transition (ZVT) soft-switching inverter for an induction motor drive is developed. The proposed soft-switchng inverter is formed from the traditional pulse-wi dth modulated (PWM) inverter by simply augmenting with auxiliary resonant circuits, and the soft switching is acheved through applying PWM switching control signals with suitable delays for the main and auxiliary switches. No additional voltage and current sensors are required in the implementation. The operations and governing equations in various modes of the proposed soft-switching inverter are first analysed then, accordingly, a quantitative design procedure is given to find the values of the auxiliary resonant circuit components and the delay times of the switches for achieving ZVT control. Finally, the designed soft-switching inverter is used for powering an indirect field-oriented ( [FO) induction motor drive to test its effectiveness. The simulation and measured results show that a smaller switching loss and higher conversion efficiency are obtained by the proposed soft-switching inverter.