A Zero-Current-Switching Based Three-Phase PWM Inverter

With remarkable progress of switching devices, the switching frequency of a voltage-source PWM inverter has been higher and higher. A high frequency PWM inverter gives great benefits in reduction of current ripples and acoustic noises. However, high frequency hard switching causes the increase of switching losses and EMI to be solved.The authors propose a zero-current-switching based three-phase PWM inverter which has small resonant circuits on the ac side. The current flowing in a switching device is a sum of the resonant current and the load current. Since the switching device is turned on and off at zero current, the switching losses and electromagnetic noises are greatly reduced. This paper describes the principle of the zero current switching operation, the design of the resonant circuits and the control scheme for the new soft switching inverter. Moreover, it shows interesting experimental results obtained by the zero-current-switching PWM inverter which drives an induction motor of 2.2kW.