New soft-commutated PWM inverter with AC current transformer

The soft-commutated PWM inverter is very attractive for high power applications. In the conventional soft-commutated PWM inverter, however, there exist some deteriorative problems such as high voltage and/or high current stresses on the switches, the necessity of the additional switches for realizing soft-commutated PWM, and the relatively large power loss caused by the large circulating current composed of the load current and the resonant current. This paper presents a new soft-commutated PWM inverter, in which an AC current transformer and a main resonant capacitor are used to detect the value and the polarity of the AC load current, and to realize the soft-commutation of the switches without causing the above deteriorative problems. The operation and the characteristics of this soft-commutated PWM inverter are analyzed and its usefulness is confirmed by experiments