NEW SOFT-COMMUTATED PWM INVERTER WITH AC CURRENT TRANSFORMER

The soft-commutated PWM inverter is very attractive for high-power app lications. In the conventional soft-commutated PWM inverter, however, there exist some deteriorative problems such as high voltage and/or hi gh current stresses on the switches, the necessity of additional switc hes for realizing soft-commutated PWM, and the relatively large power loss caused by the large circulating current composed of the load curr ent and the resonant current. This paper presents a new soft-commutate d 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 loa d current, and to realize soft commutation of the switches without cau sing the above deteriorative problems. The operation and the character istics of this soft-commutated PWM inverter are analyzed and its usefu lness is confirmed by experiments. (C) 1998 Scripta Technica.