High-frequency current-source inverters using SI thyristors for induction heating applications

An optimum control scheme for current-source inverters using static induction thyristors in various high-frequency induction heating applications is described. The optimum control scheme implies an optimal control of the firing angle and extinction angle relative to the output voltage in order to minimize the surge voltage and the switching loss during the commutation interval. The tailing current problems of the SI thyristors which significantly influence the optimum firing angle and extinction angle are discussed theoretically. The validity of the optimum control scheme is verified by experiments with a 78 kHz, 17.4 kW (290 V, 60 A) inverter. >