Practical evaluations of load-adaptive high-frequency resonant PAM inverter using static induction power transistors for industrial induction-heating plants

This paper describes the advanced developments of voltage-fed series load resonant high-frequency high-power inverters using static induction transistors (SITs) for industrial induction heating and melting power supplies. The load-adaptive variable frequency tuned-controller using PLL, the AC/DC power converter for PAM, and protective control schemes are described from a practical viewpoint. In particular, the practical short circuit testing of an SIT inverter developed for induction heat treatment applications is demonstrated in order to obtain the various basic data relating to the switching characteristics of large capacity SITs incorporated into the inverter circuit and also to design cost-effective protective circuits of SITs in addition to their optimum snubber circuits for SIT switching-legs