Latest developments and practical evaluations of load-adaptive variable-frequency and PAM-based variable-voltage high-frequency resonant inverter using static induction high-power transistors for industrial induction-heating plants

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