Latest developments of voltage-fed resonant high-frequency inverter with load resonant frequency tracking scheme for induction heating

This paper presents a pulse amplitude modulated voltage source type series load resonant inverter using the latest high power SITs, which operates a load adaptive tuned frequency-tracking scheme. The zero voltage soft switching resonant inverter using application-specific SITs is demonstrated for industrial induction heating applications, which works under a little higher inverter frequency than a resonant frequency in other to achieve lossless capacitor snubber dependent soft commutation. The resonant frequency tracking control strategy is based upon load adaptive variable frequency operation. The steady-state operating characteristics of this high frequency resonant inverter with a PLL-based resonant frequency tracking control scheme are discussed and experimentally evaluated in addition to its control performance. The actual experiments of SIT series resonant inverter with a high-frequency transformer are carried out and tested under the practical short circuit condition so as to obtain the unknown design data for the protective capability of SITs, and provide the optimum snubber circuit.