Three-Phase to Single-Phase Multi-Resonant Direct AC-AC Converter for Metal Hardening High-Frequency Induction Heater

A soft-switching three-phase utility frequency ac to single-phase high-frequency ac direct power converter for induction heating(IH) applications is presented in this paper. The newly-proposed ac-ac converter features direct frequency conversion with assists of the multi-resonant tank and soft switching operations with minimized numbers of bidirectional switches. Performances of the proposed ac-ac converter are demonstrated by experimental results based on a 3.5kW-40kHz preliminary prototype, thereby the validity of the proposed converter is discussed from a practical point of view.