Soft-switching inverter for variable frequency induction heating using magnetic energy recovery switch (MERS)

Variable frequency induction heating has great potential for industrial heating applications due to the possibility of heating distribution control. Conventional high frequency converters are not suitable for the variable frequency operation; therefore, large scale induction heating with variable frequency has not yet been introduced to practical use. This paper proposes a soft-switching converter using a concept of a magnetic energy recovery switch. Operation principles and characteristics are investigated and compared with other existing high frequency inverters. The proposed converter can be characterized by current source topology and wide frequency operating range with soft-switching. From discussions, the proposed converter is found to be suitable for high power variable frequency induction heating. The proposed converter has the challenge that semi-conductor switches must handle all of the load current and required load voltage to achieve wide frequency operation range, although conventional topologies utilize resonance capacitor to reduce semi-conductor ratings. This paper also describes current rating reduction by using shunt capacitor for the proposed converter. A simplified configuration to achieve the same concept is also proposed.