Development of a current source resonant inverter for high current MHz induction heating

Abstract

High frequency industrial induction heating processes typically employ resonant inverters to reach high efficiency at high power levels. Advancements in wide band gap (WBG) device technology has made it feasible to push the possible frequency of these processes into the MHz regime using solid state technology. Several topologies can be applied, each with advantages and drawbacks. This paper presents a current source resonant inverter (CSRI) employing a custom designed power module utilizing 1700V SiC MOSFETs for MHz operation of a high-Q resonant tank for induction heating, which presents new challenges in the inverter module design. An integrated gate driver structure is demonstrated driving four MOSFETs in parallel in MHz operation. Theoretical analysis predicts substantial parasitic influence on inverter operation, and thus an inverter is constructed to provide experimental verification of MHz operation, while the challenges associated with high frequency CSRI operation are discussed. In the experimental inverter setup, the fabricated power module achieves > 90 % efficiency for a calculated reactive power of 170 kVA and 2.3 kW output power during unloaded operation, validating the inverter design for extension to higher power loaded operation.