Comparative Study of a Single Inverter Bridge for Dual-Frequency Induction Heating Using Si and SiC MOSFETs

The induction surface hardening of parts with nonuniform cylindrical shape requires a multifrequency process in order to obtain a uniform surface hardened depth. This paper presents an induction heating high power supply composed by a single inverter circuit and a specially designed output resonant circuit. The whole circuit supplies simultaneously both medium- and high-frequency power signals to the heating inductor. An initial study is made to select the most appropriated topology for this application. The resonant output circuit is analyzed, and a design procedure is presented. The selected inverter operation is described and simulated. Simulations are experimentally verified on a 10-kW dual-frequency resonant inverter operating at 10 and 100 kHz using MOSFETs of silicon (Si) and silicon carbide (SiC) technology. A comparative study is presented based on the measurements of power losses and the energy efficiency of the inverter using both types of MOSFETs.