An Induction Heating System Using a Double-D-Shaped Auxiliary Work Coil with Parallel Connection

This paper proposes an induction heating (IH) system using a double D-shaped work coil (DD coil) as an auxiliary coil for plate heating applications. The DD coil is arranged in the center hole of the circular coil and supports the heating of a workpiece located in the center. In this arrangement, the two work coils are not coupled magnetically. Therefore, high-frequency inverters of each work coil operate stably. However, uneven heating occurs because magnetic fluxes or eddy currents from each work coil interfere with each other on the workpiece. Thus, this paper proposes controlling the phase difference between the coil currents to 90 degrees. The coil currents with 90-degree phase difference can neutralize the effect of the interference and suppress the uneven heating. In this paper, the stable operation of each converter and the heat distribution control are considered and experimentally validated by an experimental setup of the rated power of 500 W.