Dual-Frequency Induction Heating Generator With Adjustable Impedance Matching

This paper presents a new resonant generator topology for dual-frequency induction heating. The design offers functionalities that are not present in other solutions, which allow the ratio of equivalent resistance to be controlled at high (HF) and medium (MF) resonant frequencies. A simulation is performed of its interactive work during dual-frequency induction heating, using a specially developed software algorithm. The simulation combines coupled numerical calculations of the electromagnetic and thermal fields during dual-frequency heating of the workpiece with the analysis and modification of the resonance frequencies and power at HF and MF, in accordance with a user-imposed duty cycle. The results are used as the basis for a 100-kW physical model of the generator. The proposed LCLC topology for a dual-frequency resonant inverter with adjusted series inductance allows better use of the ac-dc power supply system, easier implementation of sequential dual-frequency heating, and easier control of MF and HF power waveforms.