Variable Pulse Density Modulation for Induction Heating

Induction heating enables the conversion of electrical energy to thermal energy with a fast, high conversion efficiency and the ability to partially heat be used in a wide variety of welding industries. Conventional diode/SCR rectifiers and mid-frequency/high-frequency resonant inverters used to power conventional induction heaters will have low efficiency, low input power factor, high THD input current. Recently, a research has been done on a current fed three phase-three switch PWM rectifier, producing high power factor but also high current THD. The paper proposes a voltage fed three phase-three switch PWM rectifier with simple structure and control to achieve high power factor and lower current THD. A new variable pulse density modulation without online calculation has been proposed. The preliminary simulation and experimental results verify the feasibility and efficiency of the proposed configuration.