Power Factor Improvement using PWM Rectifier in Shrink Fitting

Induction Heating (IH) systems are a popular choice for an extensive range of applications in the automotive industry. However, the input power factor is poor in conventional IH systems, which leads to higher input current. Therefore, a single switch resonant inverter with a PWM rectifier as its input is considered in the work presented. This work validates the power factor improvement of an IH system that can be used in the automotive industry, specifically for shrink fitting. PWM rectifier is implemented in the IH system, replacing diode bridge rectifier, and it is observed that both distortion and displacement power factor are improved. In order to generate pulses for the controllable switches in the PWM rectifier, hysteresis current control method is used. Prior to this selection, various types of closed-loop current control methods were analyzed, and hysteresis current control, employing a single PI controller, is selected for the closed-loop operation. A low power level laboratory prototype is constructed and tested successfully, and results are presented in the paper.