Analysis and design of a high frequency induction-heating system

Includes bibliographical references. ; Advances in power electronic semiconductor technology are making high frequency converters for induction heating more feasible at power levels up to 50kW. This research presents the development and analysis of a solid-state induction-heating system, operating directly off single-phase mains frequency, which enables optimum and efficient operation over a frequency range of 80kHz to 200kHz. The system essentially comprises a DC-DC converter configured as a controlled current source, which feeds a load resonant DC-AC inverter, driving a parallel resonant load circuit. The load circuit comprises an induction-heating coil and a reactive power compensating capacitor. The systems active switching elements comprise power MOSFET's but can be extended to almost any other controlled power devices such as IGBT's, BJT's, SCR's, GTO's or SIT's. An automatic frequency control system ensures that the DC-AC inverter drives the load at its resonant frequency, thereby achieving zero voltage switching of the power semiconductors. This operating mode always ensures maximum power transfer to the load as well as maximum operating efficiency of the DC-AC inverter. Driving the load at resonance presents an essentially resistive load to the DC-DC converter, thereby reducing the losses associated with a reactive load. A compact circuit layout combined with this optimum mode of operation eliminates the need for any snubber circuit components in both the DC-DC and DC-AC converters at this power level. An overview into various applications and technologies of induction-heating is presented in this research. A detailed analysis of the induction-heating coil and work- piece are presented in order to aid the design of the load circuit. The induction-heating technology overview presents various induction-heating power sources, discussing the configurations of various topologies. A brief mathematical analysis is used to describe the operation of power electronic converters employed in the induction-heating ...