Induction heating is widely used in metal industry for melting or heating thin slabs in a continuous casting plant. The wide application is based on good efficiency, high production rate and non-polluting conditions. For designing a parallel resonant induction heating system, calculating the capacitance for the resonant circuit is important, because its value affects resonance frequency, output power, power quality factor, heating efficiency and power factor.
In this paper, phase controlled rectifier and H-bridge inverter are modeled. Then a method of finding an optimal value for the capacitance under voltage constraint is presented. This value is selected for maximizing output power of an induction heater, while minimizing the power loss of capacitor at the same time. For this purpose, the role of equivalent series resistance in the choice of capacitance value is significantly recognized. In this regard, the heating coil and the load of induction heating are modeled at first, and then the optimal value of capacitance is selected. Finally a complete model of heater and its power is simulated and effectiveness of the proposed method is verified.