Design of a Coreless Induction Furnace for Melting Iron

nduction heating is widely used in metal industry because of its good heating efficiency, high production rate, and clean working environments. The development of high-frequency power supplies provided means of using induction furnaces for melting metals in continuous casting plants [1-4]. Rather than just a furnace, a coreless induction furnace is actually an energy transfer device where energy is transferred directly from an induction coil into the material to be melted through the electromagnetic field produced by the induction coil. A typical parallel resonant inverter circuit for induction furnace is shown in Fig. 1. The phase controlled rectifier provides a constant DC current source. The H-bridge inverter consists of four thyristors and a parallel resonant circuit comprised capacitor bank and heating coil. Thyristors are naturally commutated by the ac current flowing through the resonant circuit [5]. It is important to select the proper power rating for the system. There are many factors that influence the selection of furnace power. The first is the capacity to be melted, the type of the material to be melted (Iron, Aluminum, Tin ...) and the desired melt cycle time. To raise the temperature of a solid material to the pouring temperature, energy must be put into it based upon the characteristics of its solid specific heat, latent heat of fusion, and liquid specific heat. An improperly designed system that has an undersized power supply will reduce the efficiency of the overall system and reduce the weight of metal that can be melted per kWh