Modular Converter System, High Frequency, High Power Induction Heating

The method of induction heating is widely used in industrial applications, and it is often applied to heat metallic workpieces at a specified temperature and time. For example, it can be employed in induction hardening, through heating, melting and welding. Electric energy with high frequency and high power is required in many types of induction heating applications. In the middle of the eighties, parallel resonant converters equipped with MOSFET transistors and an output frequency up to 300kHz came to the market. Due to the low blocking voltage (<600V) of the MOSFETs, high currents are necessary to achieve the high power levels. There are high costs for the power transistors, the isolated gate drivers and the mechanical construction. Additionally, problems with the internal diode of the MOSFET have been reported. This means that the use of MOSFETs is not comfortable in high power and high frequency induction heating applications. Costs decreased, when fast-switching IGBTs became available.