Design, Analysis and Implementation of IGBT based LCL-Resonant Converter for Medium Frequency Induction Melting and Heating Application

Abstract

nduction melting heating is well-known technique used in casting foundry,metal semis product as well as in metal heat treatment plant. Recent trend is to replace thyristor used in converter with transistor like MOSFET or IGBT for better efficiency and faster switching. Various topologies have been developed in this area such as VSI CSI with series or parallel load resonant circuits. Recent developments in switching schemes and control methods have made the VSI more preferred in the application which requires output power control. In present work IGBT based full bridge inverter with LCL (Inductive coupling) configuration has been designed. Hence the price of system has also reduced,as now rectifier section is of diode which was previously thyristorised. LCL based configuration enables operation at higher voltage in order to reduce load current that flows from inverter, i.e. now inverter semiconductor devices can be chosen of lower rating as LCL tank circuit helps in boosting up of voltage and current at the load side. Also the comparative analysis with existing thyristor based converter with parallel LC tank circuit has been done. For the analysis purpose, only prototype of 1kW has been designed with suitable PWM control strategy. Also to attain the level of performance required for LCL load resonant topology ZVS ZCS of the load had been selected. This mode of soft switching is used to reduce IGBT switching losses. The circuit design had been implemented with suitable controller with control consideration. In present work the comparative study of the thyristor based converter with parallel resonant tank circuit and IGBT based inverter with third order resonance LCL configuration had been done. Also the design calculations for DC link of the inverter as well as LCL resonant circuit had been done with suitable design consideration. All design calculation data had been used for simulation purpose as well as for hardware designing and on the basis of obtained results conclusion has been drawn.