Modeling and control of temperature dynamics in induction furnace system

This paper explains modeling and control of temperature dynamics on induction furnace. Induction furnace is used for melting metal to process raw material scrap into steel ferrit rate 0.22 wt % carbons. The dynamics response of the induction furnace temperature affects the resulting product. Therefore, the controller of temperature dynamics is required to produce the desired process response. The induction furnace systems consist of electrical and thermal system dynamics. The dynamics of the electrical system represents the induction furnace system in the form of an electric circuit i.e. fed current inverter with a parallel resonant circuit. Meanwhile, the thermal system dynamics represents the thermal energy transfer process, which is developed with the principle of energy balance, including heat generated energy and heat loss. Induction furnace system dynamics is modelled in an order 2 system, with a time constant coil 1000 times faster than time constant temperature. Thus, by ignoring the time constant coil, induction furnace system dynamic model can be transformed into a first order nonlinear system. Then, linear system can be obtained by making a replacement variable. Induction furnace temperature control has been implemented by adjusting the PWM to control the input power to the induction furnace. PI controller is designed in three cases, namely linear model with linear PI controller, saturated linear model with linear PI controller, and saturated linear model with anti-windup PI controller. Each case is simulated by Simulink. To get the appropriate specifications, the temperature should be controlled at 912 Celsius degree. The best results can be achieved with maximum overshoot is 7% and the rise time is 2.9 seconds.