Modelling and Identification of a Three-Phase Electric Arc Furnace

This chapter is an attempt to illustrate the development of a mathematical model of an industrial process by combining analytical modelling techniques with a system identification study. Although both these approaches can often be applied in isolation to develop a mathematical description of a process the lack of detailed knowledge of the high power arc discharge suggests a combination of these techniques in the case of an electric arc furnace. The objective of the present study is to develop three-phase models of both arc impedance and arc current controlled electric arc furnaces. Initially, a single-phase model of the electrode position controller, arc discharge and furnace transmission system are developed for an arc impedance controlled furnace using analytical modelling techniques and assuming zero interaction between the three regulators. Th assumptions and approximations associated with this model are investigated by designing experiments and conducting tests on a production arc furnace. Properties of the arc discharge, interaction between the regulators and a pulse transfer function representation of the electrode position controller are identified. These results are extended and three-phase models of an arc impedance and arc current controlled electric arc furnace are derived.