Three Phase Electric Arc Furnace - An Introduction

EAFs produce steel by melting scrap using a threephase electrical supply as the electrical energy input.The fundamental problem in the EAF industry is the production of steel at a specified quality at the lowest cost possible. The three-phase electrical input serves as the main energy input in the electric arc furnace. The electrical energy input needs to be controlled with the aim of achieving the lowest possible production cost. Each phase of the three-phase electrical input supplies power to one of the three electrodes that is mounted above the furnace bath through the roof. The furnace roof is closed when power is supplied to the system. The furnace operation is based on heat transfer into the bath from arcs drawn between the tips of the electrodes to the metallic charge. Thus, electrical energy is converted into heat which is transmitted to the charge through the electrodes. Constant melting
causes the arc length to change and results in a change in the electric energy input if control is not supplied to the system. Two variables are mainly used to control the electrical energy input, i.e. arc impedance and arc current. Both these variables are controlled via an electrode position controller which moves the electrodes in a vertical position to adjust the arc current or arc impedance according to specified reference values.