Theoretical analysis of the secondary circuit of an electric arc furnace under three-phase unbalance condition

Abstract

 During electric arc furnace (EAF) smelting, three-phase load imbalance signifi-cantly affects electrical energy losses, temperature uniformity in the molten bath, and over-all smelting efficiency. Therefore, based on the three-phase unbalanced circuit of the EAF, this paper establishes a mathematical calculation model for key parameters related to pro-duction stability, including: neutral point voltage, three-phase voltage unbalance degree, three-phase currents, arc length, negative-sequence current, and voltage unbalance degree at the point of common coupling (PCC). Simulation results based on a 120 t EAF indicate that an increase in the impedance unbalance degree leads to a corresponding rise in neutral point voltage and three-phase voltage unbalance degree, accompanied by a marked increase in inter-phase current disparity and current unbalance degree. Notably, as the impedance unbalance degree escalates from 10% to 30%, the three-phase arc length difference widens from 26 mm to 79 mm, the relative negative-sequence current climbs from 2.89% to 8.76%, and the unbalance degree of PCC voltage increases from 0.276% to 0.846%. The theoretical findings presented in this paper provide a foundation for balanced compensation and oper-ational optimization of EAF power supply systems.