Analysis of Electrical Conditions of Electric Arc Furnaces during Different Periods of Melting

A method for determining electrical and electric process parameter characteristics (in relative units) is proposed, which enables analyzing and optimizing the operating conditions of electric arc furnaces (EAF) by accounting for the negative effect of electric arc burning process during different periods of melting. The obtained data were compared to those calculated using common electrical characteristics to show that the actual generated arc power decreases by 30 to 40 % during melting and by 20 to 25 % during heating of liquid metal. The transformer voltage effect on the arc power and electric process parameters (arc emissivity (R_F) and heating rate) has been studied. It was shown that the voltage variation effect on arc emissivity is especially strong (according to a square law), which makes it a very effective tool for intensifying the metal melting process. It was found that while maintaining a constant furnace current using a controller, it becomes necessary to reduce the transformer voltage as the required relative current value increases during melting to ensure preserving the optimal operating conditions. The following transformer voltage ratio was justified during different melting periods (melting, re-melting, and heating of liquid metal): (1.5–1.7)/(1.15–1.2)/1.0. An increase in transformer voltage without violating the optimal operating conditions is only possible by providing an optional control of the electrical circuit of the furnace using installed series reactors on the high-voltage side of the transformer.