Calculation of arc-circuit asymmetry in electric-arc furnaces

A method is described to determine the arc voltages on a per-phase basis of a 3-phase direct electricarc furnace. Having determined the arc voltages, other arc parameters, such as arc resistance, length and power, can then be obtained. By using the procedure outlined, in conjunction with experimental data on a 100 t, 5½m diameter shell furnace having a triangulated secondary electrical system, it will be shown that controlling arc powers by means of the impedance control method still results in asymmetric furnace operation. Sample calculations are included, illustrating actual conditions for this furnace.