Calculation of Inductance and Current Distribution in Low-Voltage Connections to Electric Furnaces

The special nature of the low-voltage circuit to electric furnaces is emphasized. The conductors employed vary in arrangement and cross section, and are relatively short. The very large currents carried give rise to reactive drops of greater magnitude than is usually supposed. For these reasons a detailed study of the inductance of such circuits is desirable. Fundamental theorems for deriving geometrical mean distances are first stated, leading to the well-known formulas for self-and mutual-inductance of circular and rectangular sections. Practical applications of these formulas to the problem of calculating the approximate reactive drop in three-phase arc furnace circuits are worked up in great detail. The same calculations can be used to determine the approximate operating power factor of the furnace. Unequal current distribution in multiple conductors, due to proximity and skin effects is discussed.