GB1380177A - Circuits for controlling the movement of the electrodes of a three-phase arc or electroslag refining furnace - Google Patents

Abstract

1380177 Automatic control of arc furnaces ASSOCIATED ELECTRICAL INDUSTRIES Ltd 10 April 1973 [14 Aug 1972] 37800/72 Heading G3R [Also in Division H2] A circuit for controlling the movement of the electrodes E1-E3 of a three phase arc or electroslag refining furnace comprises three voltage transformers T1-T3 each having a primary winding P1-P3 and two secondary windings S1À1-S3À2 which are connected in pairs in series opposition, and actuators M1-M3 each responsive to the difference between the voltages across an associated pair of secondary windings for moving the corresponding electrode in a direction which tends to reduce the voltage difference. The electrodes are supplied with current from a transformer T and a current regulator CR, the electrodes being carried by supports movable by electric motors which are controlled by the actuators M1-M3. The difference voltages which control the actuators ensure that a constant arc voltage is maintained by moving the electrodes towards or away from the molten material thus reducing or increasing the electrode voltage and reducing the voltage difference. In a modification current transformers in the phase leads L control relays having contacts connected to the secondary windings S1À1-S3À2 so that if the current supply to an electrode falls to zero, correct single phase control of the movement of the other electrodes continues.