GB1096790A - Electrode position control device for electrode furnaces - Google Patents

Abstract

1,096,790. Automatic control of electrode furnaces. ALLMANNA SVENSKA ELEKTRISKA A.B. April 29, 1965 [April 30, 1964], No. 18018/65. Heading G3R. A system for automatically controlling the position of the electrodes of a furnace includes an integrating device which is rendered inoperative during the periods whilst the electrodes are being moved, the use of an integrating device ensuring against unnecessary control of the electrode positions. A signal proportional to electrode current is compared with a reference value and the resulting signal is fed to an amplifier over a phase sensitive blocking device which introduces a dead band into the control. The signal fed to the amplifier is integrated by a device comprising resistors and capacitors. When the integrated voltage reaches a value set by a limiting device connected to the output of the amplifier one or other of two complementary transistors is rendered conductive thereby disabling the integrating device with the result that the amplifier instantaneously reaches maximum output. The output of the amplifier, by way of a second pair of complementary transistors, energizes one or other of a pair of relays which are operative to move the electrodes up or down to restore the electrode current to the normal value. The relays have contacts which short circuit the blocking device connected to the amplifier input and further contacts which cause a further relay to render the integrating device inoperative. The further relay also renders the integrating device inoperative when adjustment of the system is made.