FEEDBACK CONTROL SYSTEM FOR THE IMPEDANCE CONTROL OF AN ELECTRIC ARC FURNACE

摘要

A feedback control system for the impedance control of an electric arc furnace comprises at least one electrode, a hydraulic electrode actuator for adjusting the electrode, which actuator is adapted to be supplied with hydraulic fluid through a control valve, a controller, which is connected to the valve actuator for the control valve, and impedance signal generator for delivering impedance signals to one input of said controller and a setpoint signal generator for delivering a setpoint signal representing a desired impedance to another input of said controller. In order to prevent non-per-missible electrode oscillations in such a feedback control system it is proposed to provide a correcting stage for correcting the controller gain and to provide a correcting signal generator for delivering to said correcting stage a signal which represents the controlled-system gain and which causes said correcting stage to change the controller gain in a sense which is opposite to a detected change of the controlled-system gain.