HEATING CONTROLLER FOR MELTING FURNACE

摘要

PURPOSE:To avoid the cut-off of the melt and to ensure the stable working of the titled controller by obtaining an impedance deviation from the current and the output voltage of a controller and performing the suppression control and the recovery control from the upper and lower limit levels of said deviation. CONSTITUTION:The output current of a thyristor controller 2 is detected by a current transformer 5 and at the same time the output voltage of the controller 2 is detected by a voltage detector (not shown in figure). The detection value of these detectors are supplied to an impedance arithmetic circuit and a power arithmetic circuit 6 respectively. The circuit 6 sends the arithmetic outputs of upper and lower limit values of the impedance deviation which is sampled when the detection output exists as well as the arithmetic output of the suppression/recovery power. The arithmetic output given from the circuit 6 is supplied to an arithmetic processing part 7 containing a microcomputer, etc. and processed there. Then the deviation allowable value of the sampled impedance is changed according to the increase of the electric power. Thus the cut-off of the melt is prevented.