JPS57137085A - Method and device for controlling input voltage of welding transformer - Google Patents

Abstract

PURPOSE:To control the input voltage of a welding transformer by generating an alarm when the effective value of the detected primary terminal voltage of a welding transformer lowers below set voltage. CONSTITUTION:The primary terminal voltage waveform of a welding transformer 1 is transmitted by a detector 3, and the effective value is calculated by an effective value operator 4. On the other hand, necessary welding transformer input voltage is set by a voltage value setter 5 and the set voltage value by a display device 6. The set voltage of the setter 5 and the voltage obtained with the operator 4 are detected of a deviation with a comparator 7. A firing phase operator 8 calculates an optimum firing phase, and transmits a command signal to a firing phase control part 10 of the next stage. The part 10 transmits a firing signal to respective thyristors thereby conducting the same. On the other hand, an operator 11 calculates the deficient quantity of the detected voltage, and when it exceeds the prescribed value, said operator transmits an alarm signal to a sequence control part 12, which transmits an alarm for the voltage deficiency to the outside by means of a contact signal 13 or the like and performs internal processing such as stopping of a welding machine or the like according to need.