| 摘要 |
PURPOSE:To control the electric currents flowing in the electrodes of individual welding machines with good accuracy and to form the weld zones having high quality, by mounting a voltage detector to a firing pulse control device provided on the primary side of power source transformers for plural resistance welding machines and calculating the excitation currents of the transformers from the detected value of the primary voltage of the transformers. CONSTITUTION:A firing pulse control device 17 is provided on the primary side of transformers 14a-14d for resistance welding to control the firing phase angle of the AC power to be supplied to a thyristor converter 16 and to control the welding currents 13a-13d supplied from the secondary side of the transformers for resistance welding to welding materials 11a-11d. A current setting section which sets the welding currents, a feedback circuit for the welding currents, a detector 20 for the primary voltage to be applied to the transformers, a calculation section which calculates excitation current from the detected voltage and a calculation section for the firing phase angle of the thyristor are provided to add the calculated excitation current value to the set current value to provide a set reference and to control the firing phase angle of the thyristor converter in accordance with such reference, whereby the welding currents are adequately controlled. |
