| 摘要 |
PURPOSE:To control the electric current to be supplied to a work to keep always a constant value through a transformer by adjusting the igniting angle of an anti-parallel thyristor provided on the primary side of a welding transformer in a resistance welding machine and controlling the phase of AC source voltage. CONSTITUTION:An anti-parallel thyristor 4 is connected to the primary side winding 8 of a welding transformer 6, and a closed circuit is constituted of electrodes 14 and 14 and the work to the secondary winding of the transformer 6. In the case igniting of controlling the phase of the voltage of an AC power source 2 by adjusting the igniting angle of the anti-parallel thyrister and flowing constant current to the work via the transformer 6 in performing resistance welding by-pressing the work with the electrodes 14 and 14, and conducting electricity, a firing angle correction value is determined from the ratio between the source voltage during welding and reference source voltage and the function expressed by a load power factor angle phi by the equation[I], and the firing angle is adjusted by this correction value, and the phae of the AC source voltage is controlled, whereby the current value to be conducted is controlled to keep a constant value. |
