| 摘要 |
PURPOSE:To make a firing phase control circuit into one circuit and improve maintainability and stability by detecting the positive and negative periods of an AC source voltage for arc welding, and controlling the firing phase of control rectifying devices to a prescribed value with respect to the positive and negative periods. CONSTITUTION:A detecting circuit 14 for the positive and negative periods of an AC source voltage is provided, and the phase of the output pulse from a generating circuit 15 for a phase control signal is controlled in accordance with the detection signal from the circuit 14 to regulate an unbalance ratio. A distributing circuit 16 which distributes the firing signal to control rectifying devices which control the respective half waves of the AC source voltage in accordance with the positive and negative periods of said voltage is provided and the circuit 15 is made into one circuit. There is thus no need for unifying the characteristics of two firing phase control circuits and the generation of an unbalance owing to the deterioration with age is obviated. |
