| 摘要 |
PURPOSE:To reduce the capacity of a start discharge capacitor and a charge and discharge element, and to make a device inexpensive by placing in parallel a capacitor and the second diode, and in series the first diode and an anti- parallel thyristor, between an electrode and a base material, between which a current smoothing reactor is interposed. CONSTITUTION:Between circuits 12a, 12b provided between an electrode 1 and a base material 2, having a means 38 for controlling the circuit between the electrode 1 and the base material 2, within a range of correct voltage and current, a capacitor 40 and the first diode 41 are arranged in series. The second diode 42 is arranged in parallel to the capacitor 40, and a thyristor 44 being a variable impedance element is arranged in an anti-parallel relation to the first diode 41. At the time of a voltage Va and a current LW exceeding a reference voltage VS and a current LS, a main switch 16 is turned on by operating the thyristor 44 by a welding start switch ST, and a good arc start is executed irrespective of whether a temperature of base material 2 is high or low. As for the capacitor 40 and the thyristor 44, the capacity is made small and a device becomes inexpensive. |
