POWER SOURCE DEVICE FOR WELDING MACHINE

摘要

PURPOSE:To reduce size of a power source device by connecting the 2nd reverse blocking semiconductor switch in series to the circuit of the 1st reverse blocking semiconductor switch and preventing the transient phenomenon in the first half cycle of welding current. CONSTITUTION:The 1st and 2nd reverse blocking semiconductor switches 30, 28, a series reactor 32 and a phase advance capacitor 34 are connected in series to an AC power source 24. A transformer 36 for a welding machine is connected in parallel to the series circuit of the switch 30. The switch 28 is fired by the pulse formed by a control part 38 and the switch 30 is fired by another pulse formed by the part 38. The pulse for the switch 30 rises in the position where the phase position advances from the phase position of the pulse for the switch 28 to prevent the transient phenomenon in the first half cycle of the welding machine current. The power source device is made smaller in size and more inexpensive by the above-mentioned device.