| 摘要 |
PURPOSE:To control to accuratly, speedily set effective value even when power source and load fluctuate by calculating effective value of current that flows in a circuit which connects a power source circuit to a welding gun through an inverter, comparing it with set value and controlling the inverter. CONSTITUTION:When the inverter 5 operates and welding current is supplied from the power source circuit 1 to the welding gun 8, the current is detected by a detector 9, and made to voltage of waveform corresponding to effective value of the current by an arithmetic circuit 10. The voltage is compared with voltage corresponding to effective value of current value set by a current setting device 14 by a comparator 17, and when the two coincide, a signal of low level is outputted from the comparator 17. The signal controls a pulse width control circuit 21, rises up synchronously with output pulse of an oscillator 22. Pulse current that was flowing in transistors 51, 52 or 53, 54 is cut off by lowering of output of the circuit 21. Thus, the purpose can be achieved. |
