| 摘要 |
PROBLEM TO BE SOLVED: To reduce a size and a weight to the extent that a power source part is portable by arranging an overcurrent protection circuit to a DC power source circuit, reducing an output current of a DC power source lower than a holding current of a thyrister through short circuiting of a discharge circuit and turning off a thyrister to open a discharge circuit. SOLUTION: A power source part rectifies 100 V AC power source to a DC 84 V and to be charge to a capacitor C of <=22,000μF. When an electric charge of the capacitor C is discharged between a stud 1 and a base material 4 by operating a welding gun 6, by short circuiting of a discharge circuit, a chevlon shaped overcurrent protection circuit is operated, an output voltage is turned to 1.2 V, a terminal power of a thyrister SCR is lowered to 0.2 V by its drooping property and a shunt due to a low impedance of the capacitor C after discharging. A resistance value of the discharge circuit at this time is 2.15 Ω, a calculated current value of the thyrister SCG circuit is about 93 mA, a protection current value is <=159 mA, thus, the thyrister SCG is turned off to open. |
