| 摘要 |
PROBLEM TO BE SOLVED: To perform welding at high quality by forming an electrical resonance circuit with a welded material which is composed of a magnetic material and arranged between electrodes for resistance welding, and a capacitor pallely connected between the electrodes, by detecting variation magnetic distribution of the welded material accompanied with nugget generation as variation of resonance frequency of the electrical resonance circuit, and by feedback controlling welding conditions based on variation of the resonance frequency. SOLUTION: Capacitors 9 are parallely connected between electrodes 7 for resistance welding to form a resonance circuit. The resonance frequency of resonance circuit varies corresponding to variation of the magnetic permeability distribution of the welded material accompanied with nugget generation. A frequency/voltage converting part 2 supplies frequency voltage Vn corresponding to the resonance frequency to a comparison computing part 4. In the comparison computing part 4, the frequency voltage and the preset target reference voltage showing completion of welding are compared to output a welding current command value In*, so that the welding current supplied to a welding part of a welded material 8 from a welding power supply 6 via a welding power control part 5 is feedback controlled.
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