| 摘要 |
PROBLEM TO BE SOLVED: To suppress a variation in apparent arc length generated due to nonuniformity in the surface state of an object to be welded, a temp. change of the object to be welded, etc. SOLUTION: An arc voltage set signal Vs equivalent to an arc voltage average value Va corresponding to prescribed arc length and an average welding current signal Iav equivalent to a welding current average value Ia, in which a welding current Iw is detected and smoothed are made as an input and an output voltage constant Vo deciding an output voltage when an inclination signal K of a power source external characteristic and an output current of the power source external characteristic are zero, is calculated. A power source external characteristic arithmetic circuit KC, which outputs an output terminal voltage signal Vt corresponding to Vt=Vo-K×Ia, subtracting a product of the welding current average value Ia and the inclination K from the output voltage constant Vo, is provided. Based on a detected voltage average signal Vav obtained by detecting/smoothing a welding load voltage Vw, and the output terminal voltage signal Vt, a variation of the arc length is suppressed by controlling the welding current Iw of a welding power source PS.
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