| 摘要 |
PROBLEM TO BE SOLVED: To suppress generation of expulsion by conducting an auxiliary thyristor connected to a welding transformer in parallel at an arbitrary time when a main thyristor is energized to rapidly lower the welding current. SOLUTION: A part of the welding current is split by giving the synchronizing signal from a welding timer to a part of an additional control unit to ignite a thyristor in the additional control unit. The lowering ratio of the current is determined by the magnitude of the additional resistance. In place of the addition of the additional control unit, a main energization element of a part of an original current control unit is shut off using a GTO, i.e., a Gate Turn-Off thyristor or an IGBT, to lower the welding current. In this case, an additional circuit is unnecessary since the welding current is shut off by closing a main circuit by the main energization element. Fluctuation of an AC spot welding machine can be suppressed through the combination with an expulsion generation detecting device which is operable in the real time basis.
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