| 摘要 |
PURPOSE:To pertinently set the current in starting without performing a trial electrification, etc. by fixing the approximate value of the maximum current and power factor angle of a welding machine and by performing the initial electrification at the firing angle which is decided from a thyristor firing angle - relative welding current characteristics. CONSTITUTION:Since the power factor angle of a spot welding machine is generally 50-70 deg. it is given at 60 deg. as the approximate value and the approxi mate value of the maximum current is decided by the shape of the welding machine. For instance, in case of selecting 8KA for the approximate value the relative current to the set current value makes 0.5, so the corresponding firing angle makes about 105 deg. from the thyristor ignition angle - relative welding current characteristics relation chart. And the initial welding cycle electrification is performed at this ignition angle and after the 2nd cycle and on the ignition angle is controlled so as to eliminate the error in the welding current measuring value and set current. Consequently, the current at the starting time can be made optimum without performing a pilot electrification, etc.
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