| 摘要 |
PURPOSE:To increase a monitor accuracy and to reduce cost by providing the means to calculate the resistance mean value of secondary conductor and by comparing the set level with the mean value. CONSTITUTION:A spot welding gun 3 is connected via the secondary cable 5 of the positive and negative in a pair to the secondary side of a welding transformer 2. The resistance value of the secondary cable is found via division means 10 from the secondary side voltage and current values detected respectively by voltage detecting circuit 7 and current detecting circuit 6. The resistance mean value during the welding time is then found by mean value arithmetic means 11, also the comparison of the set value of a setter 13 and the output of the arithmetic means 11 is performed. In case of the arithmetic value being larger than the set value or reaching the prescribed number of times an alarm is outputted via counter means 15. The monitor accuracy of the secondary conductor is increased and the device cost is reduced as well with this method.
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