Inverter type spot resistance welding machine

摘要

PURPOSE:To supply a high electric current by making a base drive circuit to operate continuously a semiconductor device by a switching current value more than a rated current value and the semiconductor device into noncontinuity forcibly when these are made in a continued state for more than the prescribed time. CONSTITUTION:The subject inverter type welding machine is provided with an inverter part 24 which allows the semiconductor device 36a, etc., to execute switching operation to converts DC into AC. The welding machine is provided with the base drive circuit 30 to operate continuously the semiconductor device by the switching current value more than the rated current value and a timer circuit 40 to measure the continuity time of the semiconductor device. The semiconductor device can be used continuously by the current more than the rated current and the high current can be supplied to materials to be welded by monitoring the time when the semiconductor device to constitute the inverter circuit 24 is in the continued state. By this method, the semiconductor device to constitute an inverter is used in the switching rated region and the high current of several times as compared with the continuous use by the rated value can be supplied.