Matsushita Electric Industrial Co., Ltd.

Hidetoshi Ooyama

Seigo Hagiwara

Akihiko Kitajima

An arc welding machine includes a transformer a diode for rectification connected to the secondary winding of the transformer, two capacitors connected in series with each other and in parallel with the diode, and the first and second switching elements connected in series with each other and in parallel with the diode. This machine also includes an electrode having one end connected at a location intermediately of the two switching elements and the other end opposed to an object to be welded, first and second drive circuits connected to the first and second switching elements, respectively, an oscillating circuit for determining the width of pulses of the first and second drive circuits, and a timer circuit for inputting to the oscillating circuit signals required to make the oscillating circuit periodically repeat oscillating and stop operations. The object is connected at a location intermediately of the two capacitors. The second drive circuit outputs inverted signals of the first drive circuit. By this construction, an alternating current and a direct current alternately flow between the electrode and the object during welding.

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Kawanishi, Japan

Hidetoshi Ooyama