Stud welding apparatus

Abstract

According to the present invention, the inputs of the pilot power supply and the welding arc power supply are connected to a common terminal and there is provided the switching means to selectively switch the operations of the pilot power supply and the welding arc power supply with the switching means switching the power supplies to activate the pilot power supply when a pilot arc should be produced. Thus, the power supply system requires only one secondary winding in the transformer, and the single secondary winding is sufficient to make it possible to use a small and low-priced transformer. This results in reduction in the size as well as the cost of the power supply system. In addition, since the switching means can be composed of the rectifying thyristors connected to the A.C. input port and the relay contacts connected to the rear stage from the thyristor stage, so that the relay contacts select the operations of the pilot power supply and the welding arc power supply and, the thyristors determine the ON-OFF state of the electric current flowing to each of the power supplies. Thus, it is possible for the pilot power supply and the welding arc power supply to use the rectifying thyristors and the circuit concerned in common so as to simplify the circuit of the power supply and to reduce its price.

Dependencies are inferred from the claim text.