Arc welding circuit for welding thin metal pieces

An arc welding circuit for controlling current supplied to a welding electrode for welding thin metal pieces, said welding electrode being connected to a first terminal of a secondary winding of a power supply transformer through a coupling means having a capacitance circuit to supply a low voltage and high short circuit current when said electrode is placed in contact with said thin metal piece to be welded, switching means for shorting said capacitance circuit, sensing means for sensing said high short circuit current flowing through said metal piece and to produce a resultant voltage signal, circuit means to compare said resultant voltage signal with a reference voltage value to identify said high short circuit current and to produce a triggering signal to activate said switching means to short said capacitance circuit to supply a high voltage and high current to said welding electrode to initiate an arc while substantially simultaneously an open contact high voltage welding gap is established between said electrode and said metal piece by spacing said electrode therefrom, timing circuit means to cut off said triggering signal after a predetermined time constant to reconnect said capacitance circuit to said welding electrode said capacitance circuit maintaining a steady low arc current between said welding electrode and said metal piece after said arc initiating.