Arc spot weld control and power supply

Claim 1

In combination with a torch for creating an arc for spot welding, a system for providing high energy pulses of one polarity to said torch comprising a source of alternating voltage of three phases, means for rectifying said voltages to produce DC voltages of three phases, a pulse forming circuit for producing pulse signals, a plurality of normally non-conducting silicon controlled rectifiers electrically connected in a path between said torch and said source of power, said path being substantially free of inductive reactance elements, means for applying said rectified DC voltages to said silicon controlled rectifiers, a normally open switch, a timing circuit for producing electrical signals for selectively closing said switch for predetermined time periods, means for applying said pulse signals through said switch to cause said silicon controlled rectifiers to become conductive to permit high energy pulses to be applied to said torch to produce arcing current across said torch when any of said three DC voltages exceed a predetermined level.