Constant current welding power supply with an upslope starting current

Claim 1

A constant current SCR welding power supply in which current is supplied through SCR rectifier means to a welding load including an electrode to workpiece comprising: a transformer having a primary winding adapted to be connected to a source of AC line voltage and a first and second secondary winding; first DC power supply output means for providing across said welding load a high open circuit voltage at relatively low current, said first DC power output means including a first bridge rectifier having first SCR circuit means connected to said first secondary winding and first firing means for energizing said first SCR circuit means during each cycle of applied line voltage; second DC power output means for providing an arc working voltage across said output welding load, said second DC power output means including a second bridge rectifier having second SCR circuit means connected to said second secondary winding of said transformer and second firing means for energizing said second SCR circuit means in synchronism with each cycle of applied line voltage; constant current control means for controlling said second firing means so as to maintain a constant welding current; detection means responsive to the presence of an arc across the welding load for disabling said second DC power supply output means until said arc is detected; slope control means responsive to said detection means for applying a varying input signal to said constant current control means such that the current supplied by said second DC power output means is controllably increased from the detection of said arc at a predetermined rate until a predetermined level is reached; and time delay means responsive to said detection means for disabling said first DC power supply output means after a predetermined time period following detection of an arc.