Single power source arc welding apparatus

Claim 1

A pulse arc welding apparatus, comprising: (a) a D.C. voltage source (1), (b) switching means (2) for coupling said source to a welding unit (13), (c) a current detector (4) for detecting welding current supplied by said source, and (d) a control unit (30) comprising an adjustable peak current upper limiter (7), an adjustable peak current lower limiter (8), an adjustable base current upper limiter (21), an adjustable base current lower limiter (22), and a control circuit (20) for generating signals for controlling said switching means to alternately supply peak current and base current pulses to said welding unit, said control circuit comprising a first base current comparator (33) and a second peak current comparator (32), means coupling said current detector output to a first input of each comparator, means coupling outputs of said base current upper and lower limiters to a second input of said first comparator, and means coupling outputs of said peak current upper and lower limiters to a second input of said second comparator, whereby each peak current pulse of the resultant welding current cyclically varies between amplitude levels established by said peak current upper and lower limiters, and each base current pulse similarly varies between amplitude levels established by said base current upper and lower limiters.