Full digital control strategy for soft-switching gas metal arc welding machine

In this paper, a fully digitalized phase-shifted full-bridge control strategy based on symmetrical carrier is proposed. To extend the ZVS soft switching range for lagging leg, a saturable inductor is series-connected with primary winding of the transformer. Based on gas metal arc welding(GMAW) process, a novel full digital waveform control scheme is analyzed. Open loop current suppression is made to reduce spatter generation at the instance of short-circuit occurrence. A triple closed loop control model with full digital control based on instantaneous voltage and current feedback control is established. The control model also contains real time energy compensation technique for arc state. Flexibility and reliability of the proposed full digital soft switching control strategy is validated by experimental results of 20 kW welding machine. The experimental result also show that the proposed waveform control scheme is applicable for all output range and the welding process is stable and the welding bead is good with the proposed control scheme.