The peak of resonance current during commutation greatly influences the safety of commutation component in variable polarity plasma arc welding (VPPAW). It is necessary to study measure to restrain the current peak. Phenomenon of arc resonance current is studied by experiments. Analysis shows that the arc resistance is time variable. Model of commutation circuit is set up and simulated. Results indicate that adjusting damp ratio of system is valid to restrain peak of resonance current. Then a new commutation strategy is presented based on variable structure control method. The commutation circuit is redesigned to apply new commutation strategy. Experimental result shows that the peak of resonance current is restrained while commutation speed unchanged. This paper is instructive to design high power supply of VPPAW.
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