Characteristics of arc in variable polarity plasma arc welding of aluminum alloy

A double invert variable polarity plasma arc（VPPA） power source based on 16-bit MCU applied for aluminum alloys was developed. Mechanics,electrical and the produced heat mechanism of VPPAW arc were tested and analyzed. Results indicate that during the VPPA welding procedure of aluminum alloy,the arc of electrode negative（EN） has more effect on force,whereas the arc of electrode positive（EP） has more effect on heat. It should be noted that keeping the balance of the force and heat is the critical element of VPPAW. This power source had been successfully used to weld aluminum alloy with a 15 mm thickness in vertical welding. The conclusions are applicable to the variable polarity plasma arc welding technique used in the aerospace industry.