Experimental research on factors influencing the current commutation process of variable-polarity arc welding

In the current inversion process of variable-polarity arc welding of aluminum alloy, drastic changes in electron and ion concentrations in arc space may lead to the failure of current commutation and arc reignition, thus affecting the arc burning stability and weld formation quality. The novel reverse arc reignition voltage-generating circuit will produce a stable reverse voltage during the current polarity inversion process. In this circuit, the value of the reverse voltage remains unchanged with the variation in the base welding current, and thus can better meet the requirement of reverse arc reignition voltage for current inversion. Through the use of the variablepolarity welding power supply with novel reverse arc reignition voltage-generating circuit as the experimental platform, the influence of the power equipment and its control parameters, the parasitic inductance of the cable in the output welding loop, and the welding process parameters on the current commutation process of variable-polarity arc welding was investigated. The experimental results show that increasing the value of the reverse arc reignition voltage can increase the current variation rate in the polarity inversion process. Contrastingly, a large parasitic inductance of the cable in the output welding loop will reduce the current variation rate and the current value at the end of the polarity inversion process, which is detrimental by the reliable arc reignition and stable arc burning in the polarity inversion process. The lower the initial welding current is, the lower the current value at the end of the polarity inversion process. Increasing the common conduction time can increase the current value at the end of the polarity inversion process, but decrease the current value at the beginning of this process. Therefore, to improve the arc stability in the polarity inversion process, a large value of the reverse arc reignition voltage and an appropriate increase in common conduction time can be used in low-current variable-polarity welding. All of the conclusions previously presented can provide reference and basis for the selection and adjustmentof the power equipment and its control parameters for variable-polarity arc welding under various process parameters.