Experimental study on electrical property of arc column in plasma arc welding

Electrical property is a key factor to determine performance and characteristic of welding arc. In this study, the electrical property distribution of welding plasma arc was investigated by means of a novel dual active probes method. Experiments were conducted with different positions and polarities of two active probes in plasma arc column, to address the distribution of electrical conductivity in arc column and the effect of detection current direction in both radius and axis. The trend of radial electrical conductivity in different cross section of arc column could be got via calculating the V-I ratio. When the probe tips are symmetric about the center of the arc column, the gradient of the arc electrical conductivity in radial is greater than that in axial. When the probe tips are asymmetric about the center of the arc column in the same arc cross section, the V-I ratio get from the situation that the negative probe far from arc center is larger than that as negative probe closer to arc center. When the different polarity probes moved in axis direction, the negative pole effect and the arc voltage fall both act on the V-I ratio of axis direction, to make it appear contradictory trends. Such a study is significant in helping to develop and optimize novel plasma arc heat source such as cross arc and coupling arc.