Internal Voltage Gradient and Behavior of Column on Long Gap DC Free Arc

Abstract

The internal voltage gradient and behavior of column on long gap DC free arcs were analyzed quantitatively. In the analysis, an image processing technique developed by us was applied to the images shot from two orthogonal views by two high-speed video cameras to estimate the three dimensional arc column paths. Objective free arcs were ignited between the rod electrodes with the current in the range of 100 to 2000A and the gap in the range of 1.6 to 3.2m. In addition, some of objective free arcs were placed in the external magnetic field brought about by a large coil. As a result, macroscopic changes with time in terms of the arc voltage gradient along the column path, the ratio of the arc column length to the gap length and the distance from the center axis between the electrodes to the furthest point were derived. All average characteristics were shown as the experimental equations. In addition, the effect of the external magnetic field on the macroscopic velocity of the expansion was studied.