Current distribution of an electric arc at the surface of plasma torch electrodes

Current distributions of the arc foot on the surface of the electrodes in a geometry simulating a plasma torch are reported. Most of the experiments were to determine the arc current distribution at the cathode. The results were obtained using a novel technique and represent experiments using different plasma gases (Ar, He, Ar+0.3% CO, He+0.4% CO, He+0.4% N2, N2, CO) and operating conditions (magnetic field and arc velocity). It is shown that all three, the surface composition due to contamination, the transverse magnetic field used to move the arc, and the arc velocity have a strong influence on the current distribution. Higher erosion rates were found for higher current densities of the arc foot.