A THEORETICAL AND EXPERIMENTAL INVESTIGATION OF COPPER ELECTRODE EROSION IN ELECTRIC-ARC HEATERS .2. THE EXPERIMENTAL-DETERMINATION OF ARC-SPOT PARAMETERS

Two important copper electrode parameters, namely, the volt-equivalent of the are spot heat flux and the are spot effective current density have been measured experimentally in magnetically driven arcs in air. The measurements were performed for currents in the range 0.025-1 kA, magnetic field strengths 0.133-0.95 T and air pressures 1-40 atm. The volt-equivalent of the are spot heat flux is proposed to account far t he total heat flux entering the electrode surface through the are spot , An unsteady thermal method was applied in the measurements. To obtai n the effective current density, the thermophysical experiment was com bined with the application of equations of the erosion model presented in a previous companion paper. We show that the volt-equivalent of th e cathode are spot heat flux increases with increasing magnetic field. The sum of the cathode and the anode voltage drops is shown to be app roximately equal to the sum of the corresponding volt-equivalents of t he are spot heat fluxes. Good agreement with the measurements of other authors is obtained. In particular, the effective are spot current de nsity allows one to confirm the thermophysical model for the erosion o f copper electrodes indirectly.