Motion of break arcs occurring between silver electrical contacts in DC 42 Volt resistive circuit

Motion of break arcs and current density of arc spots are investigated in a DC 42 Volt resistive circuit for silver electrical contacts. The motion of break arcs is observed with a high-speed camera. The break currents are 7 A, 10 A and 14 A. The opening speed of electrical contacts varied between 10 mm/s and 20 mm/s. The areas of motion of arc spots are obtained as the results of analyzing photographs obtained with the high-speed camera. Then current densities of the cathode and anode spot regions are calculated. The dependence of the gap ds at which the motion of arc spots becomes stable on the break current and the time evolutions of the current densities of the cathode and anode spots are discussed. The gap ds at which the motion of arc spots becomes stable tends to increase with the break current and is almost independent to the opening speed. The current densities of cathode spot region are almost constant just before arc extinction for each break current.