Dependence of Motion of Breaking Arc on Contact Separating Speed for Ag and Pd Contact Pairs in a DC42V Resistive Circuit

Abstract

Ag and Pd electrical contact pairs are separated at constant separating speeds (5, 10 and 20mm/s) in a DC 42V/8.4A resistive circuit. The motion of the breaking arc is observed with a high-speed video camera. For Ag contacts, the motion of the breaking arc becomes stable at a certain critical gap at separating speeds of 10 mm/s and 20 mm/s, and the breaking arc moves extensively at the separating speed of 5 mm/s. For Pd contacts, the breaking arc moves extensively regardless of the separating speed. These results are attributed to the following causes. For Ag contacts, the difference in the motion of arc spots at each separating speed is changed by the difference in the total energy input to the contacts. For Pd contacts, the temperature of the contact surfaces is kept high because of the lower thermal conductivity of Pd than Ag.