Effect of Contact Materials of Ag/SnO₂ and Ag/ZnO on Rotational Motion of Break Arcs Driven by Radial Magnetic Field

抄録

Break arcs are generated between electrical contacts in a DC 42V resistive circuit. Contact materials are Ag/SnO₂ and Ag/ZnO. Circuit current when contacts are closed is varied from 5A to 21A. The radial magnetic field to drive break arcs is formed between the contact gap with a permanent magnet embedded in the cathode. The arc motion is observed with a high-speed camera. Experimental results with the magnet are compared with those without the magnet. Following results are shown. Similar experimental results to pure silver contacts are obtained for Ag/SnO₂ and Ag/ZnO contact pairs. The rotational motion of the break arcs and the shortening effect of the arc duration are confirmed. The ring-shaped, wide and uniform traces are observed on the contact surfaces after break operations. This result shows the prevention effect of local erosion of electrical contacts and the reduction of total amount of contact erosion. The rotational frequency f is increased with the increase of the arc current I_arc. These results for Ag/SnO₂ and Ag/ZnO contact pairs are similar to the results for pure silver contacts in our previous experiments. The rotational frequency of the break arc for the Ag/SnO₂ and Ag/ZnO contacts is lower than that for the pure silver contacts.