Polarity effect of unsymmetrical material combination on the arc erosion and contact resistance behaviour

The arc duration, material transfer, contact morphology, surface composition, and contact resistance of dissimilar contact combinations of palladium and silver were experimentally examined with breaking inductive load from 0.5 A to 4.0 A for 6/spl times/10/sup 4/ times of operations in air at atmospheric pressure. The test results have led to the conclusion that the polarity significantly affects the arc erosion and electrical contact resistance behaviours. By comparing with the previous results, it is known that the cathode material plays a main role in arc erosion, such as mass transfer, arc duration, and erosion pattern. The contact resistance is, however, dominated by the anode material due to surface contamination, especially the anode oxidation in late gaseous phase. Also, evidence is found in this work that the material transfer between two electrodes greatly influences the arc erosion and contact resistance behaviours.