Comparison of Transfer and Erosion Shapes on Ag and AgSnO2 Contacts Caused by Break Arc Discharges in a DC Inductive Load Circuit

An evaluation system enabling observation and evaluation of changes on contact surface morphologies (growth of a crater and/or a pip) caused by arc discharges during switching operations has been constructed, in which evaluation of a movable cathode surface profile by way of an optical cross-section method, as well as observation of the counterpart stationary anode surface by means of a CCD camera, can be realized. In this paper, Ag contact pairs and AgSnO2 contact pairs were operated to break a DC14V-2A or 3A load current in an inductive circuit, and changes in the contact surfaces during the switching operations were observed and evaluated. Visual observation of temporal changes in the cathode surface conditions (a crater growth process) during switching operations were tried by drawing three-dimensional images of the movable cathode samples based on profile data obtained from the optical cross-section method.