Three-dimensional observation and comparison of damage shapes on ag and AgSnO2 contact surfaces caused by break operations in DC inductive load currents

Observation and evaluation of damage growth on contact surfaces caused by arc discharges are important for realizing better understandings of contact phenomena. For that purposes, an experimental system enabling observation and evaluation of growth processes of a crater or a pip (damage shapes) during switching operations has been constructed. Up to now, 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 with a CCD camera, has been realized. For the cathode surfaces, further investigations of temporal changes in their surface conditions (a crater growth process) during the switching operations were also available by drawing three-dimensional images of the cathode samples based on data obtained with the optical cross-section method. 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 damage shapes on their contact surfaces were three-dimensionally evaluated and compared with each other by above evaluation schemes as well as measurements of numerical data based on microscope evaluation. Clear differences of damage growth processes between these two materials during the switching operations were numerically observed.