The evolution of contact erosion during an opening operation at 42V

Detailed arc erosion studies are conducted on AgSnO₂ contact materials for an opening operation at 42V and 24A. A novel experimental arrangement is developed to terminate the arc current at predetermined voltage levels as the arc is drawn between contacts opening at a constant velocity. Contact samples are studied terminating the arc current at fifteen different points as the arc is drawn between the contacts. Surface profiling of samples is conducted determining the extent of erosion at different points into the drawn arc. Spectral analysis is also conducted on the arc and related to the erosion. The results show that different features occur at particular stages as the arc is drawn. In the initial stages, the erosion data indicate that the arc root is small and immobile on both anode and cathode. Material movement is mainly anode to cathode. The spectral analysis indicates that Sn and O species dominate the arc followed by the Ag species. In the later stages, the anode has a significantly larger eroded area than the cathode. The erosion data indicate multiple arc roots. The spectral analysis indicates that Ag and N species dominate. Mechanisms of erosion are discussed and related to these species.