Arc erosion of AgSnO2 electrical contacts at different stages of a break operation

Arc erosion studies are conducted on AgSnO2 contact materials at different stages in the break operation. A resistive load arrangement is
used with up to 42 V DC at 24 A and a constant contact opening velocity. The arc current is terminated at different stages as the arc is drawn
between the contacts enabling a study of the arcing phenomena up to that point. Surface profiling of the contacts is conducted to determine
the extent of erosion at the different stages as the arc is drawn. Spectral analysis is also conducted on the arc and then related to the extent of
erosion. The results show that particular features occur at different stages as the arc is drawn. As the arc is initially established, it goes
through an “Arc Generation” regime where the arc roots are small and immobile on both the anode and the cathode. Material transfer occurs
mainly from anode to cathode. The spectral analysis indicates that Sn and O species dominate the arc followed by the Ag species. As the arc
is drawn further and enters the “Arc Degeneration” regime, the anode undergoes significantly larger erosion than the cathode. Also, both
contacts indicate that multiple arc roots have formed, which are highly mobile in the later stages of the discharge. The spectral analysis indicates
that Ag and N species are in high concentrations compared to other species. The mechanisms of erosion and deposition are discussed in
relation to the species within the arc discharge. For the complete break operation, it is found that the anode undergoes major erosion, and it is
thought that the gaseous ions species do not dominate the arc under these conditions of short arcs and voltage <42 V to cause cathode erosion.