A Study of Dynamic Welding of Electrical Contacts with Emphasis on the Effects of Oxide Content for Silver Tin Indium Oxide Contacts

The processes involved with dynamic welding of contacts are discussed and two different welding mechanisms are identified from work using a very sensitive model switch. One mechanism forms weak welds by cold bonding freshly arced surfaces and the other mechanism involves bonds formed by short arc melting of the contact surface. Using the model switch, silver tin indium oxide contacts having different percentages of oxides are studied to compare the dynamic welding properties. The results show a large decrease in weld strength as the oxide level increases from 15% to 22% by volume. The work also shows that, for contact make, contact closing force has a major effect on welding with contact weld strengths increasing as contact force decreases.