Comparison of the switching behavior of internally oxidized and powder metallurgical silver metal oxide contact materials

The switching behavior of powder metallurgical and internally oxidized silver tin oxide based and silver cadmium oxide based contact materials was compared. Computer supported analysis of contact performance (contact weld force, changes in electrical resistance and temperature) coupled with an analysis of the impact of electrical switching on physical characteristics (resistance to contact erosion, degradation of contact surface) was examined. Internally oxidized materials exhibited superior erosion resistance while powder metallurgical materials were slightly better regarding weld resistance. Both manufacturing methods produced materials with comparable electrical resistance and temperature performance. Silver cadmium oxide compositions tended to perform better with respect to electrical resistance and temperature while silver tin oxide based materials had slightly improved erosion and weld resistance. However, the relative oxide level and manufacturing method had the dominant influence on contact performance. The results indicate that consideration to both the manufacturing method as well as the composition should be given when choosing an electrical contact material.