Application of a New Ag/SnO2 contact material in AC-contactors

This paper reports about the physical and application properties of a new silver/tin oxide contact material with 14 wt. % oxides. The investigations presented comprise tests carried out in several types of commercially available contactors under conditions representing utilization category AC3 (250 kW (380-400V) and 400 kW (380-400V)) as well as AC4 (75 kW (380- 400V)). The focus of these tests is on electrical service life and over temperature behavior. Reference material is a conventional commercially used silver/tin oxide contact material containing 14 wt. % oxides (standard material). While AC3 and AC4 service life results show a certain increase the resistance against welding under short circuit conditions is substantially improved. These improvements in switching performance observed are discussed on the basis of physical and metallurgical processes caused by the switching arc in the contact material.