Guidelines for the use of Ag/SnO2 contact materials in switching devices for low-voltage power engineering

A detailed account is given of the performance of Ag/SnO₂ contact materials in a large number of switching devices for a wide variety of applications. Contactors of various sizes and design principles, as well as power relays for use in AC and DC circuits, are considered. The differences in switching behavior observed are interpreted with the aid of metallurgical model concepts for the interaction of the switching arc with the contact material. On the basis of the metallurgical considerations given and the application experience discussed, it becomes possible to derive a practical guide for the use of Ag/SnO₂ materials in switching devices. The results of this process are shown in a generalized schematic presentation of fields of applicability for Ag/SnO₂ materials. Once the important parameters for each application are defined, this schematic can be used to find the variety of Ag/SnO₂ contact material that can be expected to yield the appropriate switching performance