Volumetric erosion measurements of contacts tested in DC automotive relays

A new tool for measurement of contact arc erosion offers better means for improvement in relay and switch design. This paper presents an experimental study on the erosion of relay contacts tested in commercial devices under representative load conditions. The erosion measurement of relay contacts has been shown to be difficult since the standard method based on a mass change cannot be easily used in this type of device. The reason for this is that the contacts cannot be separated from the contact support. In the past, SEM studies have been used for rough estimates of erosion. More recently, noncontact laser measurement systems have been developed and used in this application for measurement of the volumetric erosion. In this study, using the method of “design of experiments,” a number of variables have been investigated, which include electrical current levels, material composition, and contact switching life. The objective of the study is to determine the volumetric erosion of contacts in actual automotive relays tested under a range of conditions. The study shows this technique offers a useful method for studying and improving both material and device design