Test results of different silver/graphite contact materials in regard to applications in circuit breakers

Different types of silver/graphite contact materials, all of them produced by extrusion, were tested by means of a model switch in order to get basic information on welding resistance and contact erosion. The results are compared with those obtained from tests in circuits breakers, focusing especially on the behaviour of standard silver/graphite materials on the one hand and a new type of silver/graphite based on graphite fibres on the other. It was found that the new silver/graphite material in a symmetric combination is markedly superior to conventional silver/graphite combinations with regard to contact erosion, welding resistance and overtemperature behaviour.