THE INVESTIGATION OF SURFACE CHARACTERISTICS AND CONTACT RESISTANCE OF DC RELAY CONTACTS

Examination of the contact morphology, surface composition, and contact resistance of dc relay contacts due to two levels of low current (less than 1 A) arcs has led to the conclusion that a similar contact erosion mechanism and contact resistance degradation exist for 0.5 and 0.75 A with switching resistor load. Material transfer is regarded as the result of ion sputtering during arcing, as well as the degradation of contact resistance determined at different operating cycles, which is suggested to be influenced by both of the contact morphology and surface contamination. A simple model is introduced and used to explain the process of arc erosion and contact resistance degradation during testing.