Abstract
A quantitative investigation on the relationship between arc duration and resistance in Ag contact in air were made by using a contact driving machine to open the contact at low speed (below 1 mm/s), and measured data were analized statistically. The two types of arc (metallic phase arc: short arc, and metallic phase plus gaseous phase arc: long arc) appeared at low opening speed and the type of an arcing has the correlation with the contact resistance. The contact resistance was high after generating long arc, while low after short arc. Characteristics of arc duration was that both of long arc and short arc appeared in period 1, and only short arc appeared concentratedly in period 2, and these states repeated reciprocally. A clear correlation existed between variations of arc duration and resistance
