An Experimental Study on Minimum Arc Current for Arcs Longer Than a Few Microseconds in Relay Contacts and Possible Reinterpretation of the Meaning Thereof

A minimum arc current value for each contact material is one of the very important factors in consideration and comparison of arc discharge characteristics for proper selection of contact materials. In this paper, Ag and Ag alloy contacts were operated to break various dc load currents in the range of up to 1.5 A with 10-30 V, and occurrence rates of break arcs (having durations equal to or longer than a few microseconds) were investigated at each condition. As a result, it is confirmed that at the conventional minimum arc current level, break arcs on the order of several tens of microseconds occur at occurrence rate close to 100% when sufficient energy is supplied to contacts upon opening. Thus, careful attention should be paid to when using the term ldquominimum arc currentrdquo in order to avoid misinterpretation.