Influences of contact opening speeds on break arc behaviors of Ag and AgSnO2 contacts in DC load circuits

In order to study influences of contact opening speeds on break arc behaviors of Ag and AgSnO₂ contacts in air, break operations of a DC inductive (L=20mH) current up to several amps at 14V were conducted with several different contact opening speeds in the range from 0.5 mm/s to 20 mm/s in a switching mechanism in the uncontrolled laboratory atmosphere. Durations of break arc discharges were measured, and the average break arc duration at each load current level was determined under the respective contact opening speeds. The results show that average break arc durations for Ag contacts were not influenced by contact opening speeds, while those for AgSnO₂ became slightly shorter with increases in opening speeds from 0.5 to 5 mm/s, especially at larger load current levels. When arc extinction gap lengths were calculated, however, by multiplying average break arc duration values and contact opening speed values, arc extinction gaps became larger with increases in the contact opening speeds for both Ag and AgSnO₂ contacts.