Influences of external magnetic field application and increased contact opening speeds on break arc duration characteristics of AgSnO2 contacts in DC inductive load conditions

Break operations of AgSnO2 contact pairs were conducted in a DC inductive (L=5.7mH) load circuit with 2A, 6A and 11A at 14 V under different contact opening speeds from 10 to 200 mm/s and with/without external magnetic field application of about 150 mT in air. Break arc voltage waveforms were observed, and total break arc durations and metallic phase durations were determined based on the observed arc voltage waveforms. After the experiments, averages for the total arc durations as well as the metallic phase and gaseous phase (when observed) durations were calculated at each condition. At 11A and 6A, faster contact opening speeds mainly caused metallic phase durations to be shortened, while the external magnetic field leaded to shorter gaseous phases. At 2A, the external magnetic field possibly leads to rapid transition into gaseous phase, resulting in slight shortenings of the total break arc durations.