Physical processes at opening contacts

A recent paper investigated causes of high current arc immobility at opening contacts in air. It is shown that the main causes of immobility are small breaker opening speed and inertia of arc concerned with the presence of contact material vapors, metal droplets and plasma jets. Influence of external magnetic field on high current arc mobility in narrow interelectrode gap is analyzed. In this case it is found that the time of arc immobility may be decreased to 130 /spl mu/s at current equal to 2 kA.