Observations of peculiar break arc motion of AgSnO2 contacts under applied external magnetic field in inductive DC load conditions up to 20V-17A

When AgSnO2 contacts were operated to break an inductive DC load circuit up to 20V-17A with contact opening speeds in the range from 1mm/s to 200mm/s under an applied external magnetic field of about B=120mT, apparent magnetic blowing phenomenon was not likely to be observed in the cases with slower opening speeds and smaller current levels. Even in such cases, break arc durations were slightly reduced. Observations of such non-blown-out arcs revealed that the arcs in those cases were likely to finally extinguish after moving in the direction opposite to the applied Lorentz force direction. When the direction of the applied magnetic field was reversed, the resultant non-blown-out break arcs extinguished also after moving in the direction opposite to the reversed Lorentz force direction, and confirmed not to be caused by gravity. In this paper, the magnet was disposed so that the Lorentz force was to be applied horizontally. The resultant non-blown-out arcs extinguished after moving in the direction opposite to the horizontal Lorentz force direction. Such peculiar arc behavior were repeatedly observed.