Influence of metal vapor on post-arc breakdown for intermediate frequency vacuum arc

The density of metal vapor is considered to be an important factor affecting the post-arc breakdown of vacuum arc. Especially in the case of intermediate frequency, for the anode spots are not significant according to experiment and the half-wave time of current is shortened, a large number of metal droplets produced by the contacts will be an important source of metal vapor. In this paper, it is found through experiment and simulation that the life of metal droplet is 1.6–2.8 ms, and the factors which determine the life are droplet radius, moving velocity and size of arc chamber. The distribution of metal vapors decreases outward from the center of droplet. The vapor density near a single droplet can reach 2.2 × 10¹⁹ m⁻³, and more than 80% of the vapors are distributed within 10 times radius near the droplets. The metal vapor reduces the dielectric recovery strength. When the number of metal droplets reaches more than 100, the breakdown voltage is close to 100 V.