Vacuum circuit breaker has advantages of low maintenance cost and high reliability. It reaches the priority in aviation field. This paper focuses on the arc modes of intermediate-frequency (400Hz–800Hz) vacuum arc in commercial-type vacuum interrupters with axial magnetic field (AMF) contacts. With high speed photography in conjunction with voltage-current characteristics, three different arc modes can be identified. The arc-mode evolution starts with initial free-expansion of cone-type arc column. Afterwards, the vacuum arc converts into the split constricted arc. The constricted arc is twisted and with a number of cathode spots around it. Meanwhile the constricted arc tends to diffuse and moves towards the periphery of contacts. The arc voltage has a transient peak during the second stage. The arc maintains the diffuse arc after current reaches the peak value. The arc column stops expanding and has a rapid decrease in both arc voltage and light intensity. The initial change rate of arc voltage and the arc voltage at current peak increase with the increasing frequency at a fixed current. It correlates with the increased electrons emitted from cathode at higher current frequency.
展开▼
