Experimental investigation of vacuum arc characteristics of four kinds of AMF Contacts

Axial magnetic field (AMF) contacts are widely used in vacuum interrupters. In this paper, the magnetic field distribution of 1/2 coil-type contact, 2/3 coil-type contact, 1/3 coil-type contact and cup-type contact are calculated and analyzed. It is found that the AMF strength of coil-type contacts is much greater than that of cup-type contact. The order of residual AMF from weak to strong is: cup-type contact, 1/3 coil-type contact, 1/2 coil-type contact and 2/3 coil-type contact. The order of phase shift from small to large is: 1/3 coil-type contact, 2/3 coil-type contact, 1/2 coil-type contact and cup-type contact. Triggered vacuum arc experiments about these contacts are carried out and the vacuum arc evolution process is recorded by high-speed camera. It is found that, under the same current, the arc constriction of the cup-type contact is the most serious and the arc of 2/3 coil-type contact has almost no constriction.