Investigation of arc ignition modes for drawn vacuum arc with axial magnetic field (AMF)

In a drawn vacuum arc, the arc column would form just after the rupture of the molten metal bridge. The initial arc would have a significant influence on the subsequent arcing process. In this paper, arc ignition modes for drawn vacuum arc were investigated experimentally by using a demountable vacuum chamber with peak currents up to 25kA. Axial Magnetic Field (AMF) was studied and compared with our previous research for Transverse Magnetic Field (TMF) contacts. By using a high-speed charge-coupled device (CCD) video camera, multiple-point arc ignition (MPAI) mode was observed for arc with AMF contacts. The relationship between arc ignition mode and the initial arc transition stage was studied, and the influence of arc ignition modes on the following arcing process was also investigated. It was found that the impact of arc ignition modes was more obvious for arc with TMF contacts, which would affect the arc rotation to some degree. For arc with AMF contacts, the arc ignition mode would mainly affect the initial arc expansion process.