Dynamic Arc Current Distribution of Parallel Vacuum Arcs Subjected to Bipolar Axial Magnetic Field

The objective of this paper is to determine dynamic anode and cathode arc current distribution of parallel vacuum arcs subjected to bipolar axial magnetic field. Drawn arc experiments were carried out in a demountable vacuum chamber. A split bipolar axial magnetic field electrode with diameter of 100 mm was specially designed. Arc current of two half split electrode discs were measured through Rogowski coils out of the vacuum chamber. Experimental current ranged from 4.5 to 45.0 kA. Vacuum arc behaviors were recorded by a high-speed camera. Unbalance phenomena of anode current and cathode current of parallel vacuum arcs were observed. The maximum average anode and cathode current density difference between parallel vacuum arcs at current of 45.0 kA were 2.57 and 2.52 A/mm
²
, respectively. Critical value of both anode and cathode current difference ratio at time instant of maximum arc current difference with different arc initial conditions was 0.60. The maximum critical value of time instant of maximum anode and cathode current differences between parallel vacuum arcs with one strong arc branch at arc initial were 3.5 and 4.0 ms, respectively. Moreover, a three-interval arc current development model was proposed to describe unbalance phenomena of parallel vacuum arcs.