Current constriction phenomena in high-current vacuum arc and its influence factors

Based on magnetohydrodynamic (MHD) model, current constriction phenomenon in high-current vacuum arc (HCVA) is researched and analyzed in this paper. According to simulation results, it can be found that the significant current constriction only near anode regions for lower current vacuum arc; but with the increase of arc current, the constriction of arc current also appears near cathode side, and with the further increase of arc current, the current constriction of cathode side can be more significant than that of anode side. The current constriction near cathode side in very high-current vacuum arc can be caused by the MHD process of arc column (associated with the increase of plasma density and plasma pressure). Current constriction phenomena in HCVA is associated with many factors, such as arc currents, AMF strengths, AMF distribution, electrode diameter, electrode separation, plasma status at cathode side and anode side, and so on. The increase of axial magnetic field strength will inhibit the current constriction of the whole arc column. Saddle-shaped AMF can get more uniform current density distribution than bell-shaped AMF. The experimental phenomena of current constriction near cathode side will also be discussed in this paper. Plasma status of cathode side and anode side will influence current distribution of arc column.