Based on a two-dimensional axisymmetric magnetohydrodynamic(MHD)model,the vacuum arc characteristics under four kinds of axial magnetic fields(AMFs)are analyzed,which include a bell-shaped AMF generated by a pair of commercial cup-shaped electrodes,andthree kinds of saddle-shaped ones generated by three pairs of newly designed electrodes.Thesimulation result indicates that the effect of AMF on the vacuum arc characteristics is significant.A comparison between the simulation result and experimental one shows that the distribution ofthe simulated ion density integrated along the viewing path is in agreement with the image ofthe arc column.Both the simulation result and the experimental one show that,among the fourkinds of AMFs,the saddle-shaped one with the highest strength is the best,which could resistthe constriction of the vacuum arc more efficiently,while the saddle-shaped one with the loweststrength and the bell-shaped one are the least desirable.
In this paper,based on the quasi-stationary magneto-hydrodynamic(MHD) model,vacuum arc characteristics are simulated and analyzed at different moments under power-frequency current.For a vacuum arc with sinusoidal current under a uniform axial magnetic field(AMF),simulation results show that at the moment of peak value current,maximal values appear in the ion number density,axial current density,heat flux density,electron temperature,plasma pressure and azimuthal magnetic field.At the same time,the distributions of these parameters along the radial position are mostly nonuniform as compared with those at other moments.In the first 1/4 cycle,the ion number density,axial current density and plasma pressure increase with time,but the growth rate decreases with time.Simulation results are partially compared with experimental results published in other papers.Simulations and experimental results both show that the arc light intensity near the cathode side is stronger than that near the anode side for diffusing vacuum arcs.
