Characteristics of the arc voltage under different profiles of axial magnetic field wereinvestigated experimentally in a detachable vacuum chamber with five pairs of specially designedelectrodes generating both bell-shaped and saddle-shaped magnetic field profile.The arc columnand cathode spot images were photographed by a high speed digital camera.The dependence ofthe arc voltage on arcing evolution is analyzed.It is indicated that the axial magnetic field profilecould affect the arc behaviors significantly,and the arc voltage is closely related to the arc lightintensity.
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.
Effect of the axial magnetic field(AMF)on resisting the constriction of a highcurrentvacuum arc is studied in this paper.Two typical AMF distributions were investigated,i.e.,the traditional bell-shaped AMF,and the saddle-shaped AMF.Experiments were conductedin a detachable vacuum chamber with a rms arc current in the range of 10 kA to 25 kA.The arccolumn was photographed by a high-speed digital camera with an exposure time of 2 microseconds.The constriction of the vacuum arc was compared by processing the images of the arc column underthe two different field configurations and numerically determining the dimensions of the arc columnnear the electrodes.It was also confirmed that the AMF distribution had a significant influence onits effectiveness in resisting arc constriction.Furthermore,the AMF strength near the peripheryof the arc is more influential than that at the centre of the electrodes in resisting arc constriction.
