CATHODE SPOT DYNAMICS ON PURE METALS AND COMPOSITE-MATERIALS IN HIGH-CURRENT VACUUM ARCS

An investigation has been carried out of cathode spot dynamics in a tr iggered vacuum are in a demountable chamber, A rectangular current pul se of 1-5 kA, 1-5 ms has been used, Sufficient statistics mere collect ed, The expansion of a cathode spot ring on a clean, pure metal surfac e was corroborated to be a retrograde movement in the self-magnetic fi eld which obeys the same law as the movement of a single spot in an ex ternal magnetic field, The influence of a contact gap of 0.5-8 mm and current on the dynamics of cathode spots was investigated, The gap dep endence of the proportional coefficient between the spot velocity and magnetic field in the case of a pure copper cathode was obtained, A ph enomenon was discovered, where a group of cathode spots form in the sh ort arcs on the CuCr cathodes after a transition diffuse are stage, Th e fellow-up investigation revealed that a close interrelation exists b etween the cathode and anode processes in short arcs, This interrelati on is responsible for the appearance of the discovered phenomenon, Sho rt-circuit performance tests conducted for a commercial vacuum interru pter proved cathode spot group formation to be responsible for the int erruption failure at short contact gaps.