Influence of External Synchronous AMF on the Characteristics of Vacuum Arc with Butt Electrodes

The paper is devoted to the vacuum arc control by axial magnetic field (AMF) synchronous with arc current. The special system was designed for applying to the discharge gap the external pulsed AMF which is quasi-homogeneous spatially and close to the arc current temporally. So, AMF specific induction (in mT/kA) is staying quasi-constant during the arc. The AMF amplitude was controlled in the range up to 190 mT, regardless of the amplitude of the arc current, which corresponds to the AMF specific induction of 12.7 mT / kA, for the arc current amplitude of 15 kA. Tests were done with the butt-type CuCr35 electrodes using synthetic circuit simulating vacuum circuit breaker operation with escalation of transition recovery voltage after current zero. For the diagnostics of vacuum arc behavior and arc/post-arc parameters, fast video-registration was used as well as Langmuir probe diagnostics and post-arc current measurements. Influence of the AMF on the arc/post-arc parameters as well as the threshold AMF specific induction values critical for prevent the anode spot formation are discussed.