AMF vacuum arcs at large contact separation

In order to explore the feasibility of axial magnetic field (AMF) contacts for applications requiring large contacts at large contact separation, i. e. at voltages above the typical medium voltage regime, experiments have been performed to investigate the arc behavior under these conditions. The AMF arcs were produced between AMF contacts in a synthetic test circuit; the contacts which were numerically optimized by 3- dimensional finite element modeling of the magnetic field distribution. High-speed video recording was used as a major diagnostics to investigate the arc behavior under different conditions. It was found that successful interruptions could be performed at RMS currrents of over 30 kA, at contact strokes of several tens of mm. Even at the highest currents investigated (42 kArms) the arcs are evenly distributed over most of the contact surface, indicating the suitability of AMF contacts for a current interruption capability of 40 kA of nominal short circuit current at these contact strokes.