Effect of initial opening speed on the behavior of vacuum arcs driven by transverse magnetic fields (TMF)

Transverse magnetic field (TMF) can force the arc to move circularly on the contacts thus avoid severe local overheating. In this paper, an experimental system was established to study the effect of initial opening speed characteristics on vacuum arc with two different TMF contact structures. Cup-shaped and Wan-type CuCr contacts with the same diameter of 30mm were investigated in a demountable vacuum chamber. Short-circuit currents were provided by a single-frequency oscillation circuit. By using a high-speed charge coupled device (CCD) video camera, the appearance of vacuum arcs was observed and investigated regarding different initial opening speeds. The results were analyzed by 3D finite element analysis. It was showed that with the increase of arc currents, the acceleration of opening speed will shorten the duration of transition arc mode and promote vacuum arc to go diffuse.