The Characteristics of Vacuum Arc in the Process of Transition to Diffuse Mode Under Transverse Magnetic Field

Abstract

The motion of arc between the transverse magnetic field (TMF) contacts gradually slows down and transits to the diffusion mode before the current zero crossing. The process of arc transition to diffusion mode seriously affects the contact surface ablation. However, the influence on vacuum arc transition to diffuse mode has not been deeply studied to date. In this paper, TMF contacts with different structures were investigated in a demountable vacuum chamber that contained a high-speed charge-coupled device video camera. It was found that current, arcing time, and axial magnetic field (AMF) components had significant effects on arc appearance, arc column diameter, and moment and current at which the arc transited to diffuse mode. The transition moment to diffuse mode exhibited a linear relationship with the peak current. The arc energy accumulated before diffuse mode would increase and the transition moment would be advanced when the peak current was increased. The range of the transition current to diffuse mode and small-current diffuse mode remain unchanged with peak current and arcing time. The arc column in the contacts with larger axial self-magnetic field had larger diameter while transiting to diffuse mode and also transited to the diffuse mode earlier and accumulated less energy during the transition.