The Influence of Ignition Position on Arc Characteristics in the Transition Mode of a Drawn Vacuum Arc in Cup-Shaped AMF Contacts

In a drawn vacuum arc, the arc sequence begins with the bridge column arc formed after the rupture of the molten metal bridge. This column evolves into the transition mode, which consists of a central column with few or no cathode spots outside the column, and then develops into the fully diffuse mode. In this paper, the influence of arc ignition position on arc characteristics in the transition mode of a drawn vacuum arc was investigated experimentally in a demountable vacuum chamber. Practical cup-shaped axial magnetic field (AMF) contacts were used in the experiments. Arc characteristics were investigated with the aid of a high-speed digital camera with an exposure time of 2 μs. Experimental results indicated that the characteristics of the arc and arc voltage, particularly the peak in the arc voltage waveform, in the transition mode of a drawn vacuum arc in cup-shaped AMF contacts were closely related to the arc ignition position.