Influce of Initial Opening Speed on Characteristics of a Drawn Vacuum Arc

Influence of the initial opening speed on the characteristics of drawn vacuum arcs for axial magnetic field (MF) vacuum interrupters (VIs) is studied using a high-speed charge- coupled device (CCD) camera. Two values of initial opening speed, 0.5 m/s and 1.5 m/s, were set to make a comparative study. The cup-type electrode was made of Cu-Cr (50%-50% in weight) with a diameter of 30 mm and a gap distance between electrodes of 10 mm. The results show that the transition time decreases by 0.5 ms when the initial opening speed increases from 0.5 m/s to 1.5 m/s at a peak current of 2.5 kA, while the transition time decreases by 1.0 ms when the initial opening speed increases from 0.5 m/s to 1.5 m/s at a peak current of 5.0 kA. The reason why the duration of the transition arc mode decreases is that the e®ect of electromagnetic force and Coulomb force among arcs is increased when the initial opening speed increases.