Influence of the initial opening speed on the characteristics of drawn vacuum arcs for axial magnetic field (AMF) 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 effect of electromagnetic force and Coulomb force among arcs is increased when the initial opening speed increases.
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