High-current vacuum arc: The relationship between anode phenomena and the average opening velocity of vacuum interrupter

In order to understand the influence of the average opening velocity on the high-current vacuum arc anode phenomena, a high-speed photography was used to observe anode phenomena of vacuum arc discharge in vacuum interrupters. The contact diameters used in the vacuum interrupters were 12 mm and 25 mm, respectively. The contact materials included Cu, CuCr25, and CuCr50. The arc current frequency was 50 Hz and the arcing time was controlled at about 9 ms. A permanent magnet mechanism with a contact spring was used to adjust the average opening velocity from 1.3 m/s to 1.8 m/s. The experimental results showed that with the arc current increasing, there was a threshold current I
_1st
(peak value) with which a high-current anode mode first appeared. And the first high-current anode mode was a footpoint at the velocity of 1.8 m/s. While at the velocity of 1.3 m/s, it was most probably an anode spot and sometimes it was a footpoint. The result showed that at the velocity of 1.8 m/s, the threshold current I
_1st
was lower than that of the 1.3 m/s. And the threshold current I
_1st
followed the order of Cu > CuCr25 > CuCr50 at both the velocities of 1.3 m/s and 1.8 m/s. Meanwhile, at the higher average opening velocity of 1.8 m/s, the arc energy and arc voltage were higher than or close to that with 1.3 m/s.