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

In order to understand the influence of the average opening velocity on the high-current vacuum arc anode phenomena, high-speed photography was used to observe the anode phenomena of the vacuum arc discharge in vacuum interrupters. The contact diameters used in the vacuum interrupters were 12 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 to 1.8 m/s. The experimental results showed that, with the arc current increasing, there was a threshold current I_1st (peak value) at which a high-current anode mode first appeared. Moreover, 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 at 1.3 m/s. Moreover, 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 those at 1.3 m/s.