Influence of contact contour on breakdown behavior in vacuum under uniform field

We experimentally investigated the influence of contact contour on breakdown characteristics in vacuum under uniform field. Four vacuum interrupters were used and their contact contours were designed to obtain an effective area (S_eff) from 211 mm₂ to 550 mm². The contact parameters were contact diameter 42.8 mm, contact gap 6 mm, contact thickness 16 mm and contact material CuCr50. Basic impulse level (BIL) voltage (1.2 × 50 ¿s) was applied. Experimental results revealed that the effective area S_eff had a significant influence on the conditioning process. The larger the effective area was, the slower the conditioning process was. When the breakdown voltage saturated, the breakdown probability distribution followed a Weibull distribution. The shape parameter that represented the breakdown voltage scatter was constant, independent of the effective area. The effective area (Seff) had no significant influence on the breakdown voltage under a uniform field in vacuum.