Abstract :
The negative-impulse breakdown voltage (b.d.v.) of a point-plane gap in compressed air shows, for sufficiently long gaps, the existence of a critical pressure, as in the case of positive polarity. The b.d.v. at any pressure also depends on the wavefront duration of the impulse voltage. When the wave-front is varied over a range of 1¿210¿s, a maximum b.d.v. is obtained for front times of 78¿s and 7.5¿s for a gap of 25.4 mm and 50.8 mm, respectively.
