13 / 2021-05-21 21:06:06

EVOLUTION AND POST-ARC BREAKDOWN OF INTERMEDIATE FREQUENCY VACUUM ARC

Variable intermediate-frequency (360-800 Hz) power technology is widely used in aircraft power supply systems. This paper studies the evolution and post-arc breakdown of vacuum arc in axial magnetic field (AMF) at 360-800 Hz. The experimental results show that when the contact separation was 3 mm, the vacuum arc is uniformly distributed and diffused in the AMF contacts. From the dynamic volt-ampere characteristic at different currents and different frequencies, a similar rule can be observed, that is, as the current and voltage change there are 3 stages in the vacuum arc evolution, which are arc free expansion stage, arc transition stage  and arc diffusion stage. After the current peak, the brightness of the arc gradually decreases as the current decreases, and the number of cathode spots decreases also. The density of metal vapor is considered to be an important factor affecting the post-arc breakdown of vacuum arc, and a large number of metal droplets produced by the contacts will be an important source of metal vapor. The distribution of metal vapors decreases outward from the center of droplet. The vapor density near a single droplet can reach 2.2×10¹⁹ m^-3, and more than 80% of the vapors are distributed within the radius of 10 times. The metal vapor reduces the dielectric recovery strength.