Recovery of vacuum switching gaps

Abstract

Laser-induced fluorescence imaging was used to characterize the spatial distribution of post-discharge switch vapors. It is shown that in short-pulse switching gaps, even at relatively low current levels, energy coupling into the anode drives the vapor production. This is consistent with the fact that there is a strong turn-on transient in short-pulse gaps which does not die before the recovery phase begins. In 60 Hz applications, the turn-on transient might not be so severe, any turn-on transient that does exist is substantially decoupled from the recovery phase by a long intervening conduction period. In gaps carrying long and relatively low-amplitude current pulses, bulk heating of the electrodes can occur, thus ensuring that post discharge vapors are emitted more or less uniformly from the electrode surfaces. In these switches, recovery models based on vapor emission from a multitude of small particles might be appropriate. In short-pulse switching gaps, on the other hand, the high-power turn-on dominates other processes during the recovery phase.<>