Turn-on dynamics of small-sized triggered vacuum switches at fast rising of commutated current

Results of research of starting modes for small-sized triggered vacuum switches (TVS) at fast-rising commutated currents are presented. The research was carried out for sealed-off TVS with discharge gaps of about 1 mm for switching current rise rates of more than 1010 A/s. It was shown that the stable mode of TVS turn-on was disturbed by short-time current falls accompanied by high voltage spikes as result of instabilities of initial stage of vacuum arc. Unstable mode of TVS turn-on is characterized by an increased switching delay time as well as by increased energy consumption for vacuum arc formation. It was shown that the stable starting mode of TVS operation at fast-rising currents was restored by an increasing of the power of the triggering discharge, in particular, by application of additional peaking capacitors installed close to the TVS.