Research On The Key Problems And The Applications Of The Triggered Vacuum Switch With Multi-rod Electrode System

The Triggered Vacuum Switch with multi-rod electrode(MTVS), fabricated with three pairs of parallelled rods forming several interred gaps, provides twelve possible arc conduct channels to avoid the constriction of arcs. Because of that, the MTVS have many advantages of high current, wide operational voltage and long lifetiem. Acroding to the application requerments of the pulse power system and the electric power system, some basic theoretical and experimental work is carried out on the performance of MTVS in this thesis. And the motion mechnism of vacuum arc, structures optimization, triggering characteristics and lifetime are preliminarily studyed, which can provides the theory basis of the design of the MTVS. And the popularization and application of the MTVS could be based on the results.A3D magnetic field model of the MTVS was built up. The axial magnetic filed (AMF) and the transverse magnetic filed (TMF) between the interred gaps are calculated and analyzed. Also the magnetic force applied on the arc channels and electrode rods are analyzed. The siumulation results show that the TMT play the dominant roles when one of the interred gaps is switched and the AMF play the dominant roles when all the gaps of MTVS are switched. That is why the MTVS has the high current capacity.The arc development in MTVS was observed based on the CMOS high-speed camera system. The velocity of the burning arc in MTVS reaches the order of103m/s, much higher than that of the arc in plane-type TVS. At the rise stage of the current, the motion velocity of vacuum arc is higher than that of the vacuum arc at the drop stage of the current. When the peak of current is more than20kA, all the gaps of the MTVS will be filled with vacuum arc.Electristatic filed was considered in the optimization of the MTVS. To obtain the proper chamfering angle, the influence of the rod edge chamfering on electric filed was analyzed. The simulation results show that the GEF is decrease to a minimum value of3in the case of the fillet radius of the rod top face edge and aside face edge are5mm and3mm, In addition to, the premiliary design of the MTVS with35kV work voltage was discussed from the aspect of electrostatic field.Based on the optimization as mentioned, kinds of MTVS samples were fabricated and tested on current capacity and triggered characteristics. The experiments on the triggered characteristics of the MTVS show that the structure is in relation to the initial plasma spreading process concerning the working polarity. When polarity is under N working model, the trigger process is found to be extremely hard. The conclusion is that under P working model MTVS can be successfully triggered within wide range of triggered voltage. To insure the trigger success under the N working model, a system which consists of two reverse paralleled MTVS is suggested. MTVS has a lifetime more than1000times under two conditions that pulse current peak value is100kA with the single transfer charge of45C and is30kA with the single transfer charge of120C。For the second condition, the trigger voltage was maintained at a certain range from40V to1000V and the triggered delay time also is around5μs after200times switched. When the current peak of pulse is65kA with the duration of20m and the single transfer charge of402C, the lifetime of MTVS will reach up to30times. And it has a lifetime more than30times under other that. And the experimental results also show that the lowest average of the static DC breakdown voltage of the optimization MTVS was improved obviously with62.8%and the triggering characteristic was less influenced. In addition to, the the lowest average of the static DC breakdown voltage of the optimization MTVS with CuCr electrode is20%higher than that of MTVS with Cu electrode. And the time delay of MTVS with CuCr electrode is relatively small, but the trigger voltage is relatively higher.