Research On High Power Spark GAP Switch

In recent years,the pulsed power technology has developed rapidly.And its application is more widely used in industrial,military and scientific research.As a core components of pulse power system,gas spark switch determines the performance of its output pulse.Dispersion self-breakdown voltage plays a decisive role in the stability and reliability of spark switch.The research of dispersion is not perfect up to now.In addition,high power spark switch works at high voltage.SF₆,the commonly used gas with high electric strength,has been limited worldwide to use due to its high greenhouse effect.In this paper,CF₃I,an environmental-friendly alternative to SF₆,is studied by experiments.And its characteristics as gas medium of spark switch are discussed.Firstly,the performance of spark switch and its influencing factors are discussed.Based on the traditional theory of gas breakdown,the mechanism of gas breakdown with pulsed voltage is analyzed.The working principle of spark switch and their advantages and disadvantages are compared.An equivalent circuit is proposed.Based on this circuit,the resistance,current of the conductive channel and the rising delay and width of output pulse are numerically calculated.The relationship between capacitor,inductance and rising delay,amplitude,width of output pulse is obtained.The calculation results provide a theoretical basis for the design of spark switch.Secondly,from the perspective of spark switch structure,electrode shape and material,gas gap,seal chamber and insulation,a two-electrode self-breakdown spark switch for testing was designed and fabricated.The shape of electrode is cylinder with spherical head.And the material is copper.Sealing ring is used to seal the stainless steel chamber and insulator.Thirdly,self-breakdown voltage of spark switch with different pressure of N₂ from 0.05MPa to 0.3MPa is tested.The gap distance range from 5mm to 30mm.The results show that the stability of self-breakdown voltage is positively correlated with the gap distance.And it firstly rises and then decreases with the increase of pressure.Compared with stainless steel,the electrodes made of copper have better stability.At last,the application of CF₃I in spark switch is studied.This part includes two parts.First,the breakdown characteristics of CF₃I and its mixtures are tested by power frequency AC and lightning impulse breakdown test.Results show that CF₃I and its mixtures have enough electrical strength compared with SF₆.Second,self-breakdown stability of N₂,CO₂,CF₃I/N₂ and CF3I/CO₂ is tested.The results show that adding a certain ratio of CF₃I,the stability of N₂ and CO₂ both decrease slightly.And the stability of CF₃I/N₂ is better than CF₃I/CO₂.