Study On Glycerin Dielectric Stacked Blumlein Pulse Forming Line

Compactness, long pulse duration and high power are the important developmentaltrends of pulse power technology. Stability and reliability are the desired operativecondition of pulse power systerm. Compared with Blumlein line, stacked Blumleinpulse forming line can enhance the output voltage greatly at the same charging voltage.So the voltage endurance of pulse forming line, transformer and switch will decrease.The stability of the systerm will increase. Owing to the large dielectric constant and thehigh resistivity, glycerin, as a new energy storage dielectric, has some certainadvantages, but the voltage endurance characteristic need to be verified ulteriorly. Inthis thesis, two-stage Blumlein line has been analyzed in theory and simulation. Thedifferent voltage endurance characteristics of glycerin dielectric were studied by somecorrelative experiments. Finally, we have done some elementary experimentalresearches when the glycerin dielectric was applied to the two-stage Blumlein linedevice.Firstly, two-stage Blumlein line was researched and analyzed. Because two-stageBlumlein line is charged in parallel and discharged synchronously in series, the outputvoltage will be enhanced. Both the process that two-stage Blumlein line discharges aresistive load and the effect on the waveform from switch inductance, resistive loadinductance and loop inductance were analyzed in theory. So we got the expression ofoutput voltage. Also the effect on the pulse rise time from switch inductance andresistive inductance was simulated, also the condition that both the switch induatanceand loop inductance exist in practice was simulated detailedly. We find the theoreticresults and the simulative results fit well. The results indicated that the effect on thepulse rise time from resistive load can be ignored; the effect on the pulse rise time ismainly determined by switch inductance; the trend of flat part is mainly determined byloop inductance.Secondly, some experimental researches on voltage endurance characteristic ofglycerin dielectric were studied. We assembled a high voltage endurance platform ofglycerin apparatus and interpreted the way to test and the process to assemble theplatform detailedly. We designed and created a contractible proportion coaxialapparatus which is utilized to test high voltage endurance. We have tesed voltageendurance characteristics of glycerin dielectric under different condtions. The testingresults indicated that the error between the positive and negative breakdown strength ofglycerin dielectric is small. The positive breakdown strength of glycerin dielectricreached238kV/cm and the negative reached248kV/cm at25degree centigrade. So wecan conclude that the voltage endurance of glycerin is without polarity. Temperaturehave an evidently effect on voltage endurance of glycerin dielectric. On condition that the effective time is about15μs, the breakdown strength reached304-315kV/cm at lowtemperature(50to60degree centigrade) and194-203kV/cm at high temperature(45to50subzero degree centigrade). This shows that the voltage endurance of glycerindielectric increased evidently at low temperature and decresed evidently at hightemperature. The breakdown strength of glycerin dielectric increase evidently with ahigh pressure.On condition that the effective time is about15μs, the breakdownstrength increased26.1%when the pressure on the coaxial apparatus is seven times ashigh as atmospheric pressure at35degree centigrade. The results are coincident with theJ.S.Mirza’s.Finally, we designed a two-stage Blumlein line device and did some elementaryexperiment researches. According to the way to calculate the parameter of spiral strippulse forming line, we designed the transmission line. And we did the principleexperiment on the device. When the charging voltage is4.5kV, the output voltage of theload is7.9kV, the rising time is30ns and pulse width70ns.We can get the voltageascending multiple is1.75. That the waveform shape stacked well indicated it’s feasibleto enhance output voltage by using the stacked technology of two stage-Blumlein line.