球墨铸铁电极气体开关特性研究

Research on spherical graphite cast iron electrode based gas switch

高功率容量的气体开关是国内外大型脉冲功率装置的首选,但因气体放电随机性导致的自击穿电压抖动一直以来是脉冲功率装置的瓶颈问题。电极是影响气体开关稳定性和寿命的关键,开关设计总要面临低抖动和长寿命之间的取舍,提出一种兼顾低抖动、长寿命特性的球墨铸铁气体开关。基于对球墨铸铁材料的特性分析,提出球墨均布于电极有利于提高气体开关击穿稳定性的机制,且球状石墨均布于整个电极体内,相比表面结构,具有长寿命的原生优势。设计开展了单级开关稳定性测试实验,结果表明球墨铸铁电极可将传统电极结构3%~4%的重频自击穿抖动有效降低至2.5%。最终利用低抖动球墨电极,设计了5级1 MV等自击穿概率型全密封气体开关,开关抖动进一步降低至2%以下。在测试电压范围960~980 kV,放电电流约9 kA,无维护条件下开展了开关30万脉冲寿命考核,自击穿抖动维持在2%以下,最优达1.7%。开关导通前沿小于5 ns,传输效率大于90%。此结果展现了球墨铸铁作为气体开关电极的应用潜力。

Gas switches with high power capacity are the first choice for large-scale pulsed power devices at home and abroad,but the self-breakdown voltage jitter due to the randomness of gas discharge has always been the bottleneck problem for pulsed power devices.The electrode is the key to affect the stability and life of the gas switch,and the previous designs had to face the trade-off between low jitter and long life.This paper proposes a spherical graphite cast iron gas switch that takes into account the characteristics of low jitter and long life.Based on the characterization of the spherical graphite cast iron material,it is proposed that the uniform distribution of spherical graphite in the electrode is conducive to the mechanism of improving the breakdown stability of the gas switch,and the spherical graphite is uniformly distributed in the whole electrode,which has the native advantage of long life compared with the surface structure.A single-stage switching stability test experiment was designed and carried out,and the results show that the ductile graphite electrode can effectively reduce the heavy frequency self-breakdown jitter of 3%−4%in the traditional electrode structure to 2.5%.Ultimately,a 5-stage 1 MV equal self-breakdown probability type fully sealed gas switch was designed using low jitter ductile electrodes,and the switching jitter was further reduced to less than 2%.Under the test voltage range of 960-980 kV,discharge current of about 9 kA,and maintenance-free conditions,the switch was tested for 300000 pulses,and the self-breakdown jitter was maintained at less than 2%,with an optimum of 1.7%.The switch conduction front is less than 5 ns,and the transmission efficiency is more than 90%.The results demonstrate the potential application of spherical graphite cast iron cathodes as gas switches.