电热化学发射中的过电压现象与机理研究

摘要

针对电热化学发射实验所观察到的过电压现象,基于系统的电路结构、主要元件特性和电热化学炮负载特性,通过对比实验、等离子体发生器电阻测量、等效参数测量和理论分析等研究得出过电压的产生机理.研究表明:过电压现象仅在电热化学炮发射过程中出现,与电热化学炮膛内环境下发生器的特性直接相关;机理上过电压由发生器表面断弧引起.在脉冲放电临近结束时刻,膛内环境使发生器表面电弧被强制熄灭,负载发生了突变,导致系统内部出现过电压.负载突变后调波电感的剩余磁能急剧转换为系统各处杂散电容的电能,电路满足过电压谐振条件,发生电磁振荡.根据主要元件的特性简要分析过电压对绝缘配合的影响,总结过电压带来的危害,设计了过电压缓冲电路.缓冲电路包括阻容电路、缓冲电阻和缓冲电感三部分.实验表明,缓冲电路能有效抑制发射过程中由发生器表面断弧所引起的过电压.当前电热化学发射技术正向工程应用发展,研究结果可指导发射系统的绝缘小型化设计,有助于提高系统的可靠性.%According to the phenomenon of overvoltage observed in the emission experiment, based on the circuit structure, the characteristics of the main components and the load characteristics of the electrothermal-chemical gun in the system, the mechanism of overvoltage was obtained through the contrast test, resistance measurement of the plasma generator, the equivalent parameter measurement and the theoretical analysis. The studies show that the overvoltage phenomenon occurs only during the firing process of electrothermal-chemical gun, which is directly related to the characteristics of the generator in the gun bore. The studies also show that the mechanism of overvoltage is caused by the broken arc of generator surface where the electric arc is forced to go out by environment in the gun chamber at the end of the pulse discharge and the load mutation occurs, resulting in overvoltage inside the system. Then the residual magnetic energy of pulse forming inductor is converted into the electric energy of stray capacity in the system, which causes electromagnetic oscillation. According to the characteristics of the main components, the influence of overvoltage on insulation coordination was briefly analyzed and the harm caused by overvoltage was summarized. The overvoltage snubber circuits were designed, which include resistance-capacitance circuit, buffer resistor and buffer inductor. The experimental results that the buffer circuits can effectively suppress the overvoltage caused by the broken arc of generator surface during the launching process. The electrothermal-chemical launch technology is currently developing towards engineering application. The research results can be used to guide the miniaturization design of insulation in the launching system and help to improve the reliability of the system.