三电极开关系统自击穿特性研究

发布时间：2018-05-05 05:14

本文选题：脉冲功率技术 + 三电极开关　；参考：《沈阳工业大学》2017年硕士论文

【摘要】：近年来,脉冲功率技术在科学研究和工业工程得到广泛应用,其中低电感高能密度的紧凑型Marx发生器以其体积小、重量轻、能效高,且可重复频率运行等优点获得了广泛的工程应用。气体开关作为Marx发生器的关键结构部件,直接决定着发生器的输出特性与运行特性。它不仅需要导通强电流、大电荷量脉冲,且能够准确触发,由此三电极开关与两电极开关相比具有运行可控性好、闭合时间短、抖动及延时小等优点。Marx发生器中的三电极开关自击穿过程对Marx发生器的设计和安全稳定运行至关重要。本文分别从电极本体结构设计、绝缘支撑选择、极间距、绝缘介质选择等几方面给出三电极气体开关系统设计方案。为实现系统极板间距可调,保证主放电电极内部电场均匀度要求,选择以聚四氟乙烯为绝缘支撑,提出其伞裙设计结构,以提高全场域绝缘强度的同时保证开关系统绝缘安全、可靠、稳定工作。搭建三电极气体开关系统实验平台,并分别对不同电极间隙、不同气压下进行静态击穿实验,研究结果表明,以SF_6气体介质为研究对象,随主电极间隙和极间SF_6气压增大,自击穿电压渐增;随气压升高,击穿电压分散性渐增,开关静态稳定性降低。针对所设计电极系统,得到100kPa气压以内、电极间隙为4.3mm时开关静态击穿特性最为稳定。针对系统自击穿微观过程研究,建立流体-化学混合模型,以自击穿实验数据为初始条件,数值模拟三电极开关系统初始放电过程,并对该过程的物理机理及影响因素进行定量分析。研究表明,放电初始阶段至等离子体通道形成其微观过程中,阴极因场致发射产生初始电子;电子不断向阳极运动,并与其他粒子相互作用,导致触发极与主电极极间的等离子体通道初步形成;随放电时间增加至10ns时,在近极边缘处形成相对稳定的等离子体通道。等离子体通道区域电子密度最大值出现在阴极鞘层外,阴极鞘层内电子密度近似为零;电子温度主要集中在空间电场强度最大的近阴极区。比较真空、N_2和SF_6三种介质中等离子体通道特性:真空介质中电子密度最大,SF_6中电子密度最小;N_2介质中电子温度最高。比较不同间距、不同极板面积情况下等离子体电子密度横向分布,随电极间距增大,等离子体通道形成时电子密度分布均匀度增大,且电弧区域向外扩散;上极板半径为45mm时,等离子体通道形成是电子密度最小,且横向分布最均匀。
[Abstract]:In recent years, pulse power technology has been widely used in scientific research and industrial engineering. The compact Marx generator with low inductance and high energy density has been widely used in engineering applications with its advantages of small size, light weight, high energy efficiency and repeatable frequency operation. The gas switch is a key component of the Marx generator, which is directly determined by the gas switch. The output characteristics and operation characteristics of the generator not only need strong current, large charge pulse, but also can trigger accurately, thus the three electrode switch has the advantages of good operation controllability, short closing time, low jitter and time delay compared with the two electrode switch. The self breakdown process of the three electrode switch in the.Marx generator set up the Marx generator The design of the three electrode gas switch system is given from the aspects of the structure design of the electrode, the selection of the insulation support, the polar distance and the selection of the insulating medium, to realize the adjustable pole spacing of the system, to ensure the uniformity of the electric field in the main discharge electrode, and to select the polytetrafluoroethylene as the insulation. Support, put forward the design structure of the umbrella skirt, in order to improve the insulation strength of the whole field and ensure the safety, reliability and stability of the switch system. The experimental platform of the three electrode gas switch system is set up, and the static breakdown experiments are carried out on the gap of different electrodes and at different air pressure. The results show that the SF_6 gas medium is the research object. The gap between the main electrode and the SF_6 pressure increases, the self breakdown voltage increases gradually, with the increase of the pressure, the breakdown voltage dispersion increases gradually and the static stability of the switch decreases. The static breakdown characteristics of the switch are most stable when the designed electrode system is within the 100kPa pressure and the gap of the electrode is 4.3mm. A volume chemical mixture model is used to simulate the initial discharge process of the three electrode switch system with the initial conditions of the self breakdown experimental data. The physical mechanism and the influencing factors of the process are quantitatively analyzed. The study shows that the initial phase of the discharge from the initial stage of discharge to the plasma channel is formed in the micro process. The electrons move towards the anode and interact with other particles, leading to the initial formation of the plasma channel between the trigger pole and the main electrode pole. As the discharge time increases to 10ns, a relatively stable plasma channel is formed at the edge of the near pole. The maximum electron density in the plasma channel region appears outside the cathode sheath and in the cathode sheath. The electron density is approximately zero, and the electron temperature is mainly concentrated in the near cathode area of the maximum intensity of the space electric field. Compare the characteristics of the plasma channel in three kinds of media: vacuum, N_2 and SF_6: the electron density in the vacuum medium is the largest, the electron density in the SF_6 is the least; the electron temperature in the N_2 medium is the highest. The electron density is distributed horizontally, with the increase of the electrode spacing, the distribution uniformity of the electron density increases and the arc region diffuses outward when the plasma channel is formed. When the radius of the upper plate is 45mm, the formation of the plasma channel is the smallest electron density, and the transverse distribution is the most uniform.

【学位授予单位】：沈阳工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM564;TN782

【参考文献】