【作者】 周正阳；

【导师】 邹积岩； 廖敏夫；

【作者基本信息】 大连理工大学 ， 电机与电器， 2010， 博士

【摘要】 真空触发开关(Triggered Vacuum Switch, TVS)是脉冲功率技术中一种可控性良好的大功率开关器件,其机理研究是当前开关电器领域的前沿课题之一。TVS初始等离子体的产生和发展是其能够成功导通的关键,对它的运行特性(如触发可靠性、时延特性、触发精度和工作寿命等)有重要的影响。本文研究场击穿型真空触发开关(Field-Breakdwon Triggered Vacuum Switch, FTVS)运行时初始等离子体的形成与扩散机理,并探索初始等离子体对主间隙导通特性参数的影响,重点对触发可靠性、工作时延、触发精度(抖动时间)的影响。在此基础上,设计了几种FTVS。本文可支持脉冲功率控制开关的基础研究,并可将所设计的系统用于电磁发射等脉冲功率应用场合。本文首先从宏观和微观机理两方面来描述FTVS在真空间隙中的场致发射产生初始等离子体的过程。以此分析出发,通过数学建模方法,引入热力学方程,建立了真空放电阴极斑点热传导模型来描述FTVS初始等离子体的微观特性。FTVS初始等离子体的微观发展特性很大程度上体现在FTVS的触发时延,利用建立的热传导模型计算了FTVS的触发时延,理论结果与典型的实验数据相吻合,证明了所建模型的正确性。FTVS初始等离子体微观特性研究为FTVS的开通和运行性能的优化设计提供了理论支持。为了检验本文提出的FTVS初始等离子体微观特性,设计了两种不同触发极结构的FTVS,针形触发极TVS-1和T形触发极TVS-2,通过大量的实验来研究其基本工作特性,如：触发能量对触发系统时延及其分散性的影响、触发能量对主间隙最小导通电压的影响、主间隙电压对触发时延及其分散性乃至触发成功率的影响。结果表明,优化设计后的T形触发极TVS-2在各方面表现出更好的特性。同时设计了一个不涂触发材料的特殊FTVS,探索其恶劣条件下的触发以及因触发材料燃烧殆尽后的寿命问题。为了支持FTVS在电磁发射等脉冲功率中的应用,制作了两种触发源控制器,分别采用汽车点火线圈或彩电高压包为脉冲变压器,产生负或正高压脉冲,构造不同FTVS的控制系统。在控制回路和基本触发源回路之间采用光纤隔离,可以实现高压源和信号系统的分离。控制器输出脉冲峰值高,续流能量充足,能够保证触发非常困难的不涂触发材料的特殊FTVS正常导通。围绕影响FTVS开通稳定性的关键因素触发电压和触发能量展开了进一步讨论。初始等离子体的密度直接反映在触发能量的大小上,只有触发能量充足,才能引发FTVS的稳定开通。为研究所设计FTVS的电气特性,搭建了LC振荡回路为基础的实验平台,主回路参数可调。测试结果表明设计的FTVS工作电压范围宽,在0.3-40kV之间,工作电流设计容量在60kA／10C以上。FTVS样品工作可靠性高,调节触发参数可使其在合理的工作范围内触发率达100%。由于FTVS的触发脉冲要求高和脉冲变压器性能受限,所以系统时延往往比较大,一般在几十微秒,且分散性较大。实验获得具体的触发时延结果,在数百纳秒量级,所包含的两部分时延——产生触发电弧电流的时延(t1)和主间隙电流发展的时延(t2)与热传导模型的仿真计算步骤分别相对应。结果还表明,t1决定于FTVS的结构设计和脉冲源;t2随工作电压的增加呈指数型减小。如果主电极负极性,t1和t2时延分别在10μs数量级,说明负极性下触发困难、触发时延长。FTVS的导通实际上是一个真空电弧的燃弧过程。利用高速摄影技术获得了起弧时刻的初始等离子体产生和发展图像,这是对FTVS导通起始时刻的直观展示。根据触发能量的不同对起弧过程中初始等离子体的不同发展进行了分析。结果表明为保障起弧稳定,既要有足够高的脉冲电场强度,又要有充足的触发能量。在此基础上,拍摄了真空电弧燃弧过程,分析了真空电弧的燃弧过程特点。研究了FTVS真空电弧在LC回路中的燃弧时间,结果说明FTVS样品在工作过程中的燃弧稳定,保证了真空电弧能维持到零点附近熄灭,即在小电流过零时产生有效的开断,且如果第一半波过零点电流变化率小于164.TA／μs,则FTVS表现出良好的反向截流特性。更多还原

【Abstract】 Triggered Vacuum Switch (TVS) is an important switch apparatus in the pulse power technology. Its mechanism of turning on and off is one of the forefront topics for study. The initial plasmas’ generation and development, which have an influence on the TVS’s operation characteristics (such as trigger reliability, delay characteristic, trigger accuracy, work life, etc.), becomes the key of turning on a TVS successfully. Based on Field-Breakdown Trigged Vacuum Switch (FTVS), the mechanism of initial plasmas’formation and diffusion during the turning on is proposed in this paper, and the influence of initial plasmas to the main gap switching-on is discussed, especially to the trigger reliability, delay, and trigger accuracy. Some FTVS samples are designed and fabricated. The results of this paper can support the basic research on the pulse power control switches, and the trigger system designed in this paper can be used in the fields of pulse power applications.The electrons emission is the first step of FTVS initial plasmas’generation, due to high-field emission in FTVS. Firstly, the initial plasmas’generation process in FTVS vacuum trigger gap is described from two aspects, macroscopic and microscopic view. Secondly, based on filed emission mechanism, a cathode spot heat conduction model of vacuum discharge is set up to deduce the microscopic transport characteristics of initial plasmas by mathematics model building method and thermodynamics motion equations. The microscopic transport characteristics of initial plasmas are embodied mainly in the trigger delay of FTVS. So, the trigger delay of FTVS is calculated from the heat conduction model, and the calculated results are accordant with the typical test results, which can prove the correctness of model. The research of initial plasmas’microscopic transport characteristics affords theory support to the optimum design of FTVS.Two kinds of FTVSs with different trigger structure are fabricated, i.e. needle TVS-1 and T-shaped TVS-2. Experiments are done to analyze and compare their basic work performances, such as the influence of trigger energy to the trigger system delay and its jitter time, the influence of trigger energy to the minimal break-over voltage, the influence of main gap voltage to the trigger delay, jitter time and successful trigger rate, etc. Results show that the T-shaped TVS-2 has more advantages than the needle TVS-1 from all aspects. Meanwhile, a special FTVS coated with no trigger material is fabricated to simulate the work life of FTVS coated with trigger material when the trigger material is burn out. Two kinds of trigger pulse controllers are developed respectively to build up trigger control systems for different FTVSs. Car ignition coil is used to form a negative high voltage pulse, while color TV rotary transformer is used to form a positive high voltage pulse. The optical fiber is adopted between the control circuit and trigger circuit, which can separate the high voltage source and signal system. With high peak voltage and enough continuous-flow energy, the controllers can turn on the special FTVS coated with no trigger material effectively. The trigger voltage and trigger energy during the FTVS’s work process are discussed. The density of initial plasmas is due to the trigger energy, so enough trigger energy is prerequisite to turn on FTVS steadily.In order to get the electrical characteristics of the fabricated FTVS, an experiment platform based on LC oscillating circuit is set up, whose main parameters are adjustable. Experiment results show that, the fabricated FTVS has a wide work voltage range of 0.3-40kV and a work current of 60kA/10C above. FTVS has high work reliability, and its effective trigger rate can reach 100% in the normal work voltage range. Due to high voltage of trigger pulse and limited capability of pulse transformer, the trigger system delay is long, about tens of microseconds. However, the trigger delay of FTVS is very short, about hundreds of nanoseconds. It concludes two parts, wait time t1 and collapse time t2, which are agreement with the heat conduction model calculation steps. Results also show that, t1 is due to the structure of FTVS and trigger pulse; however, t2 decreases with the increase of main gap voltage. If the main gap is negative, both of t1 and t2 are about tens of microseconds. It is indicated that the trigger is much more difficult under negative voltage of main gap.The conducting process of FTVS is an arcing process in practice. The initial plasmas’ generation and development images at the arc starting are recorded by a high speed camera. According to the different trigger energy, the different developments of initial plasmas are discussed during the arc starting process. Results show that both of enough high pulse and abundant trigger energy are needed to ensure the arc starting steadily. Whole arcing process is also recorded and some characteristics during the arcing are discussed. The arcing time of FTVS in a LC circuit is tested. Results show that the arcing of FTVS is steady and the arc will not extinguished until current crosses the zero. If the current ratio at the first zero-crossing of half-wave is less than 164.7A/μs, the FTVS works as a diode.更多还原