电工技术学报  2023, Vol. 38 Issue (4): 1032-1041    DOI: 10.19595/j.cnki.1000-6753.tces.211566
高电压与放电 |
阴极曲率半径对微米尺度气隙击穿的影响规律研究
常泽洲, 孟国栋, 应琪, 成永红
西安交通大学电力设备电气绝缘国家重点实验室 西安 710049
Study on the Influence of Cathode Radius on the Breakdown Characteristics across Microgaps in Air
Chang Zezhou, Meng Guodong, Ying Qi, Cheng Yonghong
Key Laboratory of Electrical Insulation and Power Equipment Xi’an Jiao Tong University Xi’an 710049 China
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摘要 微米尺度气隙击穿特性研究对微结构绝缘性能评价和微放电等离子体应用具有重要意义。该文建立了微米气隙击穿的二维物理模型,利用粒子模拟/蒙特卡洛碰撞(PIC/MCC)方法开展微米气隙击穿过程中电场分布及带电粒子的仿真研究,得到阴极的曲率半径对于微米气隙电场分布、带电粒子分布以及击穿路径的影响规律,并结合实验结果对仿真结果进行了验证,最后讨论分析极不均匀场下微米空气气隙击穿物理过程。结果表明,阴极曲率半径R0对微米尺度击穿特性的影响规律主要分为两个阶段:当R0<5 μm时曲率半径的变化对电场畸变的影响较大,进而导致击穿电压变化较大;当R0>5 μm时R0对电场畸变的影响逐渐变小,对击穿电压影响减弱。当间隙距离d为5 μm时阴极场发射电流占总电流的95 %以上,证明了场致电子发射成为击穿的主导机制。同时,阴极表面的放电区域面积随曲率半径的增加而增大,进而导致击穿电流增大。研究结果有助于进一步分析和理解微米尺度击穿过程的影响因素及其微观作用机制。
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关键词 微米间隙击穿粒子模拟/蒙特卡洛碰撞阴极曲率半径场致发射数值仿真    
Abstract:The characteristics and mechanism of microgap breakdown is of great significance to the insulation reliability evaluation of micro devices and plasma generation at this dimension. Based on the theory of micro-scale breakdown, field electron emission and secondary electron emission are two major cathode emission processes which may dominate the breakdown at microscale. Therefore, exploring the role of the cathode in the process of micron breakdown and further understanding the mechanism of micron-scale breakdown are very vital to the evaluation of electrical insulation performance and the application of microplasma. To address these issues, a two-dimensional physical model of microgap breakdown in air is established, and the numerical simulation on electric field distribution and charged particles in the process of microgap breakdown in air is carried out by using particle in cell/Monte Carlo collision (PIC/MCC) method, which are also verified by the experimental results.
Firstly, based on the experimental setup, a two-dimensional physical model of microgap breakdown in air is established. Secondly, with the aid of Vsim software, numerical simulation of microgap breakdown is carried out by using PIC/MCC method. Simulation results of electric field distribution characteristics show that the field enhancement factor β decreases from 2.50 to 1.65 when the cathode radius R0 increases from 1μm to 10μm. It indicates that the local electric field distortion on the cathode surface decreases, and the field emission threshold voltage increases with the increase of the cathode radius. A larger voltage is demanded for the field electron emission, so the breakdown voltage gradually increases. Simulation results on current variation characteristics during breakdown show that field emission current accounts for more than 95 % of anode current, which means field emission dominates the breakdown process. Moreover, the amplitude of the field emission current is proportional to the radius of the cathode. When R0 increases from 1 μm to 10 μm, the breakdown time t also increases from 22.4 ps to 30.6 ps, due to the fact that when the radius of the cathode is smaller, the electric field strength near the cathode is higher, so the initial velocity of electrons is larger, which speeds up the breakdown process. Simulation results on spatial distribution characteristics of charged particles show that the width of cathode discharge region increases with the increase of the cathode curvature radius. The same phenomenon is also observed in the experimental results of optical morphology of the breakdown, which shows a good agreement with the simulation results.
The following conclusions can be drawn from the simulation and experiment analysis: (1) In the 5 μm gap, the electric field strength on the surface of the needle cathode reaches up to 2×108 V/m, thus the field emission current contributes greatly to the breakdown which becomes one of the main physical processes in breakdown. (2) As the radius of curvature of the tip decreases, the electric field distortion as well as the field emission will be further enhanced, so the gap is more easily to be broken down. Therefore, the breakdown voltage and the breakdown time gradually decreases with the decrease of the cathode radius. (3) The effective area of the field emission increases with the increase of the cathode radius, which will directly lead to the increase of the field emission current. The increase of the breakdown channel width will cause more severe impact ionization in the air gap, which will eventually lead to the increase of the breakdown current.
Key wordsMicrogap breakdown    particle in cell/Monte Carlo collision (PIC/MCC)    cathode radius    field emission    numerical simulation   
收稿日期: 2021-10-01     
PACS: TM855  
通讯作者: 孟国栋 男,1985年生,博士,副教授,博士生导师,主要从事微纳尺度介质绝缘与击穿特性、电力设备绝缘状态诊断与评价技术、低维材料与器件等方面的研究工作。E-mail: gdmengxjtu@mail.xjtu.edu.cn   
作者简介: 常泽洲 男,1997年生,硕士研究生,研究方向为微米尺度电气击穿及放电等离子体。E-mail: 850025107@qq.com
引用本文:   
常泽洲, 孟国栋, 应琪, 成永红. 阴极曲率半径对微米尺度气隙击穿的影响规律研究[J]. 电工技术学报, 2023, 38(4): 1032-1041. Chang Zezhou, Meng Guodong, Ying Qi, Cheng Yonghong. Study on the Influence of Cathode Radius on the Breakdown Characteristics across Microgaps in Air. Transactions of China Electrotechnical Society, 2023, 38(4): 1032-1041.
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