针电极曲率半径对微间隙空气放电击穿特性的影响

Influence of needle electrode radius of curvature on breakdown characteristics of micro-gap discharge in air

电极结构对低压、微间隙放电击穿特性有一定影响,为了揭示本安开关变换器电容输出短路放电机理,系统研究了电极曲率半径与击穿电压之间的关系。以电极结构对微间隙放电击穿规律为研究目标,围绕针电极曲率半径,采用坐标变换法求解曲率半径与电场分布及击穿电压之间的数学关系。基于该数学表达式及流体-化学动力学理论,提出了低压、微间隙条件下综合考虑场增强因子及曲率半径的二维轴对称针-板电极几何模型,通过研究曲率半径对电子数密度、电场畸变程度的影响,阐明曲率半径对空气放电击穿特性的影响规律,并结合微纳程控放电试验平台进行试验验证。结果表明:针电极表面电子数密度增加越快,电荷积聚效应越显著,阴极表面更易形成场致发射从而击穿间隙产生放电;相同电极间距下,曲率半径越小,畸变电场强度越大,击穿电压越低,当电极间距小于等于8μm时,曲率半径对电场畸变的影响程度大;当电极间距大于8μm时,电极间距对电场畸变的影响起主导作用。研究得出曲率半径与电极间距共同影响电场分布,为进一步揭示微间隙放电机理提供理论参考。

The electrode structure has a certain effect on the breakdown characteristics of micro-gap discharge under low voltage,and the relationship between the radius of curvature of the electrode.In order to reveal the short-circuit discharge mechanism of capacitor in intrinsically safe switching converter,the relationship between the radius of electrode curvature and the breakdown voltage was systematically investigated.The law of discharge breakdown of micro-gap with electrode structure was studied,and the mathematical relationship between curvature radius,electric field distribution and breakdown voltage was determined by coordinate transformation method.Based on the mathematical expression and the fluid-chemical kinetic theory,a two-dimensional axisymmetric needle-plate physical model was proposed considering the field enhancement factor and the curvature radius under low voltage and micro-gap conditions.By exploring the influence of curvature radius on electron density and electric field distortion,the regularity of curvature radius on breakdown characteristics of discharge in air was clarified,which was verified through the discharge experiment on the micro-nano programmed platform.The results were obtained as followings accordingly:the faster the electrical density of the needle electrode surface increases,the more significant the accumulation effect of the charge is,resulting in an easy forming of field emission on the surface of the cathode,with breakdown and discharge taken place under the micro-gap.At the same electrode distance,the smaller the curvature radius is,the greater the distortion electric field is,and the lower the breakdown voltage is.When the electrode spacing does not exceed 8μm,the influence of the radius on the electrical field distortion is largest.The influence extent of the electrode space on the electrical field distortion is greater while the distance exceeds 8μm.It is confirmed that both curvature radius and electrode space affect the electric field distribution,which provides a theoretical reference for further revealing the mechanism of micro-gap discharge.