高压多脉冲真空间隙击穿实验研究

 在真空间隙击穿机理的理论基础上,设计了高压多脉冲下真空间隙的击穿实验方案,对相同材料的多对电极间隙在高压单脉冲和三脉冲下的真空击穿特性进行了实验研究。实验结果与脉冲下真空间隙的击穿机理相符,对脉冲数量增加对真空间隙宏观击穿场强的影响进行了验证,推断出了决定真空间隙宏观击穿场强的关键因素,并对多脉冲加速间隙最大宏观场强的设计提出了建议。     

Over recovery in low pressure spark gaps-confirmation of pressurereduction in over recovery

The over recovery in sparkgaps (Nagesh, 1997, Nagesh et al., 1999) operating along the left-hand side of Paschens' characteristics is due to pressure reduction in the gap after the first pulse discharge. This pressure reduction leading to over recovery in low pressure spark gaps has been verified using a low pressure spark gap with two spark gaps placed one above the other in the same chamber. The breakdown voltage strength characteristics of the second gap has been determined for gap spacings of 3.5 mm to 10 mm, diffusion of plasma in the direction of vacuum pumping and opposite, at a pressure of 2.1 Pa for hydrogen gas. The vacuum pumping direction has a great influence on the breakdown strength characteristics of second gap after the first gap discharge. The breakdown voltage of the second gap can exceed its self breakdown voltage only 1) when the diffusion of plasma and vacuum pumping direction are same and 2) when the second gap spacing is greater than or equal to first gap spacing. Shorter gaps can always have breakdown voltage lower than or equal to their self breakdown voltage. The experimental setups, behavior of self breakdown voltages of second gap due to breakdown in the first gap, over recovery characteristics of spark gaps, the results, and discussions are presented here     

横向电容自耦式紫外预电离开关

对紫外预电离技术在气体开关方面的影响进行原理研究,分析并实验验证电容并联的横向辅助电极对主开关进行紫外预电离的可行性。辅助电极击穿释放紫外光,通过光电效应在主开关表面产生初始电子,以减小主开关的击穿电压离散度。预电离效果与辅助电极击穿导通电流的峰值强度、辅助电极两端的电压以及预电离储能电容有关,优化这些参数可以提高光照强度来增强预电离效果。实验结果表明:当主开关内部充满氮气、分压电容为pF量级时,距离主电极15 cm远的横向辅助电极可以产生预电离效应。在此基础上,提出一种新型的横向型电容自耦式紫外预电离开关的设计。     

高压氮气亚纳秒开关放电特性实验研究

 利用幅值约220 kV、脉宽约4 ns的高压纳秒脉冲源，对高压氮气亚纳秒气体开关放电特性进行了实验研究。实验结果表明：当气压在3~10 MPa间变化，间隔距离在0.6~1.2 mm间变化时，氮气间隙击穿电压随气压和间隙距离的增大而增大，并随气压的增大略呈饱和趋势,最高击穿电场约为2 MV/cm。开关输出电压波形的上升时间变化范围为145~190 ps，该上升时间随气压、击穿电场以及间隙距离增大而减小。     

微秒脉冲下极性效应对碳酸丙烯酯击穿场强的影响

通过对比碳酸丙烯酯在针板电极间距分别为0.5、1.0和2.0 mm下的击穿电压大小的实验,研究碳酸丙烯酯的极性效应.实验设备包含一个充电时间在5～20毫秒的电容储能型脉冲型脉冲功率源和一个内置针板电极的击穿试件. 每一组的击穿电压通过示波器显示记录. 三组不同间距下的击穿实验数据表明碳酸丙烯酯的正电极击穿场强高于负电极击穿场强,并且击穿场强随着电极间距的增大而增 大. 对碳酸丙烯酯针板电极的击穿进行了仿真模拟实验. 基于实验结果对碳酸丙烯酯的极性效应给出了相应的解释.     

Use of a liquid-metal cathode in high-vacuum studies of electric breakdown

Studies of electric breakdown in a high vacuum involving liquid-metal (mercury and gallium) cathodes, whose surfaces are stabilized by centrifugal forces, have shown that an increase in the angular velocity at which the experimental apparatus rotates causes an increase in the breakdown field; the mechanism for the vacuum breakdown is found to be independent of the voltage across the electrodes. According to the Frenkel theory, vacuum breakdown results from a disruption of the steady state on the liquid-cathode surface in an electric field. Drops of liquid metal on the anode degrade the dielectric properties of the vacuum gap. Under these conditions, the breakdown mechanism becomes dependent on the voltage across the electrodes. Oxide films on the cathode surface also degrade the dielectric properties of the vacuum gap. It is suggested that the dielectric may be charged by positive ions emitted from the cathode.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, Vol. 12, No. 4, pp. 44–49, April, 1969.     

An experimental investigation on high-frequency vacuum arcinterruption at small gap length

An experimental study of high-frequency (126, 230 kHz) vacuum arc interruption behavior and the voltage escalation processes at a small gap length (⩽1 mm) for three contact materials (Cu, CuCr, and CuTeSe) is discussed. Two experimental methods have been used: current injection in a low-voltage circuit and in a 10-kV AC circuit. Experimental results of the high-frequency current interruption ability and the dielectric breakdown voltage are presented. Three kinds of breakdown are distinguished: the reignition voltage, the breakdown voltage, and the cold breakdown voltage. It has been found that the interruption ability is directly related to the reignition voltage     

Temperature dependence of characteristics of water-vapor electric discharge

The experimental results on breakdown characteristics of a discharge gap containing water vapor are presented. The results obtained show that the breakdown voltage between metal electrodes placed above water and when one electrode is immersed in water significantly increases at a saturated vapor temperature of 90°C and above. This effect can be an explanation of the features of the electric discharge development above the water surface.     

重频纳秒高压脉冲下变压器油击穿特性的实验研究

介绍了重频纳秒高压脉冲下变压器油绝缘特性研究的现状和成果。进行了重频（1 Hz～1 kHz）纳秒高压脉冲下25#变压器油击穿特性的实验研究。实验发现相对于单次纳秒脉冲,重频脉冲下25#变压器油的击穿场强与频率相关,频率提高,击穿场强降低,但不是线性关系,在频率超过100 Hz时变压器油的击穿场强变化较小,在10~100 Hz时变压器油的击穿场强迅速下降。初步总结了重复频率、脉冲宽度和击穿场强的关系,对重频脉冲下变压器油的击穿机理进行了初步的探讨。     

微机电系统微尺度间隙的脉冲击穿特性

利用微机电系统(MEMS)工艺制备了5~40 m间隙的金属铝薄膜电极,测取了不同间隙下施加纳秒方波脉冲时的击穿电压,得到击穿电压和平均场强随电极间隙的变化规律,研究了脉宽、极性对击穿电压的影响,结合击穿后微电极扫描电镜观察结果讨论了其击穿机理,并与相同试样在直流下的结果进行了对比。研究表明:击穿电压随微间隙距离的增大而增大,击穿场强则随着间隙的增大迅速减小;与直流同间隙的击穿电压相比,脉冲作用下的击穿电压并不像宏观尺度下那样高出很多;试样击穿机理应为流注理论。在脉冲作用下,阳极出现了分层熔化现象,由于作用时间很短,阳极表面并未出现类似于直流击穿时留下的坑洞;阴极则出现了溅射沉积现象,只是沉积物质相对较少。     

Plasma Buildup and Breakdown Delay in a Triggered Vacuum Gap

The phenomena leading to the surface flashover across solid insulators in vacuum and the subsequent spread of the trigger plasma thus formed to bridge the main gap in a triggered vacuum switch are investigated experimentally. The results show that the breakdown proceeds in two stages. In the first stage a plasma is formed by electrons releasing and ionizing absorbed gases. The electrons are field emitted at the insulator-electrode junction and the breakdown delay is primarily affected by the trigger voltage. In the second stage the trigger plasma expands into the main gap with a speed depending on the trigger current and trigger electrode geometry, in accordance with a simple model.     

Circuit modeling of a vacuum gap during breakdown

In this paper several aspects of circuit modeling of a vacuum gap during breakdown are improved or introduced for the first time. More accurate perveance formulas are derived by the method of tracing electron trajectories in the self-consistent electric field calculated by the finite element method. The formula for maximum anode current density is also derived by the same method. A practical model of anode heating is proposed, by which transient anode temperature is calculated coupled with gap voltage and current, providing more accurate modeling of anode plasma initiation. The circuit model of a vacuum gap during breakdown incorporating all these features is implemented as a subcircuit element in the PSPICE     

面向等离子体合成射流应用的微秒脉冲源研制

为了产生高能等离子体合成射流,设计了一台面向等离子体合成射流应用的微秒脉冲源,输出电压为10 kV,重复频率为100 Hz,可承受高达250 A的放电电流。详细介绍了微秒脉冲源的工作原理,比较了不同放电电容对脉冲变压器原边电流及输出电压的影响。进一步将所设计的微秒脉冲源成功应用于等离子体合成射流实验中,研究了不同间距对等离子体合成射流的影响,比较了有无放电电容条件下的能量消耗率。实验结果表明:不同放电电容在相同激励器间距的条件下,击穿电压基本相同;击穿电压随激励器间距增大而增大。有放电电容能产生较大的放电电流,且电流值随电容值的增大而增大。有放电电容条件下的能量消耗率比无放电电容要高,易于产生高能的等离子体合成射流。     

The influence of the sand-dust environment on air-gap breakdown discharge characteristics of the plate-to-plate electrode

The experiments of plane-plane gap discharge was carried out in an environment of artificial sandstorm. By comparing and analyzing the differences in gap breakdown voltage between the sand & dust environment and clean air, some problems were investigated, such as effects of wind speed and particle concentration on the breakdown voltage, differences of gap discharge characteristics between the dust & sand medium and the clean air medium. The results showed that compared with the clean air environment, the du...     

带陡化间隙的触发真空开关触发源研制北大核心CSCD

针对主电极间距20mm以上的沿面击穿型多棒极触发真空开关(TVS),研制了开关触发源。触发源利用脉冲变压器产生脉冲高压输出,在脉冲变压器高压侧并联小容值电容并在电容后串联陡化间隙。陡化间隙的加入可以使触发源输出不受触发沿面金属蒸气沉积的影响。通过调节间隙击穿电压也可以提高电容充电电压及储存能量,从而增加TVS触发沿面被击穿时注入到其中的触发能量。使用该触发源对TVS进行导通实验,结果表明,加入陡化间隙后的触发源输出能量大幅提高且不受触发沿面金属蒸气沉积的影响,能够实现TVS的100%可靠导通。     

Growth of the spark current at the breakdown of short vacuum gaps at steady voltage

The growth time of the spark current at the time of breakdown in vacuum at the constant voltage and pressure existing during this period was investigated with high time resolution. It was shown that, as in the case of a pulsed breakdown: 1) the growth time t_c of the current increases in proportion to the length d of the gap and the ratio d/t_c is 2.5·10⁶ cm/sec; 2) the transition to a rapid rate of current growth (di/dt > 10⁸ A/sec) takes place in 1–3 nsec; 3) during the period of current growth, x-ray radiation appears and a transfer of anode material to the cathode is observed. These results serve as evidence that the origin of current growth is connected with the appearance of efficient electron sources on the cathode. These, as in the case of pulsed breakdowns, are evidently cathode flares, the formation of which has an explosive character and can be identified with the act of breakdown initiation. In essence this event does not change with the rate at which voltage is supplied across the gap and consists of the explosive disintegration of emitting microspikes on the cathode. The appearance of cathode flares indicates the start of an irreversible breakdown of vacuum insulation. The emergence of a burst of x-rays and the erosion of the anode are explained by the action on the anode of a powerful stream of electrons that are emitted from the cathode flares, providing the spark current.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 9, pp. 93–97, September, 1971.The authors thank G. A. Mesyats for his constant attention to the work.     

Modeling and optimization of the multichannel spark discharge

This paper reports a novel analytic model of this multichannel spark discharge, considering the delay time in the breakdown process, the electric transforming of the discharge channel from a capacitor to a resistor induced by the air breakdown, and the varying plasma resistance in the discharge process. The good agreement between the experimental and the simulated results validated the accuracy of this model. Based on this model, the influence of the circuit parameters on the maximum discharge channel number(MDCN) is investigated. Both the input voltage amplitude and the breakdown voltage threshold of each discharge channel play a critical role. With the increase of the input voltage and the decrease of the breakdown voltage, the MCDN increases almost linearly. With the increase of the discharge capacitance, the MDCN first rises and then remains almost constant. With the increase of the circuit inductance, the MDCN increases slowly but decreases quickly when the inductance increases over a certain value. There is an optimal value of the capacitor connected to the discharge channel corresponding to the MDCN. Finally, based on these results, to shorten the discharge time, a modified multichannel discharge circuit is developed and validated by the experiment. With only 6-kV input voltage, 31-channels discharge is achieved. The breakdown voltage of each electrode gap is larger than 3 kV. The modified discharge circuit is certain to be widely used in the PSJA flow control field.     

Influence of voltage pulse shape on the delay time for vacuum breakdown

In this paper expressions are derived for the delay time of vacuum breakdown with voltage pulses of ramp and trapezoidal shape. It is shown that the voltage pulse shape has a considerable influence on the delay time. The results obtained may be useful in experimental investigations of vacuum breakdown.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 105–110, September, 1976.     

The Investigation of Copper-Chromium Contacts in Vacuum Interrpters Subjected to an Axial Magnetic Field

The characteristics of a vacuum arc between CuCr contacts under an axial magnetic field have been investigated. Test samples were made of CuCr contacts, and the arcing voltage was measured. The arcing voltage of the CuCr contacts under an axial magnetic field is lower than that of pure copper contacts by 10-20 V. From the measurement of the post-arc current and interruption test results, it was found that the arc concentrates and a part of the electrode melts at a rather low current, but that the electrode melting does not affect the interrupting capability. Also, the insulation characteristics were measured. With respect to voltage conditioning, high-current conditioning improved the breakdown voltage by 50 percent for a 20-mm gap and by 100 percent for a 3-mm gap. These test results show that CuCr contacts, used with axial magnetic fields, are promising for use in high-voltage and high-power vacuum interrupters.     

间隙长度对气体火花开关静态性能的影响

针对快放电直线脉冲变压器驱动源初级储能开关,调节开关气压,进行相同自击穿电压下不同间隙长度的开关自击穿实验。通过监测自击穿电压分布规律变化,研究开关间隙长度对开关自击穿特性的影响。结果表明,当开关间隙长度较大时,电极表面粗糙度较小,表明电极烧蚀程度较低。开关间隙长度为6 mm时,开关自击穿电压分散性达到最小,自击穿电压分布符合高斯函数,间隙长度大于6 mm时自击穿电压分布符合极限函数。适当增加开关间隙长度使自击穿电压分布失去对称性,有利于开关在低欠压比下获得更好的静态性能。针对电极结构,选择开关间隙长度为6~9 mm时能够获得最佳的静态性能。初步分析,引起开关自击穿电压分布发生改变的原因是电场强度的改变对阴极电子发射产生了影响。