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应用氧化铝陶瓷作为强流二极管中的绝缘体,实现金属化连接,是器件保真空的基础。为了提高强流二极管陶瓷界面的耐压强度,应用ANSYS有限元程序计算了陶瓷真空界面的电场分布,并根据沿面闪络理论和径向绝缘设计思想,结合具体封接工艺,提出了一种适合小尺寸陶瓷板的套封结构。数值模拟显示,该结构在400kV外加电压下,陶瓷沿面最大场强≤70kV/cm,阴极三结合点场强<30kV/cm;在水介质单线长脉冲加速器上对二极管进行了耐压测试,所设计的绝缘结构能够稳定耐受420kV、200ns脉冲电压,与理论计算比较相符。 相似文献
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《高电压技术》2015,(11)
基于静电场分析研究固封极柱局部放电对绝缘结构的设计及优化过程具有重要的意义。为此,运用静电场分析的方法得到12 kV固封极柱的电场分布云图,并提取电场较为集中区域如接地屏蔽网、螺栓附近空气域的电场分布,同时参照固封极柱组合绝缘中各绝缘介质的介电强度,指出螺栓附近空气域的电场强度超过空气的介电强度致使此区域局部放电超标。然后依据静电场组合绝缘理论,在不变更模具的前提下,提出在固封极柱螺栓固定孔与软包硅橡胶之间增设法兰屏蔽罩以降低螺栓附近空气域场强的方法。通过静电场分析得出优化后螺栓附近空气域的最大场强由5.8 MV/m降至0.32 MV/m,验证了此优化方法在理论上的可行性。局部放电测试试验结果表明,优化后的平均熄灭电压由6.5 kV提高至14.7 kV,验证了静电场分析方法可用于固封极柱局部放电的研究中,同时也确定了优化方案在工程应用上的可行性。 相似文献
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《高压电器》2021,57(7)
为分析所设计的10 kV配电房干冰清洗装置在进行带电作业时是否会发生电晕放电或气体击穿的现象,建立了配电房与干冰清洗装置的三维静电场模型,仿真得到不同喷嘴材料、形状以及不同清洗距离下的干冰清洗装置在10 kV配电房中进行清洗作业时的电场和电位分布,分析了喷嘴材料、喷嘴形状、清洗距离对喷嘴表面最大场强和最高电位的影响,并进行了试验验证。由仿真结果可知,在10 kV电压等级下,金属材料直喷嘴、绝缘材料直喷嘴、金属材料直角喷嘴、绝缘材料直角喷嘴四种工况下的最大场强值为0.22 kV/cm,小于气体临界场强值,因此清洗距离d在10~20 cm范围时不会发生电晕放电和气体击穿现象,试验结果与仿真结果一致,为喷嘴形状与材料选择提供了依据。 相似文献
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均匀电场重频脉冲作用下处理室放电问题是高压脉冲电场(pulsed electric field,PEF)技术遇到的难题。目前现有水中空气泡的击穿研究无法说明这种平均电场强度较低(<70 kV/cm)的情况下的击穿现象。为了解决这一问题,设计了金属平板电极与水溶液电极间的气体击穿实验,利用等效实验研究了有水溶液电极的大气压下短间隙(<1 cm)的气体击穿现象。通过实验得到了液体做电极的空气气隙的击穿电压,证明了阴极种类以及重频脉冲参数对击穿电压的影响,得到了均匀电场作用下水溶液中气泡的内部电场与气泡形状参数和气液介电常数的关系式。研究结果表明PEF处理室的完全击穿是由水溶液中的气泡击穿所引起的,受阴极二次电子发射系数γ的影响,并预测了水中空气泡击穿场强,为合理设计PEF处理室提出重要参考依据。 相似文献
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Cuttone G. Marchetta C. Torrisi L. Delta Mea G. Quaranta A. Rigato V. Zandolin S. 《Dielectrics and Electrical Insulation, IEEE Transactions on》1997,4(2):218-223
At the Istituto Nazionale di Fisica Nucleare Laboratorio Nazionale del Sud of Catania, a K=800 superconducting cyclotron is in operation since 1994. The accelerator beam extraction is accomplished using electrostatic deflectors constituted by HV electrodes generating electric fields to 140 kV/cm in 6 to 8 mm gaps. The electrostatic performance is strongly dependent on the presence of high magnetic fields (up to 5 T) and of high ion energy and intensity of heavy ion beams. The behavior of these systems is mainly determined by the field electron emission effects on the cathode surface, by electron focalization processes due to the magnetic field and by heating effects due to the ion beams. A detailed study of these effects is under development starting with point, the characterization of the electrode surface vs. the material used (Ti, Cu, stainless steel, etc.) and of the best mechanical and chemical treatment available, Moreover, we are studying the electrostatic performance by using titanium surfaces and nitriding over a wide temperature range (300 to 800°C). Preliminary results concerning the use of thermal processed polished surfaces are presented and discussed 相似文献
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Elizondo J.M. Rodriguez A.E. Honig E.M. 《Dielectrics and Electrical Insulation, IEEE Transactions on》1995,2(3):368-375
High current density (>100 A/cm2) electron beam diodes operating beyond 250 kV/cm in a 1 cm gap configuration are described. The principal features of the electron source are the high current density and high field without the onset of vacuum arcs or arc collapse prior to gap closure. The electron beam diode was controlled by a variable pulse-width output Marx generator. Fields to 600 kV/cm were applied for 25 to 30 ns, and to 300 kV/cm during space-charge limited current conduction at pulse lengths of 100 to 120 ns. Evidence of the transition to space-charge limited unipolar flow and transition to bipolar space-charge limited flow was obtained. Traces of the typical behavior and the different transitions are shown. Beam uniformity was measured by using a set of Faraday cups. The Faraday cup setup was then used to demonstrate suppression of electron emission from surfaces coated with a dielectric film 相似文献
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真空高压二极管的绝缘结构分析 总被引:2,自引:1,他引:1
为提高真空高压二极管中绝缘子的耐压能力,利用静电场有限元模拟、电磁PIC模拟及传统理论计算的方法,分析了计及实际环境中绝缘子与电极之间微小间隙存在时绝缘子几何形状、绝缘材料与电极接触方式、电极结构、特别是导引磁场及回流电子对绝缘子耐压能力的影响。研究表明,抑制阴极三结点处场增强效应、尽量避免电子轰击绝缘子表面以控制解吸附气体量、适当的绝缘表面处理有利于提高绝缘子耐压能力,可作为设计真空高压二极管绝缘子的基本原则,并给出了一些具体的建议。 相似文献
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Masahiro Onoi Masahiko Yamabuchi Mitsuyasu Yatsuzuka 《Electrical Engineering in Japan》2004,146(2):1-10
A virtual cathode oscillator with a stainless‐steel mesh anode of various transparencies and wire diameters was studied experimentally for the enhancement of microwave power and its repetitive operations. The maximum microwave power observed was about 20 MW at 12 GHz for a diode voltage of 250 kV and an electron beam current of 39 kA using an anode mesh with wire diameter of 0.22 mm and a transparency of 67%. The microwave emission was enhanced by decreasing the mean angle of beam scattering when a mesh of smaller wire diameters was used in the anode. The increased transparency of the fine mesh also contributed to the enhancement of the microwave emission. Use of the mesh anode afforded the operation in several repetitive shots. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(2): 1–10, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10259 相似文献
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Batrakov A.V. Pegel I.V. Proskurovsky D.I. 《Dielectrics and Electrical Insulation, IEEE Transactions on》1999,6(4):436-440
The paper considers the effect of the space charge of emitted electrons on the electric field at the tip of a field emitter. To analyze this phenomenon, the Poisson equation was solved numerically for a spherical vacuum diode with a field emission cathode. The dependence of the electric field on the geometric field has been compared with the known approximate dependencies, Strong screening of the electric field at the cathode by the space charge of emitted electrons at fields >5×107 V/cm is noted. Based on the obtained dependencies of the actual field on the geometric one and using the SuperSAM code, the field emission occurring in a Muller projector has been simulated. It has been shown that the “ring effect” appearing in field emission patterns can well be explained by field emission from the peripheral regions of the field emitter. The current density distributions over the surface and in the bulk of the emitter have been analyzed 相似文献
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Batrakov A.V. Onischenko S.A. Proskurovsky D.I. Johnson D.J. 《Dielectrics and Electrical Insulation, IEEE Transactions on》2006,13(1):41-51
Modern theoretical notations on electrical breakdown in vacuum consider cathode triggering mechanisms to be most responsible on short-pulsed (<1 /spl mu/s) breakdowns while anode mechanisms to be responsible in a part on DC and long-pulsed breakdowns. Following those notations, we tried to reveal conditions at which either mechanism steps aside to another one. The study involved several experimental techniques including the anode-probe surface scanning, pulsed electron-beam surface melting in vacuum for surface cleaning, and intentional dust particle contamination of electrode surfaces. Breakdown tests were performed using a pulser capable of producing 220 kV quasi-square pulses that were adjustable to /spl sim/30 to 80 ns pulse length. Our experiments showed that cathode emission sites are responsible for breakdowns at relatively low hold-off fields. At higher electric fields of up to 1 MV/cm, the anode share in the mechanism of triggering breakdown becomes probably more significant than the cathode mechanism. 相似文献
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The ferroelectric electron cathode is a newly developed source of electrons. The mechanism of electron emission from the ferroelectric ceramic to the vacuum is different than that of the common thermionic cathode. As a result, its useful features enable new schemes of microwave tubes with considerable advantages such as a high current electron beam. What's more, the restrictions associated with its limitations may coincide with specific needs of various new microwave generators such as a disposal microwave tube. 相似文献
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Li C.R. Sudarshan T.S. 《Dielectrics and Electrical Insulation, IEEE Transactions on》1995,2(3):483-491
Luminescence from dielectric surfaces during preflashover in vacuum was observed under pulse excitation. By preflashover luminescence, we mean light emission under no flashover conditions. Study of light emission with respect to electrode configurations and spacing between the two electrodes shows that preflashover light emission is related to electron emission from the cathode and trapping/detrapping processes on the dielectric surface layer. Spectroscopic observations of the light emission indicate that the preflashover spectrum changes from one voltage shot to another voltage shot of the same amplitude and that the spectral distribution of the light emission depends on the dielectric material used. We believe that the light emission from preflashover is electroluminescence which may be attributed to de-excitation of excited species in the surface layers of the dielectric material 相似文献