共查询到20条相似文献,搜索用时 0 毫秒
1.
Schellekens H. Shang W. Lenstra K. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1993,21(5):454-457
Contact materials fabricated by normal powder metallurgy and by plasma spray techniques are investigated for their arcing properties in commercial vacuum circuit breakers. Current chopping levels tested up to 100000 operations are found to be of the same magnitude. The high current interrupting capability is found to be comparable. The dielectric strength of the plasma sprayed materials is negatively affected by the process as spontaneous breakdowns occur more frequently. The potential of the plasma spray process is immense as it allows easy covering of different contact surfaces and shields the contact with thin sheets of contact material, thus allowing for minimizing the skin effect 相似文献
2.
Smeets R.P.P. Kaneko E. Ohshima I. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1992,20(4):439-446
In low-current vacuum arcs, short (<500-ns) peaks in arc voltage (instabilities), with a height of up to ten times the normal arc voltage, are abundantly present. The instabilities are thought to be caused by ion starvation near the anode. A number of parameters of these instabilities, occurring in vacuum interrupters with AgWC (low-surge) and CuCr (conventional) contact material, have been analyzed statistically in a practical AC circuit. A striking difference in median rate of rise and height is found. It is found plausible that these parameters reflect important switching characteristics such as recovery (peak rate of rise) and current chopping level (peak height). Also, the dependence of the parameters on momentary arc current and contact distance is studied and explained qualitatively 相似文献
3.
Watanabe K. Kaneko E. Yanabu S. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1997,25(4):609-616
New methods have been developed for investigating vacuum arcs applied to the improvements of vacuum interrupter electrodes. Electrode surface temperature measurements reveal the anode surface melting condition at the current interruption and its influence on interruption capability, and a digital image processing technology gives us a clear understanding of the arcing phenomenon. Measurements and test results have shown the advantages of axial magnetic field electrodes in increasing the interruption capability of vacuum interrupters. It is confirmed that axial magnetic field electrodes are superior to other types of electrodes, and we believe that these new investigation methods promote the optimization of the electrode structure and the realization of higher voltage and current rating vacuum interrupters 相似文献
4.
Tianping Zhang Lei Chang Xinyue Hu Runlong Wang Huijie Zhang Xianming Wu Xinfeng Sun Ning Hu 《等离子体物理论文集》2020,60(3):e201900163
To optimize thrust performance, the expression of space-charge-limited current for vacuum arc thruster is derived from Poisson's equation. The commonly used ring-type and coaxial-type vacuum arc thrusters are simplified to the equivalent current sheet in planar geometry and cylindrical capacitor, respectively, for this calculation. Both the spatial distribution and peak magnitude of space-charge-limited current are given explicitly, together with their dependences on gap distance, applied voltage, charge number, and ion mass. For typical experimental parameters of the vacuum arc thruster, it is shown that the maximum current density drops significantly when the gap distance becomes large and grows when the applied voltage increases; moreover, a cathode material of lower atomic weight yields a higher current density. The expressions of total current for these two types of vacuum arc thruster are also presented. This work, to our best knowledge, is the first application of space-charge-limited current to the vacuum arc thruster and practically very interesting for engineering design. 相似文献
5.
Bugaev A.S. Gushenets V.I. Nikolaev A.G. Oks E.M. Yushkov G.Y. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1999,27(4):882-887
Based on time of flight method, influence of short time vacuum arc current jump on arc plasma parameters were investigated. Superposition of the current pulse of a vacuum arc with a high operating voltage results in the appearance of ions of higher charge state in the discharge plasma and in an increase in the mean ion charge state for most of the cathode materials used in the experiment. The method of a “short-time current jump” can be also used to investigate the parameters of a vacuum arc, in particular to estimate the ion direct velocities in vacuum arc plasmas. Our estimates show that in the presence of a current step the ion velocities are almost identical for all differently charged ions and depend only on the peak current and the ion mass 相似文献
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The current constriction in a diffuse vacuum arc is shown theoretically and experimentally to be caused by a pressure source, to which the charged particles and neutral particles contribute. 相似文献
8.
Duning G. Lindmayer M. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1999,27(4):923-929
In vacuum circuit breakers the post-arc current caused by the remaining ions and electrons in the contact gap is an indication of the residual ionization and its decay. It coincides with the formation of a positive space charge sheath in front of the new cathode, which grows toward the new anode. In a vacuum test chamber an arc (1.5-15 kA RMS) is drawn between high current electrodes of the spiral type. At different times after current zero a transient recovery voltage is applied across a separate pair of high voltage electrodes. In contrast to real circuit breakers, where the transient recovery voltage reappears between the arcing contacts, this separation allows the study of residual plasma free from the thermal stress and melting on the contact surfaces. From the post-arc current across these electrodes, in comparison with a mathematical model of sheath growth, the density of the charge carriers can be evaluated. Such values and their temporal decay are presented 相似文献
9.
《Physics letters. A》1998,245(5):477-478
We present an analysis of the heat capacity of a superconductor carrying a constant applied electric current. We find that the heat capacity diverges with an exponent of 0.5 at a depressed transition temperature. This result is similar to a recent calculation of the heat capacity of superfluid helium under an applied heat current. 相似文献
10.
Haas W. Hartmann W. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1999,27(4):954-960
The anodic and cathodic arc roots of constricted high current vacuum arcs were investigated with a fast framing charge-coupled device camera of 1 μs exposure time. The experiments were performed with cup-shaped contacts, with sinusoidal currents of amplitudes between 20 and 100 kA, and a sine halfwave duration of 10-12 ms. The arcs were drawn by contact separation and accelerated by the Lorentz force between the arc current and the transverse magnetic field generated by the contrate contact. The anode and cathode arc roots behave reproducibility and arc scaleable within the range of currents investigated. Both types of arc roots are elliptical, with a major to minor axis ratio of 1.4. The major axis points are in the direction of arc propagation. Anodic and cathodic arc root cross-sectional areas as a function of current can both be described by a potential law with a common exponent of 0.76. For currents of 20-100 kA, mean current densities of 81-121 and 41-60 kA/cm 2 were found in anode and cathode arc roots, respectively. Estimations of their temperature and vapor densities were performed. For the investigated current range TA≈3300-3600 K, nA ≈1.6*1019-2.2*1019cm-3 and T C≈3200-3400 K, nC≈0.8*1019-1.2*10 19 cm-3 were found for anode and cathode, respectively 相似文献
11.
为获取初级试验平台(PTS)装置分层真空轴向绝缘堆的电压电流,设计、标定了微分型电容分压器和微分环。探头的频响实验表明:绝缘堆电压、电流探头的频响上限分别为270 MHz和100 MHz。两种探头均采用在线标定方法来确定幅值灵敏度系数。电压探头在标定时应当保留绝缘堆外侧的水介质,以保证探头附近电场分布不发生改变。PTS装置的实验结果表明:当装置外围馈入电流基本均匀时,绝缘堆电压电流测量结果与相关测试结果自洽,与理论值基本符合;当馈入绝缘堆的电流分布不均匀时,不同角向探头测量结果的偏差导致总电流计算结果的误差较大。 相似文献
12.
为获取初级试验平台(PTS)装置分层真空轴向绝缘堆的电压电流,设计、标定了微分型电容分压器和微分环。探头的频响实验表明:绝缘堆电压、电流探头的频响上限分别为270MHz和100MHz。两种探头均采用在线标定方法来确定幅值灵敏度系数。电压探头在标定时应当保留绝缘堆外侧的水介质,以保证探头附近电场分布不发生改变。PTS装置的实验结果表明:当装置外围馈入电流基本均匀时,绝缘堆电压电流测量结果与相关测试结果自洽,与理论值基本符合;当馈入绝缘堆的电流分布不均匀时,不同角向探头测量结果的偏差导致总电流计算结果的误差较大。 相似文献
13.
Weinert H. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1999,27(4):944-948
Based on a large number of measurements of high-frequency (HF) current interruptions in vacuum at small contact gaps (⩽600 μm), the statistical reignition behavior of vacuum switching devices after a HF current zero is investigated. Three types of reignitions can be classified. Statistical evaluation of post-arc current measurements for different parameters at current zero and different HF current ignition processes gives information about the stress of the gap as a result of the transient recovery voltage after a HF current zero (HF-TRV) and the accumulated post-arc charge. Comparing post-arc current values at the beginning of the HF-TRV and at the moment of reignition reveals a production of charge carriers during the recovery interval. Possible reasons for the different types of reignitions are discussed 相似文献
14.
Pavelescu D. Nitu S. Dumitrescu G. Trucsa V. Zoita V. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1999,27(4):938-943
The paper presents one stage of the scientific research, performed for the investigation of the post-arc (p.a.) current within low voltage switching process in vacuum, when interrupting short-circuit currents of high values. A large power equipment, supplied by the mains and providing an accurate reproduction of the processes, concerning the short circuit phenomenon (U=1.5 kV; I=100 kA) was used. An experimental model, which can reproduce the switching conditions of the power circuit-breaker in vacuum, was available as well. The influence of an axial magnetic field on the p.a. current and the switching process was also explored 相似文献
15.
Puchkarev V.F. Bochkarev M.B. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1997,25(4):593-597
Vacuum discharge burning between a broad cathode and a point anode made of Mo, Cu, and Cd has been studied. This discharge operates in anode vapors and shows major arc characteristics, although no craters were examined on the cathode. The secondary electron emission is involved to explain current transport within the cathode region. This discharge is interpreted as a high density low voltage glow discharge. Having discussed the present and previous findings, the conclusion has been drawn that the secondary electron emission and “hump of potential” are dominant in the vacuum arc cathode spot 相似文献
16.
Vozdvijensky V.A. Sidorov V.A. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1991,19(5):778-781
The dynamics of light emission accompanying the initial stage of electric discharge in a substantially undervoltaged vacuum gap was studied with a knock-down model using high-speed photorecording. Voltage across the gap was maintained within the range of 0.5-5 kV, which corresponded to the minimum operating voltage of vacuum-triggered gaps. It was found that front layers of a plasma cloud near a cathode, formed by a firing pulse, scattered at a speed of (5-8)×106 cm/s. During firing, a channel directed to the opposite electrode was formed from the plasma cloud near the cathode. It was found that the average switch-on delay time of the triggered vacuum gap is ~d (1+h /d ) If-α, where d is the interelectrode gap length, h is the trigger assembly penetration height, and I f is the firing current 相似文献
17.
In a Rapid Cycling Synchrotron (RCS), power loss due to an eddy current on the metal vacuum chamber would cause heating of the vacuum chamber. It is important to study the effect for estimating eddy current induced power loss and temperature growth. Analytical formulas for eddy current power loss for various types of vacuum chambers are derived for dipole and quadrupole repectively. By using the prototype of dipole of CSNS/RCS, an experiment was done to test the analytical formula. The derived formulas were applied to calculating the eddy current power loss on some special structures of an RCS vacuum chamber. 相似文献
18.
Rusteberg C. Lindmayer M. Juttner B. Pursch H. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1995,23(6):909-914
With the experiments presented in this paper, applications of a retarding field analyzer (RFA) for the measurement of the ion energy E i in a vacuum arc plasma are discussed. The examined plasma was produced by a sinusoidal half-wave vacuum arc current. The experiments were concentrated on evaluating the plasma parameters at the last three milliseconds before current zero. In a current range from 300 Arms to 10 kArms, the ion energy distributions and their peak values were evaluated. With the increase of the arc current, a decrease of the ion energy was found. By additional investigations of the angular distribution of the ion energies, a transition from a collision dominated interelectrode plasma to a freely expanding plasma was observed, depending on the arc current 相似文献
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Chuaqui H. Favre M. Soto L. Wyndham E.S. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1993,21(6):778-783
Experimental observations are presented of prebreakdown electron beam generation in a transient hollow cathode discharge (THCD) in a vacuum. The discharge driver consists of a 400-kV maximum voltage, 25-nF Marx operated at 450-J stored energy coupled to a 120-ns, 1.5-Ω coaxial line. Electron beams with peak currents up to tens of kA are observed when a pulsed Nd:YAG laser is used to produce a plasma at the back of the cathode surface, inside the hollow cathode region (HCR). It is found that a plasma density of a few 1018 cm-3 in a volume of a few mm3 is required to generate intense electron beams. Optimal conditions are determined by varying the position of the laser focal spot inside the HCR and the time delay between the laser and the applied voltage. The main features of the electron beams are similar to those observed in conventional THCD at pressures in the 10-200 mtorr range 相似文献