Determination of an Absolute Capacitance by a Horizontal Cross Capacitor

A cross capacitor is a calculable one whose capacitance is ideally determinable from one length measurement of its electrodes. In the Electrotechnical Laboratory of Japan (ETL), a horizontal cross capacitor was constructed. In this model, ease of checking alignment of the horizontal electrode bars, and a simple driving mechanism to move the guard electrode, were emphasized. Because the movable guard electrode rests on, and is guided by, the horizontal electrode bars no special supporting mechanism is necessary. The displacement, which defines the length of the capacitor, is observed by interference fringes using a Hg198 source. The sensitivity obtained for electrical measurement is better than 0.01 aF and for length measurement better than 1/30 fringe. The errors of this capacitor are examined in detail and confirmed by experimental tests. The absolute capacitance was determined as 0.1 pF with an accuracy better than 1 ppm.     

Density and capacitance profiles and edge effects in a two-dimensional charge layer on a dielectric surface

The density and capacitance profiles and edge effects in a two-dimensional (2D) layer of electrons held on a liquid helium surface between two horizontal plates of a parallel-plate capacitor are studied by solving Laplace's equation on a computer. An effective length for experimental cells is defined to take into account nonuniform charge density and capacitance near the edges of the cells. The profiles and edge effects are studied as a function of charge density on the helium surface, helium depth inside the cell, repelling voltages on guard electrodes around the capacitor plates, and the frequency of excitation. The results should be useful in designing cells for experiments and better analyzing the results of measurements.     

Numerical study of methods of linearization of the output characteristics of radio-frequency sensors of the level of dielectric media

Different constructions of the sensing elements of radio-frequency level sensors based on sections of long lines are numerically investigated by means of the Matlab program for the purpose of minimizing the measurement error caused by the nonlinearity of the output characteristic. It is shown that the nonlinearity is lowest for U-shaped designs. The nonlinearity factor KN may be regulated by varying the capacitance of a correcting capacitor connected to the input of the sensing element and (or) the length of one of the sections of the long line. In selecting an optimal capacitance of the correcting capacitor KN ≤ 0.15% for control media with dielectric permittivity in the range 2.2–30.     

Optimization of multi-layer ceramic capacitor geometry for maximum yield during binder burnout

The yield during binder burnout of barium titanate multi-layer ceramic capacitors with poly(vinyl) butyral as a binder and platinum as the electrode material depends on the side length and height of the devices. In general, the yield decreases with increasing volume of the capacitor and depends on the aspect ratio of the component. For capacitors of square parallelepiped geometry, the optimum aspect ratio determined from the analysis of binder burnout yield data occurs at a height-to-length ratio of approximately 1 : 3. A methodology is presented which describes how to use the yield data obtained from binder burnout experiments to guide the optimum design of capacitor geometry. Analytical expressions were developed for capacitors of cube, square parallelepiped, rectangular parallelepiped, circular cylinder, and elliptical cylinder geometry. As the dependence of the yield on the dimensions becomes more complex, the optimum shape of the capacitor becomes more asymmetric.     

Evaluation of the NBS Unit of Resistance Based on a Computable Capacitor

An evaluation of the unit of resistance maintained at the National Bureau of Standards, based on the prototype standards of length and time, is described. The evaluation is based on a nominally one-picofarad capacitor whose value may be calculated from its mechanical dimensions to high accuracy. This capacitor is used to calibrate an 0.01-microfarad capacitor. A frequency-dependent bridge involving this capacitor establishes the value of a 10⁴-ohm resistor. Comparison of that resistor with the bank of one-ohm resistors maintaining the NBS unit of resistance establishes that this unit is Ω_EU = 1.000002₃ ohms ± 2.1ppm.The indicated uncertainty is an estimated 50 percent error of the reported value based on the statistical uncertainty of the measurements and allowing for known sources of possible systematic errors other than in the speed of light, assuming that the speed of light c=2.997925×10¹⁰cm/sec.     

一种电容器底部隔声腔尺寸优化方法

电容器底部加隔声腔是目前用于降低电容器噪声主要方法之一。为了更有效地降低电容器噪声,提出一种电容器底部隔声腔尺寸优化方法。对电容器隔声腔隔声原理进行分析,给出电容器隔声腔设计理论。通过电容器测试实验确定噪声的主要贡献频率,建立隔声腔有限元模型。在LMS Virtual Lab Acoustics中以直接有限元法对隔声腔有限元模型进行声振耦合计算,得到隔声腔的隔声量与噪声频率之间的特性曲线。在LMS Virtual Lab Optimization模块中采用DOE技术对隔声腔结构参数进行优化。最后,以某型号电容器为例,对不同尺寸隔声腔进行噪声实验,实验结果表明:所提出的优化方法能有效地提高电容器底部隔声腔尺寸设计质量和速度。     

A New High-Speed Method of Testing Capacitors

A new high-speed method of determining the capacitance and a quantity which the writers call the pulse series resistance (PSR) of an unknown capacitor is presented. The unknown capacitor is assumed to consist of an ideal capacitor and a series resistor. The test circuit consists of a low-impedance driver, a low-loss coupling capacitor, and a wide-band high-input/low-output impedance video-type amplifier. The unknown capacitor is placed in a negative feedback loop of this amplifier. The input waveform is a trapezoid. The output waveform contains information that is indicative of the capacitance and PSR of the unknown capacitor. The information is obtained by measuring two voltages, one of which is completely independent of the other. Capacitors were measured from approximately 2 pf to 2 ?f with an accuracy of ±5 per cent. The PSR was not available for capacitors less than 100 pF because of test-circuit limitations. The capacitance and PSR of an unknown capacitor could be made available within 500 ?sec with modern voltage-measuring and calculating techniques.     

Oscillator Circuit for a Vibrating Capacitor Driven by an RF Electric Field

The vibrating capacitor to be discussed consists of a metalized membrane, clamped at its edges, between two electrodes. The membrane is driven by an RF electric field (309 kHz), which is amplitude modulated at the natural frequency (6 kHz) of the membrane. This RF field is caused by a voltage applied to one of the electrodes, which, together with the membrane, forms the driving capacitor. The other electrode, and the membrane, constitute the vibrating capacitor. A special RF oscillator has been designed, of which an essential part is the driving capacitor. This capacitor causes the RF voltage to be amplitude modulated at the natural frequency of the membrane. The oscillation conditions of this electromechanical system are derived from the equation of motion of the membrane and the electrical properties of the driving circuit. An oscillator circuit with optimum performance is designed with the aid of a computer. Finally, the computed results are verified by measurements.     

Sequential phase energisation technique for capacitor switching transient reduction

The application of a sequential switching scheme for the mitigation of capacitor switching transients is presented. The method utilises neutral grounding impedance connected at the neutral point of the switched capacitor bank together with sequential pole switching. The neutral impedance is sized to minimise the open-circuit contact voltage of the capacitor breaker phases. Theoretical analysis of the proposed scheme has been carried out together with computer simulation. In addition, neutral impedance sizing criteria are presented in order to achieve minimal transient over-voltage caused by capacitor switching. The proposed method was found capable of reducing the transient over-voltage at the utility switched capacitor location to 1.07 and 1.12 p.u. at the customer load bus.     

电子雷管用电子控制模块的抗冲击性能研究

针对小断面爆破时电子雷管内电子控制模块易受冲击作用失效的问题,通过钢桶冲击实验,对工作状态的电子控制模块及其核心部件分别进行抗冲击性能研究。结果表明,电子控制模块受冲击作用后,相比于物理结构损坏,易出现内部储能电容失电现象。电子雷管用储能电容受冲击失电是固有特性。储能电容受冲击失电性能由强到弱的顺序为：固态铝电解电容、电解铝电容、固态钽电容。储能电容受冲击失电量与电容类型、受冲击强度以及管壳内部防护结构的设计相关。设计的钢桶冲击实验方案能定性研究电子控制模块及内部元器件的抗冲击性能,可用于生产实践中对雷管结构设计和元器件进行筛选,从根本上控制产品质量。     

Pre-charging of module capacitors of MMC when the module switches are driven by a source derived from the module capacitor

A modular multilevel converter (MMC) is one of the latest multilevel converters used for high and medium-voltage power conversion. It is based on cascade connection of multiple identical modules using IGBTs as switching devices. Module switches of MMC are preferably driven by a source derived from the module capacitor. In each MMC module, the control circuit, consisting of gate drivers, is powered from a dc supply derived from the local capacitor. The module capacitors need to be pre-charged, to power the control circuit. The problem faced while doing so experimentally for MMC with two modules per arm and a solution have been reported earlier. If a fly-back converter is used to generate the power supply for driving the control circuit, the module capacitor voltages become unstable during uncontrolled pre-charging. It has been reported earlier that the reason for this is approximately constant power load on the module capacitor. This work provides theoretical understanding of the problem and shows by analysis that the power supply can be made stable if the load on the module capacitor is made a positive resistance load. As the complexity of MMC with more than two modules per arm is higher, the phenomenon is studied by simulation for MMC with four modules per arm. It shows that when a fly-back converter is used for generating the power supply, similar instability occurs in MMC with four modules per arm. It shows that when the module capacitor is made to have a load with positive resistance characteristics, the module capacitor voltages and consequently the power supplies stabilize even for MMC with four modules per arm. It further shows that even if the load on the module capacitor is negative resistance type, when fly-back converter is used to generate the module power supply, by switching devices in those modules where power supply becomes available first, followed by sorting algorithm, stable power supplies can be developed on all the modules and the capacitors can be fully charged to the desired voltage.     

Two capacitance dilatometers

Two different dilatometric devices designed for magneto-strictive strain measurements at low temperatures are described. Their sensitivity is of the order of 10^?10 for relative length changes. They are provided with an adjustable gap system which makes it possible to change the gap between the capacitor plates at helium temperature.     

Time-to-voltage converter for on-chip jitter measurement

In this paper, we present the concept and design of a time-to-voltage converter (TVC), and demonstrate its application to on-chip phase-locked loop (PLL) jitter measurement. The TVC operates in an analog, continuous mode without using a sampling clock. It compares the signal under measurement with a reference signal by charging and discharging a capacitor. First, the low-frequency reference signal charges the capacitor in one cycle. Then, the jitter signal discharges the same capacitor repeatedly until the voltage on the capacitor falls below a threshold. The number of times the jitter signal needs to discharge the capacitor is recorded on a binary counter. We demonstrated that a 160-ps injected jitter is successfully measured by the proposed TVC with a 2-MHz reference signal. We also demonstrated the successful measurement of a 14-ps average PLL jitter, without jitter injection. An 8% measurement error is found in both experiments, using four-bit counters. Finally, we analyze the relations between design parameters and show trade-offs between measurement resolution and measurement time.     

Structural capacitor materials made from carbon fibre epoxy composites

In this paper, an approach towards realising novel multifunctional polymer composites is presented. A series of structural capacitor materials made from carbon fibre reinforced polymers have been developed, manufactured and tested. The structural capacitor materials were made from carbon fibre epoxy pre-preg woven laminae separated by a paper or polymer film dielectric separator. The structural capacitor multifunctional performance was characterised measuring capacitance, dielectric strength and interlaminar shear strength. The developed structural CFRP capacitor designs employing polymer film dielectrics (PA, PC and PET) offer remarkable multifunctional potential.     

Reference trimmer disc capacitor for frequencies up to 200 Mc

Conclusions The above disc capacitor can be used for various purposes as a reference single-valued effective capacitance, or as a many-valued capacitance set at will to any value within its range, for testing or research purposes.The KVCh-8M capacitors are particularly convenient for determining the frequency characteristic of effective capacitances of other capacitors by the substitution method. In this method the measured capacitor is replaced at the high frequency by the KVCh-8M capacitor, which is set to the appropriate value by adjusting the distance between its plates.The preliminary adjustment is made with the capacitor screen removed, and the final adjustment through the opening in the screen.The actual capacitance of the disc trimmer is then calculated from (4) having measured its capacitance on a low-frequency bridge. Such a method of checking capacitors is very simple, since it does not require any accurate high-frequency capacity measuring devices. It is quite sufficient to have any type of Q-meter.     

四端对标准电容器频率特性的校验理论及测定方法

对四端对阻抗测量仪在其使用频段内进行校准,须确定四端对标准电容器的频率特性。空气介质四端对标准电容器频率特性的校验理论,是从四端对标准器阻抗矩阵出发,按四端对导纳定义进行简化后,再用网络分析仪在较高频率对有关参数进行测定,分析计算后将确定的频率特性曲线回归到100kHz～13MHz范围内。给出标准电寄器1000pF、100pF、10pF、1pF的频率特性曲线及不确定度分析,它将作为阻抗高频段计量的溯源依据。     

New spark-test device for material characterization

An automated spark test system based on combining field emission and spark measurements, exploiting a discharging capacitor is investigated. In particular, the remaining charge on the capacitor is analytically solved assuming the field emitted current to follow the Fowler Nordheim expression. The latter allows for field emission measurements from pA to A currents, and spark detection by complete discharge of the capacitor. The measurement theory and experiments on Cu and W are discussed.     

The Effect of a Short Pulse of Current on Small Particles in a Conducting Fluid

This letter describes the effect of a heavy current pulse, of approximately 10 kA, produced by a charge capacitor bank, on a small volume of liquid metal, confined in a cylindrical container (tube diameter is 1 cm and tube length is about 10 cm). The liquid metal contamination implies the presence of microscopic nonconducting particles. Theoretical consideration shows that a typical heavy current pulse of 15 msec duration leads to extremely large Lorentz force, due to the appearance of a self-induced magnetic field. Even though the particle contaminants are of micron size they can be moved by this force to macroscopic distances. Such a motion phenomenon can be used in the development of a cleanliness control system.     

Theoretical basis of the method of reproducing the unit of electrical capacitance

Conclusion The most important feature of the theoretical capacitor is the constancy of the average value of the sum ¯C(¹). This means that the average value of the sum of the crossed capacitances, referred to unit length of the physical model, representing the capacitor of symmetrical construction (equality of the crossed capacitances), is a constant quantity (_oln 2/). No less important is the fact that deviation from symmetry of the transverse cross section leads to correction terms of the second order of smallness. These conclusions can be used to estimate the effect on C(¹) of the parameters of the temperature field. However, the capacitance per unit length C(¹) is important and necessary but is still an insufficient parameter for estimating the total capacitance of the capacitor; i.e., for constructing its mathematical model, it is insufficient to multiply the above-mentioned constant by the total length of the physical model.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 71–76, April, 1976.     

Optimal design of a self-excited capacitor in a dual-stator winding induction generator

The design requirement of the self-excited capacitor in a dual-stator winding induction generator (DSWIG) is different from that of the conventional induction generator, because there are numerous combinations between the reactive capacitance of two windings. The efficiency optimisation is taken as the design aim for a self-excited capacitor in this paper. Based on the equivalent circuit model of the induction generator?rectifier system, the characteristic analysis of a three-phase bridge rectifier with an ac capacitor is presented, especially the comprehensive analysis on the condition with neglecting commutation angle. Moreover, the relation between self-excited capacitor and corresponding stator loss is derived, and the value of self-excited capacitor at maximum efficiency is obtained. The coincidence between the experimental results and analytical results verifies the validity of the analytical method. The results obtained herein are of importance to the optimal design of the self-excited capacitor in DSWIG.