浅析接触电流与泄漏电流的内在联系

概述了接触电流和泄漏电流的定义和测量网络,对泄漏电流测量标准的演进过程和测量网络进行了分析,阐明接触电流和泄漏电流这两个术语的内在联系,并指出修订JJG 843—2007规程的紧迫性。     

新型泄漏电流击穿电流检测仪的研制

安规测量仪是列入强制检定目录的计量器具．普遍运用于电气安全测试场合。许多安规测量仪需要进行电流测量．如泄漏电流测试仪及耐电压测试仪。目前．市场上也有专用的耐电压测试仪检定装置及泄漏电流测试仪检定装置可以进行相应电流的检定。但在实际使用中仍有各种各样的问题．如许多泄漏电流测试仪检定装置的频率误差很大．只有在工频电流下才具备较高的准确度：耐电压测试仪检定装置的击穿报警电流测量的问题．主要是响应时间较慢导致在测量阶跃变化的电流时,仪表的重复性不好。     

低温电流比较仪用于小电流测量的比例误差分析

小电流准确测量是电磁测量领域的热点和难点,低温电流比较仪作为目前最准确的电流比例量具,其电流分辨力高,在白噪声频带范围可达到甚至小于1fA/Hz1/2,电流增益准确性高.本文通过对基于SQUID的低温电流比较仪进行分析,低温电流比较仪比例误差小于10-11,可应用于nA量级电流的放大及准确测量.     

滞后电流控制三相电压型高频整流器输入电流分析

着重分析了滞后电流控制三相电压型高频整流器的输入电流．基于快速傅里叶交换（ＦＦＴ）给出了输入电流频谱．讨论了不同电感、不同滞环大小及不同死区对输入电流畸变率的影响．最后利用开关图分析了实际输入电流与参考电流形成的误差电流可超越所设滞环宽度２倍的原因。     

小电流接地系统电容电流的间接测量法

本文提出了一种测量小电流接地系统对地电容电流的新方法，它可以有效地避免系统不对称对测量造成的误差。     

泄漏电流测试仪电流示值误差的不确定度评定

文章分析了泄漏电流测试仪电流示值误差的不确定度评定。按照JJG843—2007《泄露电流测试仪检定规程》,采用直接测量法,检测泄漏电流测试仪的电流示值,根据不确定度的误差来源对测量结果进行分析计算,得到合成不确定度和扩展不确定度。     

轴电流产生及轴电流保护装置应用分析

主要对轴电流的产生原因，BZL-10C型发电机轴电流保护装置的工作原理、现场安装及故障分析处理。     

用于测量雷电流的全光纤电流传感器

雷电流测量是研究雷电的一个重要部分。为此,本文研究了一种用于测量雷电流的全光纤电流传感器。首先,介绍了光纤电流传感器的基本原理及结构组成;其次,在实验室中对该传感器的响应速度、测量精度及测量范围等性能指标进行了测试。结果表明,该传感器的响应速度为微秒级,可测量范围在1 kA~100 kA,动态范围大于40 dB,测量误差小于5%,测量波形与标准的Pearson电流探头测试波形相比一致性较好,该研究为雷电流测量提供了一种新方法。     

煤矿杂散电流探讨

杂散电流就是指任何不按指定通路而流动的电流。杂散电流分为交流杂散电流和直流杂散电流。交流杂散电流主要来源于用电负荷电流以外的零序电流。在三相三线制中性点不接地系统中,电网对地阻抗不平衡的情况下,电源对地形成杂散电流。由于其供电半径短、量值小,其危害相对较小,故在此不做介绍。而直流杂散电流主要来源于架线机车直流电源。这些电流通过电缆芯线、电动机、电气设备的导线和母线等导体,通过绝缘、电网对地分布电容,与大地构成任意通路。     

电流互感器的动稳定和短时热电流的选择方法

本文分析了电网短路电流的特点,以10k V系统为例,介绍了根据电网短路电流选择电流互感器的额定动稳定电流和短时热电流的方法。     

Development and Implementation of Current Tee for AC High Current Calibration

Thermal current converters or thermal transfer standard with AC–DC current shunts act as the reference standards for accurate and precise measurements of low frequency current in the frequency range from 40 Hz to 10 kHz. At present CSIR-NPL, India has the AC–DC current transfer difference (δ _x) calibration facility upto 20 A. To extend our AC current calibration range from 20 A to 100 A, a current Tee for AC high current using LC connectors has been indigenously designed and developed. This paper presents the development of current Tee for AC high current calibration. The calibration results for assigning ‘δ _x’ at 30 A current shunt with respect to 20 A are shown and the same measurement technique has been used to extend the current range up to 100 A.     

Bandwidth of Current Transformers

Bandwidth is one of the important performance parameters of current transformers. Transformers are required to have adequate bandwidth to regenerate the measured current, apart from uncertainties that are caused by the nonsinusoidal waveforms along with harmonics. An expression for the transresistance of the current transformer in terms of parasitic components is derived. Approximate expressions for lower cutoff frequency, upper cutoff frequency, and bandwidth are derived from the equivalent models of the current probe in the corresponding frequency range. The expressions are validated by experimental results for a current transformer using a Ferroxcube ferrite core 528T500-4C4. An overview of the effects of different parasitic components, such as magnetizing inductance, leakage inductance, and stray capacitance, on the bandwidth of a current transformer is presented.      

Displacement Current of Nanodendrimer

In the Langmuir-Blodgett (LB) technique, a monolayer on the water surface is transferred onto a substrate, which is raised and dipped through the surface. From this, multilayers can be obtained in which constituent molecules are periodically arranged. The LB technique has attracted considerable interest in the fabrication of electrical and electronic devices. Many researchers have investigated the electrical properties of monolayer and multiplayer films. Dendrimers represent a new class of synthetic macromolecules characterized by a regularly branched tree-like structure. Multiple branching yields a large number of chain ends that distinguish dendrimers from conventional star-like polymers and microgels. The azobenzene dendrimer is one of the dendritic macromolecules that include the azo-group exhibiting a photochromic character. Due to the presence of the charge transfer element of the azo-group and its rod-shaped structure, these compounds are expected to have potential interest in electronics and photoelectronics, especially in nonlinear optics. In the present paper, we give pressure stimulation to organic thin films and detect the induced displacement current.     

退役汽车有色金属涡电流分选的发展现状和展望

涡电流分选自20世纪70年代以来,共经历了5个发展阶段,目前已广泛应用于退役汽车破碎料等固体废弃物中有色金属的回收与再利用.目前,国内外对涡电流分选开展了深入研究,主要研究内容包括分选力模型、分选效率、细粒物料分选及计算机控制等4个方面.简述了报废汽车回收利用现状、破碎料分选流程及涡电流分选的重要作用,并对涡电流分选在上述4个方面的国内外研究进展及应用现状进行了总结;同时展望了涡电流分选的前景和未来发展的趋势.     

直流电车杂散电流对城市燃气管道电腐蚀的影响规律研究

为得到轨道与埋地管道并行情况下杂散电流对管道电腐蚀的影响规律,建立了基于电路原理和电力系统接地极理论的双边供电直流电车杂散电流对管地电位干扰模型,并求得了轨道电位和管地电位的分布变化函数以及杂散电流泄漏量分布函数。采用MATLAB进行了数值模拟,得到了杂散电流泄露规律及其对管地电位干扰规律,并对管道防腐蚀层单破损点、双破损点情况下管道的电腐蚀规律进行了分析。结果表明:轨道杂散电流泄露量与轨道电位大小成正比,降低轨道电阻可减小杂散电流泄露量。防腐蚀层单破损点不易产生腐蚀,双破损点导致局部腐蚀较严重,且变电站附近的点腐蚀严重。因此,应重点监测保护变电站处下方管道以减少产生多破损点的概率。     

大孔水凝胶的研究现状

综合阐述了国内外三代大孔水凝胶的发展状况,指出大孔结构提高了水凝胶的吸水速率以及吸水倍率,为满足工业、农业、医药以及工程材料等各个领域的应用需求,相关研究主要致力于改善其力学性能以及溶胀行为。同时论述了大孔水凝胶的制备方法,主要包括发泡法、致孔法、冷冻干燥法、相分离法以及前线聚合法等,重点阐述了发泡法和致孔法合成大孔水凝胶。     

纳米复合电镀的研究现状

纳米复合电镀是一种利用电化学原理制备具有某些特殊性能镀层的复合表面处理技术。首先介绍了纳米材料的特点和几种典型的纳米复合镀层形成机理,以及纳米颗粒的分散方法和对复合电镀的影响。其后重点综述了纳米复合电镀的最新研究状况及应用情况,概括了纳米复合电镀在现阶段面临的一些主要问题。     

Current problems of fatigue of materials

Translated from Fiziko-Khimicheskaya Mekhanika Materialov, No. 5, pp. 3–9, September–October, 1990.     

Behavior of Critical Current Density and Grain Misalignment of Hot-Pressed Bi-2223 Bar Current Leads

Bi-2223 bar current leads were fabricated by a combination of cold isostatic pressing (CIP) and hot pressing (HP). The critical currents were measured at 77 K by varying external dc magnetic field (B), which was applied parallel and perpendicular to the bulk sample surface, i.e., I _c (B//bar surface) and I _c (B bar surface), respectively. The critical current I _c and critical current density J _c were 119 A and 300 A/cm², respectively, for the bar current lead of 0.4 cm thick, 1.0 cm wide, and 5.4 cm long. The effective grain misalignment angle, _eff, was around 10°, calculated from its I _c (B//bar surface) and I _c (B bar surface) curves by using 2D model. For comparison, the average grain misalignment angle, _av, found in microstructure using SEM, was measured by pole figure. The obtained results were in agreement with the effective grain misalignment angle _eff. The phases and microstructure were analyzed by XRD and SEM.