美国航天局使用输电线路研究地磁天线

本文摘编自美国电气电子工程师学会网站。文章阐述了并不是所有对电网的威胁都来源于地球，有时也会是太阳活动引起的大型地磁感应电流所致。介绍了科学家们如何首次利用美国高压输电线路精确测量地磁感应电流。     

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。     

探究电流式地质雷达的可行性

地质雷达主要利用超高频电磁波探测地下介质的分布。为了探究利用电流场探测地下介质分布的作用效果;根据电法勘探的原理,通过电源发射电极发射一定大小的电流,当电流遇到探测目标时,电流场会产生一个变化,变化后的电流通过接收电极输入到DDC-6型电子自动补偿仪中,利用得到的实验数据计算得出电阻值的变化,进而判断被测目标的大小、形状以及位置的信息;将得到的数据输入surfer软件中处理,从得到的图像中能够直接观察到被测目标的相关信息。这就证明了利用电流场探测地下介质分布是可行的,这种装置就形成了一个“电流式地质雷达”。地质雷达技术设备由于利用了超高频电磁波,成本较高。如果将地质雷达技术中的超高频电磁波变为电流去探测地下介质分布,必将能够减少成本。     

一种高压计量箱误差超差分析及改进

本文通过整体检定高压计量箱,发现在不平衡状态下误差超差现象;通过分析,得出由于铁质外壳的导磁性,使得一次电流回路中产生感应电流,由此导致误差超差;通过更换磁导率较小的不锈钢外壳,感应电流大大减小,误差也符合相应要求,取得满意效果.     

接地极入地电流在地中电流场的模拟研究

在特高压直流输电工程中，接地的目的是利用地作为传导电流回路的一个元件，以保证人身和设备安全，维护系统和设施安全可靠运行。然而，接地极人地电流会在其周围的地中形成一定强度的电流场，从而引起对接地极附近输电线路杆塔接地体腐蚀的影响。由此，本文将从一个全新的角度，即利用三维电磁场仿真软件cS恻点电流源在地中电磁场的分布进行模拟研究，达到对接地极入地电流对附近输电线路杆塔接地体腐蚀影响的评估。     

电流检测传感器电路

在长期稳定性、高精度、快速响应、设定范围宽等各种条件下,采用在线路中插入将电流变化直接转换成电压变化输出的分流器,利用磁通密度随电流变化以及半导体的磁阻抗变化和磁电压变化特性的磁电转化元件及变流器等方式检测。     

光纤电焊电流测量技术研究

针对直流逆变电阻焊机焊接电流精确测量的需求,提出基于光纤电流传感技术的焊接电流测量方法。建立了光纤电流传感器闭环检测系统动态模型,通过优化系统的前向增益,提升了传感器响应速度和带宽。仿真和实验结果表明:传感器的上升时间约为4.1 μs,在DC~30kHz范围内幅频特性衰减小于0.3%。基于该动态模型计算传感器对焊接电流纹波分量的响应,仿真结果表明:系统的动态跟踪能力可满足对纹波电流的测量需求。利用等安匝法对光纤电流传感器进行校准,在直流5~50kA范围内,传感器的测量误差优于±0.05%。现场实验结果证明了光纤电流传感器用于直流逆变焊接电流测量及电焊电流测试仪现场校准的可行性。     

脉冲涡流热成像金属材料裂纹检测研究

为分析不同激励条件下不同材料感应加热特性,采用有限元仿真软件分析铁磁性材料45#钢和非铁磁性材料不锈钢感应加热时的涡流分布和温度分布,发现45#钢趋肤深度很小,裂纹边沿感应电流密度较大;不锈钢趋肤深度受激励电流频率影响很大。随激励电流频率的增大,趋肤深度减小,裂纹边沿感应电流密度增大。涡流的分布和裂纹对热扩散的阻碍作用共同决定裂纹附近温度的分布,并通过实验对仿真结论进行验证,确定两种材料表面裂纹的最佳激励条件。     

继电保护中电流保护的灵敏度分析

本文介绍了灵敏度分析在继电保护的电流保护中的应用：并根据常规电流保护受系统运行方式和故障类型影响使灵敏度有时满足不了规程的要求的原因,而介绍了一种在微机保护中利用原输入电流判别故障类型来提高电流保护灵敏度的方法,并对灵敏度进行了分析和讨论。     

机械式直流断路器弧后电流测量方法研究

目前机械式直流真空断路器是直流开断的主流方向之一,其主开关的弧后特性对其开断性能起着至关重要的作用。利用电流转移法设计了一种弧后电流的新型测量方法,并对该装置在测量机械式真空断路器弧后电流时的工作原理进行了分析。采用改进Mayr模型建立了真空电弧模型,利用MATLAB构建了机械式直流真空断路器弧后电流测量装置模型,仿真研究了转移电阻大小、主电流大小等对转移完成时刻电流值和转移电阻完全承受电流时间的影响,经过数据处理分析得到这些参数对电流转移特性的影响规律。基于得到的影响规律,确定了直流真空断路器弧后电流测量装置的参数,对研制测量装置并进行测试提供了理论基础。     

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。     

接触电流的测试方法

本文主要介绍了对信息技术设备的接触电流测试重要性，接触电流的测量原理和方法。     

逆变器驱动电机系统环路型电机轴承电流的研究

论述了正弦波驱动电机系统中的经典型的轴承电流，讨论了逆变器驱动电机系统中的高频磁通产生的轴承电流，分析了环路型轴承电流产生的机理，并且在实验的基础上，得出了环路型轴承电流与共模耦合电流之间的关系，丰富和完善了电机轴承电流的研究内容．     

摩托车用磁流变阻尼器的可控电流驱动器

提出一种摩托车用磁流变阻尼器的可控电流驱动器的原理,研究其硬件电路组成和特性测试方案,介绍了在此基础上开发的摩托车用磁流变阻尼器的可控电流驱动器及其特性测试系统.测试结果表明,摩托车用磁流变阻尼器的可控电流驱动器具有良好的瞬态响应特性和线性度,可在摩托车用蓄电池供电环境下用于磁流变阻尼器的电流驱动.     

Superconducting current stability in composite superconductors

The maximum transport current in multifilament composite superconductors has been studied. The experimentally obtained values of transport current exceed the normal phase minimum propagation current substantially. The current-voltage characteristics of the investigated samples have been studied. It is shown that the relatively high value of the maximum transport current is attributed, under the given experimental conditions, to the behaviour of the current-voltage characteristic in the region of low values of the electric field. The theory and experiment are in good agreement.     

交流磁场检测中激发频率与提离的影响分析

交流磁场检测是近年来电磁无损检测的重要进展之一,具有非接触、不需标定、检测速度快和适应性好等优点,在材料检测中具有广阔的应用前景。在检测过程中,激发频率的选取以及提离高度是影响信号分辨率的重要因素,以ANSYS软件系统为工具,建立了缺陷ACFM数值仿真模型,分析了信号对频率和提离高度的影响,结果显示ACFM方法更适合检测磁性材料。     

Application of power current microsensors to current measurements in gas-insulated switchgears

Modern primary distribution substations often adopt SF6 gas insulated switchgears (GISs) to reduce the overall construction space. Traditional current transformers (CTs), which are generally used in GISs for current measurement, consist of magnetic cores. These cores are bulky and increase the minimum space required inside GISs. Moreover, the occurrence of faults causes saturation in traditional CTs; this leads to distortion of detected current waveforms, which in turn triggers false responses in protective systems. The recently proposed power current microsensors based on the Hall effect have many advantages over traditional CTs, including smaller volume, quicker response, and wider measurement range, and they do not face the above-mentioned saturation problem. This study assesses the feasibility of replacing traditional CTs inside GISs with power current microsensors, taking into account certain actual conditions, including: (1) the actual distance between two adjoining cables inside GISs, (2) the worst unbalanced three-phase loads allowed by typical primary distribution substations, and (3) the four most common faults occurring in primary distribution substations. Current simulation and measurement results show that power current microsensors can measure current as accurately as traditional CTs. Moreover, during faults, microsensors do not encounter problems related to saturation, which exist with traditional CTs.     

Optimization and temperature distribution of a current lead for a cryogenic device

A method of optimizing the cross-sectional area of a cooled current lead is described in this paper. First, the dependence of the gas flow rate on the cross-sectional area is derived from the heat balance equations. Then, two curves are acquired, one relating to the optimum area, and the other to the corresponding temperature gradient at the cold end. The product of the utilization coefficient of the coldness together with the temperature difference is the independent variable of the functions represented by the two curves, from which the graphic changes of the minimum gas flow rate under various situations would be noted. Also mentioned here is the choice of the optimum material. On the basis of the result of the calculation given above, curves of one-dimensional temperature distribution of a lead under different conditions could be drawn up. Lastly, the designing principle of a lead with non-constant cross-sectional area is discussed.     

Relation of crack-induced current shunting to transport current and n-value in DyBCO-coated superconductor

Transport current and n-value of DyBCO-coated conductor pulled in tension were measured experimentally and their relation to crack-induced current shunting was analyzed with the partial crack-current shunting model. The following features were revealed. The shunting current increases with increasing transport current and with increasing crack size. At low voltage where shunting current is low, the transport current of cracked sample normalized with respect to the transport current in non-cracked state is described with the modified ratio of non-cracked area to overall cross-sectional area of superconducting layer. At high voltage where the shunting current is high, the normalized transport current becomes higher than the modified ratio of non-cracked area. The increase in shunting current with transport current (and voltage) leads to a decrease in n-value at high current (voltage). This phenomenon is enhanced by crack extension.