Analytical formula of induced electric fields in a spherical conductor by an ELF dipole magnetic field source

An analytical formula of induced electric field E in a spherical conductor by an ELF dipole magnetic field source is mathematically derived in vector form based on the equivalent mutlipole moment method with reexpansion technique (RE‐EMMM), where M _‖ and are parallel and perpendicular components of M , respectively. The validity of the formula is confirmed in the following three ways: (i) the derivation of the formula from the Sarvas equation with the reciprocity theorem derived by Eaton; (ii) the convergence of the formula to that of homogeneous magnetic field when M _‖ is located at the infinite distance; (iii) comparison of the analytical solutions with numerical solutions by RE‐EMMM. Furthermore, a formula for the trajectory, which satisfies E = 0 , is derived for the field by M _‖. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(3): 8– 17, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20739     

Analysis of magnetically induced ELF current in biological spherical model with biomembrane

In this paper a biological three‐medium spherical model which consists of tissue, its membrane, and the extratissue medium is employed, and detailed distributions and characteristics of the induced current in the modeled structure are calculated by using a semianalytical solution developed for this model. It is demonstrated that both the change in the thickness and electrical properties of the biomembrane and the difference in conductivity between the inner and outer substances significantly affect the current passing through the membrane and the resultant profiles of the induced current. These analytical results are consistent with the experimental results, suggesting the influence of real membranes, and they indicate an important influence of the biomembrane on the induced current characteristics under specific membrane conditions. © 2001 Scripta Technica, Electr Eng Jpn, 135(2): 17–25, 2001     

Analysis of electric field induced by ELF magnetic field utilizing fast‐multipole surface‐charge simulation method for voxel data

This paper presents a fast‐multipole surface‐charge‐simulation method for calculating three‐dimensional Laplacian fields in voxel models. This method treats a surface of a voxel that has different inside and outside conductivities as a surface element of the indirect BEM (boundary element method). The main features of the proposed method are as follows. (1) An O(D²) performance in the memory capacity and operation cost is provided by applying the diagonal form fast multipole method (FMM), when the number of voxels is about D³. (2) The boundary matching is imposed by the continuity of the total flux passing through each element, which guarantees the solution globally satisfying Gauss's law; therefore the solution is globally stabilized. This method is successfully applied to calculate the electric field induced by an applied homogeneous ELF (extremely low frequency) magnetic field in a human head model that has 1 mm ×1 mm 1 mm voxel size. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 165(4): 1–10, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20529     

Current distributions inside a cylindrical model of a human body with internal and external tissues having different conductivities in electric fields

The health effects of weak currents induced in a human body as a result of the interaction between the body and power line electric fields have been investigated. A body model (cylinder + hemisphere) filled with tissues having different conductivities was used to analyze internal current densities. In this analysis, only the magnitudes of the induced current densities were analyzed. In this paper, the finite element method is applied to the analysis of the distributions of the horizontal and vertical currents induced in the cylindrical model. The calculation method was verified by comparing the calculated results with experimental results obtained elsewhere. The basic characteristics of the induced current distributions in the cylindrical model with two tissues having different conductivities have been clarified. © 1998 Scripta Technica. Electr Eng Jpn, 122(3): 19–27, 1998     

Analysis of Magnetic Field Distribution Under Power Lines with Changing Direction and Carrying Different Current

Transmission power lines are a common source of extremely low frequency （ELF） magnetic fields which are usually analyzed as serial lines in one direction. Overhead vertical-type double-circuit power li...     

放电电流密度对DMFC交流阻抗的影响

测试了膜电极组件(MEA)在不同工作电流密度(J)下的交流阻抗谱,并用等效电路L1R1 (CR2)[ QR3(L2R4)]进行拟合.内阻变化最平缓,先减小,后略微增大,变化幅度小于初始值的10％;阴极法拉第阻抗随着电流密度的增大而减小,当J＞ 1.00 A/cm2时,产生的水膜导致三相界面减少后,该阻抗又增大;阳极反应...     

高压交流输电线路曝露场强限值下人体感应电场和感应电流分析

人体处于高压交流输电线路下方时,会产生静电感应和电磁感应。当感应电压和感应电流数值过大时,会对人体造成伤害,为此国际非电离辐射防护委员会(ICNIRP)以及IEEE规定了人体在高压输电线路不同曝露情形下的曝露场强限值。首先运用有限元法,考虑人体对地绝缘和人体接地2种情况,分析了高压输电线路曝露场强典型限值下人体所产生的感应电压和感应场强的大小;接着利用解析法计算了不同曝露限值下的人体感应电流、感应电荷密度以及感应电流密度;最后将计算结果与ICNIRP导则给出的曝露限值进行了比较。结果表明,人体处于职业曝露限值场强10 kV/m下,人体内部最大感应场强为2.082×10-3 kV/m,感应电流密度为0.176 m A/m2,接近或低于ICNIRP导则规定的限值范围,不会对人体造成不适感。     

Analysis of control laws related to rapid electric drives of alternating current

The control laws of an ac rapid electric drive are analyzed. In these drives, the electromagnetic moment is formed if the energy of the magnetic field is stabilized. The control law that secures the most rapid formation of the electromagnetic moment under limited power is also examined.     

Measurements and predictions of electric and magnetic fields from power lines

Electric and magnetic field measurements around overhead and underground power lines have been performed extensively within a transmission and distribution electric grid. Measurements have been performed at different heights of the human body close to such transmission and distribution power lines that operate at a frequency of 50 Hz, at different currents and at three different voltages of 11, 66 and 132 kV. These measurements were performed in an attempt to firstly verify that the existing measurements fall within the signified guidelines for electric and magnetic field exposure, published in 1998 by the International Commission on Non-Ionizing Radiation Protection. Furthermore, and most importantly, were used to validate/develop a model capable of predicting the magnetic field produced in both overhead and underground transmission and distribution power lines using experimental measurements. This is achieved by establishing a linear correlation between the current load of one of the two three phase circuits and the magnetic field, in an attempt to predict the magnetic fields produced in power lines using the SCADA system at overloaded periods.     

Study on dependence of AC transport current losses in YBCO‐coated conductors on distribution of critical current density and n value

We measured AC transport current losses in three kinds of thin‐film YBCO‐coated conductors made by different processes. The results showed that the loss characteristics were different and that some of the conductors did not follow the Norris strip model which is generally believed to well explain the loss characteristics of YBCO conductors. In the paper, an analytical model in which distribution of critical current density and n value of the conductor are taken into consideration is proposed to describe the AC transport current loss characteristics more generally than the Norris strip and elliptical models. It is shown that the analytical model explains well the measured loss characteristics of the three kinds of conductors. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(2): 26–38, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20056     

凸极冲击发电机端部结构及磁场分析

本采用准三维有限元端部涡流场计算方法,针对一台ＴＦ２００－８／２１５０型凸极冲击发电机的端部结构设计要求,经过理论分析、多种方案计算以及试验验证表明,推荐的部结构既具有电机端区磁场分布合理、结构件损耗小、温升低,在工程上又具有低成本,工艺上简单易行的特点。所提出的计算方法合理实用,精度完全满足工程计算的要求,可推广应用于定子采用整圆压板的常规凸极同步电机端部磁场计算。     

自耦变压器绕组漏磁场及涡流损耗的二维数值分析

利用ANSYS软件建立了油浸式自耦变压器的有限元模型,采用“场-路耦合”方法分析了变压器绕组的漏磁分布,得到绕组的涡流损耗分布情况.将有限元计算结果与工程计算结果对比,说明了计算方法的准确性,对自耦变压器的设计具有一定的理论参考价值.     

变电站220 kV及以上区域工频电磁场强度特性分析

针对500 kV变电站内500 kV配电区域的工频电场强度普遍高于220 kV配电区域和35 kV配电区域、变电站工频电场强度超标点主要集中于500 kV配电区域和220 kV配电区域等状况,选取6座不同类型的500 kV变电站进行500 kV配电区域和220 kV配电区域电磁场强度检测,分析并总结出500 kV变电站...     

500 kV变电站工频电场的测量与分析

为了掌握500 kV变电站的工频电场分布,采用EFA-300低频电磁场分析仪,选取50Hz带通滤波、最大有效值方式,在某500 kV变电站厂区内,每间隔6 m测量电场强度值,将1092个测量数据绘制成电场强度分布图,找出其中电场强度较高的区域。测量结果显示,除个别区域外变电站内工频电场基本满足ICNIRP标准限值,分析变电站电场分布规律表明,电场强度较高的区域集中在主变、开关、断路器、互感器等设备及其连接线附近的区域,且场强最大值位于三相中的边相附近,应重点考核这一区域的工频电场值。     

Transient phenomena of current and field distortion due to dynamics of packet‐like charges in LDPE films

Simultaneous measurements of space charge and external current were carried out using a PEA measurement system with an electrometer on the back of a grounding electrode in order to clarify the physical situation of a huge packet of positive space charges in LDPE films. A large number of positive charges from a semiconducting anode were accumulated at the interface between LDPE and an Al‐cathode at a mean applied field of 1.5 MV/cm and then finally disappeared. The results of simultaneous measurements showed that the external current kept a relatively high value during charge accumulation and further increased when the charges disappeared. Both the charge dynamics and the external current were restricted by addition of a low‐molecular‐weight paraffin wax, indicating that carrier transport was influenced by the microstructure of the polymer. The dynamics of the residual charges after short‐circuiting is also discussed. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 179(4): 10–17, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21256     

特高压变电站人体工频电场暴露水平评估

人体在特高压变电站内的工频电场暴露水平一直受到研究人员的关注,但相关研究却并不多见.以特高压长治站为研究对象,采用ANSYS谐响应分析方法,通过子模型技术实现了特高压变电站内含人体空间域的工频电场分布计算.研究了人体的电位、电场强度和电流密度分布及鞋子的影响;对比了站内不同路径上电场分布的数值计算结果与实地测量结果以及人体内部电流的数值计算结果与理论公式计算结果;验证了所用计算方法的正确性与所得计算结果的准确性.研究结果表明:人体内部以传导电流为主,最大感应电流密度为9.15 mA/m2,满足职业标准.该研究成果可以判定特高压变电站内工频电场对人体是否安全并为后续工程提供参考.     

电动车用电池充电状态和功率强度估计

讨论了电动车 (EV)和混合电动车 (HEV )用电池电量模型和功率模型的建立 ,提出了一种新的电池剩余电量(SOC)和电池功率强度 (Powercapability)的综合估计方法。从电化学角度建立了一个电池参考模型 ,以安时计量为主并综合考虑影响电池SOC的多种因素进行SOC估计 ,功率强度估计主要基于电池等效内阻的估算。SOC估计和功率强度估计相结合 ,实现了在功率强度估计的同时对SOC估计提供自调整机制。该综合估计方法已经在我们自主开发的实验平台上实现 ,并经实践证明是可行的     

交直流混合系统低频振荡的概率特征根分析

研究低频振荡的传统特征根方法是基于单一的系统运行方式,而概率特征根分析则计及了较宽的系统运行方式变化。高压直流输电HVDC是一种典型的柔性交流输电FACTS装置,它可以改善系统的动态特性。将现有的概率特征根分析扩展到包含HVDC功能模块,能完成交直流混合系统的概率特征根分析。对四机两区域的交直流并联系统在选定的控制器参数下进行试算,结果表明,系统在多运行方式下研究交直流混合系统的低频振荡是可行的。     

间插布置方式对交流绝缘子串覆冰特性影响

间插布置方式可以提高绝缘子冰闪电压,本文通过实验验证了覆冰绝缘子串电场仿真计算模型,并在此基础上分析研究了大盘径绝缘子的直径和绝缘子串中间插绝缘子位置对绝缘子串电场分布的影响.研究结果表明:间插布置方式下覆冰绝缘子串电压分布发生严重畸变,但比标准绝缘子串下的最大电压分布小;采用"3+1"和"4+1"间插布置方式且大盘径...     

永磁同步电机离散化建模与分析

为解决内置式永磁同步电机(IPMSM)离散化模型存在的复杂度和精度相互矛盾的问题,以磁链为状态量的对称化建模思路使得复矢量技术得以利用,模型描述得以简化.但所获得的复矢量模型在离散化过程中,依然受到电流状态的影响,其变化通过电阻压降耦合到状态方程中.为此,分析和讨论了采样间隔内电流变化的不同描述方式对离散化建模精度的影...