The wave concept iterative process (WCIP) method for electrical circuit network with triangular and hexagonal topology

This paper deals with an RLC circuit network with triangular or hexagonal grid. It is about a planar equilateral triangular grid where the passive (resistor, capacitor, and inductor) or active (voltage source for example) components are located at the sides or/and at nodes attached to the ground. The planar graph is oriented by three main direction vectors phase shifted to 60° degrees. The wave concept iterative process (WCIP) method was employed to the theoretical formulation of the problem. In the formulation, the potential difference across each circuit component is represented by an auxiliary source defined in the spectral domain. The proposed theory is developed into two definition domains: a spectral domain in which periodicity and coupling between the circuit components are defined and a spatial domain describing the network topology and imposing the continuities conditions (Kirchhoff laws). The transition between the spectral and spatial domain is ensured by the so-called fast hexagonal Fourier transform. Numerical applications demonstrate the ability of the method for solving the inhomogeneous triangular lattices. Various conceptions have been proposed including an RL, RC, and RLC triangular network circuit, a perturbed triangular RLC circuit, and a triangular circuit excited by many lumped sources.     

COMBINED ELECTROTHERMAL FINITE ELEMENT ANALYSIS OF TURBINE-GENERATORS

ABSTRACT

In this paper a hybrid finite element analysis is presented for solving the combined magnetic field and temperature distribution problem in a slice of a stator core on open-circuit operation. A two-dimensional nonlinear finite element magnetic field model is used to obtain the core losses and a three-dimensional finite element model with triangular, rectangular and trapezoidal elements is employed for determining the temperatures. The temperature distribution obtained by the method presented in this paper is compared with factory tests on a large Turbine-Generator     

带线三角结环行器的小型化研究

带线结环行器的小型化是当今微波铁氧体器件的研究热点之一。本文研究对象为带线三角结环行器,其正、负旋转本征模式的截止数kA决定了环行器的尺寸大小。通过有限元分析方法,研究了kA值与三角结中心谐振导体形状的关系。提出了对三角结中心谐振导体开槽的方法,来减小三角结中心导体的边长尺寸,从而实现环行器的小型化。实验仿真表明该方法在实现带线三角结环行器小型化的同时,使其性能完全满足GSM基站对于环行器的指标要求。     

球形电极三维静电场的球面三角形边界元算法

针对电力设备中球形电极的电场强度计算问题,提出了球面三角形边界元方法.在该方法中,定义了球面三角形单元上的形状函数.边界元积分严格取为球面积分,求解函数在球面单元上沿大圆弧线性插值,边界元的外法线方向严格取为球面法线方向.算例计算结果表明,与平面三角形边界元相比,在网格剖分情况相同时,球面三角形边界元的计算精度显著提高;在计算精度要求相同时,采用球面三角形边界元计算,节点数可以大幅度减少,从而对计算机内存需求明显减少,总体计算时间也相应减少.     

A color graphics display of the field intensity around theinsulator on 13.2 kV distribution lines

Covered conductors have been used, especially in wooded areas on low as well as high voltage overhead distribution lines for preventing brush contact and short circuit faults between conductors. Burndown on covered conductors has become a significant problem. The burndown mechanism is complicated since it is determined by combinations of the various types of insulators, ties, and conductors. In order to investigate the burndown mechanism, a finite element analysis is carried out to identify the electric field around the insulator. A newly developed electric field digital simulation system is reported in which a finite element analysis method considering isoparametric triangular and line elements is developed. A new color display method for electric potential and electric field distributions with lines of electric force is also described as a means of observing the results     

基于圆环坐标系的三维静电场曲边三角形边界元方法

针对高压电力设备中常见的圆环电极表面电场强度的计算问题,提出了圆环面曲边三角形边界元方法。在该方法中,单元积分严格在圆环表面上进行,求解函数在圆环面曲边三角形单元上沿圆环坐标线性插值,边界单元的外法线方向严格取为圆环面的外法线方向。算例计算结果表明,与直边三角形边界元相比,在网格剖分节点分布相同的情况下,圆环面曲边三角形边界元计算精度显著提高;在计算精度要求相同的情况下,采用圆环面曲边三角形边界元计算,节点数可以大幅度减少,从而对计算机内存需求明显减少,总体计算时间也相应减少。     

Multilayered transformer utilizing Mn‐Zn ferrite and its application to a forward‐type DC–DC converter

This paper describes the electrical characteristics of a multilayered transformer composed of a Mn‐Zn ferrite core, and primary and secondary conductors positioned alternately not only in the vertical direction but also in the horizontal direction. In order to elucidate the operating characteristics of the two types of transformers, one was given the conventional planar winding structure and the other the new winding structure described above, and a two‐dimensional finite element method that took account of the two conditions and a constant input voltage and load current was introduced. The coupling coefficient of the conventional multilayered transformer deteriorated with increasing load current. But the coupling coefficient of the proposed multilayered transformer was independent of the load current. A forward‐type DC–DC converter using the new multilayered transformer had higher efficiency than a converter using the conventional multilayered transformer. © 2001 Scripta Technica, Electr Eng Jpn, 135(4): 1–8, 2001     

大型水轮发电机定子最热段三维温度场的有限元计算

本文用有限元法求解了大型水轮发电机负载时定子最热段的三维温度场。首先列出三维温度场的数学模型及泛函,推导了采用三棱柱单元时的离散格式,接着用网格自动剖分和求解场的源程序计算了二台大型水轮发电机定子最热段的温度分布,并与实测值和用其他方法算出的结果进行了比较。结果表明,本文的方法是正确的,程序是有效的。     

基于ANSYS和SYSNOISE的电机噪声仿真分析方法

针对电机噪声分析时有限元软件ANSYS不能直接得到声响特性与实验数据比对的问题,研究与振动声学分析软件SYSNOISE进行联合仿真的方法.以一台永磁直流电机为例,建立基于AN-SYS的结构动力模型,计算振动频响特性并作为输入边界激励条件加入SYSNOISE,用SYSNOISE计算出声压频响特性.仿真与实验结果表明,最大...     

三角格栅排列相控阵天线近场特性研究

为了掌握相控阵天线近场辐射特点,根据波束形成原理,提出了三角格栅相控阵天线辐射近场的数学模型,并进行了仿真验证。计算结果与仿真结果相比,相控阵天线主波束上场强幅度最大偏差约1dB,吻合较好。利用该模型对相控阵天线的电场近场分布特点进行了分析。在近场未形成主波束的区域,波束存在多个波峰和波谷;该区域内法线上场强出现极大值时发射方向在指向各观察点的方向附近徘徊。随着距离增大,波峰和波谷聚拢,波束宽度逐渐收窄;发射方向的徘徊区间慢慢变小,形成主波束后发射方向与实际波束指向一致。所得结论同样适用于矩形格栅相控阵天线。研究结果为相控阵天线的电磁兼容设计、辐射近场测量提供了理论依据和指导。     

Decomposition multi-step non-iterative method for the numerical integration of short-term and long-term dynamics of power systems

A decomposition multi-step non-iterative method for the numerical integration of short-term and long-term dynamics of power systems is given. This method is derived, on the one hand, on the basis of the triangular block alternative semilinear structural property, where it is to be noted that the triangular block alternative linear dynamical system is a special case of triangular block alternative semilinear dynamical system and, on the other hand, on the basis of representing the vector function of the time variable with a special form of interpolation polynomial. The method can be applied not only for the numerical integration of short-term and long-term dynamics of power systems, but also for all other cases where the model of the dynamical system can be represented in triangular block alternative semilinear form. Numerical stability, accuracy and computation speed of this method make suitable for many applications, such as the dynamic security analysis of power systems.     

油浸式变压器顶层油温热路模型计算分析与检验

介绍了传统变压器内部热场的有限元方法模拟热路模型,并在此基础上,增加平均油温、太阳辐射等条件参数,对原有模型进行改进,利用光纤光栅温度测量系统,对变压器样机进行现场温升试验,并将热路修正模型计算结果与几台变压器实测温升数据进行对比,结果验证了该热路修正模型的精确性。     

Thermal analysis of power cables in multi-layered soil. I.Theoretical model

The heat dissipation and temperature distribution in multilayered soil surrounding a buried cable are calculated using the finite difference method and the energy conservation principle. The numerical technique proposed is very suitable for modeling any real cable installation configuration in multilayered soil. The development of the model and the effect of the parameters that influence the conversion and the stability of the numerical solution of the heat dissipation from the underground cable system are studied     

用镜像法计算变压器漏电抗的研究

本文对用镜像法计算变压器的漏电抗进行了研究,并实算了两台大型变压器的漏电抗.计算结果与用六节点三角元细剖分时算得的漏抗精度相当,而用本文的方法所需计算机内存极小.     

三维表面电荷法在位场计算中的几点改进

针对常规三维表面电荷法在位场计算中采用平面单元剖分、常值电荷估计致使计算效率低内存消耗大的缺点,对表面电荷法进行改进。采用曲面三角形单元对曲面进行剖分并通过二次多项式进行插值,利用线性或二次插值估计电荷密度以反映电极表面电荷密度的线性及非线性分布的特点,在奇异积分处理上通过切平面法解决格林函数基本解的奇异积分,并给出其具体实现。最后通过两个典型算例进行了验证,结果表明该方法精度较高,具有一定可行性。     

Scattering characteristics of FSSs with triangular conducting elements

In this paper, scattering characteristics of dielectric backed frequency selective surfaces (FSSs) having triangular conducting elements are investigated for both transverse magnetic and transverse electric incident plane waves. Since triangular conducting elements are etched periodically on such a surface, incident and scattered fields are expressed as Floquet modes. Using Floquet’s theorem and satisfying the required boundary conditions an integral equation is obtained for the induced current density on the surface of a triangular conducting element in one periodic cell. This induced current density is expressed as a finite sum of piecewise triangular basis functions having unknown coefficients. The resulting integral equation is then converted to a linear matrix equation by using the Method of Moments. Taking the inverse transform of the matrix equation yields the unknown current coefficients which are finally used to compute the reflection and transmission coefficients. Since there are no theoretical or experimental results for FSSs comprising of triangular conductors, verification of the algorithm developed is carried out by comparing the numerical results obtained using this algorithm with the experimental and theoretical results in the literature for FSSs composed of strips and L-shaped conductors. For this, in the algorithm, appropriate arms of the triangles are removed to conform them into strips or L-shaped conductors. Results obtained for strips and L-shaped apertures by using this algorithm are in excellent agreement with the results in the literature.     

A novel and simple model for estimating the hourly global solar radiation

This letter proposes a novel and simple method for estimating solar radiation, named the ‘three‐point method’. The three points used to form the model are sunrise, sunset, and the maximum radiation point. The issue of obtaining maximum radiation is performed with the weighting evaluation of the HOTTEL and ASHRAE models. The feasibility and effectiveness of the proposed model is shown by simulation results. This model is equally applicable in any part of the world with a reassessment of the weighting factors for the maximum radiation. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

One-step decomposition method for numerical integration of short- and long-term dynamics

A mathematical model is derived and disdussed that represents the structural properties of the alternative linearity and of the triangular block structural connectivity of the sets of differential equations, associated with the machines in the numerical integration of short- and long-term dynamics. In order to take into consideration the structural properties of the model, a one-step decomposition method for the numerical integration of short- and long-term dynamics is proposed. The method can be applied not only to the numerical integration of short- and long-term dynamics but also to all other cases when the model of the dynamic system is alternative-linear and triangular block connected. Numerical stability, accuracy and computation speed are the major advantages of this method, making it suitable for many applications, including the dynamic security analysis of power systems.     

Theoretical model to calculate steady-state and transient ampacity and temperature in buried cables

The temperature distribution and ampacity in a multilayered soil surrounding a system of three cables are calculated in the steady state and in emergency situations. In this paper, we present the mathematical model, which solves the heat diffusion equation in cylindrical coordinates inside the cables and in Cartesian coordinates in the surrounding soil. The finite difference method is used to solve the equations. In order to reduce the number of points studied that are of no interest to the results, a variable step discretization is used. Here, we present the development of the model and the effect of some of the parameters which influence the convergence and accuracy of the method. The application of the model in different configurations and situations is given in the second part of this work, sent for publication at the same time. The model is applicable to the study of buried cables in both the steady state and transient states for short-circuit and overload situations.     

有限元程序的前处理程序

本文采用子区域结构,等参坐标变换方法,对具有多种介质的二维复连通区域,给出一种三角形单元的网格自动剖分方法。编写了包括网格割分后处理,边界、区域信息处理,屏幕显示的前处理程序。实例计算给出了较好的效果。