变压器杂散损耗的三维有限元分析

建立了简化后的三相五柱式电力变压器三维有限元模型,利用ANSYS软件分析了变压器的漏磁分布,通过有限元计算得到变压器油箱和金属结构件的涡流分布和损耗值.将求得结果与工程计算结果对比分析,验证了有限元计算方法的准确性,对三相五柱式电力变压器的设计和运行具有一定的实用价值.     

Study of fluctuations in advanced MOSFETs using a 3D finite element parallel simulator

Two important new sources of fluctuations in nanoscaled MOSFETs are the polysilicon gates and the introduction of high-κ gate dielectrics. Using a 3D parallel drift-diffusion device simulator, we study the influence of the polycrystal grains in polysilicon and in the high-κ dielectric on the device threshold for MOSFETs with gate lengths of 80 and 25 nm. We model the surface potential pinning at the grain boundaries in polysilicon through the inclusion of an interfacial charge between the grains. The grains in the high-κ gate dielectric are distinguished by different dielectric constants. We have found that the largest impact of the polysilicon grain boundary in the 80 nm gate length MOSFET occurs when it is positioned perpendicular to the current flow. At low drain voltage the maximum impact occurs when the grain boundary is close to the middle of the gate. At high drain voltage the impact is stronger when the boundary is moved toward the source end of the channel. Similar behaviour is observed in the 25 nm gate length MOSFET.     

电力变压器磁屏蔽模型损耗三维有限元分析及实验研究

针对大型电力变压器铁磁结构件中(例如油箱)产生的电磁损耗导致局部过热,使相关的绝缘部件受损,进而危及整个变压器的正常运行现象,笔者提出以国际TEAM Problem 21基准磁屏蔽(简称为板式和立式屏蔽)模型为例,采用分离激励线圈电阻损耗和涡流损耗的测量方法(漏磁通补偿线圈测量装置),对变压器取向硅钢叠片中的磁通和损耗进行计算和试验测量。其计算与测量结果表明,该方法较好地解决了线圈损耗和结构件损耗分离的问题。同时,也验证了三维非线性涡流场分析和损耗模拟方法的有效性。     

变压器油箱涡流损耗的三维有限元分析

大型电力变压器中油箱涡流损耗占其杂散损耗绝大部分,易使变压器产生局部过热,烧损变压器。因此,为了有效降低油箱涡流损耗,提出采用ANSYS软件三维有限元法对变压器进行仿真计算,以求得到其油箱漏磁和涡流损耗分布及大小,然后采取相应的防控措施,即在变压器加入磁屏蔽。经仿真计算分析,在变压器加入磁屏蔽有利于降低油箱中的漏磁密度、减小损耗,同时也说明采用该方法计算损耗准确、可行。     

二维／三维场域有限元分析的可视化前后处理方法

介绍了二维／三维多种介质、多连通域任意形状有限元剖分的前处理方法及二维／三维结果数据的表示、等位图、向量图和数据取样的曲线的绘制方法,并给出了一个三维耦合场问题的计算实例。     

基于谱元法的三维欧拉-拉格朗日浅水模型

基于欧拉-拉格朗日法（Eulerian-Lagrangian method,ELM）计算对流项的三维水流数学模型,大时间步长计算仍保持稳定,但空间线性插值计算会产生附加数值阻力,限制了该类模型在河流工程中的应用。谱元法（spectral element method,SEM）是一种适合复杂区域计算的高阶数值方法。本文引入谱元法,将垂向线性插值改为多项式插值,构建了新的欧拉-拉格朗日法三维浅水流动数值模型。通过顺直明渠的算例分析表明,新三维模型结合了欧拉-拉格朗日法与谱元法的优点,时间步长能突破柯朗数的限制,同时消除了经典欧拉-拉格朗日法的数值阻力,计算精度有数量级的提高。     

水轮发电机定子三维温度场的有限元计算

建立水轮发电机定子三维温度场计算的数学模型和泛函,用有限元法对水轮发电机定子1／2轴向长度的三维温度场进行求解,得到任意一个截面及沿轴向方向的温度分布曲线。对一台320MW的水轮发电机进行计算。结果表明,定子最高温度值与实测值基本相符。     

水轮发电机转子三维温度场的有限元计算

建立水轮发电机转子三维温度场计算的数学模型,用有限元法对水轮发电机转子1／2轴向长度的三维温度场进行求解,给出任意一个截面的温度分布曲线。对一台320MW的水轮发电机进行了数值计算。结果表明,最高温度值与实测值基本相符。     

二维有自由面渗流分析的有限元并行计算

建立了一个基于MPI消息传递的微机机群系统,进行了有自由面渗流的有限元并行分析。通过预处理共轭梯度法和逐个单元法技术的结合来求解方程组,采用前后处理的并行、负载均衡等技术,改善了程序性能。通过对土坝渗流进行并行数值模拟验证了模型的正确性和有效性。加速比、计算效率和可扩放性的测定表明,该模型对大型问题能够减少存储空间,提高运算速度,具有良好的可扩放性,有能力对大型工程,特别是土坝的渗流问题进行快速精确的模拟。     

地下洞室三维弹塑性动力显式有限元锚杆模拟

锚杆的数值模拟方法是分析地震灾变中锚杆的作用机理及锚杆支护对地下洞室围岩抗震的加固效果的关键。基于地震动荷载作用下锚杆围岩联合受力机理,在对FLAC3D锚杆模拟算法进行一定改进的基础上,提出了一种适用于抗震分析的全长粘结式锚杆模拟方法,并将该方法应用到自主开发的地下洞室三维显式动力有限元程序中,取得较好效果。该方法继承了FLAC3D中对锚杆、锚杆与砂浆接触面、锚固砂浆、砂浆与围岩接触面及围岩本身共5种结构材料的受力破坏情况的详细模拟,但不再进行相邻锚杆计算段之间的受力平衡迭代,而是将各锚杆计算段的受力转移到单元结点上,将锚杆求解与单元求解相统一,从而降低动力求解中锚杆的计算耗时。同时,详细推导了锚杆各结构材料的屈服极限表达式,缩短了锚杆结构材料屈服判断及应力修正耗时。该锚杆模型与FLAC3D中的模型假定不同,认为锚杆变形由围岩变形引起,各锚杆计算段间受力相对独立,受力并不连续,与地震中围岩锚杆的受力情况较吻合。采用该方法对某地下厂房洞室群进行地震动力时程分析,表明该模拟方法提高了求解速度,充分反映了锚杆对围岩的支护效果。     

基于有限元的二维各向异性地层中大地电磁响应

地球介质的电各向异性现象是普遍存在的,而传统上电磁法的理论研究与实际应用多是基于各向同性理论的假设,因此研究基于各向异性理论下电磁场的响应特征就显得非常迫切.从Maxwell方程出发,推导了二维倾斜各向异性下大地电磁场的偏微分方程,并采用有限元法对设计的一系列二维各向异性模型进行数值计算.结果表明,不论改变各向异性系数...     

Magnetic field analysis of a 70‐MW‐class superconducting generator by the 3D finite element method

The three‐dimensional magnetic field and eddy current distribution of the 70‐MW‐class superconducting generator was calculated by a finite element method. The condition for the exciting armature coil was calculated by the jω‐method. In the magnetic flux distribution of the armature winding bore, the value obtained by analysis had good agreement with the measurement. An analysis that let the rotor move by the synchronizing speed was also done. The armature voltage for the nonload condition and the armature current for the three‐phase short‐circuit condition obtained by calculations had good agreement with the measurements. The validity of the analytical model for three‐dimensional magnetic field analysis of superconducting generators was confirmed from these results. In addition, the synchronous reactances were calculated using these results with eddy current in the facing. It was found that the facing had the effect of decreasing synchronous reactance by about 5%. © 2000 Scripta Technica, Electr Eng Jpn, 134(2): 53–60, 2001     

Use of a finite element model for the determination of damping and synchronizing torques of hydroelectric generators

Damping and synchronizing torque coefficients are calculated from time-stepped finite element simulations of a hydroelectric generator connected to an infinite busbar. The calculated torque coefficients are compared to those obtained from two-axis equivalent circuit simulations as well as classical analytical expressions. The influence of the damper winding type, and the size and nature of the system disturbance on the damping and synchronizing torques is explored. It is found that a finite element model of a hydroelectric generator typically exhibits both higher damping and synchronizing properties compared to a two-axis circuit equivalent of the same unit. In particular, the damping and synchronizing contributions from a continuous damper winding are substantially higher in the finite element model than in the equivalent circuit model. Moreover, explicit consideration of dynamic iron losses is found to not affect the damping and synchronizing torques predicted by the finite element model.     

12/8极双通道开关磁阻电机非线性数学模型与有限元分析

与传统的12/8极开关磁阻电机不同,双通道开关磁阻电机线圈之间采用一对极绕组反向串联的结构形式,由两套独立的功率电路驱动形成新型的双通道控制系统,该系统能够实现容错控制以提高可靠性.本文在分析双通道开关磁阻电机原理和结构的基础上,建立了电机每个通道绕组的磁路等效数学模型,在一个相周期内对磁路各部分磁导进行了详细分解计算,确定了以磁导表示的磁通矩阵,推导出绕组自感及各相之间互感的计算方法.该模型考虑了电机轭部磁路和材料非线性磁饱和的影响,提高了模型的实用性.有限元分析结果验证了该数学模型的正确性.     

有限元电场计算时模型表面网格精细控制方法

大型复杂模型有限元电场求解过程中,所关注设备表面网格的精细化控制往往难度较大。为此,对有限元电场数值计算时网格划分的相关基本原则进行讨论,考虑实体模型的基本几何结构,提出了基于多层外包实体实现设备表面网格精细控制的思想,在此基础上研究了有限元建模方法。以简单三维模型为例,分别介绍了外包实体生成算法、区域划分原则及相关操作流程。以标准模型为例介绍了所提方法的具体应用过程,同时对外包实体的参数设定进行了讨论。将该方法应用于±1100 kV特高压换流站直流阀厅设备表面电场计算中,计算所得模型表面电场过渡平滑,电场强度最大值为13.8 kV/cm。该方法有效实现了模型表面网格的精细控制,对大型复杂有限元模型的高效、精确建模具有一定的指导意义。     

基于修正车体有限元模型的列车故障模拟

研究如何建立、修正和运用有限元模型来模拟动车组车载部件故障。将三维的列车车体几何模型简化为二维模型,并建立合理的耦合约束关系。对模型进行模态分析,提取自然频率和模态振型,结合实验数据对模型的弹性模量和密度参数进行修正,并对修正模型进行动态响应分析得到车体振动响应。研究表明：1)修正后车体的一阶垂向、横向、棱形和扭转模态与实验误差大幅度缩小,仿真与实验数据的结果吻合;2)螺栓断裂故障仿真例子则表明基于修正模态的有限元模型可指导列车实验测点的布置、实验数据的分析和故障的判定。     

A 3D finite element analysis of large‐scale nonlinear dynamic electromagnetic problems by harmonic balancing and domain decomposition

The dual–primal finite element tearing and interconnecting (FETI‐DP) method is applied together with the harmonic balance method and the fixed‐point (FP) method to improve the efficiency of three‐dimensional finite element analysis of large‐scale nonlinear dynamic electromagnetic problems. The FETI‐DP method decomposes the original problem into smaller subdomains problems. Combined with parallel computing techniques, the total computation time can be reduced significantly. To account for nonlinear B‐H characteristics, the FP method is applied together with the polarization formulation. Because the FP method assumes a constant reluctivity, it decouples the systems of different harmonics. The FETI‐DP method can then be applied to speed up the simulation of each harmonic in each FP iteration. Two benchmark problems and a three‐phase inductor are simulated by the proposed method to validate the formulation and demonstrate its performance. Copyright © 2015 John Wiley & Sons, Ltd.     

铁芯式两极纵磁真空灭弧室三维静磁场有限元分析

铁芯式两极纵磁真空来弧室是我国第一个具有自主知识产权具有较高开断能力的真空灭弧室。对其纵向磁场进行数值分析可为进一步提高它的开断能力提供思路。对其三维静磁场的有限元分析结果表明,这种新型真空来弧室可产生很强的纵向磁场,纵向磁场在间隙中及触头表面上分布都较为均匀。结构参数的变化对纵向磁场的影响很大,当触头直径增大时纵向磁场强度增加较大,开距增大时则迅速减小,拐臂宽度增大时其强度呈线性减小。     

三维弹性自适应有限元及其在拱坝分析中的应用

本文将自适应有限元用于拱坝,应用ZZ后验误差估计方法以及h-型自适应策略,对典型的悬臂梁和拱坝进行三维线弹性自适应有限元计算。计算结果表明,本方法可有效提高计算精度和计算效率,特别是对于具有应力集中的结构,具有显著的效益。