Penalty-Finite Element Analysis of the Eddy Current Loss in a Fully-Stabilized Multifilamentary Superconducting Wire

The paper is mainly concerned with the penalty incurred in finite element analysis of the eddy-current loss problem in a fully established multi-filamentary superconducting wire. A finite element model with 4-node quadrilateral isoparametric elements is formulated for the present problem. Unlike the conventional vector potential scheme in use for electromagnetic field problem, the present work features a direct computational approach to eddy current loss. Simplicity and remarkable enhancement in computational accuracy can be obtained with the proposed method.

Visualization and Quantitative Evaluation of Eddy Current Loss in Bar-Wound Type Permanent Magnet Synchronous Motor for Mild-Hybrid Vehicles

This paper describes the conductor eddy current loss that occurs in a permanent magnet type synchronous motor with a distributed winding stator using a rectangular copper wire designed for mild hybrid system applications for small vehicles.Compared with the conventional round wire inserter method,the space factor can be improved and the coil-end length can be shortened by applying a so-called hairpin windings using a pre-formed into hairpin shape of bar conductor,and as a result,DC current resistance of the armature winding can be reduced.However,since the conductor cross-sectional area tends to increases,the conductor eddy current loss generated by the space harmonics linkage becomes too large to ignore.In order to study the reduction of the conductor eddy current loss,it is important to visualize the spatial leakage flux distribution which causes loss and finely analyze how the magnetic path is formed.Therefore,analysis of the conductor eddy current loss distribution generated in the bar-wound conductor is performed using the CAE model that faithfully reproduces the coil-end shape of the actual machine.Furthermore,it was qualitatively clarified what ratio of conductor eddy current loss at various driving points.Finally,the results of preliminary study on reduction of conductor eddy current loss are reported.

Novel Rotors with Low Eddy Current Loss for High Speed Permanent Magnet Machines

Due to the large rotor eddy current loss and low thermal conductivity of carbon fiber sleeve,the high temperature usually occurs in high speed permanent magnet machines(HSPMMs)at the rated operation condition,resulting in irreversible demagnetization of the permanent magnet(PM).To obtain low rotor temperature,two novel rotor structures with low rotor eddy current loss are proposed in this paper.With the output torque and air gap flux density unchanged,the performance of HSPMMs with the two proposed rotor structures are analyzed based on finite element algorithm(FEA),including eddy current loss and temperature.Finally,the appropriate parameters of the proposed rotor structures are selected,and the electromagnetic(EM)performance,rotor stress and temperature are compared with those of the conventional rotor structure.Index Terms-Eddy current loss,finite element algorithm(FEA),electromagnetic(EM)performance,high speed permanent magnet machines(HSPMMs).

Calculation of Eddy Current Loss and Short-circuit Force in SSZ11-50000/110 Power Transformer

The ?method is used in this paper to calculate the leakage magnetic field of SSZ11-50000/110 Power transformer, and by which the structures’ influences to the main leakage flux are analyzed. Through the combination of the product and TEAM Problem 21B, the surface impedance method shows its great advantage in the calculation of eddy current loss.

Bonded Terfenol-D composites with low eddy current loss and high magnetostriction

Bonded Terfenol-D composites,with high electrical resistivity and low eddy current loss,can be used in an alternating magnetic field with high frequency.However,the nonmagnetic binder impairs the magnetostriction of the composites.To achieve high magnetostriction and low eddy current loss,the mixture of the alloy powder and binder was compressed at low pressure in an oriented magnetic field.After this,the aligned samples were recompressed by cold isostatic pressing（CIP）.Besides,the effect of particle size on the magnetostriction of the bonded Terfenol-D composites was also studied.The results showed that the bonded Terfenol-D composites had excellent magnetostriction when the particle size was 50-80 μm.The oriented magnetic field and CIP could improve the magnetostriction of the bonded composites,which reaches 1020×10-6.The bonded Terfenol-D composites had good compact structure and high density（7.24 g/cm3）.The magnetic loss of the bonded Terfenol-D composites was 192 mW/cm3 at a frequency of 100 kHz in a magnetic field of 960 A/m,which was about one third of that of casting Terfenol-D alloys.

A Review of Medium Voltage Single-Core Cable Armouring, Induced Currents and Losses

Insulated underground cables have the potential to reduce power outages, maintenance costs, and transmission losses compared to overhead lines. On the other hand, they are exposed to several risks and physical damages, since they are buried in the ground. Though the cables are armoured in order to provide mechanical protection and achieve tensile strength, and also to provide effective conductance of earth fault currents. The main purpose of this paper is to introduce insulated underground cables, armouring process, and to analyze the induced currents in metallic parts such as sheath and armour that causeohmic losses which are categorized mainly in two groups as circulating current and eddy current. This paper presents a review on analytical techniques used to analyze the effect of magnetic fields, andcalculate the losses in the armour of the cables, besides providing the strategies and solutions used for armour loss reduction.

Finite Element CAD Experiments on the Effect of Magnetic Loss in Power Transformers with Laminated Cores

The paper describes a simulated experiment that focuses on the numeric computation of magnetic loss in the laminated core of a single-phase power transformer. The students’ laboratory work is part of the library of experiments of the Electrical Machines virtual laboratory and makes use of the two-dimensional open-access electromagnetic field analysis software Finite Element Method Magnetics. The idea of the simulated exercise is to demonstrate how the magnetic loss caused by time-varying excitations affects the magnetic permeability, μ, of the laminated core and the terminal quantities of the energizing winding. A parametric analysis employing different values for the electrical conductivity and maximum hysteresis-induced angle of the laminated material yields five different field problems with increasing magnetic loss. Electric circuits characterized by the (I-V) operating point and reflected impedance of the energizing winding provide the information required to compute the changes in real power ΔP, reactive power ΔQ and magnetically stored energy ΔWm between successive problems characterized by increasing magnetic loss. The concept of reflected impedance helps to explain the physical meaning of the changes in power dissipation and energy storage in the laminated core.

Identification of XLPE cable insulation defects based on deep learning

The insulation aging of cross-linked polyethylene(XLPE)cables is the main reason for the reduction in cable life.There is currently a lack of rapid and effective methods for detecting cable insulation defects in power-related sectors.To this end,this paper presents a method for identifying insulation defects in XLPE cables based on deep learning algorithms.First,the principle of the harmonic method for detecting cable insulation defects is introduced.Second,the ANSYS software is used to simulate the cable insulation layer containing bubbles,protrusions,and water tree defects,and the effects of each type of defect on the magnetic field strength and eddy loss current of the cable insulation layer are analyzed.Then,a total of 10 characteristic quantities of the total harmonic content and 2nd to 10th harmonic currents are constructed to establish a database of cable insulation defects.Finally,the deep learning algorithm,long short-term memory(LSTM),is used to accurately identify the types of insulation defects in cables.The results indicate that the LSTM algorithm can effectively diagnose and identify insulation defects in cables with an accuracy of 95.83%.

Effect of Ball Scribing on Power Loss Separation of Fe-3%Si Grain-oriented Silicon Steel

Power loss of Fe-3%Sigrain-oriented silicon steelwas measured after ballscribing with different spacing using a self-designed tool.Three different sections of power loss,including hysteresis loss,abnormalloss,and eddy current loss,were measured and calculated,respectively.The loss variation and ratio were analyzed based on the experimentaldata.At 1.0 T,hysteresis loss of tested steelwith scribing spacing of 8 mm descends by 8.2% compared to samples without scribing,which is similar to the totalloss variation,and abnormalloss descends by 16.8%.At 1.0 T,hysteresis loss ratio of the steelwith scribing spacing of 16 mm ascends from 55.7% to 57.9%,and eddy current loss increases from 17.4% to 24.1%,while abnormalloss descends from 26.9% to 23.7%.The experimentalresults show that the reduction of power loss after scribing is mainly due to decreasing of hysteresis loss and abnormalloss.

Design and Performance Analysis of Permanent Magnet Claw Pole Machine with Hybrid Cores

Permanent magnet claw pole machine(PMCPM) is a special kind of transverse flux permanent magnet machine. Compared with other electrical machines, it has the advantages of high torque density and high efficiency for high speed operation. However, because of its complex irregular structure, the manufacturing process using silicon sheets is complicated. Soft magnetic composite material(SMC) is manufactured by powder metallurgy technology, which can produce various shapes of stator core structures, so it is easier to produce various irregular shapes of the stator core. However, the raw SMC material is relatively expensive, and the mechanical strength of SMC is weak. In this paper, a PMCPM with hybrid cores is proposed. With the adoption of hybrid silicon sheet-SMC cores and amorphous alloy-SMC cores, the torque ability of PMCPM can be improved greatly and it can have higher efficiency for more wide operation frequency. Meanwhile, its mechanical strength has been improved and it can be designed for high torque direct drive applications as it is a modular machine. Furthermore, three methods are proposed to reduce the additional eddy current loss which resulted from the employment of hybrid cores in PMCPM.

核电半速汽轮发电机励磁绕组匝间短路时转子涡流损耗研究

为研究核电半速汽轮发电机励磁绕组匝间短路时转子涡流损耗特性,推导了核电半速汽轮发电机空载运行时励磁绕组匝间短路故障下,定子分数次谐波环流产生的合成磁动势表达式,分析合成磁动势相对于转子的转速,揭示了转子表面产生涡流的原因以及涡流的频率特性。结合涡流损耗计算方法,以一台核电半速汽轮发电机为例进行了仿真验证。在此基础上,对核电半速汽轮发电机励磁绕组不同位置发生相同程度匝间短路,以及励磁绕组发生不同程度匝间短路过程进行了仿真,计算了转子各阻尼条及槽楔中的涡流及涡流损耗,揭示了励磁绕组匝间短路时影响转子阻尼条及槽楔中涡流和涡流损耗的因素。为核电半速汽轮发电机励磁绕组匝间短路故障时,分析转子发热的影响因素提供了理论基础。

超磁致伸缩力传感执行器磁路优化设计与分析

以超磁致伸缩力传感执行器为研究对象,基于磁致伸缩与涡流损耗理论,应用COMSOL有限元软件进行磁场分析,系统地研究了导磁体参数对磁通密度与涡流的影响规律。为增大磁通密度、减小涡流损耗,以超磁致伸缩棒中轴线上磁通密度均匀度为评价标准,优化了导磁体参数,并将导磁体分区绝缘。静、动态磁场下与未优化时实验结果进行对比,结果表明:静磁场中优化后的磁通密度均值提升了0.0161T,均匀度提升了4.5%;动态磁场中,分区绝缘可有效减少涡流损耗,优化后的力传感器灵敏度提升了5.76%。

PMSM定子铁耗与磁极涡流损耗计算及其对温度场的影响

采用二维有限元法对交流永磁同步电动机(PMSM)定子与磁极区域电磁场进行了分析研究,阐述了定子铁心不同区域磁场的变化规律以及磁极区域涡流场的分布规律。在此基础上,综合考虑电机中交变与旋转磁场的影响,计算了电机定子饱和铁心损耗与磁极涡流损耗,并将此计算结果应用于电机的三维温度场计算中,分析了两类损耗对电机温升的影响。通过计算结果与实测值的对比分析,验证了损耗与温度场计算方法的正确性。

基于ThermNet和MagNet的水轮发电机端部电磁、温度场仿真研究

应用有限元仿真软件MagNet和ThermNet对某一100MW水轮发电机端部电磁、温度耦合场进行了仿真研究。主要工作包括:三维建模、三维复杂导体剖分中的"大尺度差别"问题的处理方法,以及MagNet和ThermNet商用软件的具体实施步骤和过程。最后,给出了模型样机涡流场、温度场的数值计算结果。

高速永磁电机铁耗精确计算两项式模型

基于分段带补偿项的铁耗计算方法,本文提出了一种适用于高速永磁电机铁耗精确计算的两项式数学模型。通过结合高速电机运行特性对频率和磁密区间进行双重划分,在Jordan损耗分离模型的基础上引入涡流及磁滞损耗补偿项考虑磁饱和、局部磁滞回环及涡流趋肤效应等非线性因素对硅钢片单位损耗特性的影响。该模型新增参数均为随频率和磁密变化的分段常函数,通过L-M算法拟合求解,在减小计算量的同时明确反映铁磁材料非线性对铁耗计算的影响,实现铁耗精确计算。最后,以某高速电机用硅钢片35SWH1900为例,对比了本文所提模型与Jordan损耗分离模型在单位损耗上的计算误差,实验结果表明所提模型计算误差基本在15%以内,能够有效提升高速永磁电机铁耗的计算精度。

考虑旋转磁通的PMSM铁心损耗数值计算

为了准确计算交流永磁同步电机(PMSM)铁心损耗,采用二维有限元法对PMSM定子与磁极区域电磁场进行了分析研究,阐述了定子铁心不同区域磁场的变化规律及磁极区域涡流场的分布规律。在此基础上,借助谐波分析的方法,综合考虑电机中交变与旋转磁场的影响,给出了一种较准确求解定子铁心损耗和PMSM转子涡流损耗的计算方法,并与传统的计算方法进行了比较。结果表明,考虑旋转磁场及谐波磁通密度影响时的定子铁心损耗计算值与传统的仅考虑交变基波磁通密度时的损耗计算值相比有显著增加,更接近于实际测量值,磁极涡流损耗值与定子槽口大小密切相关,占电机总损耗的比重较大,是不可忽略的。

基于槽极比选择的切向永磁同步电机永磁体涡流损耗抑制措施

为抑制切向永磁同步电机的永磁体涡流损耗,基于麦克斯韦方程和本构方程,对永磁体形状进行近似假设,构建了永磁体涡流损耗的估算模型。使用一种基于卡特系数概念的磁导函数来估算由于定子开槽引起的槽下磁感应强度变化。基于五台槽极比分别为1.05、1.20、1.30、2.40和3.60的电机设计方案对理论分析结论进行了验证。在负载电流和两倍负载电流下,分析永磁体损耗,得到了每台电机的径向气隙磁密曲线及其谐波含量。考虑到增加槽极比对定子铁耗和永磁体涡流损耗的削弱效果,给出了电机槽极比选择策略。研究结果表明,增加槽极比能减弱定子槽下磁感应强度变化,从而抑制气隙磁场中低次谐波含量,减小永磁体涡流损耗,使电机运行更加可靠,但也会引入更多高次谐波,从而增加定子铁耗。

分块充磁永磁体对磁齿轮磁密及涡流损耗影响

在大功率大变速比磁齿轮中,整体充磁式大块永磁体空心化问题是提升永磁齿轮性能的主要障碍之一。分块充磁工艺能够有效解决这一问题,明显提升大块永磁体性能。通过构建3D模型,对采用分块充磁技术的永磁体的永磁齿轮完成了磁热仿真分析。结果表明,分块充磁技术能够有效抑制大尺寸永磁体的磁场空心化,显著提高其剩磁,改善永磁齿轮的磁密,进而提升永磁齿轮的最大输出转矩;分块充磁永磁体块间绝缘能够有效缩减永磁体圆周弧长和轴向长度与永磁体磁场透入深度的差距,大大降低永磁体的涡流损耗。

基于密绕小直径线圈的磁感应透地无线起爆系统性能分析

为了在矿区开采时实现安全便携的透地无线起爆,提出了地上发射端采用密绕小直径线圈的磁感应透地无线起爆方案,并建立了地面发射线圈与地下接收线圈等效耦合电路分析模型,推导了地下接收端负载的电压表达式,用地面发射线圈与地下接收线圈间的互感系数表征了收发线圈间耦合强度的大小。由于地面发射线圈与地下接收线圈间的相对位置关系不是平行共轴,传统基于平行且共轴线圈的互感公式不再适用,本文从磁矢位出发推导出了考虑涡流效应的具有一般位置关系的单匝圆线圈间互感系数的通用表达式。由于地面发射线圈采用横放模式存在爆破盲区,地面发射线圈应采用竖放模式。基于负载电压公式分析了发射线圈半径与匝数、发射信号频率和垂直透地深度对透地起爆系统地下接收端负载电压和水平覆盖距离的影响。仿真结果表明:发射线圈采用竖放模式的透地无线起爆系统的水平覆盖距离可达到200~300m;随着透地深度的增加,系统的水平覆盖距离逐渐降低,但可以通过适当增加发射线圈半径和匝数、降低发射信号频率的方式提高透地无线起爆系统的水平覆盖距离,以满足在不同规模矿区开采应用场景下的透地无线起爆需求。

表贴式轴向磁通电机梯形削极分段结构研究

采用多极少槽结构和分数槽集中绕组可有效提高轴向磁通永磁(AFPM)电机的转矩密度,但磁动势谐波含量较大、频率较高,会引起永磁体涡流损耗增大和温度升高。通过优化表贴式轴向磁通永磁电机的永磁体结构可有效降低永磁体涡流损耗并抑制转矩波动,因此提出梯形削极分段结构。首先,基于精确子域法分别建立不同永磁体结构的解析模型。其次,通过解析模型和三维有限元模型对不同永磁体结构的气隙磁密、输出转矩和涡流损耗进行分析对比。然后,通过研究永磁体分段对永磁体涡流损耗的影响,确定梯形削极分段结构的参数。最后,制造一台样机并进行实验,实验结果证明,梯形削极分段结构可有效降低永磁体涡流损耗并且改善轴向磁通永磁电机输出性能。