Design Optimization for Generating a High Static Magnetic Field

This paper details the creation of a device capable of generating a powerful and consistent static magnetic field. This apparatus serves the purpose of quantifying the magnetostrictive strain found in materials like annealed cobalt ferrite and Terfenol-D, specifically those shaped as cylindrical rods. In our investigation, the use of static magnetic fields proves most advantageous. This choice is made to mitigate the generation of eddy currents, which would inevitably occur if the magnetic field intensity were varied. The fundamental idea behind this design involves employing a C-shaped iron core constructed from low-carbon mild steel. On this core, three coils are mounted, each capable of producing one-third of the required 9000 Oersted (Oe) magnetic field strength. The test specimen is situated within the “jaws” of the C-shaped core, thus completing the magnetic circuit. To manage the heat generated by each coil, a cooling system consisting of copper tubes is employed. These tubes facilitate the flow of air to dissipate the heat. To model and predict the magnetic field strength produced by the coils, finite element analysis (FEMM) software is utilized, and the results align closely with the anticipated outcomes. This design effectively generates a robust and unchanging magnetic field measuring a stable 9000 Oe in total. Consequently, this equipment finds utility in characterizing the magnetic properties of specific materials.

Numerical-Analytical Method for Magnetic Field Computation in Rotational Electric Machines

A numerical-analytical method is applied for the two-dimensional magnetic field computation in rotational electric machines in this paper. The analytical expressions for air gap magnetic field are derived. The pole pairs in the expressions are taken into account so that the solution region can be reduced within one periodic range. The numerical and analytical magnetic field equations are linked with equal vector magnetic potential boundary conditions. The magnetic field of a brushless permanent magnet machine is computed by the proposed method. The result is compared to that obtained by finite element method so as to validate the correction of the method.

Research on electromagnetic relay's dynamic characteristics disturbed by uniform static magnetic field

Electromagnetic relay is a widely used apparatus which usually works in a magnetic disturbance environment. To evaluate its electromagnetic compatibility (EMC) in a static magnetic field, dynamic characteristics of a clapper relay in a uniform static magnetic field situation based on the finite element method (FEM) is studied. Influences of the magnetic field on dynamic parameters (delay time, pick-up time, end pressure, and final velocity) as well as a situation in which the relay cannot function normally are analyzed. Simulation reveals that the external magnetic field which weakens the relay’s air-gap field has a greater influence on the relay’s dynamic parameters than the one strengthening the field. The validity of the simulation is verified by measured results of coil current and armature displacement.

High Magnetic Field Shielding for Sensitive Devices Relevant to ITER

High magnetic field shielding has been increasingly important for engineering design in recent years. In this report, a cylindric shield made from soft iron is studied using FEM （finite element method） analysis and COlnpared with experiments. The residual fields inside the shield are calculated and measured in both parallel and perpendicular fields up to 2000 Gs. The calculated results are compared with the experiments, and the input B-H curve is modified for a better conformity. The results indicate that the covers could greatly improve the shielding performance of the cylindric shield in our research. The comparison result shows that a proper B-H curve, which can well describe the material properties, is very important in FEM analysis and should be selected carefully.

Numerical simulations on the AC loss of REBCO stacks under rotating magnetic fields

AC loss presents a significant challenge for high-temperature superconducting (HTS) rotating machines. To date, the behaviour of total AC loss (Qtol) (with current) and magnetization loss (Qm) (without current) in a single HTS tape under rotating magnetic fields (RF) have been explored. However, a research gap remains in understanding how these findings translate to the more complex HTS windings of rotating machines. Further exploration is needed to understand the loss behaviour of more complex HTS structures, such as HTS stacks. In this work, Qtol and Qm, in the HTS stacks under RF and a perpendicular AC standing wave magnetic field are numerically investigated. Two different RF models are considered: one is the Uni-RF model, characterized by a uniform field with equal field amplitudes and phases at each position, and the other is a non-uniform field created by a rotating Halbach array, referred to as the Hal-RF model. The dependence of AC loss on parameters such as the number of tapes in the stacks, tape width (2a), and the inclination angle (α) of tapes, which refers to the angle between the normal direction of the stack and the vertical direction, have been explored. The number of tapes in the stacks ranges from 1 to 16, α ranges from 0° to 90°, and the tape width includes 4 mm and 40 mm. Additionally, different rotating field directions are also considered. Interestingly, the analytical values from Brandt and Indenbom equation for Q_(m) of a superconducting strip (BI-strip) are close to Q_(m) results of the stacks under the standing wave at high fields, while they are over twice as high as those in the Hal-RF model at 1 T. This suggests the BI-strip equation is not reliable for predicting Q_(m) under RF at high fields. We also show in the Hal-RF model that different rotation directions of the field lead to varying Q_(m) and Qtol when asymmetric Jc (B, θ) data are applied. Moreover, it has been observed that the inclination angle has no impact on Q_(m) under uniform RF while significantly impacts both Q_(m) and Qtol in the Hal-RF model.

3D Finite Element Analysis of the Stray Loss in Power Transformer Structure Parts

In order to analyze the leakage magnetic field and stray loss in power transformer, leakage magnetic field and stray loss in structure parts of a power transformer are calculated by three-dimensional (3-D) non-linear time harmonic finite element method (FEM). The results show that stray loss and loss density in structure parts are large and which may lead to local overheating and affect performance of the transformer. The magnetic shields are used to reduce the stray loss and loss density of power transformer. Effects of these shields on stray loss and loss density of structure parts are discussed. The results show that stray loss and local overheating can be reduced and eliminated effectively by adding magnetic shields. It provides some references for the analysis of stray loss and optimization design in transformer.

永磁无刷直流电机瞬态磁场仿真分析

瞬态磁场仿真分析可为电机的本体研究与设计提供参考依据。针对一款小型永磁无刷直流电机进行分析设计,根据理论公式计算了无刷直流电机定转子尺寸、定子槽形、绕组等,并使用Maxwell有限元仿真软件对设计方案进行了电机铁芯磁场分布、空载反电势、转矩、电机启动等内容的仿真分析,得到了符合要求的设计方案。

GMPC材料表面粘贴FBG磁场传感技术

针对目前电力系统中磁场测量需求,以及光纤自身具有绝缘、抗电磁干扰优势,将其与巨磁致伸缩复合材料结合,实现磁场的检测。其中,采用有限元分析方法,建立磁场环境下的材料仿真模型,实现材料的定性分析。另外,根据仿真分析结果,研制不同浓度比的巨磁致伸缩复合材料,并将材料表面粘贴光纤光栅,实现磁场检测。所提出的光纤磁场传感技术实现了低电磁干扰磁探测、提高探测效率、降低稀土合金消耗。

高频磁性元件的电磁场仿真实验研究与探讨

高频变压器为功率变换器的核心磁性元件,利用仿真软件对高频变压器进行电磁场仿真分析,可以节省设计时间、优化结构、提高效率。在对电磁场和温度场的控制方程、边界条件进行详细分析的基础上,建立高频变压器电磁场—温度场耦合计算流程。利用Infolytica的MagNet和ThermNet仿真软件,对一台5 k Hz/15 kW纳米晶合金磁芯三相五柱式高频变压器的漏磁场、磁芯损耗、绕组损耗和温度场进行有限元法计算,开展空载和短路实验研究,验证计算方法的准确性。

一种检测弱磁场的光纤传感器的研究与仿真

提出一种基于表面等离子共振的光子晶体光纤传感器,用于实时检测弱磁场强度变化。光子晶体光纤表面覆盖氮化硅和银薄膜,实现表面等离子共振,传感器外侧的磁流体用于感知磁场变化。针对磁场强度检测,基于折射率性能指标归纳了磁场与传感器性能指标。有限元方法的仿真结果表明,在80 Oe~1000 Oe磁场强度范围内,传感器波长灵敏度可达0.55 nm·Oe^(-1);此外,幅度灵敏度、分辨力、检测限、品质因数和拟合度分别达到了-0.107 Oe^(-1)、1.8×10^(-2)Oe、3.3×10^(-2)Oe~2·nm^(-1)、6.73×10^(-2)Oe^(-1)和0.99117。该传感器具备制作工艺简单、易于制造的特点,可以预见其在磁场检测的广阔前景。

基于热源网络法的永磁式电磁制退机热特性研究

永磁式电磁制退机以磁场为能量传输介质,有望彻底解决传统液压式制退机液体泄漏、阻力规律稳定性差等问题。然而电磁制退机工作过程中的热特性变化规律尚未探明,限制了电磁制退机的进一步发展。依据电磁制退机的结构,建立了热源网络温度场分析模型,计算了电磁制退机各主要部件的热参数,结合热路传播路径编写了温度场计算程序,得到了火炮后坐过程中电磁制退机不同时刻的瞬态节点温度,探究了电磁制退机瞬态工作过程中的温度传播规律与分布特性。同时建立有限元模型,对热源网络分析模型进行了验证。最后充分利用热源网络模型计算效率高的优势,开展了连发射击工况下电磁制退机的热特性研究、失效预测和冷却措施探究,为电磁制退机的工程设计提供了参考。

新型三定子直流无刷电机的设计与特性分析

传统直流无刷电机齿槽分布受限导致气隙磁场波动,会造成转矩输出波动较大,故需要同步匹配设计复杂的驱动控制系统与控制算法。为此,提出一种新型的三定子直流无刷电机拓扑结构。通过等效磁路法计算出三定子直流无刷电机的主要结构尺寸。设计了三定子直流无刷电机的绕线方式和换向逻辑,驱动控制简单。基于Ansoft maxwell仿真软件,建立了电机有限元模型,仿真分析了电机静态磁场分布、气隙面域磁密分布和空载反电动势等。得到了三定子直流无刷电机的转矩特性:其转矩峰值可达8.5 N·m;电感特性:其三相绕组间磁场相互解耦,互感为0,自感平均值为4.5 mH;效率与损耗特性:不计机械损耗的情况下电机理想效率可达92%。研制了试验样机并进行试验验证,有限元分析和试验结果表明:三定子结构电机磁通密度高,输出转矩大,转矩峰值较单定子电机提升了42%;输出转矩波动小,较单定子电机波动降低了30%。在额定转矩为7.5 N·m的情况下,电机转速从启动到500 r/min的响应时间仅为0.8 s;从500~1000 r/min的响应时间仅为1.5 s;从1000~1500 r/min的响应时间仅为2.1 s。

基于非线性电感的混合电磁铁磁力计算方法

为提高混合电磁铁磁力计算的准确性和效率,综合考虑解析法计算速度快和有限元法计算精度高的优势,提出一种基于非线性电感的混合电磁铁磁力计算方法.首先,分析混合电磁铁电感与电流的关系,建立考虑磁饱和的非线性电感模型;然后,采用等效面电流法,将2种典型的混合电磁铁结构(结构a、结构b)等效为多电磁线圈的纯电磁铁结构,进而利用能量平衡法推导出通用于串联磁路型混合电磁铁磁力表达式,其中非线性电感的参数变量由有限元仿真法拟合得到.研究结果表明:结构a和结构b利用本文所述方法得到的电磁力计算结果与传统有限元仿真结果的平均偏差为2.54%和2.37%,结构a与实验测量的平均偏差为2.63%,且与传统有限元法相比,计算效率极大提升,即本文所述方法通过较少任务的有限元仿真得到远高于现有解析公式准确性的电磁力计算结果.

KCS船舶尾流感应电磁场仿真分析

为了更系统地研究船舶在航行过程中引起的尾流感应电磁场,文中以有限元法为基础,利用磁流体力学、麦克斯韦方程组等电磁场和流体力学理论,对KCS船舶尾流运动产生的感应电磁场进行仿真分析。结果表明:KCS船舶尾流感应磁场量级在可探测范围内有明显的分布规律;尾流感应磁场在传播方向上存在极值,其大小与测量位置相关;尾流感应磁场先随距离增大到极值,再沿传播距离方向逐渐衰减;尾流电流密度沿传播距离方向逐渐衰减。文中的研究可为海洋电磁探测及船舶跟踪和定位等研究提供参考。

Analytical model and finite element computation of braking torque in electromagnetic retarder

An analytical model has been developed for analyzing the braking torque in electromagnetic retarder by flux tube and armature reaction method. The magnetic field distribution in air gap, the eddy current induced in the rotor and the braking torque are calculated by the developed model. Two-dimensional and three-dimensional finite element models for retarder have also been developed. Results from the analytical model are compared with those from finite element models. The validity of these three models is checked by the comparison of the theoretical predictions and the measurements from an experimental prototype. The influencing factors of braking torque have been studied.

大型永磁风力发电机整体充磁系统设计及应用

在传统的大型永磁电机磁极制造过程中,采用的“先充磁后组装”预充磁技术存在生产效率低、安全风险大等问题。为此,该文提出一种大型永磁风力发电机整体充磁技术,将传统的“先充磁后组装”改为“先组装后充磁”,有效地提高了装配精度、生产效率和安全性。首先通过研究N46SH钕铁硼永磁材料在多角度外磁场中的磁化及退磁行为,获得其在不同磁场方向下的饱和磁化判据;然后针对MW级直驱和半直驱风力发电机结构,提出其整体充磁系统中充磁线圈的设计方法,重点阐述充磁线圈的电-磁-热-力分析;最后以在2.5 MW直驱和20 MW半直驱风力发电机的整体充磁应用为例,研制了充磁线圈及其冷却系统、充磁电源、旋转推进系统和测量控制系统,成功应用于湘电和中车等企业的MW级系列永磁风力发电机的制造与维护,该文设计方法的可靠性得到有效验证。

基于热路法的自然冷却永磁同步电机定子温度计算

为获取电机运行时的温升情况,本文使用热路法对一台自然冷却永磁同步电机定子的温度进行计算。在Maxwell中进行二维电磁场仿真,得到电机定子的损耗。将电机定子分为多个部件,使用简化圆筒T型热路模型并结合立方体热路模型搭建各部件的单元模型,在计算各部件的相关热阻后,得到电机定子的热路模型。根据热平衡原理建立温度场线性方程组,求解电机定子的温度。在Fluent中建立电机定子的三维简化模型,给予材料属性、边界条件及其他相关设置后,进行电机稳态温度场仿真。最后对电机进行温升实验,使电机在额定工况下运行至热平衡状态后,进行实验测量。将热路法计算的结果与实验和仿真结果进行对比分析,验证了热路法的正确性。

电磁式灭弧空气炮理论研究

针对传统保护间隙的空气间隙无法快速熄弧、线路的跳闸率较高问题,研究、设计了电磁式灭弧空气炮.该装置利用电磁活塞理论,喷射出高速气团.高速气团会冲击电弧,带走电弧的热量并拉细电弧,显著增强电弧的去游离作用,迫使其在短时间内熄灭.且电磁式灭弧空气炮的活塞尾部安装有弹簧机构,能够在灭弧后自动将活塞复位,为下一次动作做准备.通过有限元法进行仿真计算,加装电磁式灭弧空气炮的保护间隙能在16 ms内将电弧拉细到原来粗细程度的1/8、弧心温度降低至1/3,显著增强去游离作用,迫使其迅速熄灭.因此电磁式灭弧空气炮具有较强的熄弧能力,且具备一定的自能性,能有效降低雷击跳闸率、提升电能质量.

铁氧体磁芯磁场分布的优化及其对磁纳米热疗的影响

以缠绕着载流线圈的铁氧体磁芯为基础,应用有限元方法分析载流线圈位置对磁场分布的影响,接着采用磁场不均匀性函数结合遗传算法对磁芯气隙内的磁场均匀度进行优化,优化后的磁芯磁场通过顺序耦合方式被进一步应用于磁热疗治疗温度分布分析,采用治疗期间肿瘤区域内的有效治疗温度对肿瘤体积的占比来评估磁热疗治疗效果。研究结果表明:线圈位于气隙两端所产生的磁场优于其位于左端所产生的磁场,与等效磁路分析结果基本一致。本文所提优化方法可使得气隙磁场均匀度显著提高,并使磁热疗肿瘤区域最高治疗温度达到临界值,显著提高治疗效果。

混合风路高压感应电机电磁参量与损耗计算

感应电机在电气行业占据重要位置,随着电磁负荷的不断增加,高压成为感应电机发展趋势,但其结构紧凑散热问题逐渐突显,为改善其温升,建立混合通风结构,结构变化又会改变电机磁场分布和性能。针对轴向通风结构电机等效为混合通风结构电机无法全面分析混合通风结构和通风槽板对电机电磁性能影响的问题,基于三维瞬态有限元法,以6000 V、4500 kW电机为例,建立混合通风结构电机和轴向通风结构电机三维有限元模型,进行对比分析,揭示混合通风结构电机定、转子磁场分布规律和气隙磁场分布特征。分析混合通风结构对电机电磁损耗的影响,计算转子通风槽板涡流损耗。最后通过实验验证混合通风结构对电机电磁性能的影响不可忽略,为以后混合通风结构电机设计和分析提供理论依据。