应用于磁浮列车的直线型Halbach磁体结构的优化设计

对直线型Halbach永久磁体的结构进行了优化.通过改变磁块的长度、宽度和磁化矢量的方向,得到了更强的磁场强度.首先提出优化指标,优化磁块的长度,目的是用最少的磁块得到最强的场强;然后提出合理的磁块宽度的概念,以便得到较大的水平方向的磁场强度分量;其次提出Halbach磁体的偏离结构,进一步提高水平方向的磁场强度.最后通过制造的工程实验模型来验证优化设计,为磁悬浮列车工程化奠定基础.     

直线型Halbach磁体和导体板构成的电动式悬浮系统的实验装置设计

 永磁和导体板构成的电动式悬浮系统由导体板和直线型Halbach永久磁体构成,悬浮力和磁阻力是导体板上产生的涡流和磁体的相互作用的结果.研究了实验装置的结构,包括磁体和直流电机,测试、分解电磁力为悬浮力和磁阻力的机构,最后制造实验装置.实验和仿真的对比,说明力的解耦是成功的.这是永久磁体导体板悬浮系统工程化的第一步.     

单边核磁共振Halbach磁体结构设计

传统核磁共振仪器多采用封闭式磁体结构,导致仪器开放性和便携性差,制约其应用范围。为解决上述问题,该文基于电磁场理论,利用二阶有限元方法,研究半环形Halbach磁体的结构设计方法,分析磁块几何结构和尺寸等参数对Halbach磁体产生的中心场强、横向均匀度和纵向梯度的影响。验证该磁体结构无需增加线圈,即可产生核磁共振实验所需的横向均匀纵向梯度分布的磁场。优化后的单边Halbach磁体结构为:磁块尺寸为0.5 m×0.095 m×0.095 m、磁体结构半径为0.63 m,在50 cm×50 cm区域得到中心场强为0.020 9 T,不均匀度为3.085×10~(-4),梯度为0.739 mT/cm的磁场。     

烧结Nd-Fe-B磁体的角度差与取向度

用Helmholtz线圈测量了烧结Nd-Fe-B小立方磁体组合成大组件磁体的总磁矩,实验结果表明,高取向烧结Nd-Fe-B磁体的有效宏观磁矩符合矢量线性叠加原理。烧结Nd-Fe-B磁体的取向度越高磁矩角度差越小,但磁矩角度差小的磁体其取向度不一定高。同时利用有限元方法计算了Halbach阵列的磁力线分布。     

舰船电力系统用1 MJ高温超导储能磁体设计研究

介绍了舰船电力系统用的1MJ螺管型高温超导储能磁体的设计优化步骤，给出了用Bi-2223超导带进行1 MJ磁体线圈的设计和优化结果，分析了高温超导体的各向异性对磁体临界电流的影响，讨论了储能容量一定的多螺管磁体系统在漏磁、储能密度和所需超导线材方面的变化。     

烧结钕铁硼磁体的组织结构及合金成分优化研究进展

烧结钕铁硼磁体因具有优异的磁性能、较好的机械加工性和低成本等优势而被广泛应用在现代工业和电子技术领域。然而,随着科技的不断进步,对烧结钕铁硼磁体的磁性能提出了更高要求,高剩磁、高矫顽力、高磁能积磁体成为今后发展的重要趋势。磁体组织结构决定了磁体性能,磁体组织结构又与磁体成分密切相关。成分优化是改善烧结钕铁硼磁体磁性能的有效途径。本文在分析烧结钕铁硼磁体组织结构的基础上,详细梳理了近几十年来烧结钕铁硼磁体组元元素替代和掺杂的研究成果。在此基础上,指出了元素替代和掺杂在改善烧结钕铁硼磁体磁性能中存在的问题及今后的发展方向,为进一步提高烧结钕铁硼磁体磁性能提供理论参考。     

Sm(Co_(0.74)Cu_(0.12)Fe_(0.1)Zr_(0.04))_(7.5)纳米晶烧结磁体的结构和磁性能

采用放电等离子烧结技术制备了致密纳米晶SmCoCuFeZr烧结磁体,研究了磁体的结构和磁性能.X衍射结果表明,烧结磁体具有TbCu_7结构.TEM观察显示,烧结磁体平均晶粒尺寸为35nm.室温时磁体的剩磁为0.49T,矫顽力高达1.42T,而剩磁比Mr/Ms为0.63,表明在纳米晶之间存在晶间交换耦合作用.     

氮氧自由基类有机磁体的研究与展望

氮氧自由基因其结构优势已成为有机磁体的重要构件.从纯氮氧自由基类有机磁体和含金属的氮氧自由基类有机磁体两方面综述了氮氧自由基类有机磁体的结构、种类及发展历史.分析指出氮氧自由基类有机磁体目前存在的主要问题是转换温度Tc较低及磁构关系不明确,但由于其具有诸多的优越性能而将得到大力研发.     

35 kJ高温超导磁储能(SMES)的热输运实验研究

研制了中国首台高温超导磁储能直接冷却系统,该系统不使用低温液体(液氦、液氮).在10-3Pa的真空度下,高温超导磁体线圈由1台单级GM制冷机从室温293 K冷却到19 K,Bi2223电流引线由另一台制冷机冷却到77 K以下.整个系统在通140 A直流电流的时候产生了4.5 T的磁场.系统连续运行480 h(20 d),磁体和低温系统各参数动态特性良好.实验研究表明,控制系统的漏热,优化磁体内部导冷结构,有效减少热传导部件的接触界面热阻是制冷机直接冷却高温超导磁体的关键技术.     

PSO算法在舰船磁场磁体模拟中的应用

采用磁体模拟舰船磁场是一种常用且有效的方法，然而，过去磁模拟体位置的确定常依赖于人的经验，局限性较大。文中基于舰船磁场的磁偶板子模型，利用PSO算法对磁体的位置进行了优化。试验结果表明，该方法降低了人为经验对磁体模拟模型稳定性的影响，提高了磁体模拟法的精度。     

球形永磁阵列振动能量收集器设计与优化

为实现多方向环境能量收集,设计球形电磁式振动能量采集器。基于二维Halbach阵列设计的球面Halbach永磁阵列,较传统永磁阵列能提高线圈中磁链变化梯度,从而提高结构输出性能;建立数学解析模型,据解析结果对模型各参数进行优化;对该模型进行有限元仿真分析及实验性能测试。结果表明,该模型能有效响应空间任意方向振动,进而转化为电能;外部激励为10 Hz、激励为水平方向、负载阻值50 Ω时,该球形振动能量采集器输出电能达最大,单个线圈中最大负载功率可达0.8 mW。     

磁悬浮运动平台的磁场分析及优化设计

研制了一种新型磁悬浮平台,该平台定子采用无铁心式的克莱姆绕组,消除了固有齿槽效应,动子采用Halbach 磁阵列结构方式,由于平台输出推力与悬浮的稳定性主要与其气隙磁场的分布情况有直接关系,因此提高气隙磁场的正弦分布是改善其工作特性的难点和重点. 为了改善气隙磁场的分布问题,提出了一个优化磁场分布的目标函数,并采用步长加速法对平台磁场进行了优化设计,大大降低了磁场谐波分量,改善了气隙磁场分布状态. 将优化结果运用到实际的平台中,对该运动平台进行了阶跃响应实验,实验结果表明满足平台需要达到纳米级精度的要求.     

3-D Magnetic Field and Torque Analysis of a Novel Halbach Array Permanent-Magnet Spherical Motor

We present a three-dimensional (3-D) torque model based on spherical harmonic functions of a Halbach array permanent-magnet (PM) spherical motor. Using the torque model, we show how to realize three-degree-of-freedom motion. We compare the Halbach array PM spherical motor and the conventional parallel magnet array spherical motor in terms of spherical harmonic component and amplitude of the torque. We discuss our study of variations of air-gap magnetic field with parallel magnetization directions along different spatial positions in each magnet segment. We also discuss the parasitic effect of the proposed spherical Halbach array magnet. We have verified our results by finite-element method.      

Design of a Halbach Magnet Array Based on Optimization Techniques

We have designed a Halbach magnet array by using a numerical optimization method based on finite-element analysis. The magnetization direction of each element is defined as the design variable. The optimal magnet arrays composed of two and three linear magnet layers can then be investigated to increase the attractive, repulsive, and tangential magnetic forces between magnet layers. We have applied a magnet array maximizing the tangential force to a torsional spring composed of two- and three-magnet rings. The two-dimensional finite-element analysis incorporates optimization techniques such as the sequential linear programming and the adjoint variable method.      

Analytical Calculation of No-Load Voltage Waveforms in Machines Based on Permanent-Magnet Volume Integration

We develop an analytical expression for predicting electromotive force (EMF) waveforms resulting from permanent magnets (PMs) in electrical machines. The expressions for the flux linkage are based on a volume integral over the magnet volume, rather than the usual surface integral over the coil. The proposed method consists of applying a virtual current in the coil of the machine and calculating the magnetic field generated inside the PM volume. The EMF waveform is obtained by taking the derivative of the flux linkage with respect to time. We present analytical expressions of the EMF for various PM shapes and Halbach magnetization patterns. We tested a total of four configurations of PMs, and the experimental waveforms confirmed the validity of the expressions obtained theoretically.     

A test stand to study the possibility of using magnetocaloric materials for refrigerators

A laboratory test stand for magnetocaloric effect investigations has been developed. The test stand is compact and easily reconfigurable. Gadolinium in the form of particles is used as a refrigerant. The material is magnetized/demagnetized due to the reciprocating motion of a magnetic bed. A Halbach array of permanent magnets is employed as a magnetic field source. It generates a magnetic field of about 1 T. In order to decrease the distance along which the magnetic bed has to move, a magnetic shield was used which limits the range of external magnetic field influence. The effectiveness of the shielding and the decrease in magnetic field intensity were shown in the form of magnetic field distribution maps. The paper presents first experimental results which are measured as the temperature difference between the two outermost reservoirs. The achieved results are promising – the temperature span between the heat exchangers amounts to about 2 °C.     

Investigation of the Lateral Reversible Region of YBCO Bulk above a Permanent Magnet Guideway

The lateral reversible region of the high-T _c superconductor (HTSC) bulk YBCO above a permanent magnet guideway (PMG) is investigated experimentally in this study. The dependence of the lateral reversible region upon selected parameters, such as Field Cooling Height (FH), Working Height (WH), and magnetic field structure, is studied. Results show that the lateral reversible region of the HTSC bulk is not only proportional to the magnitude of the guidance force or guide-force hysteresis, but closely related to the external applied magnetic field structure, FH, WH, and the size and shape of the HTSC bulk. A conclusion that the lateral reversible region of an HTSC bulk over the single peak symmetrical PMG prior to multipeak Halbach PMG is drawn. The results may be helpful to the design and optimization of maglev systems composed of a permanent magnet guideway and HTSCs.     

Study on a New High Frequency Moving Coil Permanent Magnet Linear Motor

In order to improve the characteristics of a conventional moving coil permanent magnet linear motor (MCPMLM), such as weak points on export force, response time, response speed, we studied a permanent magnet (PM) structure that is a key component of MCPMLM. Different magnetization techniques of single PM and different array structures of multiple PMs are compared, and a new MCPMLM magnetized along the external field force lines using eight pieces of a tegular Halbach magnet array with air gaps is proposed as well. The analysis on magnetic field and experimental results of MCPMLM demonstrates that the force between the coil and the PM increases by more than 40%. The simulation frequency is close to 350 Hz at -3 dB, and the response time is 0.005 s. In addition, the experiment frequency reaches 300 Hz at -3 dB and the response time is 0.004 s, which agrees well with the simulation results. It means that the developed MCPMLM enjoys advantages in high frequency and rapid response, and can satisfy the requirements of a high speed electro-hydraulic proportional valve.     

Design of a new magnetic refrigeration field source running with rotating bar-shaped magnets

Magnetic refrigeration (MR) based on the magnetocaloric effect (MCE) is a prime candidate for the next generation of cooling systems. The essential components of magnetic refrigeration are the magnetic field generator and the magnetocaloric material. Although, several permanent magnet systems (magnetic field sources) for MR have been developed, recent development in magnetic refrigeration technology has encouraged researchers all over the world to think about new and original systems. This paper aims to describe a new and original magnetic refrigeration system based on a simple principle of magnetism called the Halbach effect. The proposed system is running with rotating bar-shaped magnets. This structure provides the desired varying magnetic field to the magnetocaloric material. Several configurations for the proposed systems have been investigated and presented in this paper. The design and modeling have been accomplished by using the finite elements method.