一种新型Inside-Out核磁共振传感器——三圆柱磁体阵列

介绍了一种新型的inside-out核磁共振传感器。该传感器磁体结构由三个沿轴向磁化的圆柱形永磁体同轴排列而成,结构紧凑。通过调节三个磁体之间的距离,可以在磁体结构外侧建立起径向对称的均匀静态磁场或有恒定梯度的静态磁场B_0,其方向平行于传感器轴向。为了满足射频磁场B_1垂直于静态磁场B_0的要求,射频线圈采用马鞍形结构。传感器直径为2.8cm,长度为6cm,重为200g。该传感器磁体结构简单,且灵敏区域相对其本身尺寸较大。     

一种新型的旋转磁制冷机用永磁磁体系统及其磁场和涡流分析

为了克服现有的Halbach中空圆柱形磁场源为基础的"C"型结构的旋转磁制冷机永磁磁体系统,其旋转部分未被封闭在磁体之内和磁化场在转轮上产生单边磁拉力等缺点,提出一种用于旋转磁制冷机的高场强永磁磁体系统。该系统定子包括中空柱形永磁磁体和导磁极靴,转子包括转轴、导磁铁心和磁工质。本文采用有限元法分析和计算这种新型的永磁磁体系统所产生的磁化场的分布、磁工质中的涡流分布和涡流损耗,以及转子受到的电磁转矩。     

纵磁结构真空灭弧室的三维磁场数值分析

根据单积分法原理编制了一套三维磁场计算软件,对杯状纵磁、1/2匝线圈纵磁、四极纵磁三种结构的真空灭弧室自生纵向磁场进行了三维数值分析,给出磁场的总体分布以及几个主要参数对磁场分布的影响,并且对其中两种结构的磁场进行实际测量,验证了该软件计算的准确性.     

永磁直线同步电动机Halbach阵列磁场分析

直线电动机的气隙磁场是决定其性能的关键因素.针对平板动磁式永磁直线同步电动机(PMLSM),采用Halbach磁体阵列来提高气隙磁场的正弦性.给出了Halbach阵列磁体排列方式及磁化规律;利用有限元法对Halbach磁体结构与常规磁体结构的永磁直线同步电动机进行比较,分析了磁通密度在平均气隙及轭部的分布情况;在此基础上提出了一种基于Halbach阵列的改进的磁体排列方案,并分析了此方案对电机气隙磁密的影响,得出了一些有用的结论.     

一种Halbach磁体结构同心磁力齿轮传动装置的设计和实现

提出了一种使用Halbach磁体结构产生磁场,并对磁场进行调制的同心磁力齿轮传动装置。该传动装置由机壳、安装在机壳内腔的悬臂式的外转子和内转予组成。内、外转子永磁体之间有调磁环。调磁环由铁心块组成,并固定在机壳的端板上。磁体结构采用Halbach阵列,得到的气隙磁密接近正弦分布。对样机测试后表明,该装置取得了较好的正弦磁场分布、稳定的转速比值和较高的传动效率。     

一种Halbach磁体结构同心磁力齿轮传动装置的设计和实现

提出了一种使用Halbach磁体结构产生磁场,并对磁场进行调制的同心磁力齿轮传动装置。该传动装置由机壳、安装在机壳内腔的悬臂式的外转子和内转子组成。内、外转子永磁体之间有调磁环。调磁环由铁心块组成,并固定在机壳的端板上。磁体结构采用Halbach阵列,得到的气隙磁密接近正弦分布。对样机测试后表明,该装置取得了较好的正弦磁场分布、稳定的转速比值和较高的传动效率。     

产生匀强磁场的球状线圈设计

根据Biot-Savart定律和磁场叠加原理,提出了一种产生匀强磁场的三维正交球状反馈线圈系统的设计方法.为分析该系统内部的磁场分布,建立了球状线圈内磁场分布的数学模型,并讨论了其磁场分布、分布均匀度与线圈匝数,线圈间距和有关参数之间的关系.分析结果表明球状线圈能在较小的几何尺度内产生较大范围的均匀磁场,可根据磁传感器几何尺寸和对匀强磁场均匀度的需求,利用此设计方法确定球状线圈的线圈匝数和线圈间距等绕制参数,实现磁传感器的磁场反馈.     

基于Halbach阵列的永磁球形电动机磁场

Halbach阵列永磁电机与常规磁体结构电机相比,具有更接近正弦的气隙磁密分布、更大的气隙磁通及良好的自屏蔽作用等特性.因此,Halbach阵列永磁电机具有效率高、体积小、重量轻等优点.本文提出一种Halbach阵列永磁球形电动机,介绍了其基本结构和工作原理,并给出了转子磁极的Halbach阵列充磁规律.以转子4极、每极3块Halbach阵列磁体结构为例,对其磁场进行了分析,得出了磁场三维解析模型,并对磁场沿球坐标ψ和θ两个方向的谐波含量进行了研究.最后采用有限元方法对磁场进行了分析.     

Q&A真空双折射实验原型磁体的设计与制作

本文主要介绍用于Q&A真空双折射实验的600mm长原型转动永久磁体的设计与制作.该永久磁体采用高性能材料,运用聚磁技术等手段,有效提高了磁场强度,最终在2.7cm气隙中,磁场达到2.3T.磁体端部的磁屏与端轴融合,有效屏蔽了漏磁,减轻了磁体重量,并通过了620rpm的转动测试.该磁体设计制造的成功为最终长度为5m磁体的制造奠定了基础.     

行波磁场中高温超导电动悬浮磁体的热性能研究EI北大核心CSCD

地面线圈的交变磁场会在超导电动悬浮磁体中感应出涡流,产生涡流损耗,导致磁体温度上升。该文研究地面推进线圈产生的行波磁场对车载高温超导磁体热性能的影响,首先介绍高温超导磁体和推进线圈结构,分析行波磁场空间分布特征;搭建高温超导磁体热性能测试平台,测量行波磁场激扰下超导磁体内关键组件的温度分布,揭示各组件温度耦合关系;最后探究行波磁场频率和峰值对磁体温升的影响规律。结果表明,行波磁场激扰下,超导线圈的温升可忽略不计,但辐射屏温升显著,进一步使超导电流引线温度升高,增大电流引线失超风险,为此提出2种方法来限制电流引线温升。该研究成果可为高温超导悬浮磁体低温结构和电流引线的设计提供参考。     

永磁球形步进电机的结构研究与设计

介绍了一种新型永磁球形步进电机的基本结构,分析了永磁体和定子线圈在实际电机模型中的球面定位,然后介绍了一种以单相电流跟踪PWM控制实验为基础的定子线圈的选择方法。选择合适的部件设计出了永磁球形步进电机的转子球、永磁体、定子支座、定子线圈等各部分的实际参数,给出了详细设计方案,并绘出了该电机的CAD模型图,为永磁球形步进电机的进一步设计和优化提供了依据。     

A Superconducting Magnet with Center Field of 10 T and φ100 mm Warm Bore

A conduction-cooled superconducting magnet with central field of 10T and warm bore of 100 mm was designed based on a Nb3Sn and two NbTi superconducting coils. At the first stage, the NbTi coils have been fabricated and tested. A two-stage 4 K Gifford-McMahon (GM) cryocooler with the second-stage power in 1W, 4.2K is used to cool the magnet from room temperature to 4 K. The superconducting magnet with the same power supply has the operating current of 116A. The magnet can be rotated with a support frame to be operated with either horizontal or vertical position. A pair of Bi-2223 high temperature superconducting current leads was employed to reduce heat leakage into 4.2K level. The NbTi coils reachto the operating current of 120A without training effect to be observed during charging of the magnet during 40 minutes charging time and generate the center field of 6.5T. The training effect in the NbTi magnet directly cool-down by cryocooler and inter-winding support structure in magnet can be remarkably improved. The superconducting magnet has been stably operated for more than 275 hours with 6.5T. In this paper, the detailed design, fabrication, stress analysis and quench protection characteristics are presented.     

开放式低场永磁MRI磁体的匀场方法研究

在开放式低场永磁MRI(magnetic resonance imaging,磁共振成像)生产中,磁体匀场是提高质量和效率的关键技术之一.为解决国内匀场方法缺乏完整理论指导的问题,本文使用磁场球谐函数展开式分析主磁场情况并制定匀场方案.对展开式的低阶项,主动匀场方法十分适用,而对无法使用线圈的特殊情况或消除高阶项时需进行被动匀场.实验中有一组匀场线圈需要较大电流,此时采用永磁材料代替线圈可以达到很好的补偿效果.     

A Superconducting Magnet with Center Field of 10 T and φ100 mm Warm Bore

ⅠIntroductionIt is expected that the middle and small-scale mag-nets immersed in liquid helium will be replaced by theeasy-operating conduction cooled superconducting magnetin near future[1~3].For the aimof superconducting mag-net applications in the advanced material processing,awide bore conduction-cooled superconducting magnet withavailable warmbore of100 mmand center field of 10 Twas designed.The NbTi superconducting coils have beenfabricated and tested.The systemis automated by using…     

永磁球形步进电动机变结构控制算法

提出了永磁球形步进电动机的一种变结构控制算法.该算法用可控电流源控制定子电磁线圈通电电流的幅值替代继电器控制方式.首先在转子固连坐标系内基于卡尔丹角旋转建立了转子动力学模型.然后在电动机空载运行的模式下,设计了一种无需角加速度反馈信号的基于输入一输出稳定性理论的控制算法.接着针对电动机负载运行,各轴向转动惯量发生变化的情况设计了变结构控制算法.最后,在变结构控制算法中插入边界层以消除抖振现象.仿真结果表明,新的控制算法具有更小的跟踪误差,稳态误差小于0.01rad.     

Proposal of permanent magnet repulsive maglev transportation system: possibility of automobile with magnetic levitation

This paper describes a maglev transportation system for automobiles. The track is an array of permanent magnet blocks, and the levitating body is the bedplate which consists of permanent magnet plates, propulsion coils, levitation coils, and guidance coils. The feature of this system is that an automobile equipped with the bedplate is free to approach into the track or to swerve from the track by using four wheels with the lift. The force acting on the levitating body is calculated on the assumption that each permanent magnet can be expressed as a surface current. From the calculation results, it is proven that an automobile of 4.35 m length, 1.8 m width, and 1700 kg weight can run at a speed of 500 km/h against the air resistance force of 3704 N on the condition that the battery has an output of 337.5 V and a capacity of 190 Ah. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(3): 65– 76, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20491     

Proposal and Feasibility Study of the Integrated Diode Synchronous Motor

This paper presents a new type of magnet‐free motor that has concentrated stator windings and rotor coils with a pair of diodes. The most important feature of this motor is that currents in the rotor coils can be generated by utilizing the changes in the spatial second harmonic of the magnetic fields due to the concentrated stator windings, which normally increase motor losses. A prototype of the motor was designed and fabricated, and its basic performance was evaluated. First, using simplified analytic models, we explain the mechanism of inducing currents in the rotor coils by the changes in the spatial second harmonic of the magnetic fields. Second, we compare the torque performance of the proposed motor and that of other types of motors including a magnet motor through finite‐element analyses. The analyzed data show that the proposed motor can possess greater torque/volume ratio than that of the other motors. Finally, using the measured data, we validate the mechanism of inducing currents in the rotor coils, and examine the torque and power characteristics of the motor.     

Performance and conceptual design of superconducting magnet for disk MHD generator

This paper describes superconducting magnets coupled with two kinds of disk-type MHD generators. One is coupled with a disk generator in the closed-cycle MHD experimental facility FUJI-1. The other is for a full-scale disk MHD generator. These are split-pair magnets. In the magnet for the FUJI-1 facility, a unique structure which supports the coils against the electromagnetic force has been fabricated and the magnet has been operating stably. During MHD power generation experiments, an induced voltage across the terminals of the coil was measured. A magnitude of the Faraday current in the generator was calculated from this induced voltage. A possible construction of magnetics for a full-scale disk MHD generator is indicated. It is suggested that a high performance of the generator (output power density of 0.3-1 GW/m³) can be obtained with high magnetic field up to 10 T.     

永磁磁共振成像系统中磁体极板尺寸与梯度线圈的关系

本文叙述了合理确定极板尺寸的意义,描述了梯度线圈的计算方法和设计指标,给出了框产体和开放式C型磁体在典型气隙尺寸下梯度磁场线性度与梯度线圈外形尺寸关系的计算,并讨论了一些因素对梯度线圈外形尺寸的影响,从而对磁体极板尺寸提出了要求。     

永磁多维球形电动机的研究与发展现状

阐述了永磁多维球形电动机的结构和特点,概述了永磁多维球形电动机的现状和最新研究进展,探讨了其应用前景和研究发展方向,并对其中一种永磁球形步进电动机提出了磁场分析的方法,给出了仿真计算的结果.