正方形亥姆霍兹线圈三维磁场及其均匀性分析

为研究光纤陀螺的磁敏感性,利用三个正方形亥姆霍兹线圈构建三维匀强磁场,并分析其匀强磁场区域特性。将正方形亥姆霍兹线圈视为四段载流导线,采取分段计算然后进行矢量叠加的方法,分析了正方形亥姆霍兹线圈三维空间磁场强度及其均匀性,并给出仿真结果。最后给出了正方形亥姆霍兹线圈三维匀强磁场的结构模型及相关数据分析。     

用于永磁体测量系统的亥姆霍兹线圈的原理及设计

就亥姆霍兹线圈测磁原理作了较为详尽的论述,并且介绍了线圈的尺寸选择原则,最后对磁偶极子模型进行了修正,尽可能地降低了线圈设计的理论误差,对设计较为精确的亥姆霍兹永磁体测量系统有一定的参考意义.     

亥姆霍兹线圈及麦克斯韦线圈磁场分布及均匀性比较

基于毕奥-萨伐尔定律,运用椭圆积分,推导出圆环电流在空间任意一点产生的磁场公式,进而分析了亥姆霍兹线圈和麦克斯韦线圈在中心处磁场各分量的分布模型,绘出了空间分布。分析结果表明,麦克斯韦线圈磁场不均匀度小于0.0001的区域半径约是亥姆霍兹线圈的20倍。     

利用亥姆霍兹线圈测量地磁场强度及磁倾角

根据亥姆霍兹线圈轴线上磁场分布的特点,能在其轴线中点附近产生较广的均匀磁场区,根据磁场的叠加原理,推导了地磁场的水平分量、垂直分量及地磁场强度、磁倾角的实验计算公式.采用了FD-HM-Ⅰ型亥姆霍兹线圈,利用高灵敏度毫特斯拉计,探测亥姆霍兹线圈公共轴线中点的磁感应强度.通过改变亥姆霍兹线圈中电流的正、反方向,测量了延安地区当地的地磁场强度及磁倾角.测量结果与延安地区当地的地磁场要素基本相符,说明该方法是确实可行的.该实验方案充分利用了实验室现有仪器,培养了学生的创新意识,因此在实验课教学中具有较高的推广价值.     

基于亥姆霍兹线圈装置的磁热疗优化方法

该文研究了两种常见亥姆霍兹线圈产生磁场的均匀性,并根据装置线圈所产生磁场作用下的生物组织治疗温度分布分析了磁场均匀性对治疗效果的影响。其中,文中的磁纳米粒子（MNPs）以磁流体形式注射进肿瘤区域并假定以注射点为中心呈现高斯分布。该文在多种约束条件下应用改进粒子群算法优化了磁场的频率和强度、磁纳米粒子粒径,以及磁纳米粒子体积分数等参数,而涉及的约束条件包括治疗最高安全温度、治疗磁场安全范围上限、MNPs粒径范围,以及MNPs产热有效条件等。同时,该文以累积等效分钟数来评估圆形和正方形亥姆霍兹线圈及理想磁场在不同血液灌注率下的细胞热损伤程度。研究结果表明,正方形亥姆霍兹线圈相比于圆形线圈能产生更大范围的匀强磁场,这使其磁热疗效果更接近于理想磁场情况。同时,考虑温度依赖的血液灌注率相比定值情况具有更高的治疗温度。     

利用亥姆霍兹线圈测定永磁体的Pc值

介绍了利用亥姆霍兹线圈测定永磁体Ｐｃ值的原理和方法。     

一种三轴方形亥姆霍兹线圈磁场发生装置设计

介绍了一种应用于电磁生物实验的三轴方形电磁场发生装置,推导了三轴方形亥姆霍兹线圈磁感应强度表达式,并设计出整套亥姆霍兹线圈磁场发生器。该系统由lab VIEW软件控制单片机产生控制信号,送至LM1875T功率放大电路,输出驱动三轴线圈产生磁场,经磁感应强度检测后送至labVIEW软件显示。该装置的操作简单、功能多样化、人机界面友好,适合于非电子专业的人员操作。     

梯度场麦克斯韦线圈磁场及磁场梯度分析

在地质勘探、军事导航、医学诊断、目标磁异探测等领域迫切需要研制高精度的磁场梯度测量装置。设计了一种梯度场麦克斯韦线圈,用于对高精度磁场梯度仪进行标校。运用毕奥-萨伐儿定律,首先推导出梯度场麦克斯韦线圈在中心处磁场各分量的分布,然后通过数值仿真绘制出该线圈的磁场强度分布、磁场梯度分布及等值线图。结果表明,在相同的线圈匝数、激励电流和线圈半径条件下,梯度场麦克斯韦线圈产生的磁场梯度均匀区域达到0.602 m2,比反亥姆霍兹线圈产生的磁场梯度均匀区域大15倍,且产生磁场梯度的均匀性也优于反亥姆霍兹线圈。     

基于矩形亥姆霍兹线圈的大均匀区改进型三维磁场发生器设计与特性

为了克服传统磁场发生器空间利用率低的缺陷,提出了改进的三维磁场发生器,具有结构紧凑、更大的均匀区。相比传统的亥姆霍兹线圈,每个维度引入了一双辅助线圈。要设计这紧凑场发生器,五个模型参数需要根据用户的要求对均匀性进行优化。最后,研发了一台磁场发生器,用于测试新型线圈的性能以验证其设计方法。实验结果表明,测试的磁场结果与设计值吻合得很好,最大的设计偏差仅为0.12%。更重要的是,产生相同体积的均匀区,这种磁场发生器的体积仅为传统亥姆霍兹线圈的1/13.6。     

一种便携式消磁设备误差测试仪的研制

介绍了一种基于模块化思想的消磁设备误差测试仪,用于实现某型消磁设备的综合性能测试。该系统由三维亥姆霍兹线圈驱动电路、多通道信号采集和信号源3个主要模块组成。设计了基于自动控制原理的三维亥姆霍兹线圈驱动电路模块;通过滤波放大电路、隔离电路和A/D转换技术实现多通道微弱信号精确采集以及通道间相互隔离;利用直接数字频率合成技术产生标准的测试信号。用户实际测试结果表明,该误差测试仪精度高,性能稳定可靠,能够满足舰船上及消磁站内对消磁设备综合性能测试的需求。     

高匀场磁体校正线圈的设计方法

本文对高匀场磁体的轴向和径向校正线圈的设计方法进行了讨论。文章给出了考虑线圈导体分布宽度的轴向和径向校正线圈磁场的计算公式,在轴向校正线圈设计时,提出用一组线圈来补偿各次带状谐波磁场,因而可以大大减小线圈的数目。在径向校正线圈设计时,采用的方法具有较大的灵活性,可以减小线圈的长度又有较高的利用率。     

通电空心线圈系统产生的磁场分析

许多医用理疗设备都需要使用通电空心线圈产生磁场,磁场产生方式有利用线圈外部的磁场和线圈空心内部的磁场两种,而这两种方式都将由多个线圈实现。通电线圈排布的合理设计能够提高磁场的均匀性,这将对疗效产生重要的影响,因此分别研究了上述两种磁场的特性。研究结果表明:根据线圈的直径大小和线圈相对距离的配合可以产生最优均匀磁场。     

Experimental studies on a structure of eddy current probe for detection of magnetic flux distorted by a flaw

Bobbin-coil-type eddy current probes, which are conventionally used for nondestructive inspection of steam generator tubes in pressurized-water-type nuclear power plants, have poor detection sensitivity to circumferential flaws. Hence a new type of eddy current probe was proposed to effectively detect the magnetic flux component that is indicative of a flaw and thus to eliminate the dependency on sensitivity in flaw detection. In the course of development of the proposed method, probe structures were investigated based on the measurement of magnetic fields induced by variously-shaped excitation flat coils. The new type of probe proposed here consists of differential pick-up coils detecting magnetic flux and excitation coils having a parallelogrammic shape. The structure of the coils was fabricated in order to detect flaws independently of their directions in trial. Nondestructive flaw detection tests were then conducted with the probe. The results obtained concrete evidence showing that both the horizontal, the vertical slit-flaws and even the small hole of 0.5 mm in diameter can be detected successfully.     

Influence of magnetic linkage between coils of a modular SMES

To scale up the capacity of an SMES for a practical application, it is necessary to adopt a high-voltage system, a large current system or a modular system. The first system is difficult because of the very low withstanding voltage of a superconducting coil and the second also involves difficulties such as multiple connections of many convertors on the dc side and large current conductors in the superconducting coil. The third system, composed of several modules with small-scale convertor units and element coils, might be a solution of the above difficulties. In this modular system, the module coils have magnetic linkage with one another. In this paper, the influence of magnetic linkage between coils of a modular SMES is investigated by computer simulation. The magnetic linkage varies with the number of modules and the type of connection of the coils. By the effect of this magnetic linkage, each module's coil current is different at the same power. The current and energy transfer characteristics are determined for discharge from one or more of 6 modules, consisting of 18 coils. The discussion deals with the case in which there is an unused module when quenching occurs. The transfer with the same current in all modules is shown by control of convertor power of the current feedback. © 1997 Scripta Technica, Inc. Electr Eng Jpn. 118 (4): 1–9, 1997     

Improvement of inductive power collection in null-flux maglev system

In the superconducting maglev system it is important to develop a non-contact on-board power source without environmental pollution such as noise and exhaust gases; therefore, inductive power collection (IPC), which utilizes a harmonic magnetic field generated by ground coils in EDS, is being studied. However, alteration to a null-flux EDS that has a high drag ratio reduces the power collecting capacity in the IPC system. In addition, power collecting coils are located on the cryostat of the superconducting coil (SC), so eddy currents at the cryostat also reduce the power collecting capacity. Therefore, an exclusive SC type that locates the exclusive SCs and IPC and power collecting coils so as to face the upper and lower coils of ground coils, respectively, is examined; but we aim to improve the conventional type. After analyzing the influence of eddy currents at the cryostat in detail and improving the composition of the power collecting coil and cryostat, we found that the conventional type has the same capacity as the exclusive SC type. In order to prove the above-mentioned result, we measured the induced voltage of the new-type coils in a test run at Miyazaki test track and confirmed the output of this IPC system in a full-scale synthetic bench test with a PWM converter and magnetic field simulator. © 1998 Scripta Technica. Electr Eng Jpn, 122(2): 48–60, 1998     

NEMA电机单层绕组接线方法的分析

通过对实际下线顺序的分析及电机磁场极性交错特征的分析,得出与实际下线顺序一致的接线方法,以确保电机准确接线.     

新型偏磁式消弧线圈及其控制

提出了一种新结构的偏磁式消弧线圈及其控制方法。它由1个三柱铁心和5个绕组组成。在铁心的两个边柱上分别设置了两级减小截面部分，这两个部分作为铁心磁化区，磁化作用主要发生在该区域。中柱上设有气隙，确定了消弧线圈的补偿下限。3个交流绕组分别布置在3个铁心柱上，两边柱绕组并联后同中柱绕组串联。2个励磁绕组所串联后布置在两边柱上交流绕组的内部。这种结构使得交流绕组对励磁绕组的影响减至最小，使磁化区易于磁化，调节范围加大，使有功损耗和磁化功率减小，实测结果表明，新型消弧线圈孤谐波含量小于4%，损耗小于1.7%，磁化功率小于1.3%。对它的控制问题可归结为两条控制特性：高压调节特性和低压调节特性，只需精确地提供控制电流就可以准确地调整消弧线圈电感。研究了它的励磁系统，该系统励磁电泫动态响应时间小于5ms，工作电流达到稳态时间小于40ms。     

Magnetic damping of the electrodynamic suspension‐type superconducting levitation system

The damping characteristic of the bogie motion is one of the most important issues to be investigated in the superconducting magnetically levitated system based on electrodynamic suspension (EDS). We have therefore studied the damping characteristics and the mechanism of magnetic damping. Electric circuits consisting of coil resistances and inductances can describe the electromagnetic behavior of the levitation system. By numerical calculation based on the electric‐circuit equations combined with the equations of motion, damping characteristics of the bogie are examined for the system consisting only of levitation coils and superconducting coils, and also for the configuration with magnetic shielding structures incorporated. Furthermore, paying attention to the energy balance in the levitation and propulsion system when the bogie is forced to oscillate sinusoidally, we have investigated the relation between the input energy and the running speed, and compared the waveforms of levitation force and bogie oscillation to consider the characteristics and the mechanism of the damping. © 1999 Scripta Technica, Electr Eng Jpn, 127(2): 49–60, 1999     

A novel method applicable to large-scale active magnetic shielding system which effectively compensates gradient magnetic fields originated from the surrounding buildings

We propose the novel magnetic compensation method which is suitable to compensate gradient magnetic fields. The method is to be applied to a conventional large-scale, tri-axial active magnetic shielding system such as a spacecraft magnetic testing facility. The essences of this method are the adoption of compensation coils which have degrees of freedom in their coil orientations, and their installation position, which is chosen to have certain distances from the center of the shielding area. The method works with at least four compensation coils. In this research, we actually demonstrated the method with a scaled-down experiment. Disturbance magnetic field (B) at the target zone was suppressed from 21.33 nT to −1.54 nT and magnetic field uniformity (ΔB) within the test zone was improved from 2.3 nT to 0.015 nT. In terms of magnetic field gradient, improvement from over 4 nT/m to below 0.5 nT/m was achieved.