共查询到20条相似文献,搜索用时 31 毫秒
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Yuan J Rohan ML Shen GX 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2006,182(2):298-307
The use of Bi-2223 high temperature superconducting (HTS) tape as a material for gradient coils in MRI is evaluated in this paper. Bi-2223 tapes have a very high critical current and a very low power loss. A HTS tape gradient coil is expected to provide much higher gradient strength and generate much lower heating than a copper coil. Measurements of the AC power loss of Bi-2223 tapes at typical operating frequencies for gradient coils are presented. The degradation of the critical current and its effect on the increase of AC power loss is analyzed. Practical technical issues such as resistance, gradient strength and mechanical performance are also discussed. A prototype Bi-2223 HTS tape gradient coil is evaluated to verify the concept. 相似文献
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Shinichi Ishiguri Taisuke Funamoto 《Physica C: Superconductivity and its Applications》2011,471(11-12):333-337
In this paper, we establish a model to analyze the transport current performance of a high-temperature superconducting (HTS) coil, considering the dependencies of critical current and n-value of an HTS tape on magnetic field and magnetic field angles. This analysis shows that relatively large electric fields appear at the coil’s edges, preventing improvement in the transport current performance of the coil. To solve this problem, in this paper, we propose a graded coil in which several coil edges of different heights are separated and graded. Analysis of its performance shows that the coil’s critical current increases, thus confirming that there exists an optimum coil cross section at which the stored energy and central magnetic field improve 2.1 times and 45%, respectively, compared with a typical rectangular coil that employs the same total length of the HTS tape. It is recommended that these results of the coil should be applied to SMES. 相似文献
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临界电流值是描述Bi2223高温超导带材性能的一个基本参数,在一定的温度条件下,Bi2223高温超导带材的临界电流是带材所在位置磁场大小和磁场方向的函数,其短样的临界电流值可以通过四引线法测量,单根超导带材的自场很小,磁场对临界电流的影响可以忽略.高温超导磁体的临界电流被定义成引发该磁体失超的最小电流,高温超导磁体的自场比单根超导带材的自场要大得多,磁体各个位置的磁场大小和方向各不相同,很难用理论的方法准确计算磁体的临界电流.对于高温超导磁体而言,除了磁场的影响因素以外,绕制磁体所用的超导带材自身的均匀性也是影响其临界电流的一个重要因素.本文对这两个因素进行探讨,并着重讨论高温超导带材自身的均匀性对临界电流大小的影响,本文的结论可以为高温超导磁体的设计、磁体绕制时带材的选择、磁体运行时安全工作电流的确定提供帮助. 相似文献
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T. J. Hughes Y. Yang C. Beduz A. Power 《Physica C: Superconductivity and its Applications》1998,310(1-4):187-191
The magnetic interaction between two neighbouring superconducting tapes has significant influences on their self-field AC losses. While the two tapes are independent of each other when separated far apart, they are expected to be fully coupled and behave as a single tape when placed very near. One of the consequences of such coupling is the increase in the self-field loss per tape, which is double of that for an uncoupled tape carrying the same current. In order to assess the interactions among tapes in systems such as a power cable, a better understanding is necessary on the critical distance where the coupling becomes important. Experimental measurements on the self-field losses in two neighbouring Ag sheathed PbBi2223 tapes were carried out with the two tapes separated by various distances, while placed either side by side (side-configuration) or one on top of the other (top-configuration). The results indicates that the critical coupling distance for the top-configuration is about 5 mm, where the increase in loss per tape is about 10%. The critical length for the side-configuration is found to be of the same order of magnitude. 相似文献
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超导电动悬浮列车以超导磁体作为核心部件, 具有环境影响小、 高速下自稳定、 安全性能好等优点, 已成为高速轨道交通的重要发展方向之一. 然而, 传统的磁体线圈结构存在绕组内磁场过于集中的问题, 导致磁体的临界电流下降显著, 列车的悬浮及安全性能也受到影响. 针对现有悬浮磁体结构自场集中导致的临界电流衰减问题,本文提出了一种梯形高温超导磁体线圈结构. 建立了一种可以提升磁体临界电流计算效率的均质自洽模型, 设计了梯形结构线圈的结构参数并完成了磁体线圈的绕制. 实验和计算结果表明, 自洽模型计算的磁体临界电流与实验测量值吻合良好, 验证了模型的准确性. 利用该模型对日本山梨试验线上的全尺寸车载高温超导磁体进行了结构优化设计. 研究发现, 优化后的车载磁体绕组内磁场集中程度明显下降, 车载磁体的临界电流及目标区域的磁场强度显著提高. 本研究相关成果可为电动悬浮列车车载磁体的结构设计提供参考. 相似文献
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Seeking a geometry that can withstand greater transverse loads based on the electromechanical material properties of high-temperature superconducting (HTS) tape is an effective way of improving the transport performance of HTS cables. The cabling method requires the determination of the optimum twist angle of the HTS tape for withstanding transverse loads. This paper investigates the critical current characteristics of HTS tapes under combined deformation. The limit range of the twist angle under the combined deformation is measured and the optimum twist angle of the HTS tape is determined. The results show that the twisting chirality configuration obviously affects the bending strength of the HTS tape. In the elastic range, increasing the pre-twist angle increases the bending strength of the HTS tape, thereby improving the transport performance. In addition, a numerical model is built to further investigate the effect of the twisting chirality configuration on the electromechanical properties of the HTS tape, and the experimental results are explained. The experimental and simulation results generally agree well, and calculations show that there is always a sharp change in stress at the interface of different materials. These findings explain the mechanism of the effect of the twisting chirality configuration on the mechanical behavior and critical current of the HTS tape. They also provide a reference for cabling methodologies for the HTS cable configuration. 相似文献
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对具有不同临界电流的Bi2223/Ag多芯超导材的交流电流电压特性进行了测量和评价,当传输电流的有效值Inns小于临界电流Ic时,交流电压的大小与传输电流的频率成正比;但Inns接近临界电流时,不同频率所对应的交流电压的大小之间的差别减小了,所有的曲线都汇聚成一条曲线,传输电流的频率分别为40Hz,60Hz,80Hz,200Hz及300Hz时,我们测量了交变传输电流在Bi2223/Ag带材中产生的自场损耗。结果表明当传输电流的频率较低时,实验结果与基于Bean模型的Norris方程预期的结果一致;另外,实验结果表明存在一个电流I′,它的值小于任何一个样品的临界电流,本实验中I′的值是10安培,在传输相同大小的电流Inn且Inns〈I′时,Boi2223/Ag带材的交流损耗与它的临界电流成正比;但当Inns〉I′ 相似文献
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The critical current of high-temperature superconductor (HTS) tapes depends on temperature, magnetic field, and flux angle against the tape. Analyzing the performance of an HTS coil relies on the critical current equation, which has these dependencies. To date, the critical current equation has been obtained by fitting the measured data. However, this fitting method requires the time-consuming and laborious work of measuring the tapes. In this study, based on a new transition concept in applying a magnetic field, we show how to obtain the critical current equation, while keeping the temperature constant. From the wave function of the Cooper pair which distributes along a magnetic flux quantum, a wave function at the transition state is obtained; this yields the wave functions with perpendicular and parallel magnetic components against the tape. Combining these wave functions yields the conclusive critical current density equation. To confirm the accuracy of this equation, used Bi-2223/Ag tapes, it was compared with the measured critical current under various magnetic fields and flux angles; it was found that they agree well. The parameters of this equation can be obtained by measuring the perpendicular/parallel critical magnetic field component. This equation does not require fitting the measured data, therefore, it can be employed with any Bi-2223/Ag tape. 相似文献
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Bi2 2 2 3银包套超导带材是研制高温超导磁体和高温超导强电应用的基础。文中就对高温超导磁体最大运行电流有重要影响的 Bi2 2 2 3银包套带材侧向弯曲形变进行了初步探讨 ,就不同的侧向弯曲率对超导带载流能力的影响进行了实验测试 ,并提出了提高 HTS磁体最大运行电流的方法。 相似文献
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Wurui Ta 《Physics letters. A》2018,382(35):2395-2402
In recent years, several cabling methods of high temperature superconducting (HTS) cable have been proposed; e.g., the conductor on a round core cable (CORC), the Roebel assembled coated conductor cable, the helical twisted stacking-tape cable (TSTC) and the twisted-stack slotted core HTS cable (TSSC). These cabling methods allow the high temperature superconducting tapes widely used in the high-field magnets. The single superconducting tape performance under applied loads directly relates to the transport performance of the cable and the choice of the cabling method. In this paper, we investigate the effect of twisting morphology on the electro-mechanical properties of HTS tapes. Particular attention is given to the transverse Lorentz force of a pre-twisted HTS tape. The analytical solution of the deflection of the HTS tape under transverse Lorentz force is derived. Then, the current distribution and AC loss of the tape are calculated by using H-formulation. The effects of twist angle and loading conditions are examined for different HTS tape lengths. The results show that the stiffness resistance ability to Lorentz force of the HTS tape can be increased in several ranges by increasing the twist angle. The twisting structure can also reduce current degradation and AC loss, and thus enhance the transport capacity of HTS tape. This study helps understand the electro-mechanical properties of pre-twisted HTS tapes and provides theoretical reference for the design of novel HTS cable structures. 相似文献
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J. J. Rabbers B. ten Haken H. H. J. ten Kate 《Physica C: Superconductivity and its Applications》1998,310(1-4):101-105
BSCCO/Ag tape superconductors are developed for electrical power applications at liquid nitrogen temperatures. In these applications, e.g., superconducting transformers and power cables, an AC transport current and an AC magnetic field are present at the same time. A set-up to measure the influence of external AC magnetic field on the transport current loss, i.e., the voltage drop across a sample supplied with an AC transport current, has been developed. The magnetic field can be applied both parallel and perpendicular to the broad side of the tape conductor. An increase of the transport current loss due to the external AC magnetic field is observed. When a DC external magnetic field is applied the increase of the self-field loss can be described well by the decrease of the critical current due to the magnetic field. In the case of an AC external magnetic field this is only a minor effect. For magnetic field amplitudes higher than a certain threshold value the transport current loss is described reasonably well by the self-field loss and a dynamic resistance contribution calculated from the DC voltage–current relation in AC magnetic field. 相似文献
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超导磁体的场强与超导材料的载流能力、磁体口径和低温环境有密切关系.为了在中高温区域实现高磁场强度的超导磁体,采用国产第二代高温超导带材,成功绕制出内直径为100 mm的高温超导线圈.该超导线圈在77,65,55和46 K不同温区下进行了性能测试,其最大运行电流分别为65,147,257和338 A,对应的中心磁场强度分别为0.78,1.77,3.1和4.08 T.所研制的超导线圈的中平面上磁场基本一致. 相似文献
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