Bi-2223带材在自场和外场条件下电流密度分布的数值分析  

Numerical Analysis of Current Density Distributions in Bi-2223 Tapes under Self and External Fields

作　　者：王磊[1,2] 王秋良[1] 王晖[1] 

机构地区：[1]中国科学院电工研究所应用超导重点实验室,北京100190 [2]中国科学院大学,北京100049

出　　处：《稀有金属》2014年第5期755-761,共7页Chinese Journal of Rare Metals

基　　金：国家自然科学基金项目(50925726)资助

摘　　要：Bi-2223超导带材是一种具有较高载流能力的高温超导材料,被广泛用来制造高场强的内插磁体以及核磁共振(NMR),磁头振成象(MRI)等核磁共振设备。在超导磁体的设计以及交流损耗的计算中,不可避免地会涉及到Bi-2223带材中电流密度的分布。基于Brandt数值分析的方法,考虑了自场和外场对于临界电流密度的影响,利用Matlab对Bi-2223带材截面的电流密度分布进行了计算。为了便于仿真计算,用实验测得的临界电流与磁场关系的数据代替了Kim模型和Bean模型。在计算中主要施加了3种外加条件:(1)只施加横向磁场;(2)只通入传导电流;(3)将通入传导电流的带材放置于背景场中。结果显示,当Im<20 A或者Bm<100 mT时,Bi-2223带材中电流密度随着传导电流和外场的幅值增加而增长;当Im>20 A或者Bm>100 mT时,Bi-2223带材中电流密度的最大值随着传导电流和外场的幅值增加而减小;屏蔽电流会随着外磁场的频率增加而减小,传导电流的频率对于电流分布的影响可以忽略不计;当通入传导电流的Bi-2223带材放置于背景场中时,电流密度的分布相对于中心不再对称,并且饱和电流值会随着外磁场的幅值增加而减小。Bi-2223 was a kind of significant superconductor material with high current carrying capability,it was commonly applied in fields such as high temperature superconducting magnet,nuclear magnetic resonance spectrometer（ NMR）,magnetic resonance imaging（ MRI）,and other equipments. The design of superconducting magnet and the AC loss calculation were relevant to the distributions of current density and magnetic field in the conductor. The current and magnetic field distributions in Bi-2223 conductors based on Brandt＇s method through the Matlab was calculated,including the effects of self and external field. For the convenience of calculation,the perpendicular and parallel field dependence of critical current obtained by experiment substituted for Kim-type or Bean model Jc（ B） dependence. Three conditions were applied：（ 1） external magnetic field only,（ 2） transport current only,（ 3） transport current together with external magnetic field. The results showed that when the amplitude of transport current Im〈 20 A or applied magnetic field Bm 〈100 mT,Jz（ x） increased with the increase of transport current and applied magnetic field. When Im〉 20 A or Bm〉 100 mT,the max value of Jz（ x） declined with the increase of amplitude of transport current and applied magnetic field. The screening current density decreased with the increase of frequency,but the distribution of Jz（ x） was not so much relevant to the Iafrequency. If the transport current was ramped into a Bi-2223 tape with the background magnetic field,the current density would not be symmetric to the conductor center and the saturated current density would decrease with the increase of Bm.

关 键 词：BI-2223带材 横向磁场 传导电流 电流密度分布 

分 类 号：TL62[核科学技术—核技术及应用] TM152[电气工程—电工理论与新技术]