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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。
The Bi-2223 superconducting tape is a high-temperature superconducting material with high current-carrying capacity. It is widely used to manufacture high-field interpolated magnets and nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) Resonance equipment. In the design of superconducting magnets and the calculation of AC loss, the current density distribution in the Bi-2223 tape will inevitably be involved. Based on the method of Brandt numerical analysis, the influence of self-field and external field on the critical current density was considered. The current density distribution of Bi-2223 strip was calculated by Matlab. In order to facilitate the simulation calculation, the Kim model and the Bean model are replaced by the experimental data of the relationship between the critical current and the magnetic field. Three major impositions were applied in the calculation: (1) only the transverse magnetic field was applied; (2) only the conduction current was applied; and (3) the strip carrying the conducting current was placed in the background field. The results show that, when Im <20 A or Bm 20 A or Bm> when 100 mT, Bi- 2223 maximum current density in the strip increases and the magnitude of field current conduction is reduced; the shield current will increase the frequency of the external magnetic field decreases, the conduction current of a frequency distribution for the influence of the current is negligible; When a conducting current-carrying Bi-2223 strip is placed in the background field, the distribution of current density is no longer symmetrical with respect to the center, and the saturation current value decreases as the amplitude of the external magnetic field increases.