非均匀AC场中闭环HTS线圈的行为预测
Behaviour Prediction of Closed-loop HTS coils in Non-Uniform AC fields
摘要：
磁场衰减率是基于闭环线圈的超导磁体的关键特性。然而，在磁浮列车或旋转机械中，闭环磁体工作在外部交流磁场中，并且由于动态电阻通常远大于接头电阻而会表现出明显的加速磁场衰减。然而，还没有一个数字模型能够系统地研究这种行为，这是这项工作的主要议题。基于H公式，模拟了高温超导闭环线圈在不同交流磁场下的场衰减曲线。考虑电枢线圈产生的非均匀外场。实验结果与模拟结果吻合较好。在我们的数值模型中，电流松弛的影响，这是一个历史性的挑战，进行了分析，并随后消除了可接受的精度。我们的模拟结果表明，大部分比例的场衰减率是从最里面和最外面的匝。在此基础上，设计了一种磁屏蔽图案，以有效地降低磁场衰减率。该工作为磁体设计人员提供了一种有效的方法来预测闭环高温超导线圈在外部交流场中的场衰减率，并探索各种屏蔽设计。
英文摘要：
Field decay rate is the key characteristic of the superconducting magnets based on closed-loop coils. However, in Maglev trains or rotating machines, closed-loop magnets work in external AC fields and will exhibit an evidently accelerated field decay resulting from dynamic resistances, which are usually much larger than joint resistance. Nevertheless, there has not been a numerical model capable of systematically studying this behaviour, which is the main topic of this work. The field decay curves of a closed-loop high-temperature-superconducting (HTS) coil in various AC fields are simulated based on H-formulation. A non-uniform external field generated by armature coils is considered. Reasonable consistence is found between experimental and simulation results. In our numerical model, the impact of current relaxation, which is a historical challenge, is analysed and subsequently eliminated with acceptable precision. Our simulation results suggest that most proportion of the field decay rate is from the innermost and outermost turns. Based on this observation, a magnetic shielding pattern is designed to reduce the field decay rate efficiently. This work has provided magnet designers an effective method to predict the field decay rate of closed-loop HTS coils in external AC fields, and explore various shielding designs.
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