The no-insulation (NI) winding method is an effective technique for winding coils from high-$T_{\rm c}$ superconductors (HTS). NI coils are electrically and thermally robust due to their ability to radially bypass current away from the fragile superconducting path when necessary. This avoids stored magnetic energy being entirely discharged on local defects in the HTS tape. However, the increased degrees of freedom for the current distribution makes finite-element modelling of these coils a complicated and multi-level problem. Here we present and validate a 2D axially symmetric model of an NI (or partially insulated) coil that captures all the inherent electromagnetic properties of these coils, including axial vs radial current flow and critical current suppression, and also reproduces the well-known charging and discharging characteristics. The model is validated against previously reported discharge measurements, and is shown to produce results consistent with the expected equivalent-circuit behaviour. Only by solving the NI coil problem with both axial and radial fidelity can the interplay of critical current anisotropy and turn-to-turn current be properly accounted for. The reported FE model will now enable coil designers to simulate key complex behaviours observed in NI coils, such as shielding currents, magnetic field inhomogeneity and remnant field effects.

中文翻译：

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使用旋转各向异性电阻率的非绝缘高温超导线圈的有限元建模

无绝缘 (NI) 缠绕方法是一种有效的技术，可用于缠绕高 $T_{\rm c}$ 超导体 (HTS) 的线圈。NI 线圈在电和热方面都很稳健，因为它们能够在必要时将电流从脆弱的超导路径中径向旁路。这避免了存储的磁能在 HTS 带中的局部缺陷上完全释放。然而，电流分布自由度的增加使这些线圈的有限元建模成为一个复杂的多层次问题。在这里，我们展示并验证了 NI（或部分绝缘）线圈的 2D 轴对称模型，该模型捕获了这些线圈的所有固有电磁特性，包括轴向与径向电流和临界电流抑制，还重现了众所周知的充电和放电特性。该模型根据先前报告的放电测量进行了验证，并显示产生与预期等效电路行为一致的结果。只有同时解决轴向和径向保真度的 NI 线圈问题，才能正确考虑临界电流各向异性和匝间电流的相互作用。报告的 FE 模型现在将使线圈设计人员能够模拟在 NI 线圈中观察到的关键复杂行为，例如屏蔽电流、磁场不均匀性和残余场效应。只有同时解决轴向和径向保真度的 NI 线圈问题，才能正确考虑临界电流各向异性和匝间电流的相互作用。报告的 FE 模型现在将使线圈设计人员能够模拟在 NI 线圈中观察到的关键复杂行为，例如屏蔽电流、磁场不均匀性和残余场效应。只有同时解决轴向和径向保真度的 NI 线圈问题，才能正确考虑临界电流各向异性和匝间电流的相互作用。报告的 FE 模型现在将使线圈设计人员能够模拟在 NI 线圈中观察到的关键复杂行为，例如屏蔽电流、磁场不均匀性和残余场效应。