Experimental Study on the Accuracy of the Proposed LFAC Method for Measuring the Contact Resistance of NI HTS Coils
Experimental Study on the Accuracy of the Proposed LFAC Method for Measuring the Contact Resistance of NI HTS Coils
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所提出的 LFAC 方法测量 NI HTS 线圈接触电阻精度的实验研究
DOI：
10.1109/tasc.2022.3175791
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发表时间：
2022
影响因子：
1.8
通讯作者：
Noguchi So
中科院分区：
文献类型：
--
作者：
Kim SeokBeom;Miyamoto Kohei;Kobayashi Hirotaka;Inoue Ryota;Ueda Hiroshi;Noguchi So
无绝缘（NI）绕组技术提供了高热稳定性，匝间接触电阻是表征NI HTS磁体热稳定性和充电延迟的重要因素。因此，需要一种能够精确测量 NI HTS 磁体匝间接触电阻的方法。我们之前提出了一种使用低频交流电流的匝间接触电阻测量方法。仅当整个交流电流沿 NI HTS 扁平线圈的径向流动时（几乎没有线圈电感），所提出的低频交流电流（LFAC）才能准确评估匝间接触电阻。另外，沿径向流动的交流电流需要在绕组线（REBCO线）的平面内具有均匀的电流分布。因此，本研究进行了实验研究来证明所提出的LFAC方法的可靠性。实验中，准备了三个不同缠绕张力（0.5、1和2 kg）的NI测试线圈，并在每个测试线圈下方放置四个拾波线圈，以评估径向电流旁路特性。通过从室温到液氮温度的多次冷却循环，每个测试线圈的接触电阻从百分之几降低到百分之几十。虽然这是定性观察，但制备的拾波线圈证明了 LFAC 方法的有效性，并且表明即使是 NI 线圈中接触电阻的微小变化也可以测量。
No-insulation (NI) winding technique provides high thermal stability, and the turn-to-turn contact resistance is an important factor to characterize the thermal stability and charging delay of NI HTS magnets. Therefore, a method that can accurately measure the contact resistance between turns of NI HTS magnets was required. We have previously proposed a turn-to-turn contact resistance measurement method using a low frequency AC current. The proposed low-frequency-AC-current (LFAC) can accurately evaluate the contact resistance between turns only when the whole AC current flows in the radial direction of the NI HTS pancake coil (there is almost no coil inductance). In addition, the AC current flowing in the radial direction needs to have a uniform current distribution in the plane of winding wire (REBCO wire). Therefore, in this study, an experimental study was conducted to prove the reliability of the proposed LFAC method. In the experiment, three NI test coils with different winding tension (0.5, 1 and 2 kg) were prepared, and four pickup coils were placed under each test coil to evaluate the radial current bypass characteristics. The contact resistance of each test coil was decreased from a few percent to several tens of percent by multiple cooling cycles from room temperature to liquid nitrogen temperature. Although it is a qualitative observation, the validity of the LFAC method was proved by the prepared pickup coils, and it was shown that even a small change of contact resistance in NI coils can be measured.