Lee Wooseung, Park Dongkeun, Choi Yoonhyuck, Li Yi, Bascuñán Juan, Iwasa Yukikazu
MIT Francis Bitter Magnet Laboratory/Plasma Science and Fusion Center, Cambridge, MA 02139, USA.
MIT Francis Bitter Magnet Laboratory when this work was still going on, is now with Facility for Rare Isotope Beams, Michigan State University, East Lansing, MI 48824, USA.
IEEE Trans Appl Supercond. 2021 Aug;31(5). doi: 10.1109/tasc.2021.3070240. Epub 2021 Mar 31.
The No-Insulation (NI) winding provides intrinsic bypassing current paths that enable self-protection from overheating. The self-protection of the NI coil is one of the most promising protection techniques for the high field high-temperature superconductor (HTS) magnet applications. Since the additional paths are valid for an HTS magnet with a thinner matrix, the self-protection mechanism is applicable even for the higher current density magnet with reduced matrix thickness inside the HTS tape. However, reducing the matrix can cause damage to the magnet by producing excessive heat during the quench. This research introduces a new modeling method to investigate the hot-spot characteristics in the REBCO NI pancake coil. The model is also validated with a sample NI HTS coil experiment result. Radial direction Normal Zone Propagation (NZP) velocity of the sample coil is estimated based on the suggested model. The calculated radial direction NZP velocity is applied to calculate the center field drop of the NI HTS coil, and the result is well-matched with the experiment result. We also introduce one example of the model applications. The maximum current density that will not exceed a given reference temperature in the adiabatic cooling condition is estimated using the model.
无绝缘（NI）绕组提供了固有的旁路电流路径，可实现自我过热保护。NI线圈的自我保护是高场高温超导（HTS）磁体应用中最有前景的保护技术之一。由于这些额外的路径对具有更薄基体的HTS磁体有效，因此即使对于HTS带材内部基体厚度减小的更高电流密度磁体，自我保护机制也适用。然而，减小基体可能会在失超期间产生过多热量，从而对磁体造成损坏。本研究引入了一种新的建模方法来研究REBCO NI饼式线圈中的热点特性。该模型也通过一个样品NI HTS线圈实验结果进行了验证。基于所提出的模型估计了样品线圈的径向正常区传播（NZP）速度。将计算得到的径向NZP速度应用于计算NI HTS线圈的中心场降，结果与实验结果吻合良好。我们还介绍了该模型应用的一个例子。使用该模型估计了在绝热冷却条件下不会超过给定参考温度的最大电流密度。
