A simple protection evaluation method for no-insulation REBCO pancake coils during local normal-state transition
A simple protection evaluation method for no-insulation REBCO pancake coils during local normal-state transition
复制标题
一种简单的非绝缘REBCO扁平线圈局部正态转变保护评估方法
DOI：
10.1088/1361-6668/aafcd2
复制
发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Y.Iwasa
中科院分区：
文献类型：
--
作者：
S.Noguchi;S.Hahn;A.Ishiyama;Y.Iwasa
无绝缘（NI）和金属绝缘（MI）绕组技术是有前途的，以提高热稳定性的REBCO饼线圈，走向实际使用的核磁共振和磁共振成像系统。NI和MI REBCO扁平线圈在许多过电流测试中显示出很高的热稳定性。然而，缺点是由于匝间接触电阻低而导致充电延迟。因此，许多研究人员试图增加匝间接触电阻来克服充电延迟问题。同时，部分元件等效电路（PEEC）模型可以准确地模拟NI REBCO饼形线圈的过电流和充/放电测试。利用PEEC模型结合热有限元分析（FEA），在局部正常状态转变过程中的热稳定性进行了评估。从模拟结果中，它被发现，存在一个最佳的范围内的匝间接触电阻保持较高的热稳定性在一个本地正常状态转变。然而，PEEC和热FEA方法需要大量的时间和复杂的模拟方法。在本文中，我们提出了一个简单的数学公式，以获得一个适当的范围内的匝间接触电阻在当地正常状态过渡，假设一个最坏的冷却条件。简单的计算是易于使用和节省时间的大致估计的NI REBCO饼形线圈的运行可靠性。
No-insulation (NI) and metal-insulation (MI) winding techniques are promising for enhancing the thermal stability of REBCO pancake coils, toward the practical use of nuclear magnetic resonance and magnetic resonance imaging systems. The NI and MI REBCO pancake coils showed high thermal stability in many over-current tests. However, a disadvantage is a charging delay due to low turn-to-turn contact resistance. Therefore, many researchers have tried to increase turn-to-turn contact resistance to overcome the charging delay problem. Meanwhile, a partial element equivalent circuit (PEEC) model can accurately simulate the over-current and charging/discharging tests of NI REBCO pancake coils in detail. Using the PEEC model coupling with thermal finite element analysis (FEA), the thermal stability was evaluated during a local normal-state transition. From the simulation results, it was found that a best range of turn-to-turn contact resistance existed to keep a high thermal stability during a local normal-state transition. However, the PEEC and thermal FEA method requires a substantial amount of time with complicated simulation approach. In this paper, we propose a simple mathematical formulation to obtain an appropriate range of turn-to-turn contact resistance during a local normal-state transition, supposing a worst cooling condition. The simple computation is easy to use and timesaving to roughly estimate the operation reliability of NI REBCO pancake coils.