Nouailhetas Quentin, Xing Yiteng, Dorget Rémi, Dirahoui Walid, Guijosa Santiago, Trillaud Frederic, Lévêque Jean, Noudem Jacques Guillaume, Labbé Julien, Berger Kévin
Université de Lorraine, GREEN, 54000 Nancy, France.
Normandie University, ENSICAEN, UNICAEN, CNRS, CRISMAT, 14000 Caen, France.
Materials (Basel). 2024 Aug 2;17(15):3827. doi: 10.3390/ma17153827.
High temperature superconductors (HTSs) are enablers of extensive electrification for aircraft propulsion. Indeed, if used in electrical machines, HTS materials can drastically improve their performance in terms of the power-to-weight ratio. Among the different topologies of superconducting electrical machines, a flux modulation machine based on HTS bulks is of interest for its compactness and light weight. Such a machine is proposed in the FROST (Flux-barrier Rotating Superconducting Topology) project led by Airbus to develop new technologies as part of their decarbonization goals driven by international policies. The rotor of the machine will house large ring-segment-shaped HTS bulks in order to increase the output power. However, the properties of those bulks are scarcely known and have barely been investigated in the literature. In this context, the present work aims to fill out partially this scarcity within the framework of FROST. Thus, a thorough characterisation of the performances and homogeneity of 11 large REBaCuO bulks was carried out. Ten of the bulks are to be utilized in the machine prototype, originally keeping the eleventh bulk as a spare. A first set of characterisation was conducted on the eleven bulks. For this set, the trapped field mapping and the critical current were estimated. Then, a series of in-depth characterisations on the eleventh bulk followed. It included critical current measurement, X-ray diffraction, and scanning electron microscopy on different millimetre-size samples cut out from the bulk at various locations. The X-ray diffraction and scanning electron microscopy showed weakly oxygenated regions inside the bulk explaining the local drop or loss in superconducting properties. The objective was to determine the causes of the inhomogeneities found in the trapped field measured on all the bulks, sacrificing one of them, here the spare one. To help obtain a clearer picture, a numerical model was then elaborated to reproduce the field map of the eleventh bulk using the experimental data obtained from the characterisation of its various small samples. It is concluded that further characterisations, including the statistics on various bulks, are still needed to understand the underlying reasons for inhomogeneity in the trapped field. Nonetheless, all the bulks presented enough current density to be usable in the construction of the proposed machine.
高温超导材料（HTS）是实现飞机推进广泛电气化的关键因素。事实上，如果应用于电机中，HTS材料能够在功率重量比方面显著提升电机性能。在超导电机的不同拓扑结构中，基于HTS块材的磁通调制电机因其紧凑性和轻量化而备受关注。空中客车公司牵头的FROST（磁通屏障旋转超导拓扑）项目提出了这样一种电机，作为其在国际政策推动下实现脱碳目标的一部分，致力于开发新技术。该电机的转子将容纳大型环形段状HTS块材，以提高输出功率。然而，这些块材的性能鲜为人知，在文献中也几乎未被研究。在此背景下，本研究旨在在FROST框架内部分填补这一空白。因此，对11个大型REBaCuO块材的性能和均匀性进行了全面表征。其中10个块材将用于电机原型，最初保留第11个块材作为备用。首先对这11个块材进行了一组表征。对于这组表征，估算了俘获场映射和临界电流。然后，对第11个块材进行了一系列深入表征。这包括对从块材不同位置切割出的不同毫米尺寸样品进行临界电流测量、X射线衍射和扫描电子显微镜分析。X射线衍射和扫描电子显微镜分析显示块材内部存在弱氧化区域，这解释了超导性能的局部下降或丧失。目的是确定在所有块材上测量的俘获场中发现的不均匀性的原因，为此牺牲其中一个，即这里的备用块材。为了帮助更清楚地了解情况，随后建立了一个数值模型，利用从其各种小样品表征中获得的实验数据来重现第11个块材的场图。得出的结论是，仍需要进一步表征，包括对各种块材的统计分析，以了解俘获场不均匀性的根本原因。尽管如此，所有块材都呈现出足够的电流密度，可用于所提议电机的制造。
