Development and Testing of Short-End and High-Compactness Superconducting Magnets for Stator-Excitation Brushless Superconducting Machines
Zhang Zhiheng1, Hua Wei2, Li Xianglin3,4, Zhu Xinkai5, Wang Yubin6, Qiu Zhiyu2,4
1. School of Electrical and Information Engineering Zhengzhou University Zhengzhou 450001 China; 2. School of Electrical Engineering Southeast University Nanjing 210096 China; 3. College of Electrical Engineering Qingdao University Qingdao 266071 China; 4. Advanced Ocean Institute of Southeast University Nantong Nantong 226010 China; 5. Department of Electric Power Engineering North China Electric Power University Baoding 071003 China; 6. College of New Energy China University of Petroleum Qingdao 266580 China
Abstract：To meet the application demands of stationary seal stator-excitation brushless superconducting machines, this study develops and validates a novel superconducting magnet featuring short ends and high compactness. Initially, a short-end superconducting coil design is proposed and compared with conventional racetrack-shaped coils. Practical selection rules for these two configurations are summarized based on the relationship among the straight-section spacing, the minimum bending radius of the superconducting tape, and the actual bending radius. Furthermore, to achieve a close fit between the coil and the skeleton, the long straight sides are modified into micro-curved arcs, effectively eliminating gaps and mitigating stress concentration at transition points. The overall structural composition of the superconducting magnet is detailed, including the coil skeleton, double-pancake coils, side cover plates, and current leads. Compared to the conventional racetrack-shaped design, the developed superconducting magnet reduces the axial length by 22.3% and saves on superconducting tape costs by 11.4%. Finite element analysis confirms its minimal impact on key machine performance metrics, such as no-load back-EMF and load torque. The detailed manufacturing process for the modular magnet is elaborated, encompassing coil skeleton fabrication, winding procedures using a custom fixture, and assembly. Microscopic inspection of the wound coils reveals flat and smooth surfaces at corners, end sections, and micro-curved straight sections, with no local protrusions or irregularities, indicating successful elimination of gaps between the tape and skeleton. A comprehensive testing platform was established for critical current evaluation, and tests were conducted on the 12 fabricated modular magnets. The measured central magnetic field shows excellent agreement with simulation results during stable current flow, with a maximum error of only 6.79% (below 1.5% for currents above 40 A). Post-welding of the Dewar system, critical currents show only minor deviations (up to -4.66%), confirming the robustness of the manufacturing process. All tested parameters, including critical current, operating current margin, tape length, and Dewar leak rate, meet the design specifications. This research provides a valuable reference for developing high-performance, cost-effective super- conducting magnets for this category of advanced electrical machines.
张志恒, 花为, 李祥林, 朱新凯, 王玉彬, 邱志宇. 定子励磁无刷超导电机用短端部高紧凑超导磁体研制与测试[J]. 电工技术学报, 2026, 41(6): 1922-1933.
Zhang Zhiheng, Hua Wei, Li Xianglin, Zhu Xinkai, Wang Yubin, Qiu Zhiyu. Development and Testing of Short-End and High-Compactness Superconducting Magnets for Stator-Excitation Brushless Superconducting Machines. Transactions of China Electrotechnical Society, 2026, 41(6): 1922-1933.
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2026, Vol. 41 
