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| Design and Application of the Post Assembly Magnetization System for Large Permanent Magnet Wind Generators |
| Li Liang1,2, Tu Zhang1,2, Li Rui1,2, Xu Wei1,2, Ding Hongfa1,2, Peng Tao1,2, Han Xiaotao1,2, Dai Bijun3, Zhang Mingji3, He Yumin4, Luo Rongfeng5, Zou Yingdong6, Lü Yiliang1,2 |
1. Wuhan National High Magnetic Field Center Huazhong University of Science and Technology Wuhan 430074 China;
2. School of Electrical and Electronic Engineering Huazhong University of Science and Technology Wuhan 430074 China;
3. Yongji Electric Co. Ltd China Railway Rolling Stock Corporation Xi'an 710000 China;
4. Xiangtan Electric Manufacturing Co. Ltd Xiangtan 411100 China;
5. Ming Yang Smart Energy Group Limited Zhongshan 528400 China;
6. Dongfang Electric Machinery Co. Ltd Dongfang Electric Corporation Deyang 618000 China |
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Abstract In the conventional manufacturing process of large permanent magnet motors, the prevalent “magnetize then assemble” pre-magnetized technique is fraught with challenges such as low production efficiency and significant safety risks. Addressing these issues, this research introduces an innovative postassembly magnetization method for large permanent magnet wind turbine generators. This method revolutionizes the traditional approach by advocating for “assemble then magnetize”, substantially enhancing assembly accuracy, production efficiency, and safety.
This research initially focused on the magnetization and demagnetization behaviors of N46SH neodymium-iron-boron (NdFeB) permanent magnet materials under various external magnetic field orientations. It established criteria for deter mining the saturation magnetization strength in different magnetic field directions, laying the foundation for subsequent magnetizing coil design. For megawatt-level direct-drive and half-dirve wind turbine generators, a comprehensive design method was proposed for magnetizing coil systems within the post-assembly magnetization system. This involved an in-depth electromagnetic, thermal, and mechanical analysis of the magnetizing coils, with a particular emphasis on addressing the eddy current issues during magnetization, calculations of the coil cooling process, and stress distribution within the coils.
The study further introduced case studies of post-assembly magnetization applications in 2.5 MW direct-drive and 20 MW half-drive wind turbine generators, encompassing the design and functionality of magnetizing coils, cooling systems, magnetizing power sources, rotational and propulsion systems, and measurement and control systems. The application of the proposed method in the manufacturing and maintenance processes of megawatt-scale permanent magnet wind turbines generators was illustrated, especially in its adoption by industry leaders such as Xiangdian Electric Manufacturing Company Limited (XEMC) and China Railway Rolling Stock Corporation (CRRC). The stability and reliability of the magnetizing coils were validated through continuous discharge experiments. Furthermore, a comprehensive comparative analysis was conducted between post-assembly magnetized motors and pre-magnetized motors, encompassing various aspects such as magnetic pole performance and overall motor performance. The results indicated that post-assembly magnetized motors not only met all performance standards but also exhibited superior pole consistency and manufacturing efficiency. This outcome is particularly crucial for an industry increasingly focused on reliability and efficiency. Additionally, the research extended the post-assembly magnetization technique to the maintenance and recycling of damaged or retired permanent magnet motors. This application achieved complete demagnetization of the poles, reducing the demagnetization time by five orders of magnitude compared to traditional methods, and was environmentally friendly, resulting in zero pollution and promoting sustainable and green remanufacturing of permanent magnet motors.
In conclusion, the reliability of the proposed post-assembly magnetization design method was validated through comprehensive testing and analysis. This validation emphasized the technical feasibility and practical applicability of the method in the current industrial environment. The findings of this study have the potential to revolutionize the manufacturing processes and design of large permanent magnet motors, especially in the field of wind energy, by introducing a more efficient, safe, and environmentally friendly post-assembly magnetization technique.
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Received: 08 October 2023
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2023, Vol. 38 
