{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,14]],"date-time":"2025-10-14T00:51:33Z","timestamp":1760403093178,"version":"build-2065373602"},"reference-count":15,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2022,1,3]],"date-time":"2022-01-03T00:00:00Z","timestamp":1641168000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Symmetry"],"abstract":"<jats:p>This paper presents an alternative system called the axial-flux dual-stator toothless permanent magnet machine (AFDSTPMM) system for flywheel energy storage. This system lowers self-dissipation by producing less core loss than existing structures; a permanent magnet (PM) array is put forward to enhance the air\u2013gap flux density of the symmetrical air gap on both sides. Moreover, its vertical stability is strengthened through the adoption of an axial-flux machine, so expensive active magnetic bearings can be replaced. The symmetry configuration of the AFDSTPMM system is shown in this paper. Then, several parts of the AFDSTPMM system are optimized thoroughly, including stator windings, number of pole pairs and the PM parameters. Further, the performance of the proposed PM array, including back-EMFs, air\u2013gap flux density, average torque, torque ripple and over-load capacity, are compared with the Halbach PM array and spoke PM array, showing the superiority of proposed configuration. Finally, 3D simulations were made to testify for the 2D analyses.<\/jats:p>","DOI":"10.3390\/sym14010061","type":"journal-article","created":{"date-parts":[[2022,1,9]],"date-time":"2022-01-09T23:35:09Z","timestamp":1641771309000},"page":"61","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["A Novel Axial-Flux Dual-Stator Toothless Permanent Magnet Machine for Flywheel Energy Storage"],"prefix":"10.3390","volume":"14","author":[{"given":"Yong","family":"Zhao","sequence":"first","affiliation":[{"name":"College of Electronic Engineering, Nanjing Xiaozhuang University, Nanjing 211106, China"}]},{"given":"Fangzhou","family":"Lu","sequence":"additional","affiliation":[{"name":"NARI Technology Co., Ltd., Nanjing 211106, China"}]},{"given":"Changxin","family":"Fan","sequence":"additional","affiliation":[{"name":"Maintenance Branch Company, State Grid Jiangsu Electric Power Co., Ltd., Nanjing 211106, China"}]},{"given":"Jufeng","family":"Yang","sequence":"additional","affiliation":[{"name":"Automotive Engineering Research Institute, Jiangsu University, Zhenjiang 212013, China"}]}],"member":"1968","published-online":{"date-parts":[[2022,1,3]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"95","DOI":"10.1109\/TEC.2006.889547","article-title":"Compressed air energy storage in an electricity system with significant wind power generation","volume":"22","author":"Swider","year":"2007","journal-title":"IEEE Trans. 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