Affiliations: [a] School of Electrical and Information Engineering, Tianjin University, Tianjin 300072, China | [b] Tianjin Engineering Center of Electric Machine System Design and Control, Tianjin Polytechnic University, Tianjin 300387, China
Correspondence:
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Corresponding author: Changliang Xia, School of Electrical and Information Engineering, Tianjin University, No.92 Weijin Road, Nankai District, Tianjin 300072, China. Tel.: +86 22 27402325; Fax: +86 22 27402325; E-mail: [email protected].
Abstract: When the interior permanent magnet (PM) machine operates under load condition, the armature current is ahead of the back electromotive force. However, the advanced armature current produces the demagnetizing field, which makes the irreversible demagnetization appeared in PMs easily. In this paper, aiming at the U-type PM structure, the expressions of the flux density components in the corresponding magnetizing directions of PMs at each node of PMs are derived. A calculation model to analyze the demagnetization in PMs is established in the Finite Element software by utilizing the derived expressions. Several improved geometries for rotor are proposed in this paper to strengthen the anti-demagnetization ability of PM. Based on the established calculation model, effects of variables in the improved geometries on the demagnetization in PMs and the rated electromagnetic torque are analyzed in detail. Based on the analysis results, optimized improved rotor geometry is achieved giving consideration to the anti-demagnetization ability of PM and rated electromagnetic torque.
