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Analysis of permanent magnet positioning for improving performance and preventing demagnetization of LSPMSM

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Category: Content №3 2026

Last Updated on 26 June 2026

Published on 30 November -0001

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Authors:

Le Anh Tuan, orcid.org/0009-0001-8695-7457, Hanoi University of Industry, School of Electrical and Electronic Engineering, Hanoi, Socialist Republic of Vietnam

Tran Duy Khanh*, orcid.org/0009-0000-4365-8679, Saodo University, Faculty of Electrical Engineering, Haiphong, Socialist Republic of Vietnam, e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Do Nhu Y, orcid.org/0000-0001-6395-2875, Hanoi University of Mining and Geology, Hanoi, Socialist Republic of Vietnam

* Corresponding author e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

повний текст / full article

Naukovyi Visnyk Natsionalnoho Hirnychoho Universytetu. 2026, (3): 056 - 065

https://doi.org/10.33271/nvngu/2026-3/056

Abstract:

Purpose. To analyse the positioning of permanent magnets (PMs) to ensure operational parameters and prevent irreversible demagnetization (ID) during the startup of line-start permanent magnet synchronous motors (LSPMSMs).

Methodology. The research methods include theoretical methods to analyze ID phenomena and the operational parameters of the LSPMSM. The results are then validated using the finite element method in Ansys/Maxwell Version R2 2021.

Findings. The research results indicate that the PMs’ positioning in the rotor not only affects the operational parameters of the LSPMSM but also influences the PMs’ ID susceptibility. A model of a 15 kW, 2-pole LSPMSM with a symmetrical three-magnet structure and a PM slot distance, L_p (the distance from the axis center to the PM slot), ranging from 29.5 to 33.5 mm is investigated. The results show that the smaller the distance L_p, the better the LSPMSM’s startup characteristics, with the best occurring at L_p = 29.5 mm. Conversely, as L_p increases, the current characteristics and efficiency improve. To achieve an efficiency rating of IE4 according to the IEC standard (³ 93.3 %) without exceeding 5 % ID of the PMs, it is required that 33.5 ³ L_p ³ 31.5 mm. The highest efficiency of 94.2 % is achieved at L_p = 33.5 mm.

Originality. The magnet slot distance L_p is analysed in relation to the ID capacity of the PMs. The results demonstrate that not only the size of the PMs but also their positioning affects their parameters and ID susceptibility. Based on the findings, it is recommended to select L_p with a reasonable value to not only avoid partial ID but also ensure the operational parameters of the LSPMSM remain consistent with the initial design.

Practical value. The research results indicate that in the design of the LSPMSM, not only the PM size but also the PM slot distance L_p must be considered to avoid PM ID and ensure the motor’s operating parameters.

Keywords: permanent magnet, irreversible demagnetization, synchornous motor, electric motor, magnet positioning

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