The Effects of Permanent Magnet Segmentations on Electromagnetic Performance in Ironless Brushless DC Motors

• Published in: Energies (Basel) Vol. 15; no. 2; p. 621
• Main Authors: Zhai, Fugang, Yang, Liu, Fu, Wenqi, Tong, Haisheng, Zhao, Tianyu
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.01.2022
• Subjects: Asymmetry; back-EMF trapezoidal degree; Brushless motors; D C motors; Efficiency; Electromagnetic fields; Electromagnetic forces; electromagnetic torque; ironless BLDC motor; Magnetic fields; Optimization; Permanent magnets; PM asymmetrical segment; PM symmetrical segment; Segments; Torque
• ISSN: 1996-1073; 1996-1073
• DOI: 10.3390/en15020621

This paper investigates the electromagnetic torque by considering back electromagnetic force (back-EMF) trapezoidal degrees of ironless brushless DC (BLDC) motors through the two-dimensional finite element method (2-D FEM). First, the change percentages of the electromagnetic torque with back-EMF trapezoidal degrees, relative to those of PMs without segments, are investigated on the premise of the same back-EMF amplitude. It is found that both PM symmetrically and asymmetrically segmented types influence back-EMF trapezoidal degrees. Second, the corresponding electromagnetic torque, relative to that of PMs without segments, is studied in detail. The results show that the electromagnetic torque can be improved or deteriorated depending on whether the back-EMF trapezoidal degree is lower or higher than that of PMs without segments. Additionally, the electromagnetic torque can easily be improved by increasing the number of PMs’ symmetrical segments. In addition, the electromagnetic torque in PMs with asymmetrical segments is always higher than that of PMs without segments. Finally, two ironless PM BLDC motors with PMs symmetrically segmented into three segments and without segments are manufactured and tested. The experimental results show good agreement with those of the 2-D FEM method. This approach provides significant guidelines to electromagnetic torque improvement without much increase in manufacturing costs and process complexity.