Publication: Magnet segmentation to reduce torque ripple in permanent magnet synchronous motor
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Date
2024-07
Authors
Nabilah binti Che Abdul Ghani
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Abstract
Magnet segmentation is a common technique to reduce the eddy current loss and overcome manufacturing issues regarding the large permanent magnet (PM) machines, which intend to have large magnets. Magnet segmentation in Permanent Magnet Synchronous Motors (PMSM) plays a crucial role in reducing torque ripple and improving motor efficiency, addressing the primary target of energy efficiency for electric motor designers. Torque ripple refers to variations in torque output during each electrical cycle, which can lead to undesirable vibrations, noise, and reduced motor performance. Eddy current losses in the rotor can contribute to torque ripple by causing fluctuations in magnetic flux and inducing additional losses in the motor. Segmenting the magnets in a PMSM helps mitigate eddy current losses by breaking up the continuous magnetic circuit and reducing the magnitude of circulating currents induced in the rotor. This segmentation minimizes the skin effect phenomenon, where currents tend to concentrate near the surface of the magnets, further reducing eddy current losses. Additionally, segmented magnets allow for better control of magnetic flux distribution, leading to smoother torque output and reduced torque ripple. Furthermore, magnet segmentation helps overcome manufacturing challenges associated with large permanent magnet machines, as it allows for the use of smaller magnets that are easier to handle and assemble. Despite its advantages, magnet segmentation may affect motor performance, particularly in terms of back electromotive force (EMF) and developed torque. Finite Element Analysis (FEA) using software like ANSYS Maxwell 2D enables to study the effects of magnet segmentation on PMSM performance. By simulating different segmentation patterns and configurations, it can evaluate their impact on torque ripple and other performance metrics. Research has shown that magnet segmentation in PMSMs reduces electromagnetic torque ripple, leading to smoother motor operation and improved efficiency. Simulations comparing PMSM with different segmentation structures, such as one magnet per pole, two magnets per pole, and three magnets per pole, demonstrate that segmentation reduces torque ripple and improves motor performance.