Investigation of Bread-Loaf Magnet on Vibration Performance in FSCW PMSM Considering Force Modulation Effect

This article aims to disclose the negative effect of bread-loaf magnet on vibration performance in fractional-slot concentrated-winding (FSCW) permanent magnet synchronous motors (PMSMs). First, the initial phase relationship in PM flux density harmonics is clarified. Then, the effect of bread-loaf magnet on electromagnetic force, including radial and tangential components, is investigated, in which the force modulation effect is considered. Bread-loaf magnet greatly weakens PM flux density harmonics. However, the dominated electromagnetic force generated by these weakened PM flux density harmonics has an opposite phase angle to that of the synthetic one. As a result, the bread-loaf magnet has a negative effect on reducing the dominated electromagnetic force component. Afterward, two 12-slot/10-pole FSCW PMSMs with conventional and bread-loaf magnet are used to evaluate electromagnetic force and vibration response. It is found that the bread-loaf magnet significantly increases the electromagnetic force and vibration response in the FSCW PMSM. Finally, two 12-slot/10-pole FSCW PMSMs with conventional and bread-loaf magnet are manufactured and tested to validate the theoretical analyses.