Effects of slot-pole combinations on vibration and performance in fractional slot permanent magnet synchronous machines

Abstract Unbalanced Magnetic Force (UMF) is a critical factor that significantly impacts vibration and overall performance in Permanent Magnet Synchronous Machines (PMSMs). This study investigates the influence of different fractional slot combinations on UMF behavior in PMSMs using finite element analysis (FEA). The focus is on the canceling and additive effects of UMFs generated by radial and circumferential stresses. Two PMSM configurations with slot and pole numbers differing by one—26 poles/27 slots and 28 poles/27 slots—are analyzed to evaluate the effect of varying pole configurations while keeping the slot count constant. The analysis employed the Maxwell stress tensor method to quantify the UMFs in these designs. The results underscore the critical role of the magnet configuration in determining UMF characteristics, providing essential insights for optimizing machine design to minimize vibration and enhance performance. These findings serve as a valuable reference for designing and operating high-performance fractional slot PMSMs, particularly for industrial and automotive applications.