Design of low-vibration fractional slot permanent magnet synchronous machine based on teeth modulation effect

Electromagnetic vibration is a primary factor influencing the performance of permanent magnet (PM) machine. In certain pole-slot combinations fractional-slot concentrated-winding (FSCW) permanent magnet (PM) machines, high-order radial electromagnetic forces (REFs) are modulated into low-order REFs due to the stator teeth modulation effect, leading to higher vibration. In this paper, the impact of the teeth modulation effect on the REFs and machine vibration are validated through finite element analysis (FEA) and experiment. Based on these findings, a novel stator teeth structure design methodology is introduced. By inserting auxiliary slots into the stator teeth, the number of stator teeth is equivalently increased, thereby mitigating the teeth modulation effect of higher-order REFs and reducing machine vibration. To optimize the vibration reduction effect of the novel stator structure, a parameter matching design is conducted by the Taguchi method. The FEA results demonstrate that the novel stator teeth structure design methodology effectively mitigates vibration levels in the FSCW PM machine while preserving machine performance.