Investigation of Eccentric PM on High-frequency Vibration in FSCW PM Machine Considering Force Modulation Effect

This study investigates the negative influence of an eccentric permanent-magnet(PM)design on high-frequency electromagnetic vibration in fractional-slot concentrated-winding(FSCW)PM machines.First,an analytical expression for the sideband current harmonics was derived using the double Fourier series expansion method.Then,the characteristics of the flux-density harmonics are studied from the perspective of the space-time distribution and initial phase relationship.The influence of the eccentric PM design on high-frequency electromagnetic and concentrated forces was studied based on the electromagnetic force modulation effect.Consequently,an eccentric PM design is not conducive to reducing the 2pth-order high-frequency electromagnetic forces.Finally,two FSCW PM machines with conventional and eccentric PM designs are manufactured and tested to verify the theoretical analysis.The results show that the eccentric PM design worsens high-frequency vibrations.