Analysis and Reduction of Electromagnetic Vibration in Fractional-Slot Concentrated-Windings PM Machines

This article focuses on the electromagnetic vibration source and its reduction design in fractional-slot concentrated-windings (FSCWs) permanent magnet (PM) machines. First, the electromagnetic force and vibration characteristics of a 12-slot/10-pole FSCW PM machine are investigated. Then, four electromagnetic vibration sources are investigated and compared, in which the machine operating state is considered. The result shows that the electromagnetic force modulation and stator magnetomotive force (MMF) harmonics are the two sources that contribute most to the vibration underrated and heavy load condition, respectively. Afterward, two new designs to reduce the vibration caused by the electromagnetic force modulation and stator MMF harmonics are proposed, and the reduction principles are described in detail. Finally, the prototypes of the existing and proposed 12-slot/10-pole FSCW PM machines are manufactured. The tests are conducted to validate the theoretical analysis and proposed vibration reduction design.