Investigation of radial electromagnetic force density and vibration in a fractional-slot interior permanent magnet synchronous machine

This paper investigates the radial electromagnetic force density and the associated vibration of an interior permanent magnet synchronous machine (IPMSM) with fractional-slot concentrated winding (FSCW) configuration. Interactions between magneto-motive force (MMF) harmonics, stator slotting effect, and rotor saliency effect will generate various air-gap magnetic field components, as well as radial electromagnetic force density harmonics. To develop an efficient yet realistic mechanism for the understanding of the force and vibration issues of the IPMSM under study, a combination of static two-dimensional (2-D) finite element analysis (FEA) and analytical methods is used to model the low order spatial harmonics of the machine's radial electromagnetic force density. The validity of the proposed approach is confirmed by the results from the high fidelity comprehensive transient 2-D FEA and 2-D fast Fourier transformation (FFT) methods. Moreover, comprehensive mechanical FEA are employed to carry out free and forced vibration investigations of the machine, which are verified by the experimental results.