Analysis of Radial Electromagnetic Force of Fractional Slot Motor for Permanent Magnet Synchronous Motorized Spindle

An analytical model and a finite-element model of the air gap electromagnetic flux density and its harmonics of fractional slot motor for permanent magnet synchronous motorized spindle have been developed on the basis of the theory of harmonic windings. Then,the radial electromagnetic forces are obtained by the model. The orders and frequencies of radial electromagnetic force wave are calculated by the analytical method,compared with them by the finite-element method. That the predicted results contrast to the experimental results of acceleration spectrum indicates that radial electromagnetic force is the main factor causing the vibration of motor of motorized spindle. It is one of the main measures of low noise motor design that the air gap flux density waveform is reconstructed by removing the harmonic near modal frequency from original waveform. A new thought is pioneered for the further research and development of low noise and vibration permanent magnet synchronous motorized spindle.