Study on electromagnetic force in interior permanent magnet synchronous machine with distributed windings

With the development of electric vehicles, more and more attentions have been put on understanding and attenuating the noise, vibration, and harshness (NVH) of traction machines. NVH in machines are mainly caused by the electromagnetic force, which is complex vector functions of both time and space, and models are desired for accurately evaluating its characteristics. In this paper, analytical models for estimating the air gap flux density and electromagnetic force in interior permanent magnet synchronous machine (IPMSM) with distributed windings are established. The effects of stator slots and rotor saliency are taken into consideration to ensure the validity of the model. Temporal and spatial harmonic distributions of electromagnetic force are studied separately. The electromagnetic force of a 44 kW 8-pole/48-slot IPMSM is evaluated using 2-D finite element analysis (FEA) and 2-D fast Fourier transformation (FFT) method. The simulation results agree well with that predicted from the analytical model. The relationship between mode numbers and temporal harmonics is identified. In addition, it is found that tooth harmonics and rotor harmonics have strong influences on the amplitude of electromagnetic force.