A Method to Improve the Torque Density of the Multiple-pole Few-slot PMSM with Unequal Tooth Pitch

To enhance the torque density of the multiple-pole few-slot PMSM with unequal tooth pitch, a special stator structure containing additional teeth is proposed. Initially, a magnetic field model of the motor is developed, analyzing the magnetic flux density distribution under no-load conditions. The analytical expression for the no-load flux per phase is derived and corrected using the magnetic circuit method. Factors influencing the flux magnitude are examined to determine the optimal angle for the additional teeth. Finally, finite element simulation is employed for validation. The no-load back electromotive force (EMF) of the motor with various additional tooth angles is compared to that of a motor without additional teeth. Simulation results indicate that the optimal angle of the additional teeth aligns well with theoretical values, and the additional tooth structure significantly enhances the no-load back EMF, demonstrating a substantial improvement in motor torque density.