Research on Winding Coefficient and Cogging Torque of Few-pole Fractional Slot Permanent Magnet Synchronous Motor

In order to reduce the 5th and 7th harmonic winding coefficients of the fractional-slot permanent magnet synchronous motor(PMSM) with few poles, and at the same time weaken the cogging torque, a stator slotting structure with unequal tooth tip width combined with auxiliary windings is proposed. For the motor winding coefficient, it is firstly proposed to put auxiliary windings with different turns in the same direction in the motor armature teeth to improve the fundamental winding coefficient and weaken the 5th and 7th harmonic winding coefficients. On this basis, the cogging torque expression obtained by the energy method is used to analyze the auxiliary tooth tip angle by the Fourier decomposition method. The correctness of the theoretical derivation of the winding coefficient is verified by the air-gap flux density and no-load back EMF simulated by the finite element. Finally, the cogging torque of the motor and the equal-tooth motor structure are simulated and compared, and the results show that the effect of the motor to weaken the cogging torque is remarkable.