Harmonic Loss Reduction of Fractional Slot Concentrated Winding Permanent-Magnet Vernier Motor With Different Stator-Modular Designs

Permanent-magnet vernier (PMV) motor is well-known for its distinctive performances of high torque at low speeds, making it suitable for direct drive application. However, the rich harmonics lead to the high loss and low efficiency of motor system. To suppress the harmonic loss, a stator modular design concept is proposed for fractional slot concentrated winding PMV motor. First, the precondition that the motor meets the stator modular design is derived, and according to this, a variety of options for modular design are expounded, including uniform or hybrid modular designs and tooth or yoke modular designs. Then, the harmonic distributions of PM field, armature reaction field, and harmonic loss of PMV motor with fractional slot concentrated winding (FSCW) are discussed. Based on analytical analysis and finite element analysis, the inhibitory effect of modular design method on the amplitude of the harmonic with low pole pair number in the motor armature reaction field is verified. Through comparison, it is found that the proposed stator modular design method can suppress motor losses without reducing output performance. Finally, a PMV motor with modular stator is processed and tested to verify the analysis.