Influence of Stator Tooth-tip Shape on Power Factor of Surface-Mounted Permanent-Magnet Field-Modulation Motor

The power factor of surface-mounted permanent-magnet field-modulation (SMPMFM) motor is studied in this paper. By simply deriving the power factor expression, it is found that the q-axis inductance will affect the motor power factor, mainly including the tooth-tip leakage inductance and the slot leakage inductance. Hence, the variations of these inductance characteristics with the tooth-tip shape are analyzed, and the influence of tooth-tip shape on power factor of the analyzed SMPMFM motor is investigated by using the FEA. It is proved that when a straight-tooth structure without pole shoe is adopted, a high-power factor can be realized in the analyzed SMPMFM motor.