A Pole-Changing Doubly Salient Permanent Magnet Motor

This article presents a new pole-changing (PC) doubly salient permanent magnet (DSPM) motor. According to the general air-gap field modulation theory (GAFMT), the permanent magnet excitation field can be modulated by the stator and rotor teeth to a series of harmonics with different pole-pair numbers and different slot pitch angles. Thus, when the armature winding is connected and reconnected according to the different excitation field harmonics, the PC operation can be realized to obtain a high torque density at the low-speed region and a widened speed regulation range with a simple motor structure. According to the GAFMT, the operating principle of the proposed motor is introduced, and the winding connection is discussed. Then, to verify the validity, the electromagnetic performance of the proposed motor is analyzed by the finite element analysis. Finally, a prototype is built and tested.