Design Consideration of Pole-Changing Permanent Magnet Vernier Motor With Characteristic Current Variation

In this article, the design of a pole-changing (PC) permanent magnet (PM) vernier motor is discussed considering the characteristic currents before and after PC operation. First, the operating principle of the PC–PMVM motor is introduced. Then, the operation characteristic is analyzed under d–q axis coordinate system, a conclusion is made that a large d-axis inductance variation should be conducted before and after PC operation for PC–PMVM motors to obtain a good speed regulation ability. The design process considering this point is then introduced. The slot–pole combination design is first carried out considering the torque before PC to select slot–pole ratios (SPRs). The regularity of winding inductance variation is then revealed, by which the final feasible SPRs can be decided. In addition, a magnetomotive force offset angle, which shows an influence on torque before PC and speed regulation range and maximum speed after PC, is selected by using an evaluation function. The electromagnetic performances of motors with feasible SPRs are compared by finite element analysis. Finally, one prototype is manufactured and tested. The measured results agree with analytical and simulated ones, thus verifying the correctness of the analysis.