Comparative Study of Torque Production Mechanisms in Stator and Rotor Consequent-Pole Permanent Magnet Machines

This article presents a comparative study of torque production mechanisms in stator and rotor consequent-pole permanent magnet (CPM) machines. Due to the CPM design, a unipolar PM magnetomotive force (MMF) distribution can be observed in both stator CPM (S-CPM) and rotor CPM (R-CPM) machines. As a consequence, more resultant air-gap field harmonics are responsible for torque production due to the double-side slotting effect. The PM MMF-permeance-based model is employed to identify and reveal the difference of sources and patterns of the working air-gap field harmonics in the two investigated CPM machines. The torque contributions of the main-order working harmonics of the two studied machines are analytically quantified by a unified torque equation and compared with the corresponding finite-element (FE) results. Finally, some experimental measurements are carried out on a 12-slot/14-pole R-CPM machine prototype to validate the theoretical and FE analyses.