Comparative Study of Field Modulation Effects On Consequent-Pole PM Machines with Different Stator Slot Configurations

This paper presents a comparative study of the field modulation effects (FMEs) on consequent-pole permeant magnet (CPM) machines with different stator slot configurations, i.e., open-slot, semi-closed slot and close-slot. Due to the asymmetrical PM magneto-motive force (MMF) distributions and double-side slotting effect, the CPM machines exhibit more air-gap field harmonics for the torque production. In order to quantify the torque contributions of the various effective harmonics, the Maxwell stress tensor method (MSTD) is adopted. The torque proportions due to various air-gap field harmonics in the CPM machines with different stator slot configurations are subsequently investigated by finite element (FE) method, which confirms that the stator slot configurations have a great influence on FME. It can be found that the highest and the lowest torque proportion contributed by the modulated field harmonics can be observed in closed-slot and open-slot structures, respectively. Finally, some experimental measurements on a 12-slot/14-pole CPM machine prototype with a semi-closed slot configuration are carried out to validate the theoretical and FE analyses.