Novel Magnetic-Field-Shifting Techniques in Asymmetric Rotor Pole Interior PM Machines With Enhanced Torque Density

This article overviews novel magnetic-field-shifting techniques for enhancing the torque in a new class of asymmetric rotor pole interior permanent magnet (AIPM) machines. The principle for torque enhancement is introduced first. AIPM topologies are then categorized in terms of asymmetries and symmetries of PM configuration and rotor core geometry. Subsequently, the merits and demerits of various AIPM rotor topologies in each category are analyzed and compared. Finally, the torque capabilities of selected AIPM machines are compared.