MEC-Based Modeling and Design of Permanent Magnet Synchronous Machines with Axial–Radial Rotor Extensions Using Yoke and Rotor-Side Spaces

This paper proposes a solution to enhance the torque production capability of Permanent Magnet Synchronous Machine (PMSM), utilizing not only the unused space resulting from the stator end windings on the rotor side, but also the otherwise unused space around the winding on the yoke side. By implementing an additional axial rotor equipped with Permanent Magnets (PMs) in both rotor and yoke sides, the proposed design technique increases the PMSM torque output, taking advantage of the useless space on the yoke side. In the proposed configuration, one magnetic flux path circulates between the PMs on the rotor (rotor side) and the stator, while an additional flux path circulates between the PMs positioned on both sides of the stator end windings. These two flux paths contribute to generating a stronger and more effective magnetic field within the machine than conventional structure, resulting in increased torque density. A magnetic equivalent circuit (MEC) model of the proposed design is developed, and its accuracy is validated through Finite Element (FE) analysis. For a fair evaluation, the proposed structure is compared with a conventional configuration using the same volume of PM material. Furthermore, optimization of the proposed design is carried out to maximize Torque/PM.