Torque Enhancement of Electric Motor using Asymmetrical Rotor Structure Design

The permanent magnet (PM) motor is one of the feasible solutions to the energy crisis and environmental pollution. Due to the high demands in power and torque density with overall high efficiency, the permanent magnet synchronous machine (PMSM) is mainly considered.

In recent years, interior PM (IPM) motors are of growing interest in many applications, including electric vehicles (EVs), electric aircraft and helicopters, marine propulsions, and aerospace applications. However, most of the IPM motor design has symmetrical rotor structures, due to which the PM and reluctance torque components reach their maximum at different current phase angle. Consequently, the motor can only utilize a portion of its individual torque components. The magnet-field-shifting method is one of the techniques to improve the total electromagnetic torque production by arranging these magnets and air barriers. Hence it also leads to improved utilization of the rare-earth magnet volume. Using the finite element method (FEM), motor designers can design and optimize the torque generation of an electric motor having a complex structure.

In this presentation, we shall discuss examples of symmetric and asymmetrical rotor structures and its concept. Then we will dive into the FEA-based simulation analysis using EMWorks electromagnetic simulation software. Finally, a comparison between the asymmetrical rotor with the conventional symmetrical rotor design for the interior PM motor will be performed under the same operating condition.