Performance Comparison of Outer Rotor Permanent Magnet Vernier Motor For Direct Drive Systems

This paper compares four Outer Rotor Permanent Magnet Vernier Machines (ORPMVM) for direct-drive systems with the focus on a novel Vernier Machine (VM). All machines have the same rotor, but difference stator topologies and winding arrangements. The proposal has toroidal coils and an open-slot stator with a high number of slots. The other machines have split-stator. The topologies and working principles are presented in detail. Electromagnetic performance of the machines at both no-load and full-load is investigated by two-dimensional Finite Element Analysis (2D FEA). The comparison is conducted in terms of output electromagnetic torque, core loss, copper loss, efficiency, and iron volume at the same outer diameter, air-gap length, phase current, and permanent magnet volume. According to the simulation results, the proposal has higher efficiency, output torque, and lower iron volume in contrast with the conventional machines.