Abstract
Vernier double-stator permanent-magnet (DS-PM) motor incorporates the merits of high torque capability and high power factor. In order to evaluate this new topology, this paper compares two DS-PM motors, namely a conventional 42-slot concentrated winding one and a recently proposed 24-slot vernier one. For a fair comparison, both DS-PM motors are designed based on the same size. The slot-vector star graph is applied to analyze their different winding constructions. By analyzing harmonic spectrums of the flux density in the air-gap, their different operation principles are comparatively investigated. Their electromagnetic performances are predicted by using finite-element method. The results show that the vernier one can provide higher torque capability and flux-weakening capability, but suffers from higher loss even though it has lower pole and slot number than the conventional one. Hence, vernier DS-PM motors are more suitable for the applications such as high torque density, good cooling condition and wide speed range.