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The Vernier permanent magnet (VPM) machines supersede conventional permanent magnet synchronous machine (PMSM) topologies in terms of torque-density and cogging torque. This article presents a fractional-slot L-shaped magnet VPM machine, including peculiar designs for permanent magnet (PM) housing and rotor core construction for small-scale EVs such as unmanned aerial vehicles (UAVs). The idea for selecting the PM arrangement is based on combining the V-shaped and spoke-array PM topologies for achieving a higher torque-density than V-shaped PM machines and a lower cogging torque than spoke-array PM machines. The rotor core is created from nonintegrated segments to form the flux-barriers in end-portions of PM housings. In this way, the leakage flux lines in the end-portion of the PMs reduce, resulting in enhanced flux linkage and power factor. A 630 W, 12-slot/8-pole motor is designed and prototyped for model validation purposes. An innovative equivalent magnetic network model is established for analytical prediction of the performance of the machine. The Schwarz–Christoffel mapping is used to create the rotor core permeance network due to its special shaping. Two innovative pentagonal-shaped mesh cells are used in the air-gap region for more accurate capturing of flux behavior. The model is validated by comparing the results with the finite element results and experimental measurements.

The spoke-type arrangement of permanent-magnets (PMs) in rotor of Vernier-PM (VPM) machines was first introduced in a dual-stator topology to overcome low power drawback of VPM machines. However, this special structure is mostly applicable for high-power motor drives. This paper presents a fractional-slot spoke-array VPM machine with a special rotor structure for small scale electric-vehicles. The leakage flux lines tend to be aligned with the main flux routes due to special design of flux barriers in end portion of PM housings. High torque-density, low weight, torque-speed curve with a wide constant torque region, promising efficiency and power-factor are the advantages of the proposed machine. An equivalent-magnetic-network (EMN) model is established for predicting the complex behavior of flux lines and operating quantities of the proposed structure with reasonable accuracy. The contribution of the modeling method includes a special mesh cell for the air-gap permeance network to more accurately capture the flux routes, continuous positioning method for omitting spikes on post-processing waveforms due to numerical errors and a stable solving flowchart with a high convergence rate. The validity of EMN model is proved by comparing its operating waveforms with the finite-element results and experimental measurements.