Design and Enhanced Equivalent Magnetic Network Modeling of a Fractional-Slot Spoke-Array Vernier PM Machine With Rotor Flux Barriers

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.