Influence of Rotor-Pole Number on Electromagnetic Performance of Novel Double-Rotor Hybrid Excited Axial Switched-Flux Permanent-Magnet Machines for EV/HEV Applications

In this article, a novel stator-permanent-magnet (PM) double-rotor hybrid excited axial switched-flux PM (DRHE-ASFPM) machine with improved torque density and enhanced flux regulation capability is proposed for electrical vehicle (EV) applications. The operation principle is introduced and different operating modes including only PM, flux-enhancing, and flux-weakening modes are analyzed and compared based on the 2-D finite-element analysis (FEA). The influences of different stator/rotor pole combinations on the electromagnetic performance of the DRHE-ASFPM machine, including 6-stator-pole/10-, 11-, 13-, and 14-rotor-pole, are quantitatively compared in terms of the flux linkage, back electromotive force (EMF) and spectra, air-gap flux density, cogging torque, and flux regulation capability by 3-D FEA. The analysis results demonstrate that the 6-/10- and 6-/11-pole DRHE-ASFPM machines show higher amplitude of PM flux linkage and back EMF. Meanwhile, the 6-/11- and 6-/13-pole machines display smaller cogging torque. Moreover, the 6-/11-pole machine produces more sinusoidal back EMF and has excellent flux regulation capability as well as torque output capability, which is suitable for wide speed-regulation EV applications.