Design and Analysis of Novel Hybrid-Excited Axial Field Flux-Switching Permanent Magnet Machines

The axial field flux-switching permanent magnet machine (AFFSPMM) is a novel brushless AC machine. The magnets and concentrated windings are both in the stator instead of the rotor. The short axial length is beneficial to save the place of electric vehicles (EVs). Furthermore, the AFFSPMM exhibits the advantages of high power density and torque density. However, it is difficult to regulate the air-gap field since the field is produced by magnets alone. The fault-tolerant capability needs to be enhanced in the application of a direct-drive EV. Hence, a novel hybrid-excited AFFSPMM is proposed, in which the air-gap field can be easily regulated and the mutual inductance is largely reduced. In this paper, the design parameters of the novel machine, such as the split ratio, the rotor pole numbers, the rotor pole width, etc., are optimized in order to attain a sinusoidal back-EMF waveform and low cogging torque. Moreover, the static performance including each phase flux-linkage, inductance, and torque is analyzed on the basis of the 3-D finite-element method (FEM).