Investigations of Magnet Shape Impacts on Coreless Axial-Flux PM Machine Performances

Axial-flux permanent magnet (AFPM) machines are one of the potential candidates for the future higher performance drives due to their compact structure, high power/torque density, and lower losses. Nevertheless, one of the problems with these machines is the high harmonic components in their back electromotive force (EMF), which is needed to be reduced in the design process so as to compete with other electric machines. In addition, in order to easy startup and also less noisy performance, the torque ripple of the AFPM machine should be reduced. Both the back-EMF and torque ripple are relevant to rotor magnetic flux distribution, which is manipulated by the shapes of magnets. In this regard, coreless double rotor AFPM machines with different magnet shapes are designed and analyzed in this study using 3D finite element analysis (FEA). According to the investigations, magnets with sector-like shapes offer better performance indices compared with other types of magnets. Thus, the machine designed with the best magnet shape is then selected to evaluate the proposed design performances in terms of different air-gap and magnet thicknesses.