Prototype development of a fully coreless multi-stage axial-flux permanent-magnet machine (AFPM) through the performance comparison between single-stator double-rotor (SSDR) and double-stator single-rotor (DSSR) configurations

Abstract

Cascading rotor and stator in axial flux permanent magnet (AFPM) machine is a beneficial concept to increase the power density without increasing the diameter of the machine. Multi-stage AFPM can provide higher torque capability in applications requiring high power density. In this regard single-stator double- rotor (SSDR) and double-stator single-rotor (DSSR) are efficient machines compared to single -stage AFPM. Since SSDR and DSSR are also considered modular units to make multi-stage AFPM, like single-stage AFPM, this paper makes a comparison with analysis between SSDR and DSSR AFPM machines. Based on 3-D finite element analysis (FEA), the air-gap magnetic flux, voltage, current, torque, torque ripple, power and power density, efficiency are comparatively investigated to evaluate their performance. Results show that fully coreless topology only be achieved in SSDR AFPM machine with a higher power density. Finally, a prototype multi-stage coreless generator has been developed using a single stator double rotor (SSDR) configuration to justify the fully coreless concept. This prototype coreless generator eliminates eddy current losses and reduces weight, making it a suitable option for certain portable applications.