Thermal and Structural Design of Axial Flux Permanent Magnet Generators for Locally Manufactured Small Wind Turbines

Locally manufactured small wind turbines (LMSWTs) used in off-grid battery based renewable energy systems, typically utilize coreless axial flux permanent magnet generators (AFPMGs) due to their simple manufacturing process. Commercial systems with high energy requirements for rural productive applications, use LMSWTs with high power AFPMGs which need to be designed for low cost and high efficiency, but also for low mass. In this paper, thermal and structural design aspects of AFPMGs are considered, with the aim of improving the heat dissipation capabilities of the stator and reducing the mass of the back iron disc of the rotor while minimizing disc deflection. Heat dissipation experiments are conducted for low and high power AFPMG prototypes, both in indoor laboratory conditions and in real operating conditions at the SWT test site. Finally, an electromagnetic design optimization is performed, in order to specify the ‘universal’ permanent magnet dimensions that can further reduce mass and cost for AFPMGs in the power range of 3kW to 7kW, used in LMSWTs with blade rotor diameters ranging from 4.8m to 7.8m.

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