Comparison of Coreless and Soft Magnetic Composite Core Axial Flux Permanent Magnet Generators for Locally Manufactured Pico-Hydro Plants

Locally manufactured pico-hydro plants are typically used in off-grid battery based renewable energy systems and frequently utilize coreless axial flux permanent magnet generators (AFPMG) due to their simple manufacturing process. In this paper the use of iron-cored AFPMGs is investigated with the aim of reducing the permanent magnet material of the machine while minimize its cost and mass. The use of Soft Magnetic Composite (SMC) materials such as iron powder is investigated, which can provide a cost effective and simple manufacturing approach for the stator core. Two different AFPMG topologies are investigated, namely a double-rotor single-stator and a single-rotor single-stator machine topology, in order to maximize the generator efficiency and use effectively the available permanent magnet material, while allowing for simple air gap regulation of the pico-hydro plant. The Particle Swarm Optimization (PSO) is applied to the two AFPMG topologies for air-cored and iron-cored stators, in order to specify the optimum permanent magnet dimensions which maximize efficiency and minimize cost and mass, while the final designs are verified and fine-tuned with Finite Element Analysis (FEA) simulations. Finally, prototypes of the different AFPMG configurations are manufactured and tested, both on a generator test-bench and as part of a pico-hydro plant, directly driven by a locally manufactured Turgo turbine.