Coreless Axial Flux Halbach Array Permanent Magnet Generator Concept for Direct-Drive Wind Turbine

This paper proposes a concept for a coreless axial flux permanent magnet (CAFPM) generator with a double-sided Halbach array rotor for direct-drive offshore wind turbine applications. The application of printed circuit board (PCB) technology is explored as applied to a concentrated winding stator due to its high reliability, repeatability, and fast mass production. A double-sided Halbach array rotor is employed to intensify the airgap flux density and to enable the elimination of the rotor back iron, decreasing the generator's total active mass. The effect of the Halbach array rotor pole number and magnet-to-magnet (M2M) gap on the airgap flux density and power capability is studied through analytical and 2/3-dimensional finite element (FEA) methods. Multiple parametric studies are performed for an example design to investigate the power capability of the proposed CAFPM generator concept. The parametric study results indicate that Halbach array implementation can reduce active mass with the trade-off of including significantly more magnetic material for a conventional machine of a similar size. Advancements in PCB technology or transitioning to alternative windings to improve winding fill factor could provide comparable performance to conventional cored machines with lower overall active mass.