Use of Air-Cored Axial Flux Permanent Magnet Generator in Direct Battery Charging Wind Energy Systems

Low power, low cost wind energy systems make use of uncontrolled, direct battery charging where the generator is directly connected to the battery via a diode rectifier. Air-cored axial flux permanent magnet (AFPM) generators, although excellently suited for small wind energy systems, can not be used in direct battery charging systems as optimum turbine power matching is not obtained and non-sinusoidal currents are drawn due to the rectifier; with non-sinusoidal currents these generators are shown to become extremely noisy. In this paper a method is analysed whereby better maximum power matching and sinusoidal currents are obtained using AFPM generators in direct battery charging wind energy systems.