A counter-rotating axial-airgap induction generator using pole changing windings for developing country use

In a developing country context constant frequency and voltage output from a wind generator may not be a priority, since low quality loads such as water heating and pumping do not necessarily require such an input. Induction generators for stand-alone applications have the advantage of being rugged and cheap, but to make full use of the wind resource without an elaborate control system a constant frequency output is not easily or economically attained. The use of a direct-drive, axial-airgap induction generator is proposed, capable of local manufacture - in full or in part - which will deliver variable frequency and voltage for low quality loads, but have the capability for a more constant frequency and voltage output for high quality loads. This could be made possible using pole changing windings, including application of pole amplitude modulation, a technique used in motors as a means of speed changing.