Abstract: The variation of the load on a wind-driven A.C. generator (16) in accordance with a predetermined law which relates the load to the speed of rotation, is achieved by detecting the period of each half cycle with the aid of a timing unit (10), calculating the percentage conduction required in each half cycle in accordance with the predetermined mathematical law, and using the calculated result to gate a pair of thyristors (12, 14) to conduct for said calculated percentage in alternate half cycles so as to pass a unidirectional current to said load. By variation of conduction during each half cycle the effective resistance of the load can be matched to the voltage output of the A.C. generator over a wide range of speeds. Not only can the efficiency of the system be increased, but the windmill is prevented from being stalled in light breezes.

Abstract: Switching apparatus for matching an electrical load to the voltage output of a wind-driven generator in which the loads are an even number of batteries or electrolytic cells (16). The apparatus includes switching units (10) each having four terminals. Each switching unit has two switching states A and B, the odd numbered switching units (10a, 10c etc.) having pairs of batteries or cells connected between first and third, and second and fourth terminals so that when the switching unit is in State A, the batteries are in parallel and when in state B they are in series. The even numbered switching units (10b etc.) each serve for the interconnection of adjacent pairs of batteries in series or parallel.