Directly driven wind turbine generators

Paper i proceeding, 1996

This paper deals with directly driven generators for wind turbines. The aim is to discuss the efficiency, active weight and the size of a 30 rpm 500kW permanent magnet generator. An analytical design method for the generator is used together with a cost function to optimize the generator. The influence of the cost function on the optimum generator is investigated. The investigation shows that the efficiency depends mostly on the slot height and, therefore, a high efficiency leads to a high active weight. The generator diameter will probably have to be more than 2 m because of the cost of the active material, but above that diameter the optimum size can be expected to be mostly determined by the cost of the supporting structure. This type of generator has a higher average efficiency than a conventional four-pole induction generator and gear and it can probably be lighter.