Air-Gap Wound Alternators for Large-Scale Power Generation

Abstract

The airgap-wound or slotless alternator is similar to the conventional type of alternator used for central power generation, but the windings of both the fixed and rotating components are situated in the gap normally separating the two, rather than in slots milled into the steel surfaces. It is shown that this seemingly trivial modification can result in large reductions in the length, weight, losses and cost of generators if properly designed. In addition output capacities about four times that of the largest possible conventional machine could be obtained. In chapters 1, 2 and 3 the constraints applying to the new layout are explained, methods of obtaining optimum dimensions and specific loadings sre set out and several designs are compiled to demonstrate the possibilities of the slotless design. In chapter 5, comparison is made between slotless and conventional machines and it is seen that the slotless type offers several advantages. In particular, a 660 MW slotless machine would be about 4 m shorter, 150 tonne lighter, would have about 2 MW lower losses and would give a total cost saving of about £400,000. The design of certain critical components is examined in chapter 4 and some specific problem areas are considered in the appendices.