Hydro-electric machines

Large hydro-electric generators are individually designed for the specific hydraulic and system conditions of a particular site. The paper reviews the various mechanical features of such a machine, in particular the bearings and how they are disposed relatively to the rotor, the stator frame core and windings with particular reference to the problems of transport to site, and the rotor design which is influenced by the high overspeed and high inertia requirements as well as transport limitations. In common with other electrical machines, the maximum output of a hydro-generator is limited by the temperature at which the insulated parts may be operated to give an acceptable life and attention is drawn to the use of direct water cooled machines. The special requirements of machines for pumped storage application are indicated, in particular those resulting from the need to operate in both directions of rotation, the effect of cyclic operation and the means of starting in the pumping direction. Axial flow turbines require specially designed generators and the more usual types are illustrated. For small hydro-generators, adaptation of the designs from the manufacturer´s existing ranges of industrial machines is the usual approach but, irrespective of the size of the machine and its application, simplicity of construction with maximum reliability is the aim.