Constructions Géométriques by Julius Petersen

By Julius Petersen

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It must therefore be adequate to deal with the mode of control being used for the generator and this may greatly exceed the simple full-load requirement. In addition there are special operating conditions which a generator may have to meet which impose demands on the excitation system. This may require an increased ceiling voltage of excitation which results in increased excitation power and provides a measure of field forcing, or it may require a faster rate of build-up of excitation current by reducing the time constant of the excitation loop, or more usually a combination of both these factors.

A p u m p working against a fluid pressure feed, and this will result in 22 Generator performance sustained electrical generation. When the synchronous motor remains connected to a network with connected induction motors its generated electrical power will serve to continue driving these until the total connected kinetic energy is dissipated. Thus an induction motor with a high value of stored energy can make this available to the system as long as the synchronous motor can provide lagging MVAR to magnetize it by maintaining a reasonable value of voltage in relationship to the generated frequency This phenomenon can be of importance during transient conditions.

This could be an AC exciter with a separately mounted rectifier, or a DC exciter feeding direct to the rotor sliprings. Such exciters require quite low values of self excitation power and this results in better efficiencies. The rate of increase of voltage build-up is appreciably lower with a self-excited generator than with a separately excited one and the use of a pilot exciter to supply the field current of the main exciter provides a fast and convenient system. The amount of power wasted in the regulation of the pilot exciter output is very small but the benefit to the control system is significant.

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