Generalized Representation of Generator Excitation Power Requirements

Generalized relations for generator excitation power requirements are given for steady-state excitation, transient field forcing, and power damping operations. These relations give the excitation power in per-unit, on the generator MVA base, as a function of the generator per-unit reactances and field time constant. The effect upon power damping of drawing the required excitation power from the main generator shaft is also investigated. It is found that, in general, the effect of powering the exciter from the main generator is to reduce the amount of damping that can be provided by excitation control. However, in the case of a topical conventional generator, the resultant reduction in damping is usually so slight (about 2%) as to be negligible.