Damper circuits and rotor leakage in the transient performance of saturated synchronous machines

Abstract

The sudden development of short-circuit currents, and of recovery voltages at interruption of currents, depends on the effects of stator and rotor leakages as well as of saturation in the generating synchronous machines.The non-linear problem of the interaction of these features with the performance of the main windings and auxiliary damper circuits is solved analytically. This leads to a simple graphical representation which is numerically determined by the well-known magnetic and electric characteristics of machine and network and by two time constants of very different magnitudes which are derived from the ordinary data of the machines. Hence the variation with time, of short-circuit currents and of recovery voltages, can easily and rigorously be computed for every given example. The deviations of actual damper circuits from the ideal form and the effects of eddy currents in solid steel parts of the rotor are discussed so far that numerical results can be derived readily. A new transient test for synchronous machines is suggested by which rotor and stator leakage voltages can be measured separately, avoiding the uncertainties of the usual steady state leakage tests.