The paper analyses the influence of various types of field regulators on the dynamic performance of synchronous generators. Both conventional and dual-excitation generators are considered, with basic controls provided by voltage and angle regulators, which may have proportionate and derivative feedback. In the case of dual-excitation machines, both bus-rotor-angle and terminal-rotor-angle signals are employed in the quadrature-axis regulator.Stability is initially defined by computed regulation curves, and additional information is then obtained by calculating the variations of the synchronising- and damping-torque coefficients (TsandTD) with regulator gain. These graphs are superimposed on the regulation curves, to show howTsandTDdetermine the dynamic stability of the machine, and to illustrate the underlying reasons for stability.