The paper is concerned with predicting the steady-state, dynamic and transient stability of a synchronous generator, with a voltage regulator, when coupled to an infinite busbar. The effect of the main regulator loop parameters, such as gain, exciter and main field time-constants, etc., on the stability of the system are examined. The solutions of the system equations are obtained by using an electronic analogue computer. The ideal stability boundary, for a particular system, is defined, and attempts are made, by the introduction of subsidiary feedback and series networks, to obtain the ideal characteristic. The influence of the transient reactance on stability and the effect of minimizing this parameter are considered. New voltage-excitation characteristics are described which have been found useful for predetermining power-angle curves for a machine with a voltage regulator and for checking computer solutions of steady-state stability boundaries.