The steady-state stability limit of a synchronous machine can be modified considerably by controlling field excitation and prime-mover torque by means of regulators and governors. In the paper the effects of the individual alternator parameters and controller constants on the dynamic stability limit (i. e. the steady-state limit of a controlled alternator) are investigated, and optimum operating conditions for various types of regulator and governor are established.The investigation covers a general comparison of the relative dynamic stability of the common types of large alternator. In addition, the variation in dynamic stability with a change in output rating is discussed.