Stability Analysis of a Reluctance-Synchronous Machine

A stability study of a reluctance-synchronous machine (synchronous-induction machine) is performed by applying the Nyquist stability criterion to the equations which describe the behavior of the machine during small displacements about a steady- state operating point. This investigation reveals that machine instability can occur at low speeds (low frequencies) even though balanced, constant amplitude, sinusoidal voltages are applied to the stator terminals. Regions of machine instability are established from the results of a digital computer study. The results of an analog computer study are included to illustrate the modes of operation which occur within these regions. Also, regions of instability for different values of system parameters are given and discussed.