Methods of Stabilizing a Reluctance- Synchronous Machine

In an earlier paper it was shown that machine instability might occur when a reluctance-synchronous machine is operated at low speeds (low frequencies). In this paper, several methods of stabilizing a reluctance-synchronous machine during operation at low speeds are presented. The basis of the stabilizing technique is established by employing the theory of small displacements to show that system damping can be introduced by altering the effective value of the applied voltages according to the change in rotor speed. A control system which continuously adjusts the amplitude of the source voltages as well as a control which employs controlled rectifiers to adjust the effective value of the applied voltages are presented. Results of an analog computer study are given to demonstrate the feasibility and performance of these control systems with sinusoidal and stepped voltages applied to the stator terminals of the machine.