Determination of asynchronous mode and method to control the excitation of a synchronous electric motor

The paper presents the results of research aimed at identifying the asynchronous mode of excited synchronous electric motors and their safety and stability. It is proposed to identify the asynchronous mode using a power polynomial from the ratio of the degrees of active and reactive power, determined from measured instantaneous values of currents and stator voltages of a synchronous electric motor. It is proposed to control the excitation system of a synchronous motor by cyclically switching the excitation winding to an additional resistance or an exciter based on a criterion representing the derivative of the power polynomial from the ratio of the active and reactive powers of the synchronous motor. The proposed methods for detecting the asynchronous mode of excited synchronous motors and controlling the excitation system to ensure successful resynchronization of a synchronous motor without unloading the driven unit can be used in microprocessor-based protection devices for synchronous electric motors. The effectiveness of the proposed methods is confirmed through mathematical modeling.