Mathematical Model of Asynchronous Motor with Frequency-Cascade Regulation

The system of a multi-motor frequency-cascade electric drive based on asynchronous motors with a phase-rotor, which is characterized by synchronous-asynchronous speed control, is considered. Synchronous regulation is carried out by varying the frequency of the voltage on the stator of the electric motors, and asynchronous regulation is carried out by changing the counter-emf introduced into the rectified rotor current circuit. By formal transformations, expressions are obtained that determine the basic static characteristics of an electric motor with the considered control method and its T-shaped equivalent circuit. As a result of the conversion of the obtained equivalent circuit, the asynchronous motor was presented as an equivalent source of EMF, which allowed a formal transition to the equivalent circuit of the rectified rotor current circuit, to obtain a dynamic model and draw up a block diagram of the electric motor with frequency-cascade control. We also obtained a linearized dynamic model of an asynchronous electric motor with frequency-cascade control, structurally corresponding to the asynchronous-valve cascade, which, taking into account the relevant features, allows the use of classical methods of synthesis of closed-loop control systems.