Abstract
The object of research is the processes of electromagnetic transformation in powerful asynchronous electric drives during controlled starting using a thyristor voltage regulator. The problem to be solved by the research is overcoming the self-oscillating modes of powerful high-voltage asynchronous electric drives during controlled starting in the nominal slip range. A design feature of powerful high-voltage induction motors in comparison with general-purpose motors is a small value (up to 1%) of the nominal slip. Also, such electric motors have a relatively small value of their own moment of inertia. These features create conditions for the occurrence of self-oscillations when entering a steady-state operating mode. A mathematical model of an induction motor has been developed taking into account the influence of the rotor current displacement phenomenon to study the modes of controlled starting of an asynchronous electric drive of an industrial mechanism taking into account the influence of the enterprise's distribution network. From the point of view of the power supply network, an induction motor is a nonlinear active-inductive resistance, the phase angle of which can quickly change over a wide range in the vicinity of the nominal slip. The mechanism of the occurrence of self-oscillations during controlled start-up of high-voltage induction motors from a thyristor voltage regulator is disclosed. Self-oscillations occur in the nominal slip region due to the transition of the thyristor voltage regulator to an uncontrolled operating mode, when the load phase angle becomes greater than the thyristor control angle, including in the quasi-generator operating mode. To prevent the occurrence of self-oscillation modes, it is proposed to use a controlled reactive power compensator between the motor and the thyristor voltage regulator, which stabilizes the total load phase angle, which helps to improve the controllability of the electric drive.