ANALYSIS OF THE INFLUENCE OF VOLTAGE ASYMMETRY ON THE OPERATION OF THE TRACTION ASYNCHRONOUS ELECTRIC MOTOR USING THE SIMULATION MODEL

Abstract

The asymmetry of the supply voltage adversely affects the operation of electricmotors, in particular induction ones. With an uneven load of the phases of the network, the voltagebecomes asymmetric - unequal between the individual phases. Voltage asymmetry leads to the factthat the currents in the phases of the stator winding of the electric motor differ sharply from oneanother. A phase with a high current can overheat above acceptable limits even with a small voltageunbalance. In addition, the active steel of the motor rotor overheats. Overheating of the motorwinding causes an increase in electrical losses, ripples of the electromagnetic torque also appear,and other negative consequences. These factors can lead to process failure, accelerated insulationaging, or even motor failure.In the event of a mains phase failure, running three-phase motors switch to single-phase mode.If the motor load before phase failure was no more than 60% of the rated value, then the motorcontinues to operate with slightly worse energy performance, the rotor speed decreases slightly, thewinding temperature is within acceptable limits. Under heavy loads, the motor winding overheatsexcessively, and in some cases the motor rotor stops and a large current flows through two phases ofthe stator winding. After stopping the engine, it cannot be started even at idle, since a pulsatingmagnetic field is obtained in the engine with a single-phase current.To study the effect of supply voltage asymmetry on the operation of an asynchronous electricmotor, simulation modeling was carried out in the ANSYS Electronics software package for directstart of induction motor with the introduction of a supply voltage asymmetry of one of the phases ata level of 4% in the steady state operation of the electric motor. The characteristics of the rotationfrequency and electromagnetic torque were obtained with asymmetry of the supply voltage and acomparison was made with the symmetrical mode of operation of the electric motor. The results ofsimulation show a slight change in the frequency of rotation of the rotor of the electric motor,however, there are significant ripples of the electromagnetic torque.