DYNAMIC CHARACTERISTICS INVESTIGATION OF THE SYSTEM "SOFTSTARTER - INDUCTION MOTOR" IN THE MODE OF OPERATION WITH REDUSED SPEED

Abstract

In the article operation of the system "softstarter - induction motor" with reduced speed is carried out. The relative cheapness of thyristor starting devices for induction motors in comparison with frequency inverters leads to their increasing of industry installation. However, the implementation of some modes of operation, such as rotation at a reduced test speed, may not always be possible for particular processes. This is especially true of increasing the amplitude of speed fluctuations with increasing motor torque. The paper presents the settings of the serial starter SSW900 from WEG, which affect the operation of the induction motor at low speed. To study the impact in the work, a model was compiled in the MATLAB software environment using the Simulink application. The correspondence of the parameters of the functional models to the settings of the existing soft-start device is determined. The reduction of the motor speed is provided by reducing the frequency and, accordingly, the amplitude of the voltage applied to the motor windings. To reduce the carrier frequency relative to the supply frequency, the mode of passing certain voltage half-waves is used. In MATLAB, this is achieved through the use of Pulse_generator blocks, which pass control pulses only at permitted intervals. By changing the opening angle of the thyristors, graphs of transients in velocity were obtained and the amplitudes of oscillations at the fan nature of the load were determined. In addition, the results of the study of the system on a physical model were obtained and a comparative analysis of the results was performed. Thus, the formation of reduced frequency, proposed in the development of a mathematical model in MATLAB provides a reduction in engine speed to 1/7 of the nominal. The amplitude of speed fluctuations when setting the maximum torque reaches values ​​that significantly limit the possibility of using this mode for long-term operation of the equipment, which is also confirmed by experimental studies.