A Multi-Zone AC Voltage Converter. Part 2. Synthesizing the Induction Motor Soft Starting Device Control System

This article is a continuation of the study of a multi-zone AC voltage converter [1] and addresses a study of the control system for a multi-zone AC voltage converter serving as an induction motor soft starting device. The advantages, drawbacks, and specific features of modern soft starting devices for induction motors are analyzed. The results of synthesizing various control system structures are presented. The circuit of a single-phase three-zone AC voltage converter is mathematically analyzed using the differential equation algebraization method. By simulation in the Matlab/Simulink environment, the waveforms of transients triggered in speeding up a single-phase induction motor are obtained. Single-loop systems for automatically controlling the starting current using a relay controller and a PI controller have been studied. A two-loop automatic control system has been developed, using which the motor can be speeded up to the nominal rotation frequency with either linear or sigmoid acceleration, while limiting the starting current value. The obtained results have been verified on an experimental setup.