Prototype of an automatic system for monitoring the success of starting asynchronous motors in local power supply systems

Abstract

The present study aims to develop and test a prototype of an intelligent automatic system for monitoring the success of starting asynchronous motors with a squirrel-cage rotor using the physical model of a local power supply system. The prototype implements stepwise predictive control, which checks the partial conditions of the process success at each step based on critical parameter models of both the engine and the supply network. The development is based on the use of the LabVIEW software suite, parametric identification methods, physical simulation, analog and digital signal filtering, auto-regulation theory, mathematical analysis, and statistics. The study experimentally proved the possibility and effectiveness of predictive start-up control for asynchronous motors of local power supply systems in terms of the magnitude, rate, and pattern of variations in the operating parameters of motor stator windings without a direct measurement of the shaft velocity. The error of the developed models for determining the critical mode parameters, affecting the success of starting the asynchronous motor, is demonstrated to be less or equal to 4%. The error in the predictive estimate of the start-up duration for an asynchronous motor did not exceed 14%. It is demonstrated that in 91% of experiments with the start-ups of an asynchronous motor using the physical model of a local power supply system under the variations of circuit-mode conditions, the automatic system prototype reliably identified the success/failure of the engine start at various stages of the process. If a failure was detected, the prototype ensured the interruption of start-ups in the early stages. The studies revealed no cases of non-issuance by the automatic system of a command to interrupt the start-up process under the conditions of its failure. Therefore, intelligent automatic systems for monitoring the success of starting asynchronous motors in local power supply systems will reduce the likelihood of damage to motors and equipment of power supply networks, preserve their serviceability, and improve the reliability of power supply to consumers.