Методи та засоби діагностування гальмівних кіл пере- творювачів частотно-керованих асинхронних електроприводів

Abstract

The research presents the developed mathematical model of diagnostics system of brake circuits of frequency converters, the given model takes into consideration voltage derivative on capacitor filter and, unlike the existing models, enables to perform diagnosis of brake circuit in the process of electric drive operation in short and long break cycles. Using mathematical tools of wavelet-transform, mathematical model of wavelet-diagnostics of brake circuits of frequency-controlled asynchronous electric drivers converters is suggested, the given model enables to determine the de21 gree of brake circuits states of frequency-controlled asynchronous electric drive converters approach to emergency state. Applying mathematical tools of logic-time functions mathematical model for the diagnosis of brake circuits of frequency-controlled asynchronous electric drives converters is synthesized, the model enables to simplify the algorithm of determination of current state degree of frequency- controlled asynchronous electric drive converters brake circuits approach to breakdown state. Mathematical model of diagnostic system of frequency converter capacitors is developed, the given model takes into account the dynamics of operation coefficient change in time, sign of its derivative that enables to avoid taking faulty decisions of the first kind by the system, promptly warn the operation staff about critical state of operating capacitor, necessity to remove frequency converter out of service and prevent the damage of the capacitor. On the basis of mathematical tools of logic-time functions structural diagram of the device is developed, its application, unlike the already known, enables to perform diagnostics of brake circuits of frequency-controlled asynchronous electric drive converters in the process of electric drive operation. Using mathematical tools of logic-time functions and wavelet-transform, algorithms and functional circuits of microprocessor facilities are developed, they possess enhanced functional possibilities and are able to perform diagnostics of brake circuits of frequency-controlled asynchronous electric drives converters, that in its turn, allow to determine reliably technical state and be easily integrated in general diagnostic system of frequency converter. Algorithm and functional circuit of microprocessor device, having enhanced functional possibilities and allows to perform diagnostics of d.c. link capacitor of frequency converter and reliably determine technical state of electric equipment are developed. Such realization enables to improve considerably operation speed of device, decrease its energy consumption and dimensions. Computer model of frequency-controlled asynchronous electric drive with brake circuit was developed in software package Matlab Simulink, graphs of transient processes in the course of brake circuit operation of frequency-controlled asynchronous electric drive converter with fault-free circuit and in emergency modes of sudden cut off type, increase of resistor resistance and growth of internal resistance of power IGBT module are obtained. Computer model of wavelet-diagnostics of brake circuit of frequency- controlled asynchronous electric drives and computer model of brake circuits diagnostics of frequency-controlled asynchronous electric drives, applying logic-time functions are crated in software package Matlab Simulink. The obtained corresponding results of modeling prove the adequacy of the synthesized models. For verification of the adequacy of the synthesized mathematical modules and correctness of mathematical modeling full-scale experiment of frequency-controlled asynchronous electric drive, equipped with brake circuit was carried out. The experiment was performed in the process of frequency-controlled asynchronous electric drive operation with fault-free brake circuit and in emergency modes of “sudden cut off” type, increase of resistor resistance and increase of the internal resistance of power IGBT module. The obtained results of measured transient processes coincide with the results of computer modeling, confirming the adequacy of the suggested mathematical diagnostic models of brake circuit of frequency-controlled asynchronous electric drives. Assessment of the accuracy of synthesized device, developed for diagnostics of brake circuits of frequency-controlled asynchronous electric drives converters with the account of the errors of the first and second kind by the methods of minimal risk was carried in the research.