Analysis and concept of development of non-destructive test methods for diagnosing electric motor insulation

Abstract

The timely detection of a critical state and forecasting the development of an emergency situation in the insulation of AM (asynchronous motor) windings is the main direction of increasing the economic efficiency of electrical engineering systems. One of the methods of reducing electricity losses is the compensation of reactive power, both complex and local. Asynchronous motors consume more than 60% of the produced electricity. Modern microprocessor devices, which are implemented in the automation of electrical engineering complexes, enable to combine local compensation of the reactive power consumed by synchronous motors with a diagnostic system for monitoring and predicting the residual life of an asynchronous motor and detecting a winding circuit in the stator windings of an electric motor. The purpose of the work is the analysis of the existing non-destructive test methods for diagnosing the state of the dielectric property of the insulation of AM windings, substantiating the direction of the development of diagnostic test methods and forecasting the decrease in the property of the body insulation of AM windings with the use of residual energy in the conditions of using a capacitor bank. To achieve the goal, the following tasks were solved: an analysis of the control methods of body and turn insulation was conducted; for the first time, the energy remaining in the capacitors after their disconnection was used in non-destructive test methods; it was proven that to predict the residual resource of the motor housing insulation, the time constant of the capacitor discharge decay can be effectively used as a criterion parameter, similarly, to detect a short circuit in the stator windings, the periodic voltage decay time on the capacitor can serve as a useful criterion; established interrelationships between changes in the resistance of the casing insulation of the windings and the time constant of the capacitor discharge. The most important result is the establishment of a unique relationship between the state of the case insulation and the value of the voltage decay time constant on the capacitor; change in period time and the number of turned-off turns in the AM stator winding. The most significant result is that the change in the time constant was used for the first time as a criterion parameter for predicting the residual life of the dielectric properties of the motor body insulation, and the change in the time period as a criterion parameter for the detection of a winding circuit. The significance of the study is that the value obtained after the first disconnection of the electric motor from the network is taken as the basic value of the constant decay time. Methods have been proposed and software developed for the device, which allows monitoring non-phase voltage modes of the network and current circuits during the operation of the electric motor, and when the electric motor is disconnected from the network - to control the value of the insulation resistance of the stator windings of the electric motor and the cable, as well as to predict the residual life of the electric motor