Analysis of operating modes of squirrel-cage induction motors in the presence of damage to the rotor rods.

Abstract

The article determines that the main faults in induction motors are damage to the stator and rotor windings, which occur due to changes and distortions in the shape and amplitude of the supply voltage, technological overheating of the windings, mechanical damage. These factors lead to accelerated wear of the insulation of the windings, structural components of the motors, increased values of power losses and the occurrence of pre-emergency and emergency situations. Among the specified diagnostic parameters of engine operation it is possible to consider separately existence of damages of cores of a short-circuited rotor which timely diagnostics demands removal of the engine in repair and will allow to avoid emergency situations with induction motors. To diagnose the control of the rotor rods are quite diverse: determining the amplitude-frequency spectrum of stator currents, detecting the presence of current ripples in an artificial short circuit in the stator winding, the use of diagnostic curves, the selection of appropriate harmonic oscillations in the vibration of the rotor. To reduce or eliminate the negative impact of various factors on the course of technological processes, the best approach at present is the use of tools and measures to diagnose the operation of engines using modeling methods. Based on the model of an induction motor with a short-circuited rotor created in the MATHCAD software environment, graphical dependences were obtained that reflect the change of the main parameters of the induction motor operation and allow to analyze their change during the modulation time. The presence of pulsations of regime parameters and aperiodic components caused by transients was shown. Studies of the process of starting the engine without load and under load showed an increase in start-up time, and the pulsating nature of the studied parameters is observed only in the initial section. The engine start time also increases in the presence of damaged rods in the short-circuited rotor. The pulsating nature of the main diagnostic parameters can be used as a criterion for determining the presence of damage in the short-circuited winding of the rotor of an induction motor.