Analysis of the Degree of Influence of Supply Voltage Unsymmetry on the Operational Reliability of Low-Voltage Asynchronous Electric Motors

The purpose of this work is to study the effect of the imbalance of the supply voltage on the service life of an asynchronous motor (AM) with a short-circuited rotor. The main attention is paid to the dynamics of changes in the service life of low-voltage asynchronous electric motors of several series depending on the level of voltage imbalance. Asynchronous electric motors of the classic (4A and AI) and upgraded (5A and AI) series serve as objects under study. Efficient and reliable operation of electric motors is characterized by the service life of the insulation of the windings. A qualitative assessment of the operational reliability of AM is determined by the accuracy of forecasting the real life of their service. Thus, it becomes obvious that the adequate assessment of the operational reliability of low-voltage asynchronous electric motors operating under conditions of low-quality supply voltage directly depends on the complex study of such an external factor as the imbalance of the supply voltage. The problems of the study are solved using the SimPowerSystems software of the Matlab/Simulink interactive programming environment. The research was carried out on asynchronous motors with a short-circuited rotor of classic (4A132S4 and AIR160S8) and upgraded (5A132M6 and AIR132S4) series at P_l = 7.5 kW and a rated rotation rate of n = 1500 rpm. Physical processes of the electric motors are simulated using variations in the negative-sequence voltage imbalance factor (K_2U) from 0 to 5% with a step of 1%. The simulated results are used to construct diagrams of the change in the service life of AM versus external effect. The study based on the SimPowerSystems computer modeling makes it possible to predict changes in the service life of AM, estimate the limits of permissible values of the negative-sequence voltage imbalance factor, and compare electric motors with respect to stability against an external factor. A comprehensive solution of problems related to improvement of the operational reliability of low-voltage asynchronous electric motors is among the priority tasks, mainly aimed at efficient functioning of the electrical complex with an electric-motor load. A detailed assessment and analysis of the effect of imbalance of supply voltage on the operational reliability of low-voltage asynchronous electric motors are performed. The results of the study are discussed, and recommendations for the use of asynchronous electric motors in the presence of imbalance of the supply voltage are formulated.