Анализ повреждений подшипников тяговых машин на электроподвижном составе при питании от преобразователей частоты и напряжения

Abstract

The technical and economic efficiency of electric rolling stock (ERS) is determined by the characteristics of its traction electric drives, the key ones of them being the manufacturing cost, repair and maintenance costs, service life, specific energy consumption, and operational reliability. The modern ERS uses induction electric drives with pulse-width control of the voltage and frequency control of the rotation frequency. The field experience gained from operation of electric drives equipped with semiconductor converters has shown a growing number of cases involving accelerated wear of the traction machine bearings. Currents through the bearings or shaft currents, which usually flow from the electrical machine shaft through the bearings, have been known since the time the electrical machines were invented. Owing to recent achievements made in power electronics, the application field of inductor motors has become much wider. In particular, the use of inverters with pulse-width modulation (PWM) and high switching frequency make it possible to operate an electric drive with a lower acoustic noise and with more efficient energy conversion; however, the use of inverters also entails the generation of bearing currents in induction motors. The article analyzes possible factors causing the occurrence of bearing currents. Typical changes occurring in the bearings as a result of electric current flowing through them are shown: the rolling surface becomes dull, grooves on the ball race occur, and lubrication becomes degraded. The influence of operating parameters on the frequency of the occurring breakdowns and the distribution of forces in the bearing system depending on the load are considered. A conclusion is drawn that the potential problem of bearing currents should be solved using design, structural, and algorithmic methods at different stages of design and operation of electrical systems involving adjustable electric drives.