Bearing currents of driving machines in drives with semiconductor transformers

A common problem of electric drives with semiconductor converters is an accelerated wear of the drive motor bearing units. This wear is caused by generation of bearing currents in the drive motor, which can have a continuous or permanent impact on the bearing assemblies. The authors of this paper have analyzed the causes of bearing currents at driving machines of modern electric drives. The main types of bearing currents have been identified and described including their characteristics. We provide description of the main negative impact, long and short-term consequences of bearing current impact. The basic methods of measurement and control of bearing currents are provided, too. The paper offers means of minimizing bearing currents, analysis of their effectiveness, recommendations for their implementation at modern electric drives. It concerns the main international regulations specifying permissible values of bearing currents and preventive methods. The authors offer recommendations on development of this specific national regulatory framework. Further studies of bearing currents generated at semiconductor drive motors with frequency converters will be connected with mathematical models simulating their generation dependent on operation modes of the autonomous inverter, motor, ground circuit, with their simulation analysis as well as with algorithmic methods aimed at their elimination.