Multiple signature analysis for the detection of bearing currents and the assessment of the resulting bearing wear

This paper deals with the early detection and monitoring of possible bearing damage of variable-speed, converter-fed electric motors. After a brief description about the issue of bearing currents in converter-fed drives, the main subject will be outlined with the focus on practical experience. A measurement systemology is used for this purpose, where the electrical measurement of bearing current events as well as the mechanical measurement of the vibration status of the bearing is taken into account. A comparison between different vibration measurement methods leads to a systemology, which allows to detect possible changes in the motor bearing in a very early state of operation.