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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.

To fulfil the high dynamic market requirements the DC-motor has to be optimized by employing design calculation methods which yield high quality results in a short time. The presented paper summarizes new calculation procedures and shows their application in a practical example. A comparison between experimental results and simulations complete this presentation.