Incipient bearing damage montoring of 940-h variable speed drive system operation

Inverter-induced high-frequency bearing currents are a recognized cause of bearing failure in frequency converter-fed electric machines. Mechanical bearing faults are generally identified by vibration measurements. In this work, we submit bearings to electric discharge machining bearing currents, measure the electrical stress placed on the bearings, the resulting vibration signal and operating temperature, and apply time- and frequency-domain signal processing techniques for feature extraction. Experiments are run for 940 h of operation, so as to study the incipient bearing failure behavior. After the end of the test run, the bearing surfaces are inspected using scanning electron microscopy.