Detecting generalized roughness faults in synchronous-generator bearings using the energy in the current spectrum

Many synchronous generator failures are caused by degradation initiated by the onset of generalized roughness in bearings. This paper demonstrates an approach for detecting the existence of generalized-roughness conditions in operational generators. The method tracks the energy contained in the stator current. It has been tested in the laboratory using a 5kW, 480V synchronous generator. Generalized-roughness faults are produced in that setup by injecting shaft currents into the machine so that failures naturally develop during operation. An accelerated failure mechanism is described, and experimental results are presented.