Bearing damage detection in permanent magnet synchronous machines

The present work was performed in the frame of cooperation between Baumuller Nurnberg and the University of Siegen. This paper addresses the detection of damages of the bearings in servo motors and presents new results of the industrial application of a new developed diagnosis method for detecting such based on frequency response analysis. In the experimental work a permanent magnet synchronous machine (PMSM) is used and two different cases are considered: first, only the machine under no-load condition is investigated, afterwards the driving machine was installed in a two-mass-system simulating real conditions. The experimental results show that the method for damage detection works in both cases. In contrast to former publications the present paper shows results obtained on bearing faults in motors coming from the field to the repair shop. The measurement of the required signals (current and speed) can be accomplished during operation of the plant in closed loop speed control. The system is excited by pseudo random binary test-signals (PRBS). The deviations between the frequency response obtained during the commissioning of the plant and the curve measured under fault condition serve as indicators for the damage.