Generalized bearing roughness fault detection in claw-pole generators

The generalized bearing roughness fault (worn bearing) is an important type of fault in automotive claw-pole generators (CPGs). It is traditionally very difficult to detect worn bearing in electric machines using only electric signals because there is no fault signature with single or multiple characteristic frequencies. In this paper, it is found that for electric machines driven by a belt-pulley assembly, the worn bearing will result in a small but detectable change in the effective diameter of the pulley. Since the effective pulley diameter change can be reliably detected by frequency shift of generator rectifier ripple, the worn bearing fault can be reliably detected. Experimental results demonstrate the method has very good detection performance.