Diagnosis of failure of rolling-element bearings of alternators - A study

This paper deals with the causes of failure of rolling-element bearings used in alternators and establishes the reasons as to why the bearings used in a particular design of alternators fail prematurely. The voltage across the bearings leading to the passage of electric current and the development of magnetic flux density on the bearing elements, which cause premature failure of the rolling-element bearings of the alternators, are experimentally determined. The development of stray voltage and excessive magnetic flux density are established in the particular design of alternators where the bearings are located under the stator field coil and a.c. coils, as against those designs where the bearings are housed at a suitable location so as to avoid the effect of excited magnetic flux by the field and a.c. coils. The findings reported in the paper give overall guidelines to designers to avoid the premature failure of bearings.