Impact of Imbalanced Wind Turbine Generator Cooling on Reliability

Recent development of high efficiency generator and motors leading their designs with less cooling capacity. Various studies have indicated that bearing failure is the prime cause of generator failure in wind turbine application. Grease lubrication deterioration found to be leading cause of motors and generators bearing failure. Grease service life for generators is closely associated with the operating temperature. One issue with the less cooled design is higher bearing temperature. This lead to marginal lubrication, premature bearing failure and reduce generator reliability. To verify this relation, and address the issue of inadequate and imbalanced bearing cooling; this paper presents a recent experimentation performed on air to air-cooled squirrel cage induction generator. This test address a potential issue with IC6A1A6 cooled design. This paper recommends IEC/IEEE to consider this issue and update the corresponding standards. To get optimal bearing life and generator reliability, either allowed bearing operating temperature range should be reduced significantly or IEC/IEEE should come up with different intervals of lubrication for bth ends of the bearings. Issues similar as with IEEE standard 841 high-efficiency motors can be avoided, where a study performed on reliability of these motors used in refinery confirmed that motors are at greater risk. Proactive plan based on the result and recommendations in this paper will help to secure the safe wind turbines generator operation.