Abstract: In a 200 MW unit in the process of operation, abnormal vibration generator shaft with big load phase increases, generator hydrogen purity low failure.Through comparing the change of the generator bearing vibration track,develop the test plan and implement, on the basis of analysis and test data,for large generator bearing vibration fault diagnosis.Diagnostic results show that the reason for the generator rotor of the generator bearing vibration high hot bending load,lead to seal the reasons for the low hydrogen purity for vibration and shaft neck damage,hydrogen seal oil pollution.According to diagnosis,combining with the actual operation,at 7 watts slip ring and counter weight,on-site high speed dynamic balance,at the same time to repair of 6 wazhou neck,replace the seal 6,7 watts.Dynamic balance and repair results show that the generator bearing vibration has been effectively reduced,the hydrogen purity returned to normal.

Key words: generator, vibration, hydrogen purity, thermal bending, dynamic balancing