Generator Noise

[TransD]

I work at a hydroelectric plant with 6 horizontal units. Recently 2 units were rewound. The voltage rating of the stator was changed from 4000 volts to 4800 volts. There are 44 field poles on each unit which were also rewound. After they were rewound,the generators were considerably louder than before. You can hear the noise at certain speeds the loudest. Sync speed to the grid is 164 rpms. The noise is the loudest between 120 and 155 rpms for both units. The noise is there with or without voltage applied to the field. Other than vibration testing, which we are going to have done, what other tests can be done to find the cause of the noise?

 

[7anoter4]

It could be a critical speed it is involved here. See[for instance]:

http://www.sandv.com/downloads/0505swan.pdf

 

[edison123]

I would look for loose rotor poles, loose fans, loose coupling etc.

Muthu

http://www.edison.co.in

 

[waross]

Windage noise? It's hard to say without hearing the noise. Possibly fish paper was installed in such a way as to create windage noise. At higher speeds the paper may bend over and so create less noise.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[collies99]

Could be cavition of the turbine ? Perhaps the turbine seals have been disturb as another possible cause.

 

[Strong]

Measure sound first, then guess (hypothesize) what may be causing it. A good narrowband (FFT) averaged spectrum with and without noise present would be a good place to start.

Walt