hi friends
how are you all , i hope that you in good helth and job condition

i attach a time wavform and spectra of genertator- exiter side bearing and i got fluctions(amplitude changse
in the time waveform (vertical) not clear in the spectra who can help in interpretation this phenomena.
thank you

time_wavform.doc (58 Kb, 72 downloads)

Is the fluctuation random or dioes it repeat on a regular basis.

Also, tells us a bit more about your machine train. Is there a gearbox between the generator and the exciter and if so what type coupling is used for the connection?

John

hi mr john
how are you

the generator is driven by a steam turbine through a riged coupling and no gear boxes betwwen the turbine and generator or generator and exciter .
the speed of the turbine and generators are 300 rpm
the first time i see this fluctuations

thank you

the speeds of turbine and generator are 3000 rpm not 300 rpm .

Ahmad, if your generator is supported on turbine bearing? You have shown vibration spectra for steam turbine bearing only. Please provide other bearings data as well.

One thing that is clear from these is that it is exactly a multiple of line frequency (50Hz because yours is a 3000 RPM machine).

Spectra show multiples of 1L, 2L,3L, 4L clearly.

If its due to elctrical windings, bars, it could be easily detected by turning off the excitation voltage. If problem disappears, it is the generator. Then you have to look for the short windings etc etc.

hi mr yahoo and mr john

thank you very much for your help and ur explanation

the generator has its own bearings (2 journal bearings) and is connected to the turbine by rigid coupling .
the other spectra now not with me am home

thanx very much

How did your data look before? Please post if possible. Just pure 1x? If so, considering non-flexible coupling, there could be that some shift has occurred causing misalignment or minor looseness developed. Based on the spectrum vibration is not random, just non-sinusoidal.