rewinding effects

[ele.engineer]

hi friends
we have a ground fault in the synchronous generator 10 MW so we transfer it to specialized work shop for Re-winding, and after rewinding the generator and make alignment for the generator with the gear box shaft and start the generator we noticed very high vibration in the generator body ,so we make recheck for the alignment and found high deviation in reading occurred, is the generator rewinding effects on the magnetic center?? causing for the deviation in alighment

 

[edison123]

How are the rotor bearings supported, on stator end brackets or on separate bearing pedestals?

Muthu

http://www.edison.co.in

 

[electricpete]

What is the predominant frequency of the vibration?

so we make recheck for the alignment and found high deviation in reading occurred

I don't understand this statement. Can you explain specifically what you mean by this?
Example:
[ul]
[li]The machine was found out of alignment after you had just aligned it?[/li]
[li]If so, change in axial alignment or radial?[/li]
[li]And was vibration corrected after you corrected alignment?)[/li]
[/ul]

=====================================
(2B)+(2B)' ?

 

[dArsonval]

Several "unknowns" to adequately form a guess. In addition to what edison123 and electricpete are asking, what portion of the generator was rewound?

John

 

[ele.engineer]

1. the rotor bearing supported on separate bearing pedestals.
2. the predominant frequency of vibration is 1X at 1500 RPM
3. The machine was found out of alignment after start the generator and stopping it for vibration checking.
4. we just correct the alignment and expected to make running test for generator tomorrow.
5. the rewinding included 100% of stator winding.
why the alignment change from and after generator running ??
in case of misalignment occurred again or we noticed any vibration , any suggestion is respected

 

[waross]

Have you checked the air gap?

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

 

[dArsonval]

Acknowledging your number 5 answer.
We can lean away / rule out imbalance due to a rotor rewind.

 

[Yuma]

I suggest going to FSNL / sync idle and compare the vibrations with and without excitation, before paralleling.