Generator Vibration

[chief]

We have a 1MW DIESEL GENERATOR running at 900 rpm and delivering at 11KV. We are experiencing heavy vibration at the generator end.
All the usual suspects have been eliminated, vibration dampers , alignment engine /generator, anti -vibration mounts,engine fuel injection timing. Support foundation structure etc.
I recall reading an article ,where the generator vibration problem was traced to an out of sync phase, The out of sync was induced I believe by transient magnetic/induced volts.
It was corrected by the inclusion of software in the control system (possibly excitation circuit).
My question is, has anyone any experience of this phenomenon and what was the cause and fix.

Offshore Engineering&Design

 

[Strong]

Chief,

What is the dominant frequency of vibration? Does the vibration disappear at full speed no load? Is vibration present at full speed with generator excitation but no load? If it is only present under load, then does vibration tend to increase with load.

Walt

 

[chief]

Unfortunately I do not have a vibration analysis . This is a new build installation and i have yet to be present when the engine is running at no load,full speed.
I understand where you are coming from and I will advise to disconnect the excitation circuit, when the engine is run -up.
But from the article I read, the greater the load on the engine the greater one of the phase angles went out of sync,causing the vibration.
It is something I am putting out there to see if anyone has experience of this event.
The control sytem is a Siemens.

Offshore Engineering&Design

 

[Tmoose]

For 30 US bucks you can get a reed vibrometer type tachometer from the Briggs and Stratton dealer and get and idea what the frequency(s) of vibration are.

http://www.manddsmallengine.com/briggs/tools/19200.html

 

[MachineryWatch]

Strong and Tmoose are right. There really isn't too much anyone here can do to recommend anything with out knowing what frequency the dominant vibration is . Beyond that it may require relative vibration phase readings to diagnose further once the frequency is known.

http://www.machinerywatch.com

 

[powerjunx]

with due respect, if you dont have vib. meter you should provide one to the extent a forum post would be a vast straightforward answer not handful of mind guess.
"But from the article I read, the greater the load on the engine the greater one of the phase angles went out of sync,causing the vibration." Well, if you guess this right that cause the vib in your equipment, then i would say that its time to overhaul your Generator and perform a thorough check.
Most likely, as i done before, it laid on rotor windings and peripherals as it tends to loosen out upon increasing the load having it shifted the center of mass on the rotor or out of eccentricity. performing such check and repair need a call for service techs personnel.


"..the more, the merrier" Genghis Khan

 

[Skogsgurra]

You are asking for experience in matters vibration on smaller generator sets. I had one that puzzled some people, including me.

There were very heavy vibrations in the generator. Also when no load applied. Rotor was taken out for a complete dynamic balancing. No problems found and no improvement.

We finally found that the connection between different excitation windings, a solder joint, was faulty. After opening the joint, scraping the wires and doing a good solder, the machine ran quiet.

Not saying that this is your prolem. But, as experience goes, it may help.

Gunnar Englund

http://www.gke.org

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