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orlyboy
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Exciter Vibration

07/05/2023 1:17 AM

Does the defective diode affects the vibration of the exciter?
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BruceFlorida
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#1

Re: Exciter Vibration

07/05/2023 6:31 AM

Without details no one can give a very detailed response to your question. In general, if a component in a circuit is bad then the circuit will not operate properly. If you post a few details of your circuit and tell us what is happening then we might be able to help you.

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orlyboy
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#13
In reply to #1

Re: Exciter Vibration

08/16/2023 7:46 PM

Generator is rated 6MW.

During ramp-up to 2MW, vibration on the exciter side is increasing up to High alarm level.

However, further load increase, vibration tends to go down and normalized.
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PWSlack
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#2

Re: Exciter Vibration

07/05/2023 7:06 AM

What did the equipment manufacturer say over the telephone?

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SolarEagle
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#3

Re: Exciter Vibration

07/05/2023 9:22 AM

..."The rotating rectifier is prone to be damaged in the exciter of the brushless excitation system, wherein a diode open-circuit fault which is common can affect the normal and safe operations of a generator. On the basis of the structure of the brushless exciter, this study, analysed the effect that an open-circuit in one and two diodes had on armature current and armature field, and put forward a new online detection method for diode open-circuit fault. In this method, two magnetic field detection coils are installed on the stator iron yoke of the brushless exciter, and the open-circuit fault of the diodes can be reflected by the induced voltage difference of the two detection coils. Using a 16-pole, three-phase brushless exciter as an example, the performance of this new diagnosis method was verified by using a finite element simulation."...

https://ietresearch.onlinelibrary.wiley.com/doi/full/10.1049/iet-epa.2018.5161

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redfred
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#4

Re: Exciter Vibration

07/05/2023 9:50 AM

Nothing affects their vibrations.

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Brave Sir Robin
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#9
In reply to #4

Re: Exciter Vibration

07/06/2023 4:54 PM

More my speed . . . .

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redfred
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#11
In reply to #9

Re: Exciter Vibration

07/19/2023 9:07 AM

Actually, this band I prefer. I just knew some band had to take the name Exciter.

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Rixter
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#5

Re: Exciter Vibration

07/05/2023 11:44 AM

I'm going to say it's possible. The rotating exciter generates multiphase AC which is rectified by a full wave bridge rectifier. A faulty diode would result in a missing phase, which would produce high ripple in the rectified output. The exciter current ripple could cause vibration.
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Rixter
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#7
In reply to #5

Re: Exciter Vibration

07/05/2023 9:10 PM

According to this, the health of the rectifier bridge in the excitor can be determined from a spectrum analysis of the output voltage of the alternator.

"Detection of Brushless Exciter Rotating Diodes Failures by Spectral Analysis of Main Output Voltage"

https://zenodo.org/record/1270646/files/article.pdf
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SolarEagle
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#6

Re: Exciter Vibration

07/05/2023 12:06 PM

This would need to be tested and measured, the effect is likely to be subtle if reliably detectable at all...

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Stef
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#8

Re: Exciter Vibration

07/06/2023 4:00 AM

It depends on whether the generator is self excited brushless, externally excited via brushes. I was asked to look at a self excited small generator which would excite then the output voltage would fade away.

Fault was the exciter windings on the rotor had internal shorted turns which were parasitic to the voltage and the excitation would fade. Defective diodes in an exciter circuit will likely cause a loss of excitation and the generator will run unloaded or if the diode shorts then the residual magnetism in the rotor used to create the initial excitation will be lost and the rotor just be rotating as a parasitic load through windage.

If the exciter is external and a diode fails it could prevent the DC being applied and output voltage will be lost. Vibration can be generated if the excitation control circuit fails in a way that AC is applied to the rotor or higher voltage is applied to the rotor leading to a flashover in the stator.

From my experience a failed diode stops output being generated and should trigger a shutdown of the prime mover if no output is detected. It all depends on the protective systems installed.

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PWSlack
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#10

Re: Exciter Vibration

07/19/2023 6:43 AM

So, did it <...affects the vibration of the exciter...> or not?

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orlyboy
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#12

Re: Exciter Vibration

08/16/2023 7:44 PM

Hello fellows, here is the actual scenario at site, for you to visualize it in your mind:

Generator is rated 6MW.

During ramp-up to 2MW, vibration on the exciter side is increasing up to High alarm level.

However, further load increase, vibration tends to go down and normalized.

Highly appreciate and warm Thanks for the responses/contributions, and for those who will continue to response. Keep safe always.
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Users who posted comments:

Brave Sir Robin (1); BruceFlorida (1); orlyboy (2); PWSlack (2); redfred (2); Rixter (2); SolarEagle (2); Stef (1)

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