# GE SCR Voltage Regulator



## mustang08 (Jun 25, 2013)

I am working on a 1981 vintage GE SCR Static Exciter. It is on at a 150 MW power plant. It swings the generator field voltage in the downward direction causing the Reactive Power to dip down from 5 MVARs to about -20 MVARs intermittently. It may do it every 7 minutes or it may work ok for 2 weeks and then do it. Sometimes it recovers on it's own back to 5 MVARS and other times we go to DC Manual and wait awhile and go back to AC Automatic and it will be normal. Has anyone worked on such a machine?


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## walkerj (May 13, 2007)

Well if it's GE it's likely garbage


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## JRaef (Mar 23, 2009)

I've worked on GE Synchronous motors that used a similar system. Sounds as though your voltage regulator board in the controller is beginning to fail. Complete failure is generally eminent after acting like this, you need to get it fixed or replaced ASAP. It's not likely to be something you can troubleshoot down to the board level component and fix yourself, it takes some fairly sophisticated instruments and detailed knowledge to do so. There are people that do that for a living though, GE sold a LOT of those. GE used to have a network of what are called Apparatus Service Centers across the country, but they sold most of them off to private enterprises 20+ years ago. Many of them however continue to operate as service centers for GE apparatus.

I Googled them in Ohio for you, here's what it returned.
https://www.google.com/search?q=ge+...s=org.mozilla:en-US:official&client=firefox-a


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## Tonedeaf (Nov 26, 2012)

What's the cat and model number GE power group back in the day usually provided good operational manuals.


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## Big John (May 23, 2010)

I second the voltage regulator as the culprit. I had one like this not that long ago where the field would begin to swing wildly for not apparent reason, and it turned out to be the AVR overheating: Putting additional cooling fans in the control section solved the problem.

I don't know what load you guys are following, but it's possible, swing it over to manual and leave it there: If your problem disappears you know it's upstream of the gate control on the thyristors.


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## ScooterMcGavin (Jan 24, 2011)

We've had this problem before. These were Toshiba AVR's of the same vintage. One time it was bad connection on the PT drawer stab connections and the other time it was dirty contacts on the voltage setter rheostat. 

For us to to run in manual voltage control for any length of time is a huge deal. You have to notify the world and an operator has to sit there and be solely dedicated to adjusting voltage.


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## mustang08 (Jun 25, 2013)

JRaef said:


> I've worked on GE Synchronous motors that used a similar system. Sounds as though your voltage regulator board in the controller is beginning to fail. Complete failure is generally eminent after acting like this, you need to get it fixed or replaced ASAP. It's not likely to be something you can troubleshoot down to the board level component and fix yourself, it takes some fairly sophisticated instruments and detailed knowledge to do so. There are people that do that for a living though, GE sold a LOT of those. GE used to have a network of what are called Apparatus Service Centers across the country, but they sold most of them off to private enterprises 20+ years ago. Many of them however continue to operate as service centers for GE apparatus.
> 
> I Googled them in Ohio for you, here's what it returned.
> https://www.google.com/search?q=ge+...s=org.mozilla:en-US:official&client=firefox-a


 I have a used regulator board from a plant that retired their exciter. I put in in with the exciter powered up but not in service. I watched the Transfer Unbalance signal with a Fluke. It was jumping +/-12V and back so I knew it would not work in service. I put the original regulator board back in. I did the same with the AC/DC transfer board, it did the same thing, I put the original back. I know about the sophistificated equipment, Gen Sim, YEW high speed recorders and such. Still learning how to use them.


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## mustang08 (Jun 25, 2013)

Big John said:


> I second the voltage regulator as the culprit. I had one like this not that long ago where the field would begin to swing wildly for not apparent reason, and it turned out to be the AVR overheating: Putting additional cooling fans in the control section solved the problem.
> 
> I don't know what load you guys are following, but it's possible, swing it over to manual and leave it there: If your problem disappears you know it's upstream of the gate control on the thyristors.


I have tried that, it works okay in manual.


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## mustang08 (Jun 25, 2013)

It does not have any cooling fans now. I may put a portable fan in front of to blow into it and see what it does.


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## mustang08 (Jun 25, 2013)

I have checked the PT input with a Fluke in record and it always stays steady. I know all about running it in manual for an extended length of time, I have to deal with the excact same thing here.


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## mustang08 (Jun 25, 2013)

I have a manual for it.


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