Generator synchronizing time?

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Cold Fusion said:
Assumptions:
You have four generators, not running in parallel. Each generator feeding separate busses. output. That is the only way your OP makes sense. Let us know if that is correct and we'll go from there.

One other scenerio came to mind. Two pairs of parallel gens, each pair feeding a separate bus. Each generator feeding separate busses. output. This also fits your OP.
cf
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There are 2 generators that do parallel. Then feed individual breakers that in turn feed 4 ATS.

tonytonon said:
MEP, I am curious, do you know the manufacturer and model# of those ATSs?
Tony
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Kohler and I don't know the model. They are close transition.
 
Are you sure the slower ATS's are not in TDN (Time Delay to Normal)...They may not want to unload the gensets quickly therefore inducing a 3 or 5 minute time delay on re-transfer? You will typically see this on older systems that have had loads added to them since their initial install and are loaded beyond 65-75%...and a quick unload may cause a governor bounce thus causing a overspeed condition.....it may not be "sync" your waiting for it may actually be a retransfer Time Delay coupled with sync phase monitoring that makes it seem like an eternity.

If it's Kohler gear....if you can get me the numbers on the main logic board I can tell better what your dealing with - the numbers should be like "A-123456" it's a six digit number typically on a white sticker on the board with a leading letter (IE: A, B, C..up to E).

Just a quick one...on the "troublesome" ATS's do you see any external "boxes" hanging around? (Like a Woodward Sync module ect. ect.?)
 
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MEP_PM said:
Kohler and I don't know the model. They are close transition.
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MEP -
Once the first ATS closes in re-transfer, the gens and the utility are in sync - have to be, buses are connected together.

So, it appears you are telling us the ATSs are delayed as Generatorman suggested. This would mean, as soon as the sync gear pulls the two buses in sync, the first ATS closes in re-transfer (buses parallel), then opens it's gen cb. This allows the two buses to go out of sync.

Sync gear pulls the two buses in sync again, the second ATS closes in re-transfer (parallel again), then opens it's gen CB.

And so on for the rest of the ATSs.

Does this sound right? If so, what you are seeing is likely as good as you are going to get.

As the gens are step unloaded, and the buses pop in and out of sync, it would not be surprizing if the gens freq and voltage are drifting all over - maybe some overshoot and oscillation as generatorman described. At low gen loads, the VRs and Governors tend to get more sensitive. All contributes to make it harder for the sync gear to pull the two buses in sync for the nest transfer.

A description of operation and a one-line would really help. If you don't have a scanner, use my method - an inexpensive digital camera and take a picture of the sketch.

cf
 
Cold Fusion said:
At low gen loads, the VRs and Governors tend to get more sensitive. All contributes to make it harder for the sync gear to pull the two buses in sync for the nest transfer.

cf
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You bring up a point that I had not included. 2 ATS are in one room 2 in another. So, when load testing there is a min or two of delay between commanding the ATS to test or go back to normal. So when the test is complete. You have to walk to each transfer switch and cancel the test to retransfer to normal. So you have 4 different 10min delay/count downs. So they may not all transfer the first time the bus and utility are parallel. However after the 10 min delay counter for the last ATS expires. All ATS should be capable of retransferring to normal. 2 ATS took more 3 min to sycn and retransfer (After the last delay had expired). And both show a fail to snyc alarm after 1min.
These are the smaller ATS and do not have a lot of load. Low load could be the answer.
 
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