Generator Syncing



I remember having to do that manually on our emergency generators when I first started work. Watch the syncroscope and operate the breaker at about "5 to the hour". This allows time for the breaker to actually close. I can't remember the output of the generators but rated in 100s of kW The motive power was an "English Electric" 6L marine diesel, running at 375rpm; compressed air start.
Speed of generator 2 was always adjusted such that the syncroscope was rotating slowly clockwise.
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Stuart wrote:

You may find it interesting, but this is *exactly* how a 1000 MW nuclear plant (BWR) syncs onto the grid as well.
We use the governor in speed-control mode to get the 'scope going very slowly in the 'fast' direction (clockwise). And we wait a little closer to 'midnight', but the basic steps are the same.
Then we run the governor 'up out of the way' and let the pressure controls for the plant control the loading. (in BWR's the turbine is slaved to follow reactor power instead of like PWR's where it's the other way 'round)
We do have 'synch-check' relays, that interlock the closing circuit, so that if an operator screws up, he *can't* close the breaker more than a few degrees out of phase.
daestrom P.S. But these are synchronous generators, not the induction generators the OP mentioned.
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wrote:

The original thread concerned some pump motors used as generators- these turned out to be induction motors. Synching in the sense that Paul mentioned is not needed as these will be asynchronous generators operating at the frequency determined by the system. I also remember synchronising small units routinely using either a synchroscope or lamps. Larger units do need a bit more care. It's easier on the equipment.
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It is not clear to me that the OP still knows anything about his equipment in a serious way. I do not even know if he understands that he has to run with negative slip.
I do remember a machinery exercise in school over 50 years ago. I was in a group of three or four students working together. I more or less knew what I was doing. I think we were assigned synchronization of a alternator. I do not remember for sure whether synchronization was to the line or to another alternator. I think that it was two alternators because I remember we had to work furiously at it in order to finish the tests.
At least one alternator was driven by a dc motor. We got near synchronous speed. We checked out phase sequences, voltage difference etc. We were using three incandescent lamps to indicate when it was time to connect our alternator. Everything went well but we almost ran out of time during this three hour lab.
Meanwhile, the group next to us was having nothing but trouble. Maybe, they were finally getting ready to throw the big switch, Having completed our tasks, I was going to try something else while the equipment was up and running. I do not remember what it was. Whatever it was, I ended up tripping some circuit breakers that shut the other guys down. I do not remember if I had some schadenfreude from that incident.
Bill
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As the years go by, dying just before having to fill out a tax return has merit.

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wrote:

It's easy to synchronize a lab machine to the system and then to adjust loads. In that case the lab machine isn't going to measurably affect either the voltage or the frequency. It is also easy to synchronize one small machine to another, both driven by DC motors, Hold one steady and match the other in voltage and phase using lights. The fun that occurs next (and appears to be what you had) is load sharing (say with even a resistance load) and voltage control. If the people running the two units are both trying to control frequency and load as well as voltage and var sharing- you have two cats fighting in a bag. If one machine deals with load sharing and the other with voltage , it is somewhat easier but still a balancing act. It is also possible to pull a machine out of synch (under exciting can do it) in such a lab situations - so hit the breaker now or make a quick correction before any damage is done -those machines (if they were similar to what I used in class - typically about 5HP units -often Westinghouse, did have pretty good damper windings which helped. The "White and Woodson" universal machines, made by Westinghouse, which came out in the 50's for lab use could be configured as DC, or AC machines of any flavour- which was nice but they weren't typical in any mode of operation- one size doesn't fit all -but they did illustrate the principles in the White and Wilson text..
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Fortunately, it appears thay I have more than enough socked away to last my lifetime.
Unfortunately, I no longer have the physical ability to enjoy spending myself into poverty via wine, women, song, or any other expensive and hedonistic way of spending money. Where is the devil when I need him? I'm willing to deal.
Bill
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As the years go by, dying just before having to fill out a tax return has merit.

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