Generator Operation

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Thread Starter

Nagender Mantha

Generators with the same voltage level & same frequency and with the same rating, but with the different Speed (RPM) can be runned in parallel with the Synchro panel.

<b>Moderator's note:</b> I think the poster is asking "Can generators with the same voltage level & same frequency and with the same rating, but with the different Speed (RPM) be run in parallel with the Synchro panel?"
 
Presuming the Moderator's Note is correct, and the original poster is talking about synchronous generators, the answer is: Yes.

Synchronous generator speed and frequency is a function of the number of poles of the generator. A two-pole generator operating at 50 Hz would have to rotate at 3000 RPM. A four-pole generator operating at 50 Hz would have to operate at 1500 RPM.

The formula that relates frequency, speed and the number of generator poles is:

F = (P * N)/120
where F = Frequency (Hz)
P = Number of poles of generator rotor
N = Speed (RPM)

(You can solve for any variable if you know at least two of the variables.)

So, it would seem there are generators with differing numbers of poles which someone wants to synchronize together--or this is a test question that someone is looking for an answer to. Possibly a trick TRUE/FALSE question at that. (My university electrical instructor was known for misleading questions, and this would definitely qualify as one. He would expect an answer (TRUE or FALSE) but he would argue one way or the other on individual basis depending on how much he liked or disliked the student and what kind of grade he wanted that student to achieve. Suffice it to say it was not a good series of classes with that instructor.)

A lot of times people think the prime mover (turbine; reciprocating engine; etc.) is the same as generator speed--but it's not always. Many times there is a gear between the prime mover and generator which decreases (in most cases) or increases (in a few cases) the speed of rotation of the prime mover to the generator. But, a synchronous generator MUST operate at a specific speed that is proportional to the number of poles of the generator rotor in order to operate at a specific frequency.

It's even possible for generators of different rating and different voltages to be synchronized together--presuming there is a transformer between them if the voltages are not the same to "equalize" the voltage at some point in the grid/system.

Keywords to use when searching the World Wide Web with your preferred search engine for more information include: synchronous generator; synchronous speed; synchronization; AC generator fundamentals. That should help with getting more information.

If the generators are capable of operating at the same frequency, and at the same voltage level (per the original "statement") then they can be synchronized together using a synchronizing panel.

Hope this helps!
 
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