Assuming I have a 160MW generator. I want to load my generator at 20MW for a few hours. Is it safe to do it? If the best generator efficiency happens to be at 140MW, how much its efficiency will drop if it is loaded at 20MW?

Thank you for your response.

 

This question should be asked of and answered by the generator's manufacturer. We can't really answer this question without knowing a lot about the generator, it's cooling system, and it's operational characteristics.

Generator efficiency isn't affected by load factor to any great extent. And, I'm curious about how you arrive at a "maximum" efficiency of 140 MW for a 160 MW generator? It's quite common for generators to be rated higher than the maximum rated output of the prime mover driving the generator, just so that the generator isn't the limiting factor in the unit. Are you talking about the efficiency of the prime mover?

Contrary to singular opinion, a generator just converts torque to amps. More torque, more amps; less torque, less amps. But the efficiency of the generator at converting torque to amps doesn't really change very much over the load range of the generator. The efficiency of the prime mover might vary significantly over the load range of the unit, but typically not the generator.

I can say that <b>in general</b> the amount of load carried by a generator below it's nameplate rated value (as long as it's "positive" load) is relatively irrelevant to the generator. (I can just guess that a certain poster is going to take exception to that statement with some off-the-wall, one-off occurrence, which will be a two-off occurrence for the purposes of his posting.)

Many times, the load carried by a prime mover and the generator it's driving is limited by the prime mover's operational characteristics or requirements. For example, some steam turbines can't operate for very long at low loads because of overheating due to low steam flows, or possible internal condensation due to low steam flows, or vacuum problems due to low steam flow.

So, without knowing a lot more about your generator and its prime mover, it's really difficult to provide anything other than generalizations. The generator manufacturer, or the packager of the generator and the prime mover, should really be consulted for any operational limitations at low loads.

And making assumptions is not good for anyone....ever.

 

Thank you CSA. I just want to know typical characteristic of a generator. Not specifically to any brand.

Because prime mover is always the limitation that is why I have to ask others. We seldom have the opportunity to study generator performance at very low load factor. Moreover nobody seriously wants to know it since he may not operate it at a very load factor. I need to know it for some reasons.

I have a few generator efficiency curves with me. You are right it does not change much with load factor but it does change by the order of 1-1.5%. In my post I just made up its peak efficiency value to occur just below it rated maximum.

I can extrapolate my curve to determine the value at very low load factor. The only thing worries me is I'm not sure the physics remains the same at a very low load factor.

Thank you again CSA.

 

Physics down to that level ain't my thing. You can find many others here who would be happy to provide formulae or speculation or downright incorrectly inferred anecdotal data.

You will have to decide which is which.

I suggest using your preferred Internet search engine and looking on the World Wide Web for the information you seek. Or, in a library or reference- or text book.

Best of luck with that.

 

Namatimangan08… As CSA said the information you seek could be obtained from the generator manufacturer. However, one reason it isn’t readily available is that operating with such low loads raises concern about stability. Furthermore, I don’t agree that the deviation is in the order of 1–1.5% lower than rated efficiency.

If you’re interested I have a series of curves that can be used for a generic analysis. The curves plot kVA, from 0.15 per-unit to 1.10 as the X-axis (abscissa) and % Efficiency as the Y-axis (ordinate) for three PF cases; 1.0, 0.9, and 0.8.

Regards, Phil Corso

 

Dear Mr Phil Corso,

Thank you for your kindness. I like to have them. I will e-mail you soon.