So whats my actual generator rating?

[Engineer54]

Since its a 240/415v gen, 520kw/(415 * sqrt of 3)=723 amps so imho
they tested it at (792/723) = 110% of its rated 520KW output.
520kw = 640 KVA at 80% pf.
The KVA ratings arent meaningful as a true real-life output. kw is the true rated output,
on a continuous basis for prime power gens. most prime power gens are capable of providing 110% of rated output for a limited period of time defined in their definition of prime power.

Haha, ...So explain away the 900A rating on the alternators data plate then??

 

[1capybara]

The alternator maybe rated 900A but does that mean the generator is?
And at what ambient temperature and elevation? Prime power or standby?
Why do you think the generator is sold at rated 640kva/520kw?

 

[Engineer54]

The alternator maybe rated 900A but does that mean the generator is?
And at what ambient temperature and elevation? Prime power or standby?
Why do you think the generator is sold at rated 640kva/520kw?

You don't know much about generators at all, ...do you??

As engines are sized accordingly to the alternator, Yes it does mean the generator is rated at the full load of the alternator, in this case around 900A!!

So what do you consider is the difference between a stand-by and a prime power generator??

All generators and distribution transformers are manufactured/sold to a KVA rating, in the case of generators generally with a stated PF % figure, which is where they derive the KW figure, which will rise or fall according to the PF %. In this case it has been stated as 0.80, which relates to the 520KW ...640KVA at 0,80 PF.... If an alternator is rated to deliver a stated current output, that's basically what the generator can deliver, it doesn't care what that current consists of, be it all resistive, all inductive or as in the majority of cases a mixture of both types of load....

 

[1capybara]

Sir, I must respectfully disagree. You arent taken into account altitude or ambient temperature. The alternator rating is a maximum not an absolute. IMHO, altho you take every opportunity to dis me, I will not now dis you, Sir!

 

[Rockingit]

As it's probably impractical for you two gents to duel at dawn using alternator data plates instead of pistols, how about we try the time proven rock and roll method instead? You know, the one where we just keep plugging stuff in until it starts coughing and chugging. Ambient conditions normally a boggy field.

 

[Knobhead]

I can’t understand this argument.
640KVA 415V @ unity PF = 890A
520KVA 415V @ 0.8 PF = 868A
As near as damn it 900A

 

[sheephat]

The altitude and the ambient tempurature must surely be irrelevant how can it affect the generator rating that much, beside lets pretend we have ideal conditions.

@Rockingit - I wanted to turn the load bank up and take over the whole testing process but they wouldnt let me lol.

 

[1capybara]

640 kva @ 80% pf = 520 kw, actual usable power.
but I like the duel at dawn method with alternator plates. or the rock and roll method

 

[Engineer54]

640 kva @ 80% pf = 520 kw, actual usable power.
but I like the duel at dawn method with alternator plates. or the rock and roll method

No-ones trying to dis you...

But i can assure you, that if an alternator has a a current value stated on it's data plate, then that alternator should be expected to be able to provide that current.. You can play with KW and KVA designations all day, but they will both be based on the capability on what the alternators current output has been designed to deliver. As stated previously, the generator will not care a jot what that current is made up from, it will still provide that stated current, ...be it useful current or otherwise.

As for the ambient temperature and altitude, were talking about an in-situ generator installation in a UK City, so the altitude can be ruled out. As for ambient temperature, ...well that is clearly fine going by the test report readings... So let's take it that in this case, both are well within the manufacturers design thresholds, and that no de-rating factors need to be applied.