3 Phase Generator Output - Electrician Talk - Professional Electrical Contractors Forum

Beauc · 11-07-2018, 10:51 PM

Could someone please confirm my understanding of 3 phase generators power output. I'm in Australia so all calculations are in 240v

A 30kVA generator in total can provide a theoretical maximum of 30,000/240 = 125A which would be 41.6A per phase? Using a power factor or 0.8 we get a total of 125*0.8 = 100A or 33.3A per phase.

So a 30kva generator is capable of running 3x32 amp distribution boxes?

Cheers

telsa · 11-07-2018, 10:57 PM

In the real world, the alternator is loaded by real loads.

Distribution boxes are NOT real loads. They are distribution nodes.

You have to ask yourself: "What are the actual net loads to be served?"

This calculation is termed a load-calc... what else?

Set-up a spread sheet program and punch in the numbers.

You'll want to look at actual Watts as well as keep an eye on Power Factor.

( If poor, the latter doesn't load up the alternator, but does figure in conductor sizing. )

Beauc · 11-07-2018, 11:20 PM

Thanks

So assuming unrealistic ideal loads I'm correct? Just after a sanity check that I'm not out by a factor of 3.

Helmut · 11-08-2018, 07:29 AM

Quote:

Originally Posted by Beauc

[COLOR=#212121][FONT=sans-serif]A 30kVA generator in total can provide a theoretical maximum of 30,000/240 = 125A which would be 41.6A per phase?

Huh?

AK_sparky · 11-08-2018, 12:43 PM

Quote:

Originally Posted by Beauc

A 30kVA generator in total can provide a theoretical maximum of 30,000/240 = 125A which would be 41.6A per phase? Using a power factor or 0.8 we get a total of 125*0.8 = 100A or 33.3A per phase.
So a 30kva generator is capable of running 3x32 amp distribution boxes?

Quote:

Originally Posted by Beauc

Could someone please confirm my understanding of 3 phase generators power output.

I can confirm it is not correct. Are you an electrician? I don't see anything in your profile.

EDIT: I just realized I may be misreading this. Is the 240V L-L or L-N?

Helmut · 11-08-2018, 02:36 PM

240v x 1.73 x 33.3a= @13KW

brian john · 11-08-2018, 07:29 PM

30X1000/240x1.732= 72.23 amps

30X.8/x1000/240X1.723= 57.78 amps

or somewhere close to that

11-07-2018, 10:51 PM	#1
Beauc Junior Member Join Date: Nov 2018 Posts: 2 Rewards Points: 4	3 Phase Generator Output Could someone please confirm my understanding of 3 phase generators power output. I'm in Australia so all calculations are in 240v A 30kVA generator in total can provide a theoretical maximum of 30,000/240 = 125A which would be 41.6A per phase? Using a power factor or 0.8 we get a total of 125*0.8 = 100A or 33.3A per phase. So a 30kva generator is capable of running 3x32 amp distribution boxes? Cheers

11-08-2018, 02:36 PM	#6
Helmut German Spy Join Date: May 2014 Location: THE United States Of America Posts: 4,138 Rewards Points: 4,643	240v x 1.73 x 33.3a= @13KW brian john likes this. __________________ I see nooothing, I was not here. I did not even get up this morning.

11-08-2018, 07:29 PM	#7
brian john Senior Member Join Date: Mar 2007 Location: Gilbert's Corner VA Posts: 30,862 Rewards Points: 3,498	30X1000/240x1.732= 72.23 amps 30X.8/x1000/240X1.723= 57.78 amps or somewhere close to that __________________ Ah, but I was so much older then, I'm younger than that now Last edited by brian john; 11-08-2018 at 07:32 PM.

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11-07-2018, 10:57 PM	#2
telsa Senior Member Join Date: May 2015 Location: Sacramento, California Posts: 14,311 Rewards Points: 26,868	In the real world, the alternator is loaded by real loads. Distribution boxes are NOT real loads. They are distribution nodes. You have to ask yourself: "What are the actual net loads to be served?" This calculation is termed a load-calc... what else? Set-up a spread sheet program and punch in the numbers. You'll want to look at actual Watts as well as keep an eye on Power Factor. ( If poor, the latter doesn't load up the alternator, but does figure in conductor sizing. ) Last edited by telsa; 11-07-2018 at 11:10 PM.

11-07-2018, 11:20 PM	#3
Beauc Junior Member Join Date: Nov 2018 Posts: 2 Rewards Points: 4	Thanks So assuming unrealistic ideal loads I'm correct? Just after a sanity check that I'm not out by a factor of 3.