Transformer Sizing

[Stevan812]

I have a project coming up and I seem to have drawn a brain cramp. So please help me with this question and also please let me know the proper formula to figure it out the next time for myself.

Power company supplies 480 volts to new building, We need 1600 amps 240/120 distributed to 9 meter socket distribution center. If the power company makes us buy and maintain our own transformer I need to be able to figure out what size transformer to buy. I can't remember if input current is the same is output current.

1600x240x1.732/1000=665kva so transformer would have to be 700KVA transformer then? or am I in a terminal brain fart condition and should take up turd chasing for a carrer choice.

Please help I want to learn

 

[RonShap]

To size the single phase transformer
VA=A*V
or
kVA=A*V/1000
so
1600*240/1000= 384kVA minimum size for the transformer

 

[Donale]

Your 3ph formula is correct for the basic approximation but, check the NEC for overload and loading factors. I'd suspect a 750kVA xfmr is closer to the choice. Don't forget harmonics and their effects. Also future expansion or loading should be considered. I'm sure the power company will work with you to determine the correct size. Use them, they have alot of expertese.

 

[Stevan812]

Thank you Both for your input. I will not forget this time. You have both very helpful.

 

[BJC]

Where did you get the 1600 Amp figure?
Did you apply a demand factor to the building to get it? Utilities will typically apply a demand factor of 20-30 % of the connnected load. You utility has a formula they use for it.
If they won't share it with your try the NEC sizing criteria for feeders ( Artical 200 is a start).
A 750 KVA transfromer could connected to a buidling as larges as 500,000 Sq ft depending on where you are and things like electric heat ( got it or not). Weather it's a residence or a store or a business park.
1600 amps at 120/240 is large for a single phase load, have you considered a 3 phase transformer with a 208/120 secondary. Most devices that run at 240 will run ( or can be had to run) at 208). If you have any large HVAC or other motor loads 3 phase 208 is much cheaper.

 

[jbartos]

Suggestion: Please, would you provide more info.
Else, the most common interpretation of what was stated is: there will be a "minimum" transformer indicated in RonShap posting, and 9 meters drawing covering about 178A for 240/120V single phase three wire service. Probably, 9 pieces of 200A meter sockets, 240/120V single phase 3wire will be needed. There are also some rules about jaws in the meter sockets. Check with the Utility.