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Steve G.
Steve G., Electrical Engineer
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Experience:  27 years in Electrical Engineering, designing electrical plans and specifications.
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on a 200 amp 3 phase 480 feeder how is the amps divided among

Resolved Question:

on a 200 amp 3 phase 480 feeder how is the amps divided among the phases or can one phase carry 200 amps at a given time ??
Submitted: 1 year ago.
Category: Electrical
Expert:  Steve G. replied 1 year ago.

Hello there and welcome to Just Answer. My name is XXXXX XXXXX I will be assisting you today. I am an engineer with over 30 years of electrical and electronic training, repair and installation experience. I will try and answer your question accurately and precisely so that we can get you on your way.

It is 200A per phase.

Theoretically on a 200A feeder (ignoring code requirements for breakers) you can power 480 x 200 x 1.732 for a total of about 166KW of balanced load.

I'll be here if you need further help with this issue. Please let me know.

Regards

Steve

Customer: replied 1 year ago.


I'm going to feed a transform 400ft away, that is going to supply 8 trailers so what size wire do I need for this 200amp feeder

Expert:  Steve G. replied 1 year ago.

I think the better question for me to ask would be what size is your transformer in KVA?

If you don't know, what are your anticipated 120/208V loads?

That is going to determine your 480V feeder sizes and the primary and secondary overcurrent protection.

Any idea?

Please let me know so that we can continue.

Regards

Steve

Customer: replied 1 year ago.

150 kva 120 /208v

Expert:  Steve G. replied 1 year ago.

Ok, so you have a 150KVA 480V 3 phase 3 wire to 120/208V 3phase 4 wire transformer?

Any idea of the actual total load from those 8 trailers?

And it's 400 feet from the primary breaker to the transformer?

Confirm that and I'll tell you what you need.

Steve

Customer: replied 1 year ago.


8 trailers and each will have 125 Main

Expert:  Steve G. replied 1 year ago.

Ok, so that gives you a max theoretical load per trailer of about 36KW. I assume that you won't be seeing anything like that.

For a 150 KVA transformer you need a 250A breaker for primary overcurrent protection. You can run the 400 feet with a single set of (three) 4/0 (90 degree) copper conductors plus your ground. You can put them all in a 2.5" pipe.

A quick volt drop based on likely loads is less than 1.4% so you are good to go there.

On the secondary side you need a 600A breaker for secondary overcurrent protection. You will then need to split that up and distribute it to your trailers. Each run needs an overcurrent device (125A).

I'll be here if you need further help with this issue. Please let me know.

Regards

Steve

Steve G., Electrical Engineer
Category: Electrical
Satisfied Customers: 17062
Experience: 27 years in Electrical Engineering, designing electrical plans and specifications.
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