How am I going to get 208 3ph. from 240V 3ph.?

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stuartdmc

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Newport Beach, Irvine, CA
My question seems simple, I have a client that requires 400A of 120/208 3ph power. The building they have chosen to set up shop has (1) 200A 120/240v 3ph service, at the service providers tap (over head) they've taped and ran down to a second service a 200A 120/240v 1 ph. service. I want to change out the Existing 200A 3phase service to a 400A 120/240V 3ph. service (keeping the overhead service feeds) and the feed a 240V 3phase primary transformer and convert the power to 400A of 120/208V 3 phase power to meet my clients needs.
(we will be deleting the second taped 200A single phase service)

My question is, do you see a better way to met the clients need and/or what type of transformer will I need to convert the Voltage to from 240V to 120/208V?
 
It's not very often that a load rated for 208 can't also use 240. If you absolutely need 208, you can either use a 240x208 transformer to serve many pieces of equipment (or a 208 panel) or just use a buck-boost for one particular piece of equipment.
 
My first inclinaton would be to take a real close detailed look at what they had vs what the truely need. You have 400 amps (realizing one service is single phase) A lot of equipment can operate on 208 or 230.
You also might be able to satisy the 120 volt load from existing and use a buck&boost on items that truely needed 208 or a smaller 240/208Y120 for just the 208 volt loads..

sorry marc..I was on top of you..at least we think alike
 
That's what I suggested as well, However, the clients are a bank which more then likely have a Proto type Plan that are looking for a building to house themselves, Their asking us to provide in the building (their requirements) of 400A 120/208v. They probably don?t even understand the deferent?s in the voltages. My struggles are with the power company (LA. DWP), will they drop overhead a 400A 3 ph. line?
 
sounds like from their standpoint they have already dropped you 400 amp line as you now have (2) 200 amp services.
since you state "you wonder about POCO", have you asked them about 208Y120 ?
 
augie47 said:
My first inclinaton would be to take a real close detailed look at what they had vs what the truely need. You have 400 amps (realizing one service is single phase) A lot of equipment can operate on 208 or 230.
/QUOTE]
But it is a code violation:
110.4 Voltages.
Throughout this Code, the voltage considered shall be that at which the circuit operates. The voltage rating of electrical equipment shall not be less than the nominal voltage of a circuit to which it is connected.
This is specific for 208 equipment on 240.
Operating 240 equipment on 208 is a violation of 110.3(B)

Motors don't like under voltage or overvoltage. The tolerance of a motor is +/- 10%, so a 200 volt motor on 240, the tolerances is 24 volts, 200+24 = 224.
On overvoltage the magnetic fields become saturated and the motor draws more current.
Click to expand...
 
Tom, From the OP's standpoint, thanks for the clarification.
I did not mean to suggest that he could operate at other than rated voltages, but we have no knowledge of the equipment.. dual rated ? etc.
thus the suggestion "take a real close detailed look"
 
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