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Computing amps (220v 3 phase) from 250 amp, 400 v equipment

Computing amps (220v 3 phase) from 250 amp, 400 v equipment

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  #1  
Old 11-14-14, 12:04 PM
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Computing amps (220v 3 phase) from 250 amp, 400 v equipment

Hello, first time poster here. I have a quick question regarding converting from European voltage to US voltage.

The equipment is wired for 250 amp 400 volt service. I need to know how many amps that would pull after using a transformer to step it down to 220v 3 Phase.

If I use the general equation Watts = Volts X Amps I get 100,000 watts. If I plug that number into the equation using 220v I get 454.5 amps (100,000/220 = amps), which seems like far too much.

Is there a different equation for this conversion?


Thanks in advance
 
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  #2  
Old 11-14-14, 12:12 PM
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Yes, there are different equations used with three-phase. I don't often work with three-phase so I have to look it up every time but it involves multipliers which include the following numbers. 1.41, 0.707 and 1.73 I honestly don't remember which you use or where you use it. It also depends upon the transformer connection you use.

One of the commercial electricians should be able to answer the question but it could be a few hours to even a couple of days for them to respond.
 
  #3  
Old 11-14-14, 02:17 PM
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So the scenario is you want to operate the equipment at 400V 3P from a 220V 3P (odd) service, using a transformer?
 
  #4  
Old 11-14-14, 05:29 PM
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What kind of equipment is this?
If it was designed to run at 400V, you may not be able to successfully use it at 220V.
And if you're talking 3 phase, you will likely be looking at running it at 208V.
 
  #5  
Old 11-14-14, 05:43 PM
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Sounds like European equipment. UK voltage 415VAC + 6% and - 10% and European is 380VAC +10% and -6%
 
  #6  
Old 11-14-14, 08:13 PM
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There are too many things to remember already so I don't worry about trying to remember formulas. I just use this site to select the formula I need.

Reliance - Formulas & Calculations
 
  #7  
Old 11-14-14, 08:58 PM
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Lots of useful formulas there.... thanks Joe.
 
  #8  
Old 11-14-14, 09:25 PM
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Joe,
I think the formula the OP is thinking of is for output voltage when wiring in delta and wye configurations.
 
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