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Old 06-16-2011, 05:29 PM   #1
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Transformer wiring

I have 3 phase 480 power coming into a new building we are building. 200amp approx.

In this building we are going to use the 480 3 pahse and use a step down to run 1 phase 120/240

We are also going to subfeed the 480 3 ph to another building step down to 1 phase 120/240 for lights and misc.

From the second building we are going to sub feed our office with 100 amp of 120/240 power 1 phase

Each subfeed is about 120 distance from the next building.


Most tranformers I find are 480 primary with a 208/120 secondary on them. The 208 is no use to me.

Do these types of tranformers have two legs of 120 that can make the 240?

How do you get the 240 1 phase?

Do I need a transformer that is 480 primary and 240/120 secondary


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Old 06-16-2011, 07:55 PM   #2
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The transformers that provide 208/120 output are 3 phase transformers.

You need to get a single phase transformer with a 480 input, and 120/240 output ...



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Old 06-17-2011, 11:13 AM   #3
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Main building.Connect 480 volt to 120/240 volt transformertto legs A andB of the 3 phase line. Next building connect another 480 volt to 120/240 volt transformer to legs B and C. Run just legs A and C to the third building (office) and connect up another 480 to 120/240 volt transformer there.
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Last edited by AllanJ; 06-17-2011 at 11:16 AM.
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