How does 480 volt electric convert to 220 or 110 volt?

Question

We are opening a retail store and need to run new electric.  I need some help to figure out exactly what the electricians and contractors are talking about.  

We currently have 480 volt 60 amp electric run into our site.  I believe there is a 100 amp wire even though the box only has 60 amps. 

We need to run a bunch of 208-230 volt 3 phase equipment - between 7 and 10 freezer compressors that require a dedicated 20 amp fuse (each).  There will also be other refrigerator equipment that is single phase, 110 volt, plus lighting and things like that.

I need to determine how much additional electric (480v) we need to run to our site.  So, how does 480 volt covert to 220 or 110?  I know there is a transformer involved, but how does it work?  Will we need two transformers?  

Any info is very helpful.  Thanks in advance.

Anonymous · Accepted Answer

Just touch the 480 voltage with your bare hand.

Kris_B · Answer

The building has a 3 phase 277/480 system.  Each phase is 277 volts to neutral.  Phase to phase is 480 volts.
277 x 1.73 = 480v

A 3 phase transformer would be required to step down the voltage to 120/208v 3 phase
120 x 1.73 = 208v

The 3 phase system once stepped down to 120/208 will be able to run the 120 v refrigerator equipment.

Without knowing the actually amp rating for each unit it is hard to give an accurate answer.
Typical 3phase freezer pulls 12 amps.

I would recommend you paying an electrical engineer to compute the loads and what you should use to do it safely.  Not saying your electrician could not do this but it doesn't hurt to get a second opinion.

Rick · Answer

Hire a qualified contractor.

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How does 480 volt electric convert to 220 or 110 volt?

3 Answers