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AssuredElectrical, Master Electrician
Category: Electrical
Satisfied Customers: 4241
Experience:  Contractor-42+ Years in the ElectricalTrade
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I have a 3 phase 480v 400amp feed coming into my shop, I want

Customer Question

I have a 3 phase 480v 400amp feed coming into my shop, I want to install a transformer and step the power down to single phase 120/240v 200amp.
Would stepping the power down increase the available amps on the secondary side?
Basically does 200amps at 480v still equal 200amps at 120v? Or would the amps increase with the drop in the lower voltage? I was told that if i step the power down I can actually get more amps than what is actually supplied on the primary side of the transformer.
Submitted: 2 years ago.
Category: Electrical
Expert:  AssuredElectrical replied 2 years ago.
Welcome. My name is ***** ***** would be glad to assist.You are correct with the assumption on the situation.The transformer for a 480/120-240 at 200 amp would be a 50 KVA in size.The transformer would pull approx 104 amps on the primary 480 volt side and output 208 amps on the 120/240 volt side.The voltage being higher on the feed is the difference, the higher the voltage, the lower the amperage used on the same load.Watts/Volts = ampsSo, install the 200 amp 50 KVA transformer and you will have only 100 amps of load added tot he 480 volt side of the service.Let me know anything further needed, Thanks