Is it possible to step up a single phase transformer?

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Solidsnake646

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Denver, CO
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Master Electrician
My project is requiring a 200A service to go up the side of a mountain, and the engineer wants a step up transformer (208 to 480 single phase 50kva) set at the bottom of the mountain and a step down (480-240 single phase 50kva.) My question is, is it possible to step up a single phase transformer? I have been trying to simulate it with a single phase transformer in my shop but have only been able to get 456v on the secondary. I would appreciate any help. Thanks!
 
A common single phase transformer would be 240 to 480. If you are supplying with 208 you will get the same % drop as you see. If the transformer has taps you might be able to adjust the voltage some
 
How were you running the test? Have you considered converting a 3-phase transformer to 1-phase for the step up side?
 
Also these step up step down schemes are often a poor choice. Rarely do people do a fair analysis of these. Make sure the $600/yr in no load losses and the voltage drop of the transformers are taken into account. Unless you are around 2000 feet or more, it likely won't be worth it over just running larger wire.
 
Solidsnake646 said:
My project is requiring a 200A service to go up the side of a mountain, and the engineer wants a step up transformer (208 to 480 single phase 50kva) set at the bottom of the mountain and a step down (480-240 single phase 50kva.) My question is, is it possible to step up a single phase transformer? I have been trying to simulate it with a single phase transformer in my shop but have only been able to get 456v on the secondary. I would appreciate any help. Thanks!
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Make sure your 'engineer' has included long term core loss power in his trades!

Our poco will run the primary up the side of a mountain. Poco pulls primary in the 2-1/2 or 2" pvc conduit that YOU supply buried 42 in deep. You also pay for buried vaults every 400 feet and obviously pay for the 200 A service and meter box. Overall costs come to over 20 bucks a foot, took a BIG jump (nearly doubled - thanks Joe) a couple years ago. Also, any small bridges over streams, etc require RMC for that section.

Depending on power cost in your area, the core losses 24/7 of 2 vs one transformer, with YOU vs poco paying for core losses makes the 2 240/480 transformer solution a bad option over the long term, and power prices will only go UP.

PS: +1 Electro posted 'Rarely do people do a fair analysis of these" while I was typing
 
I done one similar a couple of years ago, idle current was las than an amp. Our kw rates are not bad. The payoff having the poco run a line that distance would be decades, unless you live where the rates are ridiculously high like California. Ground the center tap on the 480 volt side, less stress on the direct burial than grounding one leg.
 
Solidsnake646 said:
My project is requiring a 200A service to go up the side of a mountain, and the engineer wants a step up transformer (208 to 480 single phase 50kva) set at the bottom of the mountain and a step down (480-240 single phase 50kva.) My question is, is it possible to step up a single phase transformer? I have been trying to simulate it with a single phase transformer in my shop but have only been able to get 456v on the secondary. I would appreciate any help. Thanks!
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To answer your question: Yes, any AC voltage can be stepped up or down with a transformer - single phase or multiphase, it doesn't matter. Whether it would be practical or not is another question entirely.
 
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