# Transforming 208Y VAC into 480 VAC



## HARRY304E (Sep 15, 2010)

davidsq said:


> Hi, I have a mechanical engineering background and have practically no experience with transforming power.
> 
> My application: I need to drive a 3-phase, 208-230/460VAC, 3HP motor. The leads are set up in a 9 lead wye configuration. I have 3-phase, 4-wire 208Y/120 VAC power coming in. I am using a motor drive as well that takes in 380-480VAC, 9.6A.
> 
> ...


Read this....http://literature.rockwellautomation.com/idc/groups/literature/documents/wp/150-wp004_-en-p.pdf

Welcome to the forum.:thumbsup:


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## erics37 (May 7, 2009)

davidsq said:


> Hi, I have a mechanical engineering background and have practically no experience with transforming power.
> 
> My application: I need to drive a 3-phase, 208-230/460VAC, 3HP motor. The leads are set up in a 9 lead wye configuration. I have 3-phase, 4-wire 208Y/120 VAC power coming in. I am using a motor drive as well that takes in 380-480VAC, 9.6A.
> 
> ...


Your motor is 3-phase, dual voltage, so you could run it straight off your 208 supply if you wanted. However, if you are supplying it through a drive that requires 480, then the transformer is necessary. The answer to your question is no, the motor won't care where its 3 phases come from as long as they are the proper voltage and phase angle.

There are considerations to take when stepping your voltage up. If you reverse feed your transformer, you'll most likely need to find a way to ground it. If you use the transformer you found in reverse, there is probably no common neutral tap on the 480 side to ground so you'd be stuck either corner-grounding it or running ungrounded, both of which are feasible but can be irritating, and may even have some restrictions against them in some applications. The best thing is to get the right transformer to begin with - a 208 Delta primary 480/277 Wye secondary would be a good deal. Easy to ground on the secondary side.

Another idea is to get rid of the transformer entirely and get a drive designed to run at 208. Your motor current will increase from the 480 volt option so you might need a bigger circuit.


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## davidsq (Feb 12, 2013)

Thanks for your response eric. After countless hours of searching I found a 208delta to 480y transformer that will suit my application perfectly.


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## erics37 (May 7, 2009)

davidsq said:


> Thanks for your response eric. After countless hours of searching I found a 208delta to 480y transformer that will suit my application perfectly.


So getting a different drive isn't an option, huh? That would be my preference over a transformer.


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## JRaef (Mar 23, 2009)

erics37 said:


> So getting a different drive isn't an option, huh? That would be my preference over a transformer.


Yeah, I agree. You are adding losses in the transformer just to be able to use a VFD that is not the right thing for the application. In the long run you could have paid for that 230V class VFD in probably less than a year of added electricity costs on top of the cost of that transformer, added fusing, wire and installation costs. A 3HP 230V class VFD is likely to only cost a few hundred dollars.


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