boosting from 120 to 277

[scruf]

Is there any such thing as a single phase transformer that you can get 277V (for a lighting circuit) from 120/208 source. Can you get this done with a coulple of buck/boost transformers or is this totally the wrong approach?

The reason for the inquiry is perhaps to save some $ to change out a bunch of expensive 277V 1% dimming ballasts. This is a health care application where I have to put some selcted fluorescent fixtures on a critical branch source that has no 277 within several floors of the main electric room. The load in this case would be real small, around 600VA-1000VA

 

[advidana]

yea: you can boost to 277 from 208 , check with the mfg representative of the buck boost selected. They will help you select the kva and furnish you with a diagram.try seimens, ge, acme, etc. if you are the guy doing the hareware connection then they are a little tricky so be careful not to mix circuits up with other loads. basically it's just an autotransformer and works like a step up coil.
I don't like using them because someone else may try to use the circuit for something else and cause trouble. your best bet is to use a standard step up transformer with a panel board. Because you will find that other loads will crop up in the future that need more 277 volts lighting. buck boost are kind of a work around method for one shot application. most people don't use them because they are odd ball and have cause troubles with mis-applications.

 

[advidana]

I just remembered-code will not allow you to go from 120v to 277V with a buck boost ( it is too great a step up) and I think that the lights from UL are rated 277 (from neutral to 277v) so I don't thnk it is allow. Use a step up transformer with panel board. good luck

 

[busbar]

 
One kVA is about 8½ amperes at 120V and under 4 amps at 277V, and by NEC 450 a transformer with 2-wire primary — 2-wire secondary could be protected by a primary overcurrent device alone.

Typical is

http://www.acmepowerdist.com/pdf/Page 11.pdf

"Group VI".