Wiring 277V Lighting

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alittleee

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I realize that 277V is derived from a 3-phase Y transformers' line-line voltage (480V/1.732). So, my way of thinking is that if you draw a 3-phase Y transformer, you would connect your load (in this case lighting) say from a-phase to b-phase. But that is not the case, there are not 2 phases there, there is instead a hot and a neutral. Where did the neutral come from? How is 277V lighting wired? And why is it dangerous to work on energized 277V lighting circuits?
 

iwire

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Location
Massachusetts
I realize that 277V is derived from a 3-phase Y transformers' line-line voltage (480V/1.732). So, my way of thinking is that if you draw a 3-phase Y transformer, you would connect your load (in this case lighting) say from a-phase to b-phase. But that is not the case, there are not 2 phases there, there is instead a hot and a neutral. Where did the neutral come from? How is 277V lighting wired? And why is it dangerous to work on energized 277V lighting circuits?
The source would be 480 Wye not 480 delta and you would have 480 line to line and 277 from any line to neutral.

This is no different than 208Y/120 ..... other than the voltage itself.
 

augie47

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Location
Tennessee
wye_detail1.jpg Attached may help

and
It's dangerous to work on any energized circuits (and a violation except in extreme circumstances)
 

alittleee

Member
sorry

sorry

I am sorry. I was just getting ready to argue with you and I was typing out the "formula" and realized I was thinking just bass ackward. Line voltage is higher than phase voltage in Y connections. Sorry to waste your time. But - it made me think strait by trying to argue with you anyway.
 

augie47

Moderator
Staff member
Location
Tennessee
I am sorry. I was just getting ready to argue with you and I was typing out the "formula" and realized I was thinking just bass ackward. Line voltage is higher than phase voltage in Y connections. Sorry to waste your time. But - it made me think strait by trying to argue with you anyway.
Go ahead and argue ;) ,To quote G B Shaw:

I learned long ago, never to wrestle with a pig. You get dirty, and besides, the pig likes it.
George Bernard Shaw
 
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