Have an application that requires 277VAC, but only have 480VAC. I know I can get 277VAC by going from one leg to ground. Is this appropriate? Do I need a transformer? What happens if ground is lost - or do I need to worry about ground lost?

 

You should NEVER use Earth Ground as a circuit conductor, for mains power, anyway.
If by one leg to ground you really mean neutral, and it is a valid neutral as per the electrical code then it would be OK, e.g. a transformer star point has been earth grounded at the transformer, and a separate conductor set up as the neutral.
Ensure the total load connected to your supply is not sufficient to unbalance the other phases.
Max.

 

You should hire a competent electrician ASAP.

 

Presumably your 480V AC is a 3-phase supply and you are considering using the voltage from one phase terminal to neutral?

 

Presumably your 480V AC is a 3-phase supply and you are considering using the voltage from one phase terminal to neutral?

Yes, this is correct. Wondering where I get a valid neutral. Normal installations that I see have three phases and a ground. Or - am I missing that they all have a neutral? Or - is the neutral not being brought to me?

 

You have to understand the difference between "ground" and "neutral", then go look at the wires, maybe even verify with a volt meter, to see if a neutral is provided. We can't see it from here, so you have to do it. And be really careful! This kind of voltage will blow your fingers off and turn a Harbor Freight voltmeter into a ball of flames.

 

Yes, this is correct. Wondering where I get a valid neutral. Normal installations that I see have three phases and a ground. Or - am I missing that they all have a neutral? Or - is the neutral not being brought to me?

Are you in N.A.?
If you have three 3 phase conductors and a ground, it would most likely mean that the Neutral point has been Earth grounded, but if this is the case, you cannot use this as a conductor, a separate neutral would have to be ran from this star point or ground point origin.
You need to determine exactly what the supply consists of to progress any further.
Max.

 

480 3 phase with a WYE connection will have a neutral, 480 DELTA does not have a neutral. You need to find out which you have. On some service panels, if you open the door there is a placard stating whether it's delta or wye.

Failing that, the removal of the panel cover, by someone qualified, will reveal a neutral if there is one there.

 

I am in North America. Is 480V Wye uncommon in North America - Michigan? I understand the difference between ground and common also - essentially that's why I'm asking the question. Thanks for your help on this.

 

I am in North America. Is 480V Wye uncommon in North America - Michigan? I understand the difference between ground and common also - essentially that's why I'm asking the question. Thanks for your help on this.

WYE is very common. Where I worked last we had 480 WYE and used 277 volts for all the plant lighting. Where I work now we have 208 WYE, if anything I have seen less DELTA connections.

edit: did you check the panel for the specs?