# Calculate using 277v

How do you calculate wattage for 277v's?
Is it the same as 277(15A)=4155 watts (If the amps is 15)
If so, does this mean if I wanted to supply 150w (output) HID light fixtures that are 277v, I could supply 28 lights using a 15 amp circuit?

Just learning, not thinking of doing 3phase, but curious.

Also, where does 277 come from?
What with all the voltages (120, 240, 208, 240, 277, 480... I even seen 380?? )

Sorry for all the questions. My main question is the first one.

 Missouri Bound Posts: 1,301, Reputation: 393 Ultra Member #2 Aug 14, 2009, 08:54 PM
Ohms law is consistent, everything else is variable. Your calculations will be accurate if you follow the rules.
 Learning101 Posts: 8, Reputation: 1 New Member #3 Aug 14, 2009, 09:00 PM
Quote:
 Originally Posted by Missouri Bound Ohms law is consistent, everything else is variable. Your calculations will be accurate if you follow the rules.
Really! That's interesting. Looks like you get more out of three phase than single. May be best to have everything 3 phase!

Another question: How do you get 277 from a 3 phase transformer. I still don't get it. I know 120(1.732)=207.84 or 208V. But where does 277 come from (line to neutral)?
 KISS Posts: 12,620, Reputation: 4388 Uber Member #4 Aug 14, 2009, 09:04 PM

277 = 480/sqrt(3) -----> Was 460. 480 is correct
 Missouri Bound Posts: 1,301, Reputation: 393 Ultra Member #5 Aug 14, 2009, 09:07 PM
One thing to keep in mind with high intensity ballasted lamps... the ballasts consume energy as well, in addition to the lamp wattage. All ballasts (or fixtures) have amperage information on them. A 150 watt fixture may very well consume 200 watts. You need to check the fixture for this information when doing your calculations.
 Learning101 Posts: 8, Reputation: 1 New Member #6 Aug 14, 2009, 09:09 PM
Quote:
 Originally Posted by KeepItSimpleStupid 277 = 460/sqrt(3)
That comes to 265.58
I just tried 480/1.732, and it came to 277.
Still doesn't make sense On why 277? Lost!
 Learning101 Posts: 8, Reputation: 1 New Member #7 Aug 14, 2009, 09:12 PM
Quote:
 Originally Posted by Missouri Bound One thing to keep in mind with high intensity ballasted lamps....the ballasts consume energy as well, in addition to the lamp wattage. All ballasts (or fixtures) have amperage information on them. A 150 watt fixture may very well consume 200 watts. You need to check the fixture for this information when doing your calculations.
I see! I was told (Dad--is an electrician. He has me researching, so I can have a better understanding of my venture) you could use input to calculate HID's?
 Learning101 Posts: 8, Reputation: 1 New Member #8 Aug 14, 2009, 09:14 PM

Sorry, I mean output.
 KISS Posts: 12,620, Reputation: 4388 Uber Member #9 Aug 15, 2009, 02:03 AM

I know, things get messy with 3 phase power.

Look here:

How does a delta-wye 480/277 volt system work? - Yahoo! Answers

Particularly look at reference 2 at the bottom of the page:

Three-phase electric power - Wikipedia, the free encyclopedia
 KISS Posts: 12,620, Reputation: 4388 Uber Member #10 Aug 15, 2009, 11:00 AM

Basically there are two electrical ways to utilize 3 phase power. One being Wye (Y) and Delta. In the Y mode, the phase to phase voltage is 208 volts and phase to neutral is 120V or 208/sqrt(3).
The neutral is the center point or 0 volts in the system.

Similarly the 480/277 comes from the similar case where 480 gets replaced by 208 V and 277 gets replaced by 120V.

277 and 120 V are a phase to neutral voltages. Whereas 480 and 208 are phase to phase voltages.

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