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.

Ohms law is consistent, everything else is variable. Your calculations will be accurate if you follow the rules.

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)?

277 = 480/sqrt(3) -----> Was 460. 480 is correct

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.

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!

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?

Sorry, I mean output.

I know, things get messy with 3 phase power.

Look here:

How does a delta-wye 480/277 volt system work? - Yahoo! Answers (http://answers.yahoo.com/question/index;_ylt=A0LEVIYHaYZKz_MA8eYPxQt.;_ylu=X3oDMTExN GFsN2V0BHNlYwNzcgRwb3MDNwRjb2xvA3JlNAR2dGlkAwRsA1d TMQ--?qid=20090408094923AAjBO5D)

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

Three-phase electric power - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Three-phase_electric_power)

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.

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. Why not just use 277--if we can get more wattage, or voltage amps? I guess install three phase on residential houses id ridiculous!

I know, things get messy with 3 phase power.

Look here:

How does a delta-wye 480/277 volt system work? - Yahoo! Answers (http://answers.yahoo.com/question/index;_ylt=A0LEVIYHaYZKz_MA8eYPxQt.;_ylu=X3oDMTExN GFsN2V0BHNlYwNzcgRwb3MDNwRjb2xvA3JlNAR2dGlkAwRsA1d TMQ--?qid=20090408094923AAjBO5D)

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

Three-phase electric power - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Three-phase_electric_power)
Thanks for the links!

It's rare to have 3 phase for residential, but it does happen. Three phase motors are more efficient and that's usually what happens in commercial. Cooling and heating take motors.

Lighting in commercial spaces is 277 V usually.

Our bi-phase 240 is probably a little safer than other 240 system.

Some countries, like Japan have a 100V system. Usually the frequency is 50 or 60 hz.

It's rare to have 3 phase for residential, but it does happen. Three phase motors are more efficient and that's usually what happens in commercial. Cooling and heating take motors.

Lighting in commercial spaces is 277 V usually.

Our bi-phase 240 is probably a little safer than other 240 system.

Some countries, like Japan have a 100V system. Usually the frequency is 50 or 60 hz.

I see, thanks!!