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# Single Phase and Three Phase Voltages

#1
07-28-06, 08:14 PM
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Join Date: Mar 2006
Posts: 58
Single Phase and Three Phase Voltages

OK, I think I am close but not there yet in terms of understanding the various voltages available for single phase and three phase. I had people explain it to me with pictures. I can not draw the prictures, but can provide the voltages and wonder if I am missing any or have some wrong:

Single Phase Voltage Possibilities:
1. 120/240 volt (line to ground, line to line)
2. 240/480 volt (line to ground, line to line)
3. 240/208 volt (2 lines tied together to ground, line to line for the two lines tied together)
4. 277/480 volt (line to ground, line to line)

No more options for single phase available for the USA, although I understand you can tap a transformer for 115, 110, 130 volts or something like that if you need a little more or less volts for your equipment.

Three Phase Voltage Possibilities:
1. 277/480 volts (line to ground, line to line)
2. 120/208 volts (line to ground, line to line)
3. 120/240 volts (line to ground, line to line)

No more options for three phase available for the USA, although I understand you can tap a transformer for 490, 110, 130 volts or something like that if you need a little more or less volts for your equipment.

#2
07-28-06, 08:59 PM
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Very good start... Research some more'

Check into the differences between Delta and WYE.

#3
07-28-06, 09:07 PM
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Join Date: Jun 2004
Location: USA
Posts: 9
Originally Posted by eeee
OK, I think I am close but not there yet in terms of understanding the various voltages available for single phase and three phase. I had people explain it to me with pictures. I can not draw the prictures, but can provide the voltages and wonder if I am missing any or have some wrong:

Single Phase Voltage Possibilities:
1. 120/240 volt (line to ground, line to line)
2. 240/480 volt (line to ground, line to line)
3. 240/208 volt (2 lines tied together to ground, line to line for the two lines tied together)
4. 277/480 volt (line to ground, line to line)

No more options for single phase available for the USA, although I understand you can tap a transformer for 115, 110, 130 volts or something like that if you need a little more or less volts for your equipment.

Three Phase Voltage Possibilities:
1. 277/480 volts (line to ground, line to line)
2. 120/208 volts (line to ground, line to line)
3. 120/240 volts (line to ground, line to line)

No more options for three phase available for the USA, although I understand you can tap a transformer for 490, 110, 130 volts or something like that if you need a little more or less volts for your equipment.
yes you are really close but like you said no there yet
i'm not sure about this one " 3. 240/208 volt (2 lines tied together to ground, line to line for the two lines tied together)"
someting doesn't sound right in there !!!

yes you could tap the transformer(maybe not a good idea)

#4
07-28-06, 09:22 PM
Member
Join Date: Mar 2006
Posts: 58
Voltage Differences

Indeed, I overlooked the delta 3 phase connection in my presentation and beleive I only presented the 3 phase wye. I have a right up on the differences between delta and wye I got off the net and will reread it. I know the delta can be corner grounded, have a open leg, etc. I can't remember all the details.

Seems like the delta was a straight 480 volts as one option. There is no phase to nuetral since there is no nuetral, but there is a ground. I think it also comes in a straignt 240volt flavor and maybe some others, can't remember, but will check.

#5
07-28-06, 09:27 PM
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Join Date: Apr 2006
Location: USA
Posts: 133
Originally Posted by eeee
Indeed, I overlooked the delta 3 phase connection in my presentation and beleive I only presented the 3 phase wye. I have a right up on the differences between delta and wye I got off the net and will reread it. I know the delta can be corner grounded, have a open leg, etc. I can't remember all the details.

Seems like the delta was a straight 480 volts as one option. There is no phase to nuetral since there is no nuetral, but there is a ground. I think it also comes in a straignt 240volt flavor and maybe some others, can't remember, but will check.
Please do not try to work with any of this. You don't have a clue as to what you are doing. This is not a game. You can be killed. This is for a licensed electrician. Not a home owner.

#6
07-29-06, 09:07 AM
Member
Join Date: Mar 2006
Posts: 58
Voltages

Electrilee,

You seemed to not be sure about 3., the single phase connection where two hot legs are tied together yielding the 208volts line to line and 240 volts line to ground. A Master Electrician who is manager of a whole lot of electricians told me this I believe it was. He has been an electrician for 40 years. There may be an application for this single phase connection; I don't know maybe some sort of street light has a tap on it's ballast that reqiures 208volt single phase line to line?

#7
07-29-06, 10:34 AM
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Join Date: Apr 2006
Location: New Bern, NC
Posts: 1,623
208 v line to line is from a wye transformer. three phase
240 v line to line is from a delta transformer. three phase

240 v line to line can also be from a single phase transformer

The only way to get 240v line to ground is with a center tap delta. this cannot be explained without diagrams. It is rare.

#8
07-29-06, 10:15 PM
Member
Join Date: Mar 2006
Posts: 58
voltages

jwhite,

Are you telling me I can not have single phase 240 volt line to ground leaving 480 volts line to line?

If your pole mounted single phase transformer steps down from a 12,470 volt primary to 240 volts line to ground rather than 120 volts line to ground, then you have 240 line to ground/480 line to line (between the two legs) single phase at your panelboad correct?

I was writing this down straight from the electricians and maybe copying it from their board.

Thanks,

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