Okay, there still seems to be some "corn"fusion out there about typical single phase and three phase AC power systems so heres a summary of typical installations:
1) TYPICAL HOUSEHOLD
Thats 120/240 Volt Single Phase Three Wire
Its a single transformer thats tapped in its
center. Its has 120 volt from EITHER outside
leg L1 or L2 to Neutral but 240 Line to
Line. Out at the transformer PLUS at the
service entrance, the Neutral is tied to
Mother Earth, a GroundING Electrode.
2) A TYPICAL COMMERCIAL SERVICE that uses
mostly 120 volt but has some 208 3 phase
HVAC requirement.
Thats a 208 Y 120 Volt Three Phase FOUR Wire
It has three legs of single phase 120 volt
ANY leg to Neutral is 120 but its 208 line
to line. The 208 three phase can be used to
run smaller HVAC loads. Its a Grounded system
3) A TYPICAL OLDER INDUSTRIAL PLANT with lots of heavy three phase or single phase 240 or 480 equipment and a small amount of 120
May be a 240 or 480 Volt Three Phase Three
Wire DELTA. It can serve 240 or 480 single
or three phase equipment. Generally it floats
its NOT a grounded system!!!!!!! In later
years we used them less and less as we
preferred a grounded system
If the utility didnt give us a 120/240 then we
used dry transformers to get it.
4) AN INDUSTRIAL PLANT with lots of 240 single
or three phase and a small amount of 120
That could be the 120/240 volt Three Phase
FOUR Wire center tapped DELTA.
It has three legs of 240 single phase and
240 volt three phase and can supply 120.
It has two legs of 120 to Neutral (via the
center tapped transformer) but the red/high
leg is 208 to Neutral (NOT used)
There are OTHER systems including open deltas etc but in all my years we didnt get into them. I forgot, sometime we used a 480 Y 277 Volt Three Phase Four Wire for heavy 40 3 phase HVAC and we used the 277 for lights. Of course, dry transformers for 120 as needed. Our Primary was 12470 Y 7200 Three Phase Four Wire. NOTE how as above, 12470 = 7200 x square root of 3.
Nuff said, got it?? Any questions??
John T toooooo long retired Electrical Engineer this stuff is gettin more stale alll the time lol SO AS ALWAYS NO FREAKIN WARRANTY
1) TYPICAL HOUSEHOLD
Thats 120/240 Volt Single Phase Three Wire
Its a single transformer thats tapped in its
center. Its has 120 volt from EITHER outside
leg L1 or L2 to Neutral but 240 Line to
Line. Out at the transformer PLUS at the
service entrance, the Neutral is tied to
Mother Earth, a GroundING Electrode.
2) A TYPICAL COMMERCIAL SERVICE that uses
mostly 120 volt but has some 208 3 phase
HVAC requirement.
Thats a 208 Y 120 Volt Three Phase FOUR Wire
It has three legs of single phase 120 volt
ANY leg to Neutral is 120 but its 208 line
to line. The 208 three phase can be used to
run smaller HVAC loads. Its a Grounded system
3) A TYPICAL OLDER INDUSTRIAL PLANT with lots of heavy three phase or single phase 240 or 480 equipment and a small amount of 120
May be a 240 or 480 Volt Three Phase Three
Wire DELTA. It can serve 240 or 480 single
or three phase equipment. Generally it floats
its NOT a grounded system!!!!!!! In later
years we used them less and less as we
preferred a grounded system
If the utility didnt give us a 120/240 then we
used dry transformers to get it.
4) AN INDUSTRIAL PLANT with lots of 240 single
or three phase and a small amount of 120
That could be the 120/240 volt Three Phase
FOUR Wire center tapped DELTA.
It has three legs of 240 single phase and
240 volt three phase and can supply 120.
It has two legs of 120 to Neutral (via the
center tapped transformer) but the red/high
leg is 208 to Neutral (NOT used)
There are OTHER systems including open deltas etc but in all my years we didnt get into them. I forgot, sometime we used a 480 Y 277 Volt Three Phase Four Wire for heavy 40 3 phase HVAC and we used the 277 for lights. Of course, dry transformers for 120 as needed. Our Primary was 12470 Y 7200 Three Phase Four Wire. NOTE how as above, 12470 = 7200 x square root of 3.
Nuff said, got it?? Any questions??
John T toooooo long retired Electrical Engineer this stuff is gettin more stale alll the time lol SO AS ALWAYS NO FREAKIN WARRANTY