120/208, 1Ph, 3 Wire

Status
Not open for further replies.
mivey

mivey

Senior Member
MAC702 said:
If you describe it has having two "lines" present, then it's easy to describe it as a single phase between the lines.
Click to expand...
The line-line voltage was covered in my post as there only being a single phase present.

Each line-neutral voltage peaks at a different time (each has a different phase position at a single instant in time). Two phase positions are present in the line-neutral voltage system at a single instant in time. However, it is not labeled as the "two-phase" system because the phase difference is 120 degrees instead of 90 degrees (quadrature displacement) and the "two-phase" system label is reserved for a quadrature system.

edited typo and clarification
 
Last edited:
mivey

mivey

Senior Member
MAC702 said:
Exactly. It has four lines/poles, with two phases: one between each pair.
Click to expand...
With four lines and the neutral you have four unique pairings/voltages of the same magnitude. Four line-line voltages in one system, and four line-neutral voltages in another system of equal magnitude voltages.

With three lines you have three unique pairings/voltages of the same magnitude. Three line-line in one grouping and three line-neutral in another grouping.

Consider again the 5-wire two-phase system. There are actually four phases present and is noted in engineering references to be more accurately described as a four-phase system. Still gets the "two-phase" label.

Set that aside for a moment and consider the two-phase system where you only have two ungrounded lines of the 5-wire two-phase system: looks like an even "L" or corner. Two lines and one neutral. Here you only have one line-line voltage but it is still labeled a two-phase system. It also has two line-neutral phases.

Now look a the OP system where you also have two lines and one neutral but a different phase separation. It is labeled a network system but is also commonly called a single-phase system. Just like the two-phase system you have one line-line voltage and two line-neutral voltages. The only difference is a 120 degree difference vs. a 90 degree difference.

Think about it: the same number of voltages but a slight difference in phase separation. One is called two-phase and one is called single-phase.

So I'll repeat it once again: the label does not always accurately describe the physical system. It is just a label.
 
S

Skokian

Member
Location
Skokie, Illinois
Single or three Phase.

Single or three Phase.

This sounds like a 120/208 Vac Open Delta. E.g.: 208 Vac line to line and 120 Vac line to neutral. You would measure 120 Vac from either line to neutral if I have this figured out correctly.

The nameplate is not very clear IMHO.
 
ActionDave

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min from the winged horses.
Occupation
Licensed Electrician
Skokian said:
This sounds like a 120/208 Vac Open Delta. E.g.: 208 Vac line to line and 120 Vac line to neutral. You would measure 120 Vac from either line to neutral if I have this figured out correctly.

The nameplate is not very clear IMHO.
Click to expand...
There is no 208V open delta or closed. There is a 240V delta with a high leg of 208V.

The nameplate is perfectly clear, it's two legs of a Wye system, 208V line to line, 120V line to ground.
 
kwired

kwired

Electron manager
Location
NE Nebraska
ActionDave said:
There is no 208V open delta or closed. There is a 240V delta with a high leg of 208V.

The nameplate is perfectly clear, it's two legs of a Wye system, 208V line to line, 120V line to ground.
Click to expand...

Though I was thinking sort of same thing when I read that, it is possible but not common at all to have 208 volts delta. If you did have such a system and grounded mid point of one phase you would have 104 volts to two corners and have a high leg of 180 volts.
 
jumper

jumper

Senior Member
Location
3 Hr 2 Min from Winged Horses
kwired said:
Though I was thinking sort of same thing when I read that, it is possible but not common at all to have 208 volts delta. If you did have such a system and grounded mid point of one phase you would have 104 volts to two corners and have a high leg of 180 volts.
Click to expand...

Have you ever seen, heard, or even imagined such a system in the US?:roll:

A 208D/104V supply............

Maybe in some Frankenstein lab perhaps.:D
 
ActionDave

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min from the winged horses.
Occupation
Licensed Electrician
kwired said:
Though I was thinking sort of same thing when I read that, it is possible but not common at all to have 208 volts delta. If you did have such a system and grounded mid point of one phase you would have 104 volts to two corners and have a high leg of 180 volts.
Click to expand...
But you wouldn't have 120V to neutral and it wouldn't be part of a standard power system.
 
Status
Not open for further replies.
Top