×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Single Phase or Three Phase
2

Single Phase or Three Phase

Single Phase or Three Phase

(OP)
Could someone please explain to me why when a device is tied into a three phase panel, and is fed with a two pole breaker, why is that device refered to as a single phase 208?  From my understanding, it is drawing from two of the three phases 120 degrees from one another.  Thanks for any assistance.

RE: Single Phase or Three Phase

2
If you have just two wires, the voltage between the two wires is a single value, regardless if the source is one-phase or three-phase. There is no way to determine, by measuring the single voltage, that it originated from 3-phase source. It appears and in fact is one and the same as a voltage from a single-phase source.

If you add a neutral to the circuit, then you could argue that it should be called 2-phase. But 2-phase is usually intended for sources that are 90 degrees out of phase rather than 120 - and is fairly unusual in power systems.

RE: Single Phase or Three Phase

Should'a looked there first...

RE: Single Phase or Three Phase

A phase is not a single conductor or reference point. Phases require two points either usually Line and Line. A 1-phase system has 1 set of L-L conductors, a 3-phase system has 3 possible sets of L-L conductors, and the very rare 2-phase system has 2 sets of L-L.

You probably don't refer to a household range as a 2-phase device even if it is connected to (2) hot conductors. So when describing a single phase transformer, instead of saying "it is drawing from two of the three phases" say it is drawing from 2 of the 3 line conductors and see if it is easier to explain.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources