×
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

Phase-to-neutral voltage Uo calculation

Phase-to-neutral voltage Uo calculation

Phase-to-neutral voltage Uo calculation

(OP)
Hi,

Could anyone please let me know how to calculate the phase-to-neutral voltage for a single phase circuit and a two phase circuit? Is it the same as for a 3-phase one, i.e. Uo=U/sqrt(3)?

Many thanks,

RE: Phase-to-neutral voltage Uo calculation

Hi Mariaki,

It depends on the configuration of the source.

If your single-phase circuit is made of two phases of a three-phase wye system, your calculation is correct.

If your single-phase circuit originates from two ends of a single-phase transformer with a center tap, the phase-to-neutral voltage will be half the phase voltage.

It would help to get a definite answer if you could post a diagram or describe your source in detail.

Good on ya,

Goober Dave

RE: Phase-to-neutral voltage Uo calculation

(OP)
Hi Dave,

My question refers to the phase-to-neutral voltage for a 2 phase 500V power cable. I was also wondering what this would be for a single phase cable of 500V.

Hope this is more helpful.  

Many thanks,


 

RE: Phase-to-neutral voltage Uo calculation

A true two phase supply with the phases in quadrature? Or two phases from a three-phase group with a 120° phase displacement?
 
  

----------------------------------
  
If we learn from our mistakes I'm getting a great education!
 

RE: Phase-to-neutral voltage Uo calculation

(OP)
Hi,

It is a two phase supply cable, not one from a three-phase group.  

RE: Phase-to-neutral voltage Uo calculation

What does this supposed "two phase" cable connect to?  What is the source.  True two phase is practically non-existent.  Two phases from a three phase source is vastly more common.

RE: Phase-to-neutral voltage Uo calculation

(OP)
I believe it's connected to a three phase source.
Thanks in advance

 

RE: Phase-to-neutral voltage Uo calculation

For a true two phase system the line-neutral voltage will be Vline/√2.

I agree with David - there's not much 2-phase stuff left. I think there was some in the outlying parts of north-east England but even that might have gone by now.
  

----------------------------------
  
If we learn from our mistakes I'm getting a great education!
 

RE: Phase-to-neutral voltage Uo calculation

(OP)
thanks for this! Actually it is a cable within an umbilical powering a motor, if this makes more sense. I have not been given the exact source type though. However, the umbilical contains 3-phase cables as well so I would assume all cables should be powered from the same source. I've read about the Scott transformer, used to supply 2-phases from 3-phases. In that case, should I divide with the transformer ratio, i.e. 0.5*sqrt(3) (http://en.wikipedia.org/wiki/Scott_connection)?

RE: Phase-to-neutral voltage Uo calculation

I can think of three possible configurations from your description.
The term ground is often used to indicate neutral. Are you using the term neutral to indicate ground?
My best guess is that you have a single phase circuit fed from two phases. You don't have a neutral but the voltage to ground of either line MAY be (Line to line Voltage/Root Three)
or, for 500 Volts, 289 Volts.

Bill
--------------------
"Why not the best?"
Jimmy Carter

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