×
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

PT / CPT SWAP

PT / CPT SWAP

PT / CPT SWAP

(OP)
Can a PT be used as a CPT? . Iam working on a 42000 volt HV contactor that the cpt is missing.A person said why not use a PT ,We have some 42000 volt 750 VA , 35: 1 ratio.
I thought PTS were used for metering only.

RE: PT / CPT SWAP

PTs are designed to optimize accuracy, not capacity.
CPTs are designed to optimize capacity, not necessarily accuracy.
The ratio may be the same, but the capacity is not. The PT is not meant to have much of a load on it. If you have specs, see if they match what your load requirements are.

RE: PT / CPT SWAP

Quote:

We have some 42000 volt 750 VA
You should be safe as long as the loading does not exceed 750 VA.  

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

RE: PT / CPT SWAP

Hi wirepuller
Usually PT does not supply control circuitry as you already said.
If the contactor is located in an enclosure with other breakers or contactors you may use the local control source as more reliable [provided with reserve supply source] rather than PT.
Control power transformer usually is built for 5-15 KVA .But if you don't need more than 750 VA[ depends on the current required by the control coil of the contactor] it is possible to use PT .The problem is if the 42 KV will fail no control supply source for the contactor will be available.
I think as the PT is built specially for measurement an accuracy class of 3[or more] would be better. For CPT you could see:
http://library.abb.com/global/scot/scot235.nsf/veritydisplay/af157f28b05dde0d85256d9c005dbc70/$File/CPT_Flyer.pdf
Best Regards
 

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