×
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

Paralleling Transformers

Paralleling Transformers

Paralleling Transformers

(OP)
What are the effects of operating two power transformers of different impedances in parallel?

RE: Paralleling Transformers

If you operate two transformers with different impedance in parallel, (assuming that the transformers are of the same rating) the transformer which has low impedance path will try to carry most of the loads (because current always follows the least impedance path) and the other will carry slightly lesser load. This may be seen as in power system a case of unbalance and chances of circulating current flowing through the transformer is high. The chances of circulating current are high, if the taps of both the transformers are kept in different positions while paralleling.

-nag400

RE: Paralleling Transformers

This is a good response by Nag400.

Paralleling transformer seen to be a hot topic in this forum.

Please see the enclose threads that address similar question:  Thread238-7093 Thread238-16427 Thread238-30275

A related topic could be the phase shifting transformer use to increase the power flow in a paralleling situation. The following thread has good reference Thread238-27103


RE: Paralleling Transformers


A couple of added comments...  If the transformers are not in close proximity, the system’s line-impedance characteristics will affect circulating current also.  

It may be obvious, but circulating currents will present a highly reactive load to the source, and will exist regardless of loading.  
  

RE: Paralleling Transformers

hi govender1,
please put your values (i.e. uk,Sn,S)in to
basic formulas given here under and calculate the loads shared by transformers.Then you will see the effects.

uk = S /((Sn1/uk1)+(Sn2/uk2)) [total imp.of parallel tr's.]
S1 = S*(Sn1/Sn)*(uk/uk1)
S2 = S*(Sn2/Sn)*(uk/uk1)

where;
Sn1;uk1 = rated power;imp.of TR1
Sn2;uk2 = rated power;imp.of TR2
S1,S2   = load shared by TR1,TR2
S       = existing load fed by parallel transformers.
Sn      = Sn1+Sn2






RE: Paralleling Transformers

(OP)
Thanks guys for the valuable information. Note that the transformers are approximately 8m apart will this still create circulating currents. The impedance of the transformers are 7.69% and 8% respectively. Is there an impedance tolerance where paralleling the transformers will not have any negative effects or rather must the impedances be identical?

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