×
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

Transformer Impedance and voltage drop

Transformer Impedance and voltage drop

Transformer Impedance and voltage drop

(OP)
I am trying to calculate voltage drop on my transformer...
Primary voltage 16000V ,Secondary voltage 120/240
TX= 100 KVA %z=3.3 1phase

Can anyone help me how to calculate voltage drop on transformer.
The result of my calculation is given me 3.28% voltage drop, However my Supervisor has Voltage drop on Xfmr at 5.26%



RE: Transformer Impedance and voltage drop

At full load secondary current, the voltage drop is equal to the transformer impedance rating. That's how percent systems representation works. Your answer is closest.

xnuke
"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

RE: Transformer Impedance and voltage drop

Why not ask him?

It looks like he is either adding cable impedance - or he is calculating voltage drop for a much higher load. There is something said about 230 kVA just above the 5.26%

Are you interpreting the task correctly? Or is it your supervisor that hasn't?

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Transformer Impedance and voltage drop

The voltage drop depends on the R/X ratio of the transformer and on the power factor of the load. Your answer is closer.

RE: Transformer Impedance and voltage drop

To expand on bacon's post;
The transformer impedance is comprised of the transformer internal resistance and the transformer inductive reactance.
For voltage drop, use the transformer % regulation at the appropriate power factor. It will be less than the % impedance.
For loads of high power factor the transformer internal resistance predominates.
You must know either the transformer % regulation or the X/R ratio to calculate the voltage drop under normal loads.
The % impedance is only valid for short circuit calculations where the transformer impedance is the only impedance in the circuit.

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

RE: Transformer Impedance and voltage drop

(OP)
My supervisor is not here at the moment , and he is using special calculator.
So base on this information :
Primary voltage 16000V ,Secondary voltage 120/240
TX= 100 KVA %z=3.3 x/R=3.1
Do you guys get 3.28% voltage drop as well?
This is only voltage drop on Transformer...
Thank you

RE: Transformer Impedance and voltage drop

That calculator shows the voltage drop for a 100 KVA transformer with a 230.52 KVA load.
That's 230.52% of full load current. Is this for calculating voltage dip during motor starting?
If you convert your supervisors figure to 100% loading it comes out as 2.28% voltage drop under full load.
That is probably correct at some power factor.
The voltage drop calculated by % impedance times rated voltage is a directed value. It is predominantly inductive. It can not be subtracted numerically from the rated voltage. It must be considered as a vector.

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

RE: Transformer Impedance and voltage drop

Is the 230kva a value taking advantage of a transformer's overload ability? I somehow have the feeling (though I could be wrong), your supervisor is interested about what the voltage drop will be above the nameplate kva rating.

RE: Transformer Impedance and voltage drop

(OP)
Yes Waroos, this calculation is for voltage drop on initial stage .
There are loads attached to Transformer , But I don't know Which Kva he used! 100kva or 230KVa.
I am getting only 3.6% on transformer . I believe I am using either wrong voltage or Kva..

RE: Transformer Impedance and voltage drop

(OP)
I think you are right Mbrooke. He might done it opposite way.
He has from
TX-------------------Point A Cable-----------------------point B cable.
5.26% --------- 1.26%dropA + 5.26------------- 2% drop on cableB + 5.26
Voltage drop--------=6.52% Total drop on point A---------=7.26%

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