# CT transformer Burden formula transposition?

#### stinky111

Joined Apr 7, 2011
39
Hi guys,

stuck on one final question revising for a transformers final..

A CT has a 25VA Burden rating. The connected ammeter requires 4A for full scale deflection. What is the maximum allowable impediance??

The only burden formula I have in my notes is: Burden = I2Z (VA)

Im very average on formula transposition, obviously I must need to transpose above formula to allow me to find maximum allowable impediance..

#### t_n_k

Joined Mar 6, 2009
5,455
That formula

Burden=I^2Z [VA]

will do just fine.

So make Z the subject of the equation and you will hopefully have the correct solution.

#### stinky111

Joined Apr 7, 2011
39
That formula

Burden=I^2Z [VA]

will do just fine.

So make Z the subject of the equation and you will hopefully have the correct solution.
Would it be Z=I^2/VA???
Thx

#### t_n_k

Joined Mar 6, 2009
5,455

#### stinky111

Joined Apr 7, 2011
39
Try

Z=burden[VA]/I^2

....
Thx very much yet again for your time Last edited: