power transformer short circuit impedance voltage

[usamaegypt]

hi,
I would like to know the physical meaning of transformer short circuit impedance voltage written on the name plate of transformer as %
Best regards.

 

[ScottyUK]

Per the IEEE, “impedance voltage” is defined as

“The voltage required to circulate rated current through one of two specified windings of a transformer when the other winding is short-circuited, with the windings connected as for rated voltage operation.” (IEEE C57.12.80)

You might also Google "open circuit test" + transformer and "short circuit test" + transformer.



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

 

[edison123]

or decoding IEEE

If you have a 110 KV/11 KV trafo with 10% impedance, you apply 11 KV on the 110 KV winding with 11 KV winding shorted across the three phases to get 100% rated current on both windings.

 

[rbulsara]

In other words, numerically the impedance voltage is also the impedance of the transformer.

The impedance a transformer is measure by the method described by scottyuk above..

 

[thinker]

Edison123, the rated current should be only through the winding to which a reduced voltage is applied, and not in both windings as you state. Under short circuit conditions the current is limited by a leakage inductance (impedance) which is quantified as a short circuit voltage value.

 

[davidbeach]

thinker, if you have rated current in one winding, why would you not expect to have (close to) rated current in the other winding? Only the current that flows through the excitation branch will cause a difference between primary and secondary currents. The current ratio of the transformer holds regardless of voltage as the Amp*Turns value on the primary must equal the Amp*Turns value on the secondary.