Impedance Voltage 3

[siberhusky]

If a transformer test report, etc. references an "impedance voltage" in "%", then are they really giving you the impedance? [My understanding is that the impedance voltage is the voltage used during the short circuit test which causes the full load current to circulate; and that the impedance is then calculated via the ratio of this value and the "rated voltage".]

thx,

- john

 

[DanDel]

The percent of the rated voltage used during the short circuit test which causes the full load current to circulate is equal to the percent impedance.

 

[busbar]

You have the gist of it. See IEEE C57.12.90 if you need a formal reference.

 

[mvcjr]

Impedance voltage (in p.u.) is the voltage required to overcome the transformer impedance and cause rated current to flow.

ImpedanceVoltage (in p.u.) = (RatedCurrent * Z)/RatedVoltage

thus,

Z (ohms) = (RatedVoltage * ImpedanceVoltage)/RatedCurrent