per unit impedance values of a transformer
per unit impedance values of a transformer
(OP)
how do you calculate the per unit impedance value of a transformer given the percentage impedance value? How do you also estimate the per unit vales of resistance and reactance from the percentage impedance value?






RE: per unit impedance values of a transformer
So, if you have 5.6 % that will be equal to 0.056 p.u.
The impedance of a power transformer (10+ kVA) is almost purely reactive. You can safely assume close to 90 degrees impedance. If you need better values, you have to ask the manufacturer for data,
Gunnar Englund
www.gke.org
RE: per unit impedance values of a transformer
You can calculate %R from the load (copper) losses divided by the rating times 100. %X is sqrt(%Z²-%R²).
RE: per unit impedance values of a transformer
Gunnar Englund
www.gke.org
RE: per unit impedance values of a transformer
RE: per unit impedance values of a transformer
%impedance means, the ratio of impedance voltage drop at full load to the normal voltage, when multiplied by 100.
Let us take LV side of the trafo as base values,
%Z= I Z ÷ V, where Z is actual impedance or leakage impedance referred to LV side, and V & I are rated values of LV side.
then,
Z = %Z V ÷ I --- referred to LV side of trafo
%R = Full Load Cu losses ÷ trafo rating in VA ,
(R = Full Load Cu losses /I*I - ref to LV)
%X = sqrt {%Z*%Z - %R*%R}
P.U. impedance = % impednace / 100
or
actual impedance / base impedance.
Where, base impedance = V / I (rated values of base side i.e LV side )
or
KV* KV*1000 / KVA, ( where KV is LV side voltage).
hope this help you.
Varri
RE: per unit impedance values of a transformer
X~Z ==> R~Z/(X/R)