Answer / 7anoter4

I think it is the active [real] part of the transformer short-
circuit impedance.
Let’s say uk% it is the short-circuit voltage-4-25% percent of
rated voltage supplied at primary terminals when secondary
terminal are short-circuited and the current will be the rated
current. Then the short-circuit impedance Zk=R+jX
=uk%/100*Vrated/sqrt(3)/Irated –for 3 phases transformer. If
we’ll know kxr= X/R [6-40 ] then X=Zk/sqrt(1+1/kxr^2)
and R=X/kxr.

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