PROBLEM $1$:

The equivalent parameters of a $110$kVA, $2200$V$/110$V transformer, are R$1=0\mathrm{.}22,$ R$2=0\mathrm{.}5$m$,$ X$1=2,$ X$2=5$m$,$ Rc$=5494\mathrm{.}5,$ and Xm$=1099.$ Using the approximate equivalent circuit referred to the primary side, when the transformer is operating at $80\%$ full load with unity power factor determines:

$1.$Voltage regulation.

$2.$The transformer power loss.

$3.$Efficiency$.$