A $15$ KVA, $1710/380-$V$,60$ Hz $,$ single$-$phase conventional transformer is supplying

$12$ KW power to a load at $0\mathrm{.}8$ Lagging power factor, and a load voltage of $380$ Volts.

If $I_S=39\mathrm{.}5L-36\mathrm{.}87$ Amperes, and $V_s=3800$ Volts, Calculate the following:

The Voltage Regulation is: $\%$VR $=\%.$

The output power $P_{\text{o}\text{u}\text{t}}=$ Watt.

The Copper Losses $P_{cu}=$ Watt.

The Core Losses

$P_{\text{c}\text{o}\text{r}\text{e}}=$ Watt.

The efficiency of the transformer is $\%=\%.$