gate 2017 EE(Set-B) q43-solution

25kVA,
$$400V,\Delta$$ -connection
$$V_{oc}=360V$$
$$I_{SC}=I_{rated},I_f=5A$$
$$I_L=\frac{25\times10^3}{\sqrt{3}\times 400}=36.084 Amps$$
$$I_{ph}=20.833Amps$$
$$X_s=Z_s=\frac{V_{oc}/phase}{I_{sc}/phase}=\frac{360}{20.833}=17.28\Omega $$
$$E=\sqrt{(Vcos\phi +I_aR_a)^2+(Vsin\phi -I_aX_s)^2}=\sqrt{(400\times0.8+0)^2+(400\times0.6-20.833\times 17.28)^2}$$
$$E_{ph}=341.758 volts$$
$$\%Reg=\frac{341.758-400}{400}=-14.6\%$$
Hint: Obtained regulation should be negative.