Question

A salient –pole synchronous generator has the following per-unit parameters; Xd = 1.00, Xq=

0.60, ra= 0.02Ω. If the generator is delivering rated KVA at rated voltage and at 0.8 p.f leading,

compute the power angle and the excitation e.m.f. Draw the phasor diagram also.

Answer 1

As per the given in the question,

$X_d =1$

$X_q=0.6$

$r_a=0.02\Omega$

Power angle=?

Excitation emf=?

We know that $V\cos \delta =X_d I----(i)$

and $V\sin \delta =X_q I---(ii)$

From (i) and (ii)

$\tan \delta =\frac{X_q}{X_d}=\frac{0.6}{1}$

$\delta =\tan ^{-1}(0.6)=30.96^\circ$

$E=\sqrt{(Ir_a)^2+(IX_d)^2}$

$\Rightarrow E =\sqrt{I^2+0.0004I^2}$

But here the value of I is not given in the question, so it can not be determined