Question:-
A, 3 phase alternator has a direct axis synchronous reactance of 0.7 pu and a quadrature axis synchronous reactance of 0.4 p.u.

What is the load angle for full load 0.8 p.f. lagging ??
Option (A)
16.5°
Option (B)
8.25°
Option(C)
33.0°
Option(D)
None
Correct Option:
(A)
Question Solution:
V = 1 p.u.
Xd = 0.7 p.u.
Xq = 0.4 p.u.
cos Æ = 0.8 => Æ = 36.9°, Ia = 1 p.u.
tan δ= (Ia Xq cos Æ) /( V+ Xq sin Æ)
=(1*0.4*0.8)/(1+0.4 x 0.6)
=0.258
d = 16.5°
question-answer-faq-1635