Electrical Power Systems

86 Electrical Power Systems
The rated current is
Ia = S
*
3f
*
3V
80 -36.
87º
=
= 666. 5 -36. 87º
Amp
3 ´ 4001 . 0º
\ E = 40. 01 0º
+
j10
´ 6665 . -36.
87º
1000
= 40. 01 + 6. 665 5313 . º
\ E = 40.01 + 4 + j 5.33 = 44.01 + j 5.33
\ E = 44. 33 6. 9º
k V
\ magnitude of generated emf = 44.33 kV and d = 6.9º Ans.
4.5 SALIENT POLE SYNCHRONOUS GENERATORS
A salient pole synchronous machine (ig. 4.5) is distinguished from a round rotor machine by
constructional features of field poles with a large interpolar air gap. The reluctance along the
polar axis, commonly referred to as the rotor direct axis is less than that along the interpolar
axis, commonly referred to as the quadrature axis. Therefore direct axis reactance x d is higher
than the quadrature axis reactance x q. These two reactances give voltage drop in the armature
and can be taken into account by resolving the armature current I a into two components I d in
quadrature and I q in phase. The phasor diagram with zero armature resistance is shown in
ig. 4.6.
ig. 4.5: Schematic representation of a salient pole
synchronous generator (four poles).