# ONLINE Multiple Choice Questions EE- Synchronous Generator PART 10

136. Zero power factor method of an alternator is used to find its
(A) field resistance
(B) armature resistance
(B) armature
resistance
(C) efficiency
(D) voltage
regulation.

137. The power factor
of an alternator is obtained from its
(A) excitation
(B)
speed
(D)
none of the above.

138. For parallel
operation, alternators must have
(A) same speed
(B) same kVA rating
(C) same
voltage rating
(D) none
of the above.

139. For alternation
having fractional pitch of 5/6 the coil span is
(A)90°
(B)120°
(C)150°
(D)180°

140. Fractional pitch
to eliminate 7th harmonic from alternator emf is
(A) 7/6
(B) 6/7
(C) 6/5
(D) 3/5.

141. Consider the
following statements about a three-phase synchronous generator synchronized to
an infinite bus when its mechanical input is increased gradually with field
current held constant:
1. The power factor of
the current supplied becomes more lagging.
2. The power factor of
the current supplied improves.
3. The power factor
remains unity.
increased.
Of these statements
(A) 1 alone is correct
(B)
2 alone is correct
(C) 2 and 4 are
correct
(D) 3 and 4 are
correct.

142. A 3-phase
synchronous generator, with its armature resistance and the leakage
reactance
being neglected, is synchronized to an infinite bus and its field
excitation
is kept constant thereafter. Now the machine is loaded by Supplying
mechanical
input to the shaft so that the load-angle δ reaches a value of 60°
Under this condition, the operating power-factor would be
(B) 0.866
lagging
(D) 0.5
lagging.

143. A round rotor
synchronous generator has a leakage reactance of 10%, armature reaction
reactance of 90% and negligible armature resistance. With the machine initially
running at rated speed and terminal voltage of 1.0 p.u., a 3-phase
short-circuit is applied. The sustained armature current will be
(A) 1.25 p.u.
(B) 1.11 p.u.
(C) 1.0
p.u.
(D) 0.9 p.u.

144. Following a
sudden short-circuit at the terminals of a 3-phase unloaded synchronous
generator, the initial effect of the pole-face damper windings, is to
(A) establish
the armature flux through the direct-axis magnetic circuit of the machine
(B) allow
only partial linkage of the armature flux with the main field winding
(C) confine
the armature flux to completely link the damper winding
(D) repel
the armature flux and confine it to the leakage flux path in the air-gap.

145. In a synchronous
generator operating at zero pf lagging, the effect of armature reaction is
(A)
magnetizing
(B) demagnetizing
(C) cross-magnetizing
(D) both
magnetizing and cross-magnetizing.

146. Which of the
following limit the reactive power output of a synchronous generator
?
1. Armature current
2.
Field current
4. Prime
mover input.
using the codes given below:
Codes
(A) land
2
(B) 2 and 3
(C) 3 and 4
(D) land
4.