# ONLINE Multiple Choice Questions EE- Synchronous Generator PAR 3

31. The
armature reaction of an alternator influences
(A) windage losses
(B)
operting speed
(C) generated voltage per phase
(D)
waveform
of voltage generated.

32. For
the same power rating, a lower voltage alternator will be
(A)
more
efficient
(B) larger in size
(C) operating at high rpm
(D)
more
costly.

33. An
alternator is supplying 10A to an inductive load at 220 V, while running at
1000 rpm. Now if the speed of the alternator is reduced to 750 rpm but the
field current remains unchanged, the load current will become
(A)
18 A
(B) 13.3 A
(C)
10 A
(D) 7.5 A.

34. Dampers
in a large generator
(A)
increase
stability
(B)
reduce
voltage fluctuations
(C)
reduce
frequency fluctuations.

35. An
alternator is rated for 75 kW at 0.8 power factor. It means that
(A)
alternator
has 4 poles
(B)
alternator
can supply 75 kW at 0.8 power factor
(C)
alternator
can supply power only to loads having power factor 0.8 only
(D)
the
peak efficiency of alternator occurs only at 75 kW load having 0.8 lagging
power factor.

36. The
regulation of an alternator is
(A)
the
reduction in terminal voltage when alternator is loaded
(B)
the
variation of terminal voltage under the conditions of maximum and minimum
excitation
(C)
the
increase in terminal voltage when load is thrown off
(D)
the
change in terminal voltage from lagging power factor to leading power factor.

37. A
magnetisation curve represents the relationship between
(A) reactive and non-reactive components of
voltage
(B) exciting currents and terminal voltage
(C) power factor and terminal voltage
(D) magnetic flux and armature current.

38. In
an alternator if the armature reaction produces demagnetisation of the main
field, the power factor should be
(C) Unity.

39. In
an alternator if the armature reaction produces magnetisation of the main field
the power factor should be
(C) Unity.

40. When
an alternator is supplying unity power factor load, the armature reaction will
produce
(A) magnetisation of the main field
(B) demagnetisation of the main field
(C) distortion of the main field.

41. An
alternator has full load regulation of 4% when the power factor of the load is
0.8 lagging while alternator runs at 1500 rpm. The full load regulation of 1400
rpm for 0.8 pf lagging load will be
(A)
15/14 x 4
percent
(B)
14/15 x 4 percent
(C) 4
percent
(D)
Depends
on other factors also.

42. The
Potier’s triangle separates the
(A) iron losses and copper losses
(B) field mmf and armature mmf
(C) stator voltage and rotor voltage
(D) armature leakage reactance and armature
reaction mmf.

43. In
the Potier’s triangle, the Potier reactance drop per phase is 22 volts per
phase at 88
amperes
per phase. The Potier’s reactance per phase is
(A) 0.22
(B)
0.25
(C) 0.30
(D)
0.44.

44. Two
alternators are running in parallel. The excitation of one of the alternator
is increased. The result will be
(A) machine with excess excitation will burn
(B) both machines will start vibrating
(C) power output will decrease
(D) wattless component will change.