# ONLINE Multiple Choice Questions EE- Synchronous Generator PAR 4

46. The
power output of an alternator is 40 kW and KVAR component is – 25. What will be
the value of tanφ (φ being the
power factor angle) ?
(A)
0.625 lagging
(C) 0.375 lagging

47. When
short pitch coils of 160 are used in an alternator, which harmonic component
will not be present in the output emf ?
(A) third
(B)
fifth
(C) seventh
(D)
ninth.

48. A
120 MW turbo alternator is supplying power to 80 MW load at p.f. lagging.
Suddenly the steam supply to the turbine is cut off and the alternator remains
connected to the supply network and the field supply also remains on. What will
happen to the alternator ?
(A) The stator winding of the alternator will
get burnt
(B) The rotor winding of the alternator will
get burnt
(C) The alternator will continue to run as a synchronous motor rotating in the same
direction
(D) The alternator will
continue to run as a synchronous motor rotating in the opposite direction.

49. The figure shows the characteristics of an alternator. Which curve represents synchronous
impedance ?

(A) curve
A
(B) curve B
(C) curve C
(D) curve D.

50. In
the above figure (Figure of Question 49) which curve represents short circuit ?
(A)
curve A
(B) curve B
(C)
curve C
(D) curve D.

51. In
the above figure which curve represents open circuit voltage ?
(A) curve A
(B) curve B
(C)
curve C
(D) curve D.

52. For
a peripheral speed of 314 m/s, a 2 pole cylindrical machine will have maximum
diameter of
(A)
255 cm
(B) 235 cm
(C)
200 cm
(D) 170 cm.

53. The
rotor of the salient pole alternator has 24 poles. The number of cycles of emf
in one revolution would be
(A) 24
(B) 12
(C) 6
(D) 4.

54. Two
alternators A
and B are
sharing an inductive load equally. If the excitation of alternator A is
increased
(A) alternator B will deliver more
current and
alternator A will deliver less current
(B)
alternator B will deliver less current and alternator A will deliver more current
(C)
both
will continue to share load equally
(D)
both
will deliver more current.

55. Desirable
feature for the parallel operation of two alternators is
(A)
both
should have same resistance
(B)
both
should have same reactance
(C)
both
should have less of resistance as compared to synchronous reactance
(D)
both
should have more of resistance as compared to synchronous reactance.

56. Alternators
used in aircraft systems usually have frequency of
(A)
25 Hz
(B) 50 Hz
(C)
100 Hz
(D) 400 Hz.

57. High
frequency on aircraft alternators is selected in order to
(A)
free
the systems from external disturbance
(B)
compensate
for high speeds
(C) compensate for high altitudes
(D)
reduce the bulk.

58. A 20
pole ac generator rotates at 600 rpm. The periodic time of current in seconds
per cycle is
(A)
0.009
(B) 0.004
(C)
0.008
(D) 0.01.

59. What
kind of rotor is most suitable for turbo alternators ?
(A)
salient
pole type
(B) non-salient pole type
(C) both (A) and (B) above
(D)
none
of the above.