ONLINE Multiple Choice Questions EE-Synchronous Motors PART 6

76. The curve for 20 k W is expected to be

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

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77. In a
synchronous motor hunting can be minimized
(A)
by
using damper bars
(B) by using a flywheel
(C) by designing the motor for adequate
synchronizing power
(D) by any of the above methods.

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78. A
three phase 400 V, 50 Hz synchronous motor is working at 50 percent load. In
case an increase in the field current of the motor causes a reduction in the
armature current, it can be concluded that
(A)
the
motor is delivering reactive power to the mains
(B)
the
motor is absorbing reactive power to the mains
(C) the motor is neither absorbing nor
delivering reactive power.

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79. Inverted
V-curves for a synchronous motor show
(A)
Variation
of power factor with dc field current when load on the motor remains constant
(B)
Variation
of field current and supply voltage when excitation remains constant
(C)
Variation
of power factor and supply voltage when motor is hunting
(D)
none
of the above.

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80. The
armature current of the synchronous motor has large values for
(A)
low
excitation only
(B)
high
excitation only
(C)
both
low and high excitation.

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81. In
which range the cost of a synchronous motor can be comparable to the cost of a
induction motor ?
(A)
Low
HP high speed
(B) High HP low speed
(C)
High
HP high speed
(D)
Low
HP low speed.

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82. Insulation
resistance test on synchronous motor can be conducted to measure which of the
following resistances ?

(A) Stator winding to
earthed frame
(B) Rotor winding to
earthed shaft
(C) Phase to phase winding resistance
(D) All of the above.

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83. Which
curve represents the open circuit characteristic of a synchronous motor

(A) Curve A
(B)
Curve B
(C) Curve C
(D)
Curve D.

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84. During
short circuit test which of the following is short circuited ?
(A) Armature terminals
(B) One of the phase windings of stator
(C) AH phase windings of stator
(D) All phase windings of stator and
armature.

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85. The
duration of sudden short circuit test on a synchronous motor is usually
(A) about one second
(B) about one minute
(C) about one hour
(D) 40 minutes.

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86. The
maximum torque which a synchronous will develop at rest for any angular
positions of the rotor, at rated stator supply voltage and frequency, is known
as
(A) Reluctance torque
(B) Synchronous torque
(C) Locked-rotor torque
(D) Pull up torque.

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87. The
maximum constant load torque under which a synchronous motor will pull into
synchronism at rated rotor supply voltage and frequency is known as
(A) Synchronous torque
(B) Pull in torque
(C) Pull up torque
(D) Pull out torque.

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88. The
maximum sustained torque which a synchronous motor will develop at synchronous
speed for 1 mm with rated frequency and rated field current is known as
(A) Pull out torque
(B) Reluctance torque
(C) Synchronous torque
(D) Average torque.

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89. The
total steady state to drive synchronous motor and the load at synchronous speed
is known as
(A)
Synchronous torque
(B) Asynchronous
torque
(C) Reluctance
torque
(D) Pull-up
torque.

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90. The space angle between the axis of the
stator revolving magnetic field and the rotor-pole axis, both looked and
running at synchronous speed, is known as
(A) angle
of lead
(B) power
angle
(C) power
factor angle
(D)
reactive power angle.

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ONLINE Multiple Choice Questions EE-Synchronous Motors PART 7
ONLINE Multiple Choice Questions EE-Synchronous Motors PART 5

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