Synchronous Motors PART 8
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(A) infinite
(B) 1.0
(C) 0.5
(D) 0.Get Answer
107. Synchronous motors for power factor correction operate at
(A) normal load with minimum excitation
(B) normal load with zero excitation
(C) no load and greatly over-excited fields
(D) no load and under-excited fields.
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108. The construction of a synchronous motor resembles which of the following machines?
(A) Slip ring induction motor
(B) DC shunt generator
(C) Single phase reluctance motor
(D) DC compound motor.
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109. The construction of a synchronous motor resembles which of the following machine ?
(A) An induction motor
(B) A rotor converter
(C) An alternator
(D) A series motor.
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Synchronous Motors PART 8
110. In a synchronous motor, “hunting” may be due to variation in any of the following EXCEPT:
(A) Load
(B) Supply voltage
(C) Frequency
(D) Winding friction.
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111. A synchronous motor is switched on to supply with its field winding short-circuited, the motor will
(A) not start
(B) bun out
(C) start and run as induction motor
(D) start as induction motor and run as synchronous motor.
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112. In a synchronous motor, at no load, the armature current is
(A) in phase with the applied voltage
(B) leading the applied voltage by 90°
(C) lagging the applied voltage by 90°
(D) zero.
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113. In a synchronous motor, during hunting when the rotor speed exceeds the synchronous speed
(A) field excitation increases
(B) harmonics are developed
(C) negative phase sequence currents come into action
(D) damper bars develop induction generator torque.
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Synchronous Motors PART 8
114. For a synchronous motor when V is the supply voltage, the breakdown torque will be proportional to
(A) V2
(B) V
(C)1/ V
(D) 1/ V2
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115. When the field winding of an unloaded salient pole synchronous motor is open – circuited, the motor will
(A) burn with dense smoke
(B) stop
(C) run as induction motor
(D) function as static condenser
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Synchronous Motors PART 8
116. In case one of the three phases of a synchronous motor is short-circuited, the motor will
(A) not start
(B) get overheated
(C) bum out
D) run normally.
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117. The fact that a synchronous motor with salient poles will operate, even if field current is reduced to zero, can be
explained by
(A) magnetization of rotor poles by stator magnetic field
(B) rotating magnetic field of the rotor
(C) rotating magnetic field of the stator
(D) interlocking action between stator and rotor fields.
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Synchronous Motors PART 8
118. The negative phase sequence in a three phase synchronous motor exists when the motor is
(A) under loaded
(B) overloaded
(C) supplied with unbalanced voltage
(D) hot.
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119. The regulation of a synchronous motor is
(A) 0%
(B) 1%
(C) 50%
(D) 100%.
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120. In a synchronous motor, the angle between the rotor poles and stator poles is known as
(A) synchronizing angle
(B) torque angle
(C) angle of retardation
(D) power factor angle.
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