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MCQs

Total Questions : 395 | Page 7 of 40 pages
Question 61. When the voltage applied to a synchronous motor is increased, which of the following will reduce ?
  1.    Stator flux
  2.    Pull in torque
  3.    Both (A) and (B)
  4.    None of the above
 Discuss Question
Answer: Option D. -> None of the above
Question 62. When the excitation of an unloaded salient pole synchronous motor suddenly gets disconnected
  1.    the motor stops
  2.    it runs as a reluctance motor at the same speed
  3.    it runs as a reluctance motor at a lower speed
  4.    none of the above
 Discuss Question
Answer: Option A. -> the motor stops
Question 63. The effect of increasing the load on a synchronous motor running with normal excitation is to
  1.    decrease both armature current and power factor
  2.    decrease armature current but increase power factor
  3.    increase armature current but decrease power factor
  4.    increase both its armature current and power factor
 Discuss Question
Answer: Option C. -> increase armature current but decrease power factor
Question 64. Synchronous motor always runs at
  1.    the synchronous speed
  2.    less than synchronous speed
  3.    more than synchronous speed
  4.    none of the above
 Discuss Question
Answer: Option A. -> the synchronous speed
Question 65. A synchronous motor can operate at
  1.    lagging power factor only
  2.    leading power factor only
  3.    unity power factor only
  4.    lagging, leading and unity power factors
 Discuss Question
Answer: Option D. -> lagging, leading and unity power factors
Question 66. A pony motor is basically a
  1.    small induction motor
  2.    D.C. series motor
  3.    D.C. shunt motor
  4.    double winding A.C./D.C. motor
 Discuss Question
Answer: Option A. -> small induction motor
Question 67. The maximum power developed in a synchronous motor will depend on
  1.    the rotor excitation only
  2.    the supply voltage only
  3.    the rotor excitation and supply volt-age both
  4.    the rotor excitation, supply voltage and maximum value of coupling angle (90°)
 Discuss Question
Answer: Option D. -> the rotor excitation, supply voltage and maximum value of coupling angle (90°)
Question 68. Armature of a synchronous machine is
  1.    Of reducing number of slip rings on the rotor
  2.    Armature is associated with large power as compared to the field circuits
  3.    Of difficulty of providing high voltage insulation on rotor
  4.    All of the above reasons
 Discuss Question
Answer: Option D. -> All of the above reasons
Question 69. A synchronous motor installed at the receiving end substation operates with such an excitation that it takes power at lagging power factor. Now if the applied voltage of the synchronous motor goes down, the power factor of the synchronous motor will
  1.    remain same
  2.    go down
  3.    improve
  4.    none of the above
 Discuss Question
Answer: Option C. -> improve
Question 70. Synchronsizingpower of a synchronous machine is
  1.    direcly proportional to the synchronous reactance
  2.    inversely proportional to the synchronous reactance
  3.    equal to the synchronous reactance
  4.    none of the above
 Discuss Question
Answer: Option B. -> inversely proportional to the synchronous reactance

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