Single Phase Induction Motors

81. To reverse the direction of rotation of acapacitor start motor while it is running we should

  1. disconnect motor from the supply till it stops then reconnect it to supply with reversed connection of main or auxiliary winding
  2. disconnect motor from supply and immediately reconnect it to supply with reversed connections of the main winding
  3. reverse the direction of connection of the auxiliary winding and after motor comes to rest then connect auxiliary winding to the supply
  4. reverse the direction of connections of the auxiliary winding and immediately connect it to supply

Correct answer: (A)
disconnect motor from the supply till it stops then reconnect it to supply with reversed connection of main or auxiliary winding

82. Torque developed by a single phase induction motor at starting is

  1. pulsating
  2. uniform
  3. none of the above
  4. nil

Correct answer: (D)
nil

83. Two-value capacitor motor finds increased application as compressor motor in small home air-conditioners because

  1. it is comparatively cheaper
  2. it has almost non-destructible capacitor
  3. it has low starting as well as running currents at relatively high power factor
  4. it is quiet in operation

Correct answer: (C)
it has low starting as well as running currents at relatively high power factor

84. When a D.C. series motor is connected to A.C. supply, the power factor will be low because of

  1. high inductance of field and armature circuits
  2. induced current in rotor due to variations of flux
  3. fine copper wire winding
  4. none of the above

Correct answer: (A)
high inductance of field and armature circuits

85. Which motor is normally free from mechanical and magnetic vibrations?

  1. Split phase motor
  2. Universal motor
  3. Hysteresis motor
  4. Shaded pole motor

Correct answer: (C)
Hysteresis motor

86. Which of the following applications always have some load whenever switched on?

  1. Vacuum cleaners
  2. Fan motors
  3. Pistol drills
  4. All of the above

Correct answer: (C)
Pistol drills

87. Which of the following motor will give relatively high starting torque?

  1. Capacitor start motor
  2. Capacitor run motor
  3. Split phase motor
  4. Shaded pole motor

Correct answer: (A)
Capacitor start motor

88. Which of the following motor will give the highest starting torque?

  1. D.C. shunt motor
  2. Schrage motor
  3. Repulsion start and induction run motor
  4. Universal motor

Correct answer: (B)
Schrage motor

89. Which of the following motor will have relatively higher power factor?

  1. Capacitor run motor
  2. Shaded pole motor
  3. Capacitor start motor
  4. Split phase motor

Correct answer: (A)
Capacitor run motor

90. Which of the following motors can be run on AC. as well as D.C. supply?

  1. Universal motor
  2. Repulsion motor
  3. Synchronous motor
  4. Reluctance motor

Correct answer: (A)
Universal motor

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