Most Synchronous Motors

111. When the rotor speed, in a synchronous machine, becomes more than the synchronous speed during hunting, the damper bars develop

  1. inductor motor torque
  2. induction generator torque
  3. synchronous motor torque
  4. d.c. motor toque

Correct answer: (B)
induction generator torque

112. When the stator windings are connected in such a fashion that the number of poles are made half, the speed of the rotor of a synchronous motor

  1. remains same as the original value
  2. decreases to half the original value
  3. tends to becomes zero
  4. increases to two times the original value

Correct answer: (D)
increases to two times the original value

113. 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

Correct answer: (D)
None of the above

114. When V is the applied voltage, then the breakdown torque of a synchronous motor varies as

  1. V
  2. V312
  3. V2
  4. 1/V

Correct answer: (A)
V

115. Which of the following losses is not dissipated by the stator core surface in a synchronous motor ?

  1. Eddy current losses in the conductors
  2. Iron losses in the stator
  3. Copper losses in the slot portion of the conductors
  4. Windage losses

Correct answer: (D)
Windage losses

116. Which of the following losses, in a synchronous motor, does not vary with load?

  1. Windage loss
  2. Copper losses
  3. Any of the above
  4. None of the above

Correct answer: (A)
Windage loss

117. Which of the following methods is used to start a synchronous motor ?

  1. Damper winding
  2. Star-delta starter
  3. Damper winding in conjunction with star-delta starter
  4. Resistance starter in the armature circuit

Correct answer: (C)
Damper winding in conjunction with star-delta starter

118. Which of the following motors is non-self starting ?

  1. D.C. series motor
  2. synchronous motor
  3. Squirrel cage induction motor
  4. Wound round induction motor

Correct answer: (B)
synchronous motor

119. Which of the following motors will be used in electric clocks ?

  1. D.C. shunt motor
  2. D.C. series motor
  3. A.C. induction motor
  4. A.C. synchronous motor

Correct answer: (D)
A.C. synchronous motor

120. Which of the following resistances can be measured by conducting insulation resistance test on a synchronous motor ?

  1. Phase to phase winding resistance
  2. Stator winding to earthed frame
  3. Rotor winding to earthed shaft
  4. All of the above

Correct answer: (D)
All of the above

Previous
Page 12 of 13
Next
Copyright © EngineeringMCQ.com