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MCQs

Dc Motors

Total Questions : 240 | Page 22 of 24 pages
Question 211. For the same H.P. rating and full load speed, following motor has poor starting torque
  1.    Shunt
  2.    Cumulatively compounded
  3.    Series
  4.    Differentially compounded
 Discuss Question
Answer: Option D. -> Differentially compounded
Question 212. If a D.C. shunt motor is working at no load and if shunt field circuit suddenly opens
  1.    This will make armature to take heavy current, possibly burning it
  2.    This will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses
  3.    Motor will run at very slow speed
  4.    Nothing will happen to the motor
 Discuss Question
Answer: Option B. -> This will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses
Question 213. If a D.C. shunt motor is working at full load and if shunt field circuit suddenly opens
  1.    Motor will come to stop
  2.    This will make armature to take heavy current, possibly burning it
  3.    Nothing will happen to motor
  4.    This will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses
 Discuss Question
Answer: Option B. -> This will make armature to take heavy current, possibly burning it
Question 214. The armature torque of the D.C. shunt motor is proportional to
  1.    field flux only
  2.    both (A) and (B)
  3.    None of these
  4.    armature current only
 Discuss Question
Answer: Option D. -> armature current only
Question 215. Which D.C. motor is generally preferred for cranes and hoists?
  1.    Cumulatively compounded motor
  2.    Shunt motor
  3.    Differentially compounded motor
  4.    Series motor
 Discuss Question
Answer: Option D. -> Series motor
Question 216. Which one of the following is not necessarily the advantage of D.C. motors over A.C. motors?
  1.    Low cost
  2.    Stability
  3.    Wide speed range
  4.    High starting torque
 Discuss Question
Answer: Option A. -> Low cost
Question 217. D.C. series motors are used
  1.    Where constant operating speed is needed
  2.    Where load changes frequently
  3.    None of these
  4.    Where load is constant
 Discuss Question
Answer: Option C. -> None of these
Question 218. Three point starter can be used for
  1.    Both shunt and compound motor
  2.    Shunt motor only
  3.    Series motor only
  4.    Compound motor only
 Discuss Question
Answer: Option A. -> Both shunt and compound motor
Question 219. The main disadvantage of the Ward-Leonard control method is
  1.    All of these
  2.    Low efficiency at high loads
  3.    High initial cost
  4.    High maintenance cost
 Discuss Question
Answer: Option A. -> All of these
Question 220. In D.C. shunt motors as load is reduced
  1.    The speed will reduce
  2.    The speed will increase abruptly
  3.    The speed will remain almost/constant
  4.    The speed will increase in proportion to reduction in load
 Discuss Question
Answer: Option C. -> The speed will remain almost/constant

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