DC Motors Most Important Interview Questions - Electronic Engineering


DC Motors Most Important Interview Questions and Answers. Viva Questions DC motors important question and Answers DC motors.


    Question 1: Which of the following application requires high starting torque?

  • Lathe machine
  • Centrifugal pump
  • Locomotive
  • Air blower
  • Answers: Locomotive

    Question 2: The condition for maximum power in case of dc motor is ?

  • back EMF = 1/2 x supply voltage
  • back EMF = 2 x supply voltage
  • supply voltage= back EMF
  • supply voltage = 1/2 x back e.m.f.
  • Answers: back EMF = 1/2 x supply voltage

    Question 3: The speed of a motor falls from 1100 RPM at no-load to 1050 RPM at rated load. The speed regulation of the motor is?

  • 8.40%
  • 6. 77%
  • 2:36 %
  • 4.76%
  • Answers: 4.76%

    Question 4: The condition for maximum efficiency for a DC generator is?

  • eddy current losses= stray losses
  • variable losses = constant losses
  • hysteresis losses= eddy current losses
  • copper losses = 0
  • Answers: variable losses = constant losses

    Question 5: Which method of braking is generally used in elevators ?

  • Rheostatic braking
  • Regenerative braking
  • Plugging
  • Nope of the above
  • Answers: Plugging

    Question 6: A DC shunt motor is rotating in clockwise direction as viewed from one end. The polarity of connection of the armature and field winding are reversed simultaneously. The motor will ?

  • will not rotate at all
  • rotate in anti-clockwise direction
  • gain excessively high speed
  • rotate in clockwise direction
  • Answers: rotate in clockwise direction

    Question 7: The armature shaft of a DC motor must be able to withstand?

  • any unbalanced magnetic pull on the armature core
  • all of the above
  • twisting strains due to transmission of torque
  • bending moment due to the weight of the armature and commutator
  • Answers: all of the above

    Question 8: Which losses can be determined by performing the retardation test ?

  • Copper losses
  • Eddy current losses
  • Stray losses
  • Friction losses
  • Answers: Stray losses

    Question 9: Speed control by varying the armature circuit resistance, in a DC motor, provides a ?

  • constant torque drive
  • variable power drive
  • constant power drive
  • variable torque drive
  • Answers: constant torque drive

    Question 10: A face plate starter is employed for starting ?

  • induction motor
  • universal motor
  • synchronous motor
  • DC series motor
  • Answers: DC series motor

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