Servo Motors MCQ

1. For servo application, the A.C. motor used is

  1. Single-phase induction motor
  2. Synchronous motor
  3. Three-phase induction motor
  4. Two-phase induction motor

Answer. d

2. DC servomotors are used in

  1. Purely AC control systems
  2. Both AC & DC control systems
  3. Purely DC control systems
  4. None of these

Answer. c

3. A servo system must have

  1. Power amplifier to amplify the error
  2. Feedback system
  3. Capacity to control position or its derivative
  4. All of these

Answer. d

4. A servomechanism is a feedback control system required to control

  1. Position
  2. A derivative of position
  3. Either option (a) or (b)
  4. None of these

Answer. c

5. Synchro transmitter also acts as

  1. Input to a servomotor
  2. Error detector
  3. Comparator
  4. Compensator

Answer. a

6. The performance of servo motors is _________ than stepper motors.

  1. Very accurate
  2. Highly controlled by feedback
  3. Both very accurate & highly controlled by feedback
  4. None of these

Answer. c

7. If D is the rotor diameter and L, the axial length, then a high-performance a.c. servomotor is characterized by which one of the following?

  1. Large D and Large L
  2. Large D and Small L
  3. Small D and Small L
  4. Small D and Large L

Answer. d

8. Synchro machines are used for which one of the following?

  1. Converting single-phase supply to 3-phase supply
  2. Stepping up low-frequency signal to high frequency
  3. Detection of positional error in a.c. servo system
  4. Detection of positional error in d.c. servo system

Answer. c

9. To detect the position error in a position control system, which of the following may be used?

  1. Potentiometers
  2. Synchros
  3. LVDT

Select the correct answer using the code given below:

  1. i and ii
  2. i and iii
  3. i, ii and iii
  4. ii and iii

Answer. c

10. Which one of the following is the correct statement?

The rotor resistance to reactance ratio and the moment of inertia of an ac servomotor in comparison to an ordinary 2-phase induction motor of similar rating are, respectively,

  1. lower and lower
  2. lower and higher
  3. higher and higher
  4. higher and lower

Answer. d

11. Which one of the following is required for stability of an ac servomotor?

  1. A negative slope on the torque-speed curve
  2. A linearized torque-speed curve
  3. The ratio of the rotor reactance to rotor resistance should be high
  4. The rotor diameter should be less and axial length large

Answer. b

12. A linear ac servomotor must have

  1. High rotor resistance
  2. High rotor reactance
  3. A large air gap
  4. Both high rotor resistance and reactance

Answer. a

13. Consider the following statements:

  1. Servomotors have lighter rotor as compared to ordinary motors and hence lower inertia
  2. Back e.m.f. in field controlled d.c. motors act as minor loop feedback and results in increased damping and improved transient response
  3. Permanent magnet d.c. servomotors can be used in either armature-controlled or field-controlled modes.

Which of the above statements are not correct?

  1. ii and iii
  2. i and ii
  3. i, ii and iii
  4. i and iii

Answer. b

14. Consider the following statements regarding A.C. servomotor:

  1. The torque-speed curve has negative slope
  2. It is sensitive to noise.
  3. The rotor has high resistance and low inertia.
  4. It has slow acceleration.

Which of the following are the characteristics of A.C. servomotor as control component?

  1. i and ii
  2. ii and iii
  3. i and iii
  4. ii and iv

Answer. c

15. A synchro transmitter consists of a

  1. salient pole rotor winding excited by an ac supply and a three-phase balanced stator winding
  2. three-phase balanced stator winding excited by a three-phase balanced ac signal and rotor connected to a dc voltage source
  3. salient pole rotor winding excited by a dc signal
  4. cylindrical rotor winding and a stepped stator excited by pulses

Answer. a

16. If the rotor axis of the synchro transmitter is along the axis of S2 stator winding when will be the electrical zeroing?

  1. Vs1Vs2 is maximum
  2. Vs2Vs3 is maximum
  3. Vs2Vs3 is minimum
  4. Vs3Vs1 is minimum


Answer. d

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