Industrial Motor Drives — MCQs – EE

1. What is an industrial motor drive?
(A) A system that controls the speed and torque of an electric motor
(B) A power supply unit
(C) A data storage system
(D) A mechanical gear system

2. The main components of an electrical drive are:
(A) Power modulator, motor, controller, and load
(B) Battery, cable, resistor, and switch
(C) Transformer, relay, diode, and capacitor
(D) Modem, router, and server

3. Which of the following is an example of a DC motor drive?
(A) DC shunt motor with converter control
(B) Synchronous motor
(C) Induction motor
(D) Stepper motor

4. The most commonly used motor in industrial drives is:
(A) Induction motor
(B) DC series motor
(C) Stepper motor
(D) Universal motor

5. Variable Frequency Drives (VFDs) are used to:
(A) Control the speed of AC motors
(B) Control DC voltage
(C) Change current to voltage
(D) Maintain constant torque only

6. A DC drive controls motor speed by varying:
(A) Armature voltage or field current
(B) Rotor resistance
(C) Supply frequency
(D) Stator current

7. In an AC motor drive, the output frequency determines:
(A) Motor speed
(B) Motor torque
(C) Supply voltage
(D) Power factor only

8. The speed of an induction motor can be controlled by:
(A) Varying supply frequency and voltage
(B) Changing rotor material
(C) Adjusting shaft diameter
(D) Using mechanical brakes

9. The torque of a DC motor is directly proportional to:
(A) Armature current
(B) Supply voltage
(C) Field resistance
(D) Speed only

10. A servo drive is primarily used for:
(A) Precise position and speed control
(B) Heavy-duty constant torque applications
(C) Fixed-speed operation
(D) Mechanical braking

11. In industrial drives, regenerative braking refers to:
(A) Returning energy to the supply during deceleration
(B) Mechanical friction braking
(C) Dynamic braking
(D) Manual stopping of motor

12. Which type of motor drive is best suited for constant speed operation?
(A) Synchronous motor drive
(B) DC shunt motor drive
(C) Induction motor drive
(D) Stepper motor drive

13. The power modulator in a motor drive performs:
(A) Voltage and current control to the motor
(B) Speed measurement
(C) Signal amplification
(D) Thermal management

14. The main advantage of AC drives over DC drives is:
(A) Less maintenance and higher efficiency
(B) Simpler speed control circuit
(C) Lower cost of installation only
(D) Higher current rating

15. In a closed-loop control drive, feedback is taken from:
(A) Speed or current sensors
(B) Output voltage only
(C) Input switch
(D) Circuit breaker

16. The open-loop control drive operates:
(A) Without feedback
(B) With continuous feedback
(C) With torque monitoring
(D) Using adaptive control

17. Which motor drive is best for robotics applications?
(A) Servo motor drive
(B) Induction motor drive
(C) Universal motor drive
(D) Stepper motor drive

18. The V/f control method in VFD maintains:
(A) Constant torque in AC motors
(B) Constant speed
(C) Constant current
(D) Constant power factor

19. A chopper-fed DC drive is a:
(A) DC-DC converter-based motor control system
(B) AC voltage controller
(C) DC-AC inverter system
(D) Constant frequency converter

20. In a multi-motor drive system, several motors are controlled:
(A) From a single power converter
(B) Individually without synchronization
(C) Using mechanical coupling only
(D) Manually by switches

21. The purpose of a soft starter in AC motor drives is to:
(A) Limit inrush current during motor startup
(B) Increase torque
(C) Reduce voltage continuously
(D) Maintain speed constant

22. Vector control of an induction motor provides:
(A) Independent control of torque and flux
(B) Constant voltage
(C) Fixed frequency operation
(D) Pure mechanical braking

23. A drive isolation transformer is used to:
(A) Protect the drive from power line disturbances
(B) Increase current
(C) Reduce power loss
(D) Step down motor voltage

24. The main disadvantage of DC motor drives is:
(A) Frequent maintenance due to brushes and commutator
(B) High cost of control circuits
(C) Complex speed control
(D) Poor torque response

25. A braking resistor in drives is used to:
(A) Dissipate energy during dynamic braking
(B) Store energy
(C) Control acceleration
(D) Improve power factor

26. The PID controller in drives is used for:
(A) Precise control of speed or position
(B) Power amplification
(C) Frequency conversion
(D) Reducing harmonic distortion

27. A constant torque load example is:
(A) Conveyor belt
(B) Fan
(C) Pump
(D) Centrifugal blower

28. A constant power load example is:
(A) Rolling mill
(B) Conveyor
(C) Fan
(D) Pump

29. The efficiency of industrial drives typically lies in the range:
(A) 85–98%
(B) 50–60%
(C) 60–70%
(D) 40–50%

30. The main benefit of industrial motor drives is:
(A) Energy efficiency and precise control of industrial machinery
(B) Increased manual operation
(C) Reduced automation
(D) Higher noise generation