Electric motors and drives for EVs – MCQs – EE

1. The most commonly used electric motor in modern electric vehicles is:
(A) DC shunt motor
(B) Induction motor
(C) Permanent Magnet Synchronous Motor (PMSM)
(D) Stepper motor

2. The main function of an electric drive is to:
(A) Control lighting in the vehicle
(B) Control the operation of the electric motor
(C) Store electric energy
(D) Reduce friction losses

3. The torque produced by an electric motor depends on:
(A) Voltage and current
(B) Speed and temperature
(C) Pressure and density
(D) Magnetic field and mass

4. In an EV, the motor drive system converts:
(A) Mechanical energy into electrical energy
(B) Electrical energy into mechanical energy
(C) AC into DC
(D) Solar energy into electricity

5. The main advantage of PMSM motors in EVs is:
(A) High efficiency and torque density
(B) Low cost
(C) High maintenance
(D) Poor speed control

6. The type of motor that does not require brushes or a commutator is:
(A) DC motor
(B) BLDC motor
(C) Universal motor
(D) Series DC motor

7. The regenerative braking feature in EVs is enabled by:
(A) Fuel injectors
(B) Motor acting as a generator
(C) Cooling fans
(D) Power resistors

8. The rotor in a Permanent Magnet Synchronous Motor contains:
(A) Windings only
(B) Permanent magnets
(C) Slip rings
(D) Commutators

9. The torque-speed characteristic of an induction motor is:
(A) Constant torque at all speeds
(B) Variable torque depending on slip
(C) Constant speed operation
(D) Independent of voltage

10. The motor controller in an EV is responsible for:
(A) Controlling motor speed and torque
(B) Storing energy in the battery
(C) Converting mechanical energy
(D) Managing cooling systems

11. The efficiency of modern EV traction motors is approximately:
(A) 50–60%
(B) 65–75%
(C) 85–95%
(D) 100%

12. The torque in a DC motor is directly proportional to:
(A) Armature current and field flux
(B) Speed and resistance
(C) Voltage and resistance
(D) Frequency and inductance

13. Field-Oriented Control (FOC) is used in:
(A) DC motors
(B) PMSM and Induction motors
(C) Stepper motors
(D) Universal motors

14. The BLDC motor is preferred in EVs due to:
(A) Simplicity, high power density, and low maintenance
(B) Need for frequent maintenance
(C) High mechanical noise
(D) Complex control system

15. The slip in an induction motor is defined as:
(A) Ratio of rotor to stator voltage
(B) Difference between synchronous and rotor speed as a fraction of synchronous speed
(C) Ratio of current to voltage
(D) Torque per unit speed

16. The main disadvantage of induction motors for EVs is:
(A) High cost
(B) Low power-to-weight ratio
(C) Need for field weakening
(D) Poor control at low speed

17. The drive inverter converts:
(A) AC to DC
(B) DC to AC
(C) DC to DC
(D) AC to mechanical power

18. The motor used in Tesla Model S is primarily:
(A) DC series motor
(B) Induction motor
(C) Stepper motor
(D) Universal motor

19. Torque ripple in BLDC motors can be minimized by:
(A) Using more stator poles and better control algorithms
(B) Increasing voltage
(C) Decreasing current
(D) Reducing battery capacity

20. The vector control technique allows:
(A) Independent control of torque and flux
(B) Only speed control
(C) Only voltage control
(D) Control of rotor position

21. The inverter in an EV motor drive is controlled using:
(A) PWM (Pulse Width Modulation)
(B) Frequency modulation
(C) Voltage doubling
(D) Phase shift modulation

22. The power factor of an induction motor at full load is typically:
(A) 0.2
(B) 0.5
(C) 0.85
(D) 1.0

23. The BLDC motor back-EMF waveform is:
(A) Sinusoidal
(B) Trapezoidal
(C) Square
(D) Triangular

24. The PMSM motor back-EMF waveform is:
(A) Square
(B) Sinusoidal
(C) Trapezoidal
(D) Constant

25. The main difference between BLDC and PMSM motors is:
(A) Shape of back-EMF waveform
(B) Type of magnets used
(C) Number of poles
(D) Cooling method

26. Regenerative braking is most efficient at:
(A) High speeds
(B) Low speeds
(C) Constant torque
(D) Zero speed

27. The drive system ensures smooth motor operation by:
(A) Varying voltage and frequency
(B) Reducing mechanical load
(C) Increasing current only
(D) Reducing magnetic flux

28. The torque constant of a motor relates:
(A) Current to torque
(B) Voltage to speed
(C) Power to resistance
(D) Frequency to temperature

29. Thermal management in electric drives is essential to:
(A) Prevent overheating of motor and power electronics
(B) Increase magnetic losses
(C) Reduce battery voltage
(D) Improve color of wires

30. The main goal of drive control in EVs is to:
(A) Ensure smooth acceleration and regenerative braking
(B) Reduce vehicle weight
(C) Increase gear ratios
(D) Control battery voltage