AC Motor MCQs : This section focuses on the "AC Motor" in Electric Drives. These Multiple Choice Questions (MCQ) should be practiced to improve the Electric Drives skills required for various interviews (campus interview, walk-in interview, company interview), placement, entrance exam and other competitive examinations.
Question 1
__________ is an electric motor driven by an alternating current
A. DC motor
B. AC motor
C. Both A and B
D. None of the above
View Answer
Ans : C
Explanation: An AC motor is an electric motor driven by an alternating current (AC).
Question 2
The AC motor commonly consists of _______ basic parts.
A. 1
B. 2
C. 3
D. 4
View Answer
Ans : B
Explanation: The AC motor commonly consists of two basic parts, an outside stator having coils supplied with alternating current to produce a rotating magnetic field, and an inside rotor attached to the output shaft producing a second rotating magnetic field.
Question 3
Which of the following is a types of AC motors?
A. induction motors
B. synchronous motors
C. asynchronous motors
D. Both A and B
View Answer
Ans : D
Explanation: The main types of AC motors are induction motors and synchronous motors.
Question 4
Alternating current technology was rooted by Michael Faraday's and Joseph Henry's in?
A. 1830
B. 1840
C. 1845
D. 1850
View Answer
Ans : A
Explanation: Alternating current technology was rooted in Michael Faraday's and Joseph Henry's 1830–31 discovery that a changing magnetic field can induce an electric current in a circuit.
Question 5
The difference between synchronous speed and actual speed is called?
A. Polyphase cage rotor
B. Polyphase wound rotor
C. Slip
D. Rotor
View Answer
Ans : C
Explanation: The difference between synchronous speed and actual speed is called slip, and loading the motor increases the amount of slip as the motor slows down slightly. Even with no load, internal mechanical losses prevent the slip from being zero.
Question 6
A typical two-phase AC servo-motor has a squirrel cage rotor and a field consisting of two windings
A. TRUE
B. FALSE
C. Can be true or false
D. Can not say
View Answer
Ans : A
Explanation: True, A typical two-phase AC servo-motor has a squirrel cage rotor and a field consisting of two windings.
Question 7
Calculate peak-peak voltage if Vmax=80 V and Vmin=20 V.
A. 40V
B. 50V
C. 60V
D. 70V
View Answer
Ans : C
Explanation: Peak-Peak voltage is equal to the difference between the maximum and minimum voltage. It is mathematically represented as Vp-p=Vmax-Vmin=80-20=60 V.
Question 8
Length of rotation is directly related to ____
A. Torque
B. Number of input pulses
C. Frequency of input pulses
D. Solenoid
View Answer
Ans : B
Explanation: The length of rotation is directly proportional to the number of input pulses applied. In the other options, the speed of rotation of input pulses is directly related to the frequency of input pulses, the motor has full torque at standstill. Solenoids are used as electrical actuators
Question 9
Which among the following is not the type of a stepper motor?
A. Variable reluctance
B. Permanent magnet
C. Hybrid
D. Variable magnet
View Answer
Ans : D
Explanation: Variable magnet is not the type of a stepper motor. Variable reluctance stepper motor consists of a soft iron multi-toothed rotor and a wound stator. Permanent magnet stepper motors have a rotor made up of the permanent magnet. Hybrid stepper motor provides better performance with respect to step resolution, torque and speed.
Question 10
Single-phase motors have a unique rotating magnetic field like multi-phase motors.
A. TRUE
B. FALSE
C. Can be true or false
D. Can not say
View Answer
Ans : B
Explanation: False, Single-phase motors do not have a unique rotating magnetic field like multi-phase motors.