Induction Motor MCQ #1

1) The frame of an induction motor is usually made of
            A) Silicon steel
            B) Cast iron
            C) Aluminium
            D) Bronze

2) The frequency of the induced emf in an induction motor is
            A) Greater than the supply frequency
            B) Lesser than the supply frequency
            C) Same as the supply frequency
            D) None of these

3)  In an induction motor, rotor speed is always
            A) Less than the stator speed
            B) More than the stator speed
            C) Equal to the stator speed
            D) None of these

4) The efficiency of an induction motor is about
            A) 100%
            B) 80-90%
            C) 50-60%
            D) Less than 50%

5) In induction motor, greater the number of poles
             A) Lesser the frequency
             B) Greater the speed
             C) Lesser the speed
             D) All of these

6) A 4-pole three-phase induction motor has a synchronous speed of 25 rev/s. The frequency of the supply to the stator is:
             A) 500 Hz
             B) 100 Hz
             C) 25 Hz
             D) 50 Hz

7) The slip speed of an induction motor depends upon:
            A) Armature current
            B) Supply voltage
            C) Mechanical load
            D) Eddy currents

8) A 50 Hz, 3-phase induction motor has a full load speed of 1440 r.p.m. The number of poles in the motor is

            A) 2 pole

            B) 4 pole

            C) 6 pole

            D) 8 pole

9) An induction motor can be said analogous to

            A) transformer

            B) synchronous motor

            C) universal motor

            D) stepper motor

10) Mechanically air gaps in induction motor are kept very low to avoid

            A) lower power factor

            B) lagging nature

            C) magnetising current

            D) all of the mentioned

ANS: (1)-B | (2)-C | (3)-A | (4)-B | (5)-C | (6)-D | (7)-C | (8)-B | (9)-A | (10)-D | 

11) Which of the following motor has high starting torque?

            A) Slip ring Induction motor

            B) Squirrel cage induction motor

            C) Both 1 & 2

            D) None of the above

12) At stand still condition the value of slip is

            A) 0

            B) Infinity

            C) One

            D) None of the above

13)The condition for maximum running torque is

            A) R= S* X/2

            B) R = X/2

            C) R =X*S

            D) R =X

14) Rotor resistance speed control method is not applicable in

            A) Synchronous motor

            B) Squirrel cage induction motor

            C) Slip Ring induction motor

            D) None of the above

15) A 4 pole 50 Hz induction motor is running at 1300 rpm. Find the speed of stator magnetic field with respect to the rotor?

           A) 1500 rpm

           B) 200 rpm

           C) 1300 rpm

           D) 3000 rpm

16)  The condition for maximum starting torque is

            A)R= S* X/2

            B) R = X/2

            C) R =X*S

            D) R =X

17) Blocked rotor test in an induction motor is used to determine

            A) Leakage impedance

            B) Copper loss

            C) Both 1 & 2

            D) None of the above

18) If an induction machine is run at above the synchronous speed it acts as

            A) Synchronous Motor

            B) Synchronous Generator

            C) Induction Generator

            D) None of the above

19) Induction motors have the advantage of

            A) Less Maintenance

            B) Less cost

            C) Simple in construction

            D) All of the above

20) What happens if fifth harmonics is given to induction motor?

            A) Short-circuit the motor

            B) Motor will rotate in reverse direction

            C) Motor will rotate in the same direction

            D) None of the above

(11)-A | (12)-C | (13)-C | (14)-B | (15)-B | (16)-D | (17)-C | (18)-C | (19)-D | (20)-B | 

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