T4Tutorials .PK

Chapter 6 THREE PHASE AC MOTORS MCQs

1. . Current is induced in the rotor of three-phase induction motor by _______

(A) AC supply


(B) DC supply


(C) All of above


(D) Induction effect




2. . The ________ supply is used in induction motor.

(A) DC


(B) None


(C) Both


(D) AC




3. . The two prominent parts of induction motor are ________ and ________

(A) Stator, rotor


(B) Slip ring, bearing


(C) Core, end housing


(D) Shaft, stator




4. . Frame of induction motor is made of _________

(A) Wrought iron


(B) Cast steel


(C) Silicon


(D) Cast iron




5. . Supply is provided to ________ in order to start an induction motor.

(A) Rotor


(B) Field


(C) a & b


(D) Stator




6. . There are generally ________ slip rings on squirrel cage induction motor.

(A) Two


(B) Three


(C) None


(D) Four




7. . _________ is placed at rotor of wound rotor induction motor.

(A) Single-phase winding


(B) None of above


(C) Both (a) & (b)


(D) Three-phase winding




8. . The three-phase wound rotor induction motor has ________ slip rings.

(A) Two


(B) Eight


(C) Four


(D) Three




9. . The direction of rotation of three-phase motor can be reversed by ________

(A) By changing the two supply wires


(B) By changing all the supply wires


(C) (a) and (b)


(D) Any of above




10. . If the two phases are interchanged of a three-phase motor then the motor ________

(A) Keeps on running in same direction


(B) Will be reversed


(C) Stopped


(D) Draws excessive current




11. . At starting the motor draws ________ times current of its full load.

(A) Two


(B) Three


(C) Five


(D) Up to 7




12. . If line voltage is 400 V then the phase voltage will be _________

(A) 230 V


(B) 210 V


(C) 220 V


(D) 200 V




13. . In ________ method, the motor draws more current.

(A) All


(B) Auto transformer


(C) Star-Delta


(D) D.O.L




14. . The speed will ________ by reducing the supply frequency.

(A) Decreased


(B) Increased


(C) No change


(D) All




15. . By increasing the stator poles of induction motor, the speed is ________

(A) No change


(B) Increased


(C) Decreased


(D) All




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