Polyphase Induction Motor MCQ - Set 03 - ObjectiveBooks

# Practice Test: Question Set - 03

1. The purpose of using short-circuit gear is
(A) To short circuit the rotor at slip rings
(B) To short circuit the starting resistances in the starter
(C) To short circuit the stator phase of motor to form star
(D) None of the above

2. The starting torque of a three phase induction motor can be increased by
(A) Increasing slip
(B) Increasing current
(C) Both (A) and (B)
(D) None of the above

3. In medium sized induction motors, the slip is generally around
(A) 0.04 %
(B) 0.4 %
(C) 4 %
(D) 14 %

4. A double squirrel-cage induction motor has
(A) Two rotors moving in opposite direction
(B) Two parallel windings in stator
(C) Two parallel windings in rotor
(D) Two series windings in stator

5. The torque developed in the cage induction motor with auto-starter is
(A) k/torque with direct switching
(B) K × torque with direct switching
(C) K2 × torque with direct switching
(D) k2/torque with direct switching

6. An induction motor is
(A) Self-starting with zero torque
(B) Self-starting with high torque
(C) Self-starting with low torque
(D) Non-self starting

7. A 3-phase induction motor stator delta connected, is carrying full load and one of its fuses blows out. Then the motor
(A) Will continue running burning its one phase
(B) Will continue running burning its two phases
(C) Will stop and carry heavy current causing permanent damage to its winding
(D) Will continue running without any harm to the winding

8. A pump induction motor is switched on to a supply 30% lower than its rated voltage. The pump runs. What will eventually happen? It will
(A) Stall after sometime
(B) Stall immediately
(C) Continue to run at lower speed without damage
(D) Get heated and subsequently get damaged

9. The shape of the torque/slip curve of induction motor is
(A) Parabola
(B) Hyperbola
(C) Rectangular parabola
(D) Straight line

10. Blocked rotor test on induction motors is used to find out
(A) Leakage reactance
(B) Power factor on short circuit
(C) Short-circuit current under rated voltage
(D) All of the above

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