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Electrical Engineering Objective Questions { Induction Motors }



36.  Slip ring motor is recommended where
A. speed control is required
B. frequent starting, stopping and reversing is required
C. high starting torque is needed
D. all above features are required

37. As load on an induction motor goes on increasing
A. its power factor goes on decreasing
B. its power factor remain constant
C. its power factor goes on increasing even after full load
D. its power factor goes on increasing upto full load and then it falls again

38.  If a 3-phase supply is given to the stator and rotor is short circuited rotor will move
A. in the opposite direction as the direction of the rotating field
B. in the same direction as the direction of the field
C. in any direction depending upon phase squence of supply
D. with synchronous speed

39. It is advisable to avoid line starting of induction motor and use starter because
A. it will run in reverse direction
B. it will pick up very high speed and may go out of step
C. motor takes five to seven times its full-load current
D. starting torque is very high

40. The speed characteristic of an induction motor closely resemble the speedload characteristic of which of the following machines
A. D.C. series motor
B. D.C. shunt motor
C. universal motor
D. none of the above

41. Which type of bearing is provided in small induction motors to support the rotor shaft?
A. Ball bearings
B. Cast iron bearings
C. Bush bearings
D.None of the above

42.  A pump induction motor is switched on to a supply 30% lower than its rated voltage. What will eventually happen? It will
A. start after sometime
B. start immediately
C. continue to run at lower speed without damage
D. get heated and subsequently get damaged

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