Single phase induction motors

41. Which of the following applications always have some load whenever switched on ?

Vacuum cleaners
Fan motors
Pistol drills
All of the above

Detailed SolutionWhich of the following applications always have some load whenever switched on ?

42. In a split phase motor, the running winding should have

high resistance and low inductance
low resistance and high inductance
high resistance as well as high inductance
low resistance as well as low inductiance

Detailed SolutionIn a split phase motor, the running winding should have

43. In which single-phase motor, the rotor has no teeth or winding ?

Split phase motor
Reluctance motor
Hysteresis motor
Universal motor

Detailed SolutionIn which single-phase motor, the rotor has no teeth or winding ?

44. A centrifugal switch is used to disconnect starting winding when motor has

run for about 1 minute
run for about 5 minutes
picked up about 50 to 70 per cent of rated speed
picked up about 10 to 25 per cent of rated speed

Detailed SolutionA centrifugal switch is used to disconnect starting winding when motor has

45. In repulsion motor direction of rotation of motor

Is opposite to that of brush shift
Is the same as that of brush shift
Is independent of brush shift
nan

Detailed SolutionIn repulsion motor direction of rotation of motor

46. Which of the following statements regarding repulsion-start induction motor is incorrect ?

It requires more maintenance of commutator and other mechanical devices
It makes quite a bit of noise on starting
In fractional horse power motors, it has replaced the capacitor motors
It is not easily reversed

Detailed SolutionWhich of the following statements regarding repulsion-start induction motor is incorrect ?

47. In case of a reluctance motor, when the load is increased so that it cannot maintain synchronous speed the motor will

Become unstable
Draw excessive armature current and may burn out
Fall out of synchronism and come to stand still
Run as induction motor

Detailed SolutionIn case of a reluctance motor, when the load is increased so that it cannot maintain synchronous speed the motor will

48. In a

through resistance
through reactances
series motor armature coils are usually connected to commutator A. through resistance B. through reactances C. through capacitors
solidly

Detailed SolutionIn a

49. If the centrifugal switch does not open at 70 to 80 percent of synchronous speed of motor, it would result in

Damage to the starting winding
Damage to the centrifugal switch
Overloading of running winding
None of the above

Detailed SolutionIf the centrifugal switch does not open at 70 to 80 percent of synchronous speed of motor, it would result in

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