Induction Motors Objectives Part 04

61) In terms of slip S, the ratio (Rotor Copper Loss / Rotor Input) = S.

62) If the air gap of an induction motor is increased, more ampere turns will be needed to produce same flux density in the air gap.

63) In the rheostatic speed control method for induction motors, as the speed increases, torque decreases.

64) As the load on a squirrel cage induction motor is increased, slip increases.

65) Which of the following could not be the value of power factor of an induction motor under no load conditions 0.2 lagging.

66) A 3-phaseinduction motor while running on 25% of rated load, has one of its fuses removed. The line current in two phases will increase to compensate for the dead phase.

67) In a 3-phaseinduction motor, iron loss in rotor is negligible as compared to that in stator.

68) When a 3-phaseinduction motor is subjected to blocked rotor test, the power factor of the full load short circuit current as compared to that at no load is high.

69) For identical ratings, which of the following machines takes more lagging current? Single phase Induction motor.

70) An induction motor operates at maximum power factor when operating on Full load.

71) A three-phase induction motor takes A amperes on full load at a power factor cosθ the component responsible for producing magnetism is Asinθ.

72) The direction of rotation of a 3-phaseinduction motor can be reversed by interchanging any two phases.

73) Two induction motors A and B have efficiencies of 80% and 90% respectively. It can be concluded that Motor A will be smaller in size as compared to motor B.

74) If a 3-phaseinduction motor needs frequent starting and operation in forward and reverse directions, which type of starter will be preferred? Direct Online.

75) A wound rotor induction motor is usually not selected when cost is the main consideration.

76) A squirrel cage induction motor is not selected when higher starting torque is the main consideration.

77) The starting torque of a three-phase induction motor can be increased by increasing the rotor resistance.

78) The essential condition for the injected e.m.f in the rotor of induction motor is, it should have the same frequency as the main supply voltage frequency.

79) If two machines are running in synchronism and the voltage of one machine is suddenly increased, synchronizing torque will be produced to restore further synchronism.

80) An induction motor when started on load, does not accelerate up to full speed but runs at 1/7th normal full speed, the motor is said to be crawling.