3-PHASE INDUCTION MOTOR-7

61. A wound rotor induction motor can be distinguished from squirrel cage induction motor by ________________

diameter of the shaft

size of frame

presence of slip ring

dircetion of rotation

62. Which of the following A.C.motors is used for industrial application?

commutator motor

3-phase induction motor

DC series motor

synchronous motor

63. When a squirrel cage induction motor fails to start which of the following could not be the reason for the same?

uneven air gap

blown fuses

overload

one or two phase open

64. The direction of the rotation of a 3-phase induction motor can be reversed by ________

interchanging any two leads

supplying low voltage

reducing load

reducing frequency

65. Whenever any polyphase induction motor is loaded __________

induced e.m.f. decreases and frequency increases

induced e.m.f. in the rotor remains constant

induced e.m.f. in the rotor increases and its frequency also increases

induced e.m.f. in the rotor increases and its frequency falls

66. If a three phase squirrel-cage induction motor runs slow, which of the following could not be the reason for the same?

shorted stator coils

low voltage

overload

high frequency

67. The probable reason for an induction motor running too hot could be _____

low voltage

uneven air gap

clogged ventilating ducts

any of the above

68. In a 3-phase induction motor, iron loss ___________

in rotor is negligible as compared to that in stator

in stator does not occur

in rotor is equal to iron loss is stator

in rotor is much more than the iron loss in stator

69. Which of the following parameters for an induction motor varies as square of the supply voltage?

slip

synchronous speed

starting current

maximum running torque

70. In case single phasing occurs in delta connected motor _________

one phase will be seriously overloaded and two others will be slightly overloaded

two phases will be seriously overloaded and there will be no current in the third phase

there will be no current in one phase

there will be no current in two phases