A 500 kW, 3-phase, 440 volts, 50 Hz, A.C. induction motor has a speed of 960 r.p.m. on full load. The machine has 6 poles. The slip of the machine will be__________?
A. 0.01
B. 0.02
C. 0.03
D. 0.04
Polyphase Induction Motors
The power scale of circle diagram of an induction motor can be found from__________?
The power scale of circle diagram of an induction motor can be found from__________?
A. stator resistance test
B. no-load test only
C. short-circuit test only
D. noue of the above
A change of 4% of supply voltage to an induction motor will produce a change of approximately ________?
A change of 4% of supply voltage to an induction motor will produce a change of approximately ________?
A. 4% in the rotor torque
B. 8% in the rotor torque
C. 12% in the rotor torque
D. 16% in the rotor torque
The shape of the torque/slip curve of induction motor is__________?
The shape of the torque/slip curve of induction motor is__________?
A. parabola
B. hyperbola
C. rectangular parabola
D. straigth line
The vafcie of transformation ratio of an induction motor can be found by__________?
The vafcie of transformation ratio of an induction motor can be found by__________?
A. open-circuit test only
B. short-circuit test only
C. stator resistance test
D. none of the above
In a three-phase induction motor__________?
In a three-phase induction motor__________?
A. power factor at starting is high as compared to that while running
B. power factor at starting is low as compared to that while running
C. power factor at starting in the same as that while running
In three-phase induction motors sometimes copper bars are placed deep in the rotor to___________?
In three-phase induction motors sometimes copper bars are placed deep in the rotor to___________?
A. improve starting torque
B. reduce copper losses
C. improve efficiency
D. improve power factor
Which is of the following data is required to draw the circle diagram for an induction motor ?
Which is of the following data is required to draw the circle diagram for an induction motor ?
A. Block rotor test only
B. No load test only
C. Block rotor test and no-load test
D. Block rotor test, no-load test and stator resistance test
In case of 3-phase induction motors, plugging means__________?
In case of 3-phase induction motors, plugging means__________?
A. pulling the motor directly on line without a starter
B. locking of rotor due to harmonics
C. starting the motor on load which is more than the rated load
D. interchanging two supply phases for quick stopg
In a three-phase induction motor_______________?
In a three-phase induction motor_______________?
A. iron losses in stator will be negligible as compared to that in rotor
B. iron losses in motor will be neg¬ligible as compared to that in rotor
C. iron losses in stator will be less than that in rotor
D. iron losses in stator will be more than that in rotor