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.Management Sciences
Category: Polyphase Induction Motors
When the equivalent circuit diagram of doouble squirrel-cage induction motor is constructed the two cages can be considered__________?
A. in series
B. in parallel
C. in series-parallel
D. in parallel with stator
Blocked rotor test on induction motors is used to find out?
A. leakage reactance
B. power factor on short circuit
C. short-circuit current under rated voltage
D. all of the above
A 3-phase slip ring motor has____________?
A. double cage rotor
B. wound rotor
C. short-circuited rotor
D. any of the above
The starting torque of a three phase induction motor can be increased by__________?
A. increasing slip
B. increasing current
C. both A. and (b)
D. none of the above
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
In case the air gap in an induction motor is increased____________?
A. the magnetising current of the rotor will decrease
B. the power factor will decrease
C. speed of motor will increase
D. the windage losses will increase
An induction motor is__________?
A. self-starting with zero torque
B. self-starting with high torque
C. self-starting with low torque
D. non-self starting
An induction motor is identical to_________?
A. D.C. compound motor
B. D.C. series motor
C. synchronous motor
D. asynchronous motor
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
The power factor of an induction motor under no-load conditions will be closer to_____________?
A. 0.2 lagging
B. 0.2 leading
C. 0.5 leading
D. unity
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