Related Questions

Which type of bearing is provided in small induction motors to support the rotor shaft?
A Ball bearings
B Cast iron bearings
C Bush bearings
D None of the above
In squirrel cage induction motors, the rotor slots are usually given slight skew in order to
A Reduce windage losses
B Reduce eddy currents
C Reduce accumulation of dirt and dust
D Reduce magnetic hum
Which one of the following is not necessarily the advantage of D.C. motors over A.C. motors?
A Low cost
B Wide speed range
C Stability
D High starting torque
In an induction motor if air-gap is increased
A The power factor will be low
B Windage losses will be more
C Bearing friction will reduce
D Copper loss will reduce in an induction motor
In case the air gap in an induction motor is increased
A The magnetizing current of the rotor will decrease
B The power factor will decrease
C Speed of motor will increase
D The windage losses will increase
The good power factor of an induction motor can be achieved if the average flux density in the air gap is
A Absent
B Small
C Large
D Infinity
In medium sized induction motors, the slip is generally around
A 0.04 %
B 0.4 %
C 4 %
D 14 %
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
For three-phase induction motors which of the following is the least efficient method of speed control?
A Cascade control
B Pole changing
C Rheostat control
D Combination of cascade and pole changing
In three-phase squirrel-cage induction motors
A Rotor conductor ends are short-circuited through slip rings
B Rotor conductors are short-circuited through end rings
C Rotor conductors are kept open
D Rotor conductors are connected to insulation

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