Computer Programming MCQs

5739 MCQs  (Page 66 of 574)

The stating torque of the slip ring induction motor can be increased by adding__________?
A. External inductance to the rotor
B. External resistance to the rotor
C. External capacitance to the rotor
D. Both resistance and inductance to rotor
What will happen if the relative speed between the rotating flux of stator and rotor of the induction motor is zero ?
A. The slip of the motor will be 5%
B. The rotor will not run
C. The rotor will run at very high speed
D. The torque produced will be very large
The torque of a rotor in an induction motor under running condition is maximum__________?
A. At the unit value of slip
B. At the zero value of slip
C. At the value of the slip which makes rotor reactance per phase equal to the resistance per phase
D. At the value of the slip which makes the rotor reactance half of the rotor
In the squirrel-cage induction motor the rotor slots are usually given slight skew__________?
A. To reduce the magnetic hum and locking tendency of the rotor
B. To increase the tensile strength of the rotor bars
C. To ensure easy fabrication
D. None of the above
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
Which motor is preferred for use in mines where explosive gases exist ?
A. Air motor
B. Induction motor
C. D.c. shunt motor
D. Synchronous motor
The torque developed by a 3-phase induction motor least depends on__________?
A. Rotor current
B. Rotor power factor
C. Rotor e.m.f.
D. Shaft diameter
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