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.Management Sciences
Category: D.C. Motors
Which of the following loss in a D.C. generator varies significantly with the load current ?
A. Field copper loss
B. Windage loss
C. Armature copper loss
D. None of the above
The starting resistance of a D.C. motor is generally_______________?
A. low
B. around 500 Q
C. 1000 Q
D. infinitely large
For a D.C. shunt motor if the excitation is changed_______________?
A. torque will remain constant
B. torque will change but power will remain constant
C. torque and power both will change
D. torque, power and speed, all will change
In D.C. machines fractional pitch winding is used__________?
A. to improve cooling
B. to reduce copper losses
C. to increase the generated e.m.f.
D. to reduce the sparking
Ward-Leonard control is basically a____________?
A. voltage control method
B. field divertor method
C. field control method
D. armature resistance control method
The speed of a D.C. shunt motor more than its full-load speed can be obtained by_____________?
A. decreasing the field current
B. increasing the field current
C. decreasing the armature current
D. increasing the armature current
A three point starter is considered suitable for______________?
A. shunt motors
B. shunt as well as compound motors
C. shunt, compound and series motors
D. all D.C. motors
Which motor should not be started on no-load ?
A. Series motor
B. Shunt motor
C. Cumulatively compounded motor
D. Differentially compounded motor
D.C. series motors are used______________?
A. where load is constant
B. where load changes frequently
C. where constant operating speed is needed
D. in none of the above situations
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