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.Management Sciences
Category: D.C. Motors
The armature voltage control of D.C. motor provides____________?
A. constant torque drive
B. constant voltage drive
C. constant current drive
D. none of the above
In the D.C. motor the iron losses occur in____________?
A. the field
B. the armature
C. the brushes
D. the commutator
In variable speed motor___________?
A. a stronger commutating field is needed at low speed than at high speed
B. a weaker commutating field is needed at low speed than at high speed
C. same commutating field is needed at low speed than at high speed
D. none of the above is correct
In D.C. motor which of the following can sustain the maximum temperature rise?
A. Slip rings
B. Commutator
C. Field winding
D. Armature winding
D.C. motor is to drive a load which has certain minimum value for most of the time and some peak value for short duration. We will select the________________?
A. series motor
B. shunt motor
C. compound motor
D. any of the above
Which of the following load normally needs starting torque more than the rated torque?
A. Blowers
B. Conveyors
C. Air compressors
D. Centrifugal pumps
Armature reaction in dc motor results___________?
A. decrease in speed
B. increase in speed
C. short circuit
D. open circuit
A direct on line starter is used: for starting motors___________?
A. up to 5 H.P
B. up to 10 H.P
C. up to 15 H.P
D. up to 20 H.P
If a D.C. shunt motor is working at full load and if shunt field circuit suddenly opens____________?
A. this will make armature to take heavy current, possibly burning it
B. this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses
C. nothing will happen to motor
D. motor will come to stop
The losses occurring in a D.C. generator are given below. Which loss is likely to have highest proportion at rated load of the generator ?
A. hysteresis loss
B. field copper loss
C. armature copper loss
D. eddy current loss
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