Which one of the following is not the function of pole shoes in a D.C. machine ?
A. To reduce eddy current loss
B. To support the field coils
C. To spread out flux for better uniformity
D. To reduce the reluctance of the magnetic path
D.C. Motors
If the supply voltage for a D.C. motor is increased, which of the following will decrease ?
If the supply voltage for a D.C. motor is increased, which of the following will decrease ?
A. Starting torque
B. Operating speed
C. Full-load current
D. All of the above
Which of the following motor is preferred for operation in highly explosive atmosphere ?
Which of the following motor is preferred for operation in highly explosive atmosphere ?
A. Series motor
B. Shunt motor
C. Air motor
D. Battery operated motor
Sparking at the commutator of a D.C. motor may result in____________?
Sparking at the commutator of a D.C. motor may result in____________?
A. damage to commutator segments
B. damage to commutator insulation
C. increased power consumption
D. all of the above
In case of conductively compensated D.C. series motors, the compensating winding is provided______________?
In case of conductively compensated D.C. series motors, the compensating winding is provided______________?
A. as separately wound unit
B. in parallel with armature winding
C. in series with armature winding
D. in parallel with field winding
For the same H.P. rating and full load speed, following motor has poor starting torque_____________?
For the same H.P. rating and full load speed, following motor has poor starting torque_____________?
A. shunt
B. series
C. differentially compounded
D. cumulativelyc’ompounded
D.C. series motors are used______________?
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
If a D.C. shunt motor is working at no load and if shunt field circuit suddenly opens__________?
If a D.C. shunt motor is working at no load and if shunt field circuit suddenly opens__________?
A. nothing will happen to the motor
B. this will make armature to take heavy current, possibly burning it
C. this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses D. motor will run at very slow speed
Which D.C. motor will be suitable along with flywheel for intermittent light and heavy loads?
Which D.C. motor will be suitable along with flywheel for intermittent light and heavy loads?
A. Series motor
B. Shunt motor
C. Cumulatively compounded motor
D. Differentially compounded motor
Which D.C. motor has got maximum self loading property?
Which D.C. motor has got maximum self loading property?
A. Series motor
B. Shunt motor
C. Cumulatively compounded ‘motor
D. Differentially compounded motor