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.Management Sciences
Category: D.C. Motors
Buses, trains, trolleys, hoists, cranes require high starting torque and therefore make use of_____________?
A. D.C. series motor
B. D.C. shunt motor
C. induction motor
D. all of above motors
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
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
D.C. generators are normally designed for maximum efficiency around_____________?
A. full-load
B. rated r.p.m.
C. rated voltage
D. all of the above
Which of the following motors is most suitable for signalling devices and many kinds of timers ?
A. D.C. shunt motor
B. D.C. series motor
C. Induction motor
D. Reluctance motor
In D.C. machines the residual magnetism is of the order of_________________?
A. 2 to 3 per cent
B. 10 to 15 per cent
C. 20 to 25 per cent
D. 50 to 75 per cent
Which of the following motor has the poorest speed regulation ?
A. Shunt motor
B. Series motor
C. Differential compound motor
D. Cumulative compound motor
These days D.C. motors are widely used in____________?
A. pumping sets
B. air compressors
C. electric traction
D. machine shops
Which D.C. motor is preferred for elevators ?
A. Shunt motor
B. Series motor
C. Differential compound motor
D. Cumulative compound motor
The speed of a D.C. series motor is_____________?
A. proportional to the armature current
B. proportional to the square of the armature current
C. proportional to field current
D. inversely proportional to the armature current
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