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
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 ?
(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____________?
(A) damage to commutator segments
(B) damage to commutator insulation
(C) increased power consumption
(D) all of the above
Which of the following method of speed control of D.C. machine will offer minimum efficiency ?
(A) Voltage control method
(B) Field control method
(C) Armature control method
(D) All above methods
As -the load is increased the speed of D.C. shunt motor will____________?
(A) reduce slightly
(B) increase slightly
(C) increase proportionately
(D) remains unchanged
Which of the following motor has the poorest speed regulation ?
(A) Shunt motor
(B) Series motor
(C) Differential compound motor
(D) Cumulative compound motor
In a differentially compounded D.C. motor, if shunt field suddenly opens____________?
(A) the motor will first stop and then run in opposite direction as series motor
(B) the motor will work as series motor and run at slow speed in the same direction
(C) the motor will work as series motor and run at high speed in the same direction
(D) the motor will not work and come to stop
Flywheel is used with D.C. compound motor to reduce the peak demand by the motor, compound motor will have to be_____________?
(A) level compounded
(B) under compounded
(C) cumulatively compounded
(D) differentially compounded
Speed control by Ward Leonard method gives uniform speed variation_____________?
(A) in one direction
(B) in both directions
(C) below normal speed only
(D) above normal speed only