Hi friends, this is post about objectives of electrical engineering with emphasis on dc motor check out and comment...
1) The shunt armature control method of speed control for dc shunt motors is
A) less expensive
B) less wasteful
C) suitable for rapidly changing loads
D) none of the above
Ans:C
2) Ward leonard control is basically a ................ control method
A) armature control
B) field
C) field divertor
D) armature resistance
Ans:A
3) Ward-leonard control provides speed control
A) in one direction only
B) in both directions
C) above rated speed
D) below rated speed
Ans:B
4) The main disadvantage of the ward leonard system is
A) high initial cost
B) poor overall efficiency
C) high maintenance cost
D) all of the above
Ans:D
5) The armature voltage control is considered suitable for a dc motor driven at constant
A) torque
B) speed
C) power
D) current
Ans:A
6) Variation in speed by ward Leonard control of dc motors occurs due to variation in
A) field excitation
B) armature current
C) armature voltage
D) supply voltage
Ans:C
7) For a constant supply voltage, what are the effects of inserting a series resistance in the field circuit of a dc shunt motor, on its speed and torque?
A) speed will decrease and the torque will decrease
B) speed will increase and the torque will increase
C) speed will increase and the torque will decrease
D) speed will decrease and the torque will increase
Ans:C
8) In ward leonard system, the lower limit of speed is imposed by
A) armature resistance
B) field resistance
C) residual magnetism of the generator
D) none of the above
Ans:C
9) Ward-Leonard system for controlling the speed of a dc motor is used where
A) the speed in both the directions is required
B) very fine speed control over the whole range from zero to normal speed is required
C) the accuracy in speed control is required
D) all of the above
Ans:D
10) For very sensitive and wide speed control, the preferable control method is
A) field control
B) armature control
C) multiple voltage control
D) Ward Leonard system
Ans:D
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