The hysteresis loss in a D.C. machine least depends on____________?
A. Frequency of magnetic reversals
B. Maximum value of flux density
C. Volume and grade of iron
D. Rate of flow of ventilating air
D.C. Motors
Regenerative method of braking is based on that___________?
Regenerative method of braking is based on that___________?
A. back e.m.f. is less than the applied voltage
B. back e.m.f. is equal to the applied voltage
C. back e.m.f. of rotor is more than the applied voltage
D. none of the above
The main disadvantage of the Ward-Leonard control method is______________?
The main disadvantage of the Ward-Leonard control method is______________?
A. high initial cost
B. high maintenance cost
C. low efficiency at Hght loads
D. all of the above
In Ward-Leonard control the lower limit of speed is imposed by________?
In Ward-Leonard control the lower limit of speed is imposed by________?
A. residual magnetism of the generator
B. core losses of motor
C. mechanical losses of motor and generator together
D. all of the above
For constant torque drive which speed control method is preferred ?
For constant torque drive which speed control method is preferred ?
A. Field control
B. Armature voltage control
C. Shunt armature control
D. Mechanical loading system
Ward-Leonard control is basically a____________?
Ward-Leonard control is basically a____________?
A. voltage control method
B. field divertor method
C. field control method
D. armature resistance control method
Which motor should not be started on no-load ?
Which motor should not be started on no-load ?
A. Series motor
B. Shunt motor
C. Cumulatively compounded motor
D. Differentially compounded motor
Which of the following motors is most suitable for signalling devices and many kinds of timers ?
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
Which of the following motors is usually used in house-hold refrigerators ?
Which of the following motors is usually used in house-hold refrigerators ?
A. D.C. shunt motor
B. D.C. series motor
C. Single phase induction motor (split phase start or induction run motor)
D. Reluctance motor
E. Synchronous motor
Why are the D.C. motors preferred for traction applications ?
Why are the D.C. motors preferred for traction applications ?
A. Torque and speed are inversely proportional to armature current
B. Torque is proportional to armature current
C. Torque is proportional to square root of armature current
D. The speed is inversely proportional to the torque and the torque is proportional to square of armature current