July 2018

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________?

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 ?

A. Field control
B. Armature voltage control
C. Shunt armature control
D. Mechanical loading system

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 ?

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 ?

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 ?

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 ?

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

If the speed of a D.C. shunt motor is increased, the back e.m.f. of the motor will_________?

A. increase
B. decrease
C. remain same
D. become zero

Which of the following motors one will choose to drive the rotary compressor ?

A. D.C. shunt motor
B. D.C. series motor
C. Universal motor
D. Synchronous motor