A. high initial cost
B. high maintenance cost
C. low efficiency at Hght loads
D. all of the above
Related Mcqs:
- 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 - Ward Leonard method of speed control is basically a______________?
A. field control method
B. armature controlled method
C. field diverter
D. frequency control method - Ward-Leonard control is basically a____________?
A. voltage control method
B. field divertor method
C. field control method
D. armature resistance control method - 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 - In a D.C. shunt motor, speed is______________?
A. independent of armature current
B. directly proportional to the armature current
C. proportional to the square of the current
D. inversely proportional to the armature current - The mechanical power developed by a shunt motor will be maximum when the ratio of back e.m.f. to applied voltage is______________?
A. 4.0
B. 2.0
C. 1.0
D. 0.5 - The condition for maximum power in case of D.C. motor is______________?
A. back e.m.f. = 2 x supply voltage
B. back e.m.f. = | x supply voltage
C. supply voltage = | x back e.m.f
D. supply voltage = back e.m.f - The speed of a motor falls from 1100 r.p.m. at no-load to 1050 r.p.m. at rated load. The speed regulation of the motor is______________?
A. 2.36%
B. 4.76%
C. 6.77%
D. 8.84% - The condition for maximum efficiency for a D.C. generator is______________?
A. eddy current losses = stray losses
B. hysteresis losses = eddy current losses
C. copper losses = 0
D. variable losses = constant losses - 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
