761. If a D.C. motor designed for 40°C ambient temperature is to be used for 50°C ambient temperature, then the motor_____________?
A. of lower H.P. should be selected
B. of higher H.P. should be selected
C. can be used for 50°C ambient temperature also
D. is to be derated by a factor recommended by manufacturer and select the next higher H.P. motor
762. If the terminals of armature of D.C. motor are interchanged, this action will offer following kind of braking?
A. regenerative
B. plugging
C. dynamic braking
D. none of the above
E. any of the above
763. 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
764. 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
765. 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
766. 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
767. Which of the following motors is most suitable for signaling devices and many kinds of timers ?
A. D.C. shunt motor
B. D.C. series motor
C. Induction motor
D. Reluctance motor
768. Which motor should not be started on no-load ?
A. Series motor
B. Shunt motor
C. Cumulatively compounded motor
D. Differentially compounded motor
769. Ward-Leonard control is basically a____________?
A. voltage control method
B. field divertor method
C. field control method
D. armature resistance control method
770. 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
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