July 2018

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

The armature voltage control of D.C. motor provides_____________?

A. constant voltage drive
B. constant current drive
C. constant torque drive
D. none of the above

The plugging gives the____________?

A. zero torque braking
B. smallest torque braking
C. highest torque braking
D. none of the above

For a D.C. shunt motor if the excitation is changed_______________?

A. torque will remain constant
B. torque will change but power will remain constant
C. torque and power both will change
D. torque, power and speed, all will change

Which motor has the poorest speed control?

A. Differentially compounded motor
B. Cumulatively compounded motor
C. Shunt motor
D. Series motor