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 de-rated by a factor recommended by manufacturer and select the next higher H.P. motor
Answer: Option D
This Question Belongs to Electrical Engineering >> D.C. Motors
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
If a D.C. motor is connected across the A.C. supply it will
A. Run at normal speed
B. Not run
C. Run at lower speed
D. Burn due to heat produced in the field winding by eddy currents
The speed of a D.C. shunt motor can be increased by
A. Increasing the resistance in armature circuit
B. Increasing the resistance in field circuit
C. Reducing the resistance in the field circuit
D. Reducing the resistance in the armature circuit
The armature voltage control of D.C. motor provides
A. Constant torque drive
B. Constant voltage drive
C. Constant current drive
D. None of the above
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