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
Answer: Option A
This Question Belongs to Electrical Engineering >> D.C. Motors
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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
We get the speed below the base value by reducing armature voltage, which is the simple method of reducing back emf which is proportional to the residual magnetism. Thus, lower limit of speed is imposed by residual magnetism of the generator.