23 hp, dc shunt motor is running at 1000 rpm when the armaturevoltage is 600 V. The armature resistance of the motor is 0.8 ohm,and the field resistance is 900 ohm. The efficiency of the motor atfull load is 92 %.
a) Calculate the value of the resistance of the dynamic brakingat full load. The armature current should be limited to 150% of therated value.
b) If the motor operated in regenerative braking at a speed of1100 rpm, calculate the line current.
c) Design a circuit for countercurrent braking (by reversingsupply voltage) so that the line current will not exceed 120% ofthe rated value.
