1) A 40-hp, 500 V, 1200-rpm DC shunt motor has rotationallosses of 2000 W at rated speed. The armature resistance is 0.46Ω and the field resistance is300Ω. A) Calculate the armature current when the motor is delivering rated load at rated voltage andrated RPM. B) Determine the
electromagnetic torque, shaft-output torque, and efficiency ofthe shunt wound motor.
2) A 15 hp, 440 V, 1250 rpm separately excited dc motor drawsan armature current of 30 A at rated load. The no-load armature current is 5.0 A. Thearmature resistance is 0.75 Ω. Consider that the rotational losses (core + mechanical) areproportional to the speed. Neglect the field winding losses. The field current is kept constant and themachine is not saturated. For a 360 V armature voltage, the recorded shaft speed is 1000 rpm. Find:A) The value of the armature current and type of operation of the machine(motor/generator); B) The electromagnetic
(induced/converted) power and torque; C) The shaft power andtorque; D) The efficiency of the machine; E) What would be the shaft speed and torque requiredfor the machine to supply (generator mode) 15 hp to a 440 V dc bus? Any problems withthis operating condition?