1. A 230-V DC shunt motor has the following parameters: Ra = 0.5 Q Rf = 75 Q Prot = 500 W at 1,120 r/min When loaded, the motor draws 46 A from the line. Find a. The speed, Pdev, and Tsh. b. If Lf = 25 H, La = 0.008 H, and the terminal voltage has a 115-V change, find ia(t) and ωm(t).
2. A 200-V DC shunt motor with an armature resistance of 0.1 Q and a field resistance of 100 Q draws a line current of 5 A when running with no load at 955 r/min. Determine the motor speed, the motor efficiency, the total losses (i.e., rotational and I 2R losses), and the load torque Tsh that will result when the motor draws 40 A from the line. Assume rotational power losses are proportional to the square of shaft speed.