1. A DC shunt Motor has the following parameters as shown in Fig. 1: Prated 15 hp: Vrate: 240V: nrated 1200 r/min; R = 0.40 0: R = 100 QR = 100 to 400.02. Rotational losses are 1800 W at full load. The magnetization curve for the dc motor was made at a constant speed of 1200 r/min as shown in Fig. 2. a) If the resistor Rad is adjusted to 175 what is the rotational speed of the motor at no-load conditions? b) Assuming no armature reaction. What is the speed of the motor at full load? What is the speed regulation of the motor? what c) If the motor is operating at full load and if its variable resistance R is increased to 250 is the new speed of the motor? Compare the full -load speed of the motor with R = 1750 to the full-load speed with Rag = 250 0. (Assume no armature reaction, as in the previous problem.) d) Assume that the motor is operating at full load and that the variable resistor Rag is again 175 Q. If the armature reaction is 1200 A- turns at full load. What is the speed of the motor? How does it compare to the result for b? e) If Rad can be adjusted from 100 to 400 Q. what are the maximum and minimum no-load speeds possible with this motor? R w 040 = & pe 320 300 280 20 240 230 200 180 RF 300 £2 Vy240 V 140 120 100 NO O 40 30 2 ய Speed 200 04 05 06 07 as a 1.0 1.12 134 SA