Answer Happy

Question 2: (4+7+9=20 Marks) "approximtly 25 min" RG In a 15-hp, 240-V, 1200-rpm shunt DC motor, the armature resistance is 0.40 02 and the field resistance is 1000. The magnetization curve of the motor is assumed to be linear in the operating region. Neglect mechanical losses and armature reaction. a) If the motor is running at 1200RPM at no-load and R 100 ohms, what will be the motor EMF?) b) If an additional adjustable resistance is inserted in series with the shunt field, and it can be varied between zero and 100 , find the possible range for no-load speed with the adjustable resistance connected. c) With the adjustable resistance in series with the shunt field set to zero, what is the speed regulation of the motor if its net output is 15HP? Note: the speed regulation is given by : Speed Regulation = (No Load Speed - Full Load Speed)/(No Load Speed) BONUS [5 marks] (Applies for Prof. Ehab's Section Only) If the motor drives a mechanical load whose torque varies as the square of the speed, find the additional armature resistance required to give half-rated speed at the rated voltage. (adjustable filed resistance is set to zero). T Ra