Exam Question

(a) Discuss different methods of speed control of a d.c. series motor by adjusting field ampere turns. (6)

(b) A 230 V, d.c. shunt motor runs at 1000 r.p.m. and takes 5 amperes. The armature resistance of the motor is 0.025 Ω and shunt field resistance is 230 Ω. Calculate the drop in speed when the motor is loaded and takes the line current of 14 amperes. Neglect armature reaction. (10)