A shunt motor operating from a 230-V line draws a full-load armature current of 46.5 A and runs at a speed of 1300 r/min at both no load and full load. The following data is available on this motor: Armature-circuit resistance (including brushes) = 0.17? Shunt-field turns per pole ? 1500 turns The magnetization curve taken with the machine operating as a motor at no load and 1300 r/min is

a. Determine the shunt-field current of this motor at no load and 1300 r/min when connected to a 230-V line. Assume negligible armature-circuit resistance and armature reaction at no load.

b. Determine the effective armature reaction at full load in ampere-turns per pole.

c. How many series-field turns should be added to make this machine into a long-shunt cumulatively compounded motor whose speed will be 1210 r/min when the armature current is 46.5 A and the applied voltage is 230 V? Assume that the series field has a resistance of 0.038?.

d. If a series-field winding having 20 turns per pole and a resistance of 0.038? is installed, determine the speed when the armature current is 46.5 A and the applied voltage is 230 V.

E,, V Ir, A 240 220 250 180 200 1.15 2.27 1.93 1.46 0.98