When operated at rated voltage, a 230-V shunt motor runs at 1750 r/min at full load and at no load. The full-load armature current is 70.8 A. The shunt field winding has 2000 turns per pole. The resistance of the armature circuit (including brushes and Interpoles) is 0.15?. The magnetization curve at 1750 r/min is

a. Compute the demagnetizing effect of the armature reaction at full load.

b. A long-shunt cumulative series field winding having four turns per pole and a resistance of 0.038? is added to the machine. Compute the speed at full-load current and rated voltage. The shunt field current will remain equal to that of part (a).

c. With the series-field winding of part (b) installed, compute the internal starting torque in N ??? m if the starting armature current is limited to 125 A. Assume that the corresponding demagnetization effect of armature reaction is 230 ampere-turns per pole.

Transcribed Image Text:

200 220 230 250 0.71 E,, V 210 240 0.49 0.55 I, A 0.40 0.44 0.61