The constant-speed magnetization curve for a 25-kW, 250-V dc machine at a speed of 1200 r/min is shown in Figure. This machine is separately excited and has an armature resistance of 0.14?. This machine is to be operated as a dc generator while driven from a synchronous motor at constant speed.

a. What is the rated armature current of this machine?

b. With the generator speed held at 1200 r/min and if the armature current is limited to its rated value, calculate the maximum power output of the generator and the corresponding armature voltage for constant field currents of

(i) 1.0 A,

(ii) 2.0 A and

(iii) 2.5 A.

c. Repeat part (b) if the speed of the synchronous generator is reduced to 900r/min.

Transcribed Image Text:

300 250 200 150 100 S0 0.5 1.0 1.5 2.0 2,5 Field current. A Generated emf, V