sheet 4 Qs - ME1331 Problem Sheet 4 Dr. M. K. Darwish 1) A...

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ME1331 Problem Sheet 4 Dr. M. K. Darwish 1) A 230 V motor has an armature circuit resistance of 0.6 . If the full-load armature current is 30 A and the no-load armature current is 4 A, find the change in the back e.m.f. from no-load to full-load. (15.6 V) 2) A 440 V shunt motor has an armature resistance of 0.8 and field resistance of 200 . Determine the back e.m.f. when giving an output of 10 h.p. at 85% efficiency. (425.8 V) 3) The armature resistance of a 200 V shunt motor is 0.4 and the no-load armature current is 2 A. When loaded and taking an armature current of 50 A, the speed is 1200 r.p.m. Find approximately the no-load speed. (1328 r.p.m.) 4) A 25 kW, 250 V, d.c. shunt generator has an armature and field resistances of 0.06 and 100 respectively. Determine the total armature power developed when working (i) as a generator delivering 25 kW output and (ii) as a motor taking 25 kW input. (26.25 kW, 23.8 kW) 5) A 20 kW compound generator works on full load with a terminal voltage of 250 V. The armature, series, and shunt windings have a resistance of 0.05 , 0.025 , and 100 respectively. Calculate the total e.m.f. generated in the armature when the machine is connected short-shunt. (256.126 V)
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sheet 4 Qs - ME1331 Problem Sheet 4 Dr. M. K. Darwish 1) A...

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