Prob.4- The rated values for a separately excited DC motor are 5 kW, 140 V, 1800 r/min and the efficiency n is 91% (the losses such as mechanical losses and iron losses are ighored). The armature...

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Extracted text: Prob.4- The rated values for a separately excited DC motor are 5 kW, 140 V, 1800 r/min and the efficiency n is 91% (the losses such as mechanical losses and iron losses are ighored). The armature resistance is 0.25 2. Evaluate the following questions. 1. the amature current and the rated torque 2. the speed at full-load when the armature voltage is reduced by 10% 3. the speed at full-load current when the flux is reduced by 10%. 4. the output torque available by amature curent at this speed