GATE 2017 EE – Question 59
A separately excited DC generator supplies 150 A to a 145 V DC grid. The generator is running at 800 RPM. The armature resistance of the generator is 0.1 $\Omega$. If the speed of the generator is increased to 1000 RPM, the current in amperes supplied by the generator to the DC grid is ________. (Give the answer up to one decimal place.)
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Correct answer: 548 to 552
Explanation
The generated emf at 800 rpm is $145 + 150 \times 0.1 = 160$ V. The field is unchanged, so at 1000 rpm the emf is $160 \times \frac{1000}{800} = 200$ V. The current into the 145 V grid is $\frac{200 - 145}{0.1} = 550$ A.