GATE 2016 EE – Question 57
A DC shunt generator delivers 45 A at a terminal voltage of 220 V. The armature and the shunt field resistances are 0.01 $\Omega$ and 44 $\Omega$ respectively. The stray losses are 375 W. The percentage efficiency of the DC generator is ________.
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Correct answer: 86 to 88
Explanation
The shunt field current is $\frac{220}{44} = 5$ A, so the armature current is $45 + 5 = 50$ A. The armature copper loss is $50^2 \times 0.01 = 25$ W and the field loss is $5^2 \times 44 = 1100$ W. With the stray loss of 375 W, the total loss is 1500 W. The output is $220 \times 45 = 9900$ W, so the efficiency is $\frac{9900}{9900 + 1500} = 0.868$, or 86.8 percent.