GATE 2015 EE – Question 61
Two single-phase transformers $T_1$ and $T_2$ each rated at 500 kVA are operated in parallel. Percentage impedances of $T_1$ and $T_2$ are $(1 + j6)$ and $(0.8 + j4.8)$, respectively. To share a load of 1000 kVA at 0.8 lagging power factor, the contribution of $T_2$ (in kVA) is ________.
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Correct answer: 554 to 556
Explanation
Parallel transformers share the load current in inverse proportion to their impedances. The share of $T_2$ is $S\frac{Z_1}{Z_1 + Z_2}$. Here $|Z_1| = \sqrt{1 + 36} = 6.083$, and $Z_1 + Z_2 = 1.8 + j10.8$ has magnitude 10.949. So $S_2 = 1000 \times \frac{6.083}{10.949} = 555.6$ kVA.