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GATE 2016 EE – Question 35

Electrical Machines · Single phase transformer: equivalent circuit, phasor diagram, open circuit and short circuit tests, regulation and efficiency · 1 mark · Multiple choice

If an ideal transformer has an inductive load element at port 2 as shown in the figure below, the equivalent inductance at port 1 is

An ideal transformer with turns ratio $n : 1$ between port 1 and port 2, with an inductor $L$ connected across port 2.
  1. $nL$
  2. $n^2 L$
  3. $\frac{n}{L}$
  4. $\frac{n^2}{L}$

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Correct answer: (B) $n^2 L$

Explanation

With a turns ratio of $n : 1$ between port 1 and port 2, an impedance on the secondary side appears at the primary multiplied by the square of the ratio. So the inductor $L$ looks like $n^2 L$ at port 1.