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GATE 2026 EE – Question 17

Electrical Machines · Auto-transformer, Electromechanical energy conversion principles · 1 mark · Multiple choice

A 15 kVA, 1100 V/220 V, single-phase two-winding transformer is configured as a 1.32 kV/1.1 kV autotransformer.

What will be the rating of the autotransformer?

  1. 60 kVA
  2. 75 kVA
  3. 90 kVA
  4. 100 kVA

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Correct answer: (C) 90 kVA

Explanation

The 220 V winding is put in series with the 1100 V winding ($1100+220=1320$ V). The current in the 220 V winding is limited to its rating $15000/220=68.18$ A, and this same current flows in the autotransformer's high-voltage terminal. The autotransformer rating is $1320\times68.18=90$ kVA.