GATE 2014 EE (EE2) – Question 22

Electrical Machines · Auto-transformer, Electromechanical energy conversion principles · 1 mark · Numerical answer

A single-phase 50 kVA, 1000/100 V two-winding transformer is connected as the autotransformer shown. Find its kVA rating.

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Correct answer: 545 to 555

Explanation

The100Vwinding originally carries50kVA/100V=500A. As the series winding it carries the autotransformer output current at1100V. Therefore the new rating is1100×500=**550kVA**. This is11times the two-winding rating because most power transfers conductively rather than magnetically.