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GATE 2014 EE (EE2) – Question 49

Electrical Machines · Types of losses and efficiency calculations of electric machines · 2 marks · Multiple choice

A single-phase two-winding transformer’s supply voltage and frequency both increase 10%. Find percentage changes in hysteresis and eddy-current losses respectively.

  1. 10 and 21
  2. −10 and 21
  3. 21 and 10
  4. −21 and 10

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Show answer and explanation

Correct answer: (A) 10 and 21

Explanation

Peak flux is proportional to V/f,so raising both by10%keeps flux density unchanged. Hysteresis loss varies as fBm^n and therefore rises10%. Eddy-current loss varies as f²Bm² and rises(1.1²−1)×100=21%. The requested pair is **10%,21%,A**.