GATE EE 2018 Set 1 — Question 61
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Electrical Machines → Three-Phase Transformers → Connections & Vector Groups
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Question
A 3-phase 900 kVA, 3 kV / kV (/Y), 50 Hz transformer has primary (high voltage side) resistance per phase of 0.3 and secondary (low voltage side) resistance per phase of 0.02 . Iron loss of the transformer is 10 kW. The full load % efficiency of the transformer operated at unity power factor is _______ (up to 2 decimal places).
Correct answer
97.2 to 97.55
Solution
1.Transformer Rating and Voltages:
- Rating kVA
- Primary Voltage V (Delta connected)
- Secondary Voltage V (Star connected, phase voltage is V)
- Primary line current A.
- Primary phase current (Delta) A.
- Secondary line current A.
- Secondary phase current (Star) A.
- Total Copper Loss
- W = 14.4 kW.
- Iron Loss kW.
- Total Loss kW.
- Output Power kW.
- Efficiency
- .
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