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LMRC Assistant Manager Electrical : 2018 Paper

Option 1 : Copper loss is equal to core loss

NTPC Diploma Trainee 2020: Full Mock Test

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Copper loss:

A loss in a transformer that takes place in the winding resistance of a transformer is known as the copper loss.

Copper loss = i2R

Iron loss:

Iron losses = Eddy current loss + hysteresis loss

Eddy current loss = Ket2f2B2

Hysteresis loss = KhfBx

The transformer will give the maximum efficiency when their copper loss is equal to the iron loss.

Efficiency is maximum at some fraction x of full load.

\(x = \sqrt {\frac{{{W_i}}}{{{W_{cu}}}}}\)

Where Wi = iron losses

Wcu = copper losses

kVA at maximum efficiency is given by,

\(kVA\;at\;{\eta _{max}} = full\;load\;kVA \times \sqrt {\frac{{{W_i}}}{{{W_{cu}}}}}\)