Correct Answer - Option 1 : coper loss = iron loss
Copper loss:
A loss in a transformer that takes place in the winding resistance of a transformer is known as copper loss. These are variable losses.
Copper loss = i2R
Iron loss:
Iron losses = Eddy current loss + hysteresis loss
Eddy current loss = Ket2f2B2
Hysteresis loss = KhfBx
These are constant losses.
Efficiency:
The efficiency of the Transformer \((\eta ) = \frac{{XS\cos \phi }}{{XS\cos \phi + {P_i} + {X^2}{P_e}}}\)
Where, X = Fraction of load
S = Apparent power in kVA
Wi = Iron losses
Wcu = Copper losses
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,
\(kVA\;at\;{\eta _{max}} = full\;load\;kVA \times \sqrt {\frac{{{W_i}}}{{{W_{cu}}}}}\)
