A 40KVA transformer has a core loss of 450 W and total loss of 800 W. Find the copper loss for Maximum efficiency

• A. 350 W
• B. 300 W
• C. 800 W
• D. 450 W

Answer: (D)

It means that the efficiency is maximum at a load when the copper-loss (variable loss) equals the core-loss (constant loss). Thus for maximum efficiency
Copper loss(Variable loss) = Core loss(constant loss)
Core loss = 450 Watt = Copper loss
Cooper loss = 450 Watt