Efficiency

$$\mathrm{Efficiency (\eta) = \frac{Pout}{Pin}}$$$$\mathrm{Efficiency (\eta) = \frac{Pout}{Pout+\mathrm{Losses}}}$$ Ther are two types of losses in a transformer:

• Constant Losses: Core Losses (Eddy, Hysteresis) $$\frac{V_1^2}{Rcore}$$
• Variable Losses: Copper Losses $$I_1^2 (R_1 + R_2')$$ A transformer has maximum efficiency when:

Copper Losses = Core Losses

Example:

For the same transformer used in the previous problems, calculate the efficiency at rated current and 0.8 pf lagging.