Question

If a transformer is designed for maximum efficiency at rated current and voltage, the full-load copper loss will be
1. much less than the core loss
2. much greater than the core loss
3. equal to the core loss
4. Not definable by these given parameters

Answer 1

Correct Answer - Option 3 : equal to the core loss

Concept:

If the maximum efficiency of the transformer occurs at 'k' times of the full load, then:

\(k=\sqrt{\frac{P_i}{(P_{cu})_{fl}}}\)   ---(1)

Where:

Pi = Core iron loss

(P_cu)_fl = Full load copper loss

The maximum efficiency occurs at rated current and voltage.

∴ k = 1

Analysis:

Putting k = 1 in the Equation (1), we can write:

\(1=\sqrt{\frac{P_i}{(P_{cu})_{fl}}}\)

∴ Pi = (P_cu)_fl

∴ The Full load copper loss will be equal to the core loss.