Question

The power measured during the open-circuit test mainly represents

• A. Copper loss
• B. Core loss
• C. Leakage loss
• D. Stray loss

Hint:

Transformer tests: \[ \boxed{ \begin{aligned} \text{Open-circuit test} &\rightarrow \text{Core (iron) loss} \text{Short-circuit test} &\rightarrow \text{Copper loss} \end{aligned} } \]

Answer 1

The Correct Option is B

Step 1: Recall the purpose of the open-circuit test. In the open-circuit (no-load) test of a transformer, - the secondary winding is kept open, - the rated voltage is applied to the primary, - the no-load current is very small. Hence, copper loss is negligible.

Step 2: Identify the measured power. Since copper loss is negligible, the wattmeter reading mainly represents \[ \boxed{\text{Core (iron) loss}} \] which consists of hysteresis and eddy current losses. Therefore, \[ \boxed{(B)} \] is the correct answer.