Which statement about transformer regulation is true?

Which statement about transformer regulation is true?

• A. It is the ratio of primary to secondary voltages at full load.
• B. It is the efficiency of the transformer at no load.
• C. It is the change in secondary voltage with load expressed as a percentage of no-load voltage.
• D. It is the change in secondary voltage from no-load to full-load expressed as a percentage of full-load voltage.

Answer: (D)

Transformer regulation measures how much the secondary voltage changes when a transformer goes from no-load to full-load, relative to the voltage under full-load. It is defined as the change in secondary voltage from no-load to full-load, expressed as a percentage of the full-load voltage. This captures the voltage drop caused by winding resistance and leakage reactance when current flows. For example, if the secondary voltage is 120 V with no load and 114 V at full load, the regulation is (120 − 114) / 114 × 100 ≈ 5.26%. The other statements describe different quantities: one is the turns ratio at full load, another is no-load efficiency, and the last uses no-load voltage as the base, which is not the standard definition.

Transformer regulation measures how much the secondary voltage changes when a transformer goes from no-load to full-load, relative to the voltage under full-load. It is defined as the change in secondary voltage from no-load to full-load, expressed as a percentage of the full-load voltage. This captures the voltage drop caused by winding resistance and leakage reactance when current flows.

For example, if the secondary voltage is 120 V with no load and 114 V at full load, the regulation is (120 − 114) / 114 × 100 ≈ 5.26%. The other statements describe different quantities: one is the turns ratio at full load, another is no-load efficiency, and the last uses no-load voltage as the base, which is not the standard definition.