What is voltage regulation in a transformer?

What is voltage regulation in a transformer?

• A. Percentage change between no-load and full-load secondary voltage.
• B. Ratio of primary voltage to secondary voltage under load.
• C. Efficiency of the transformer at full load.
• D. Impedance of the winding when the transformer is hot.

Answer: (A)

Voltage regulation is about how much the secondary voltage changes as the transformer goes from no-load to full-load, with the primary voltage held fixed. When there’s no load, there’s almost no current, so the voltage on the secondary is near its rated value. Once a load is connected, current flows through the winding’s own resistance and leakage reactance, causing a voltage drop and a lower secondary voltage than at no-load. The regulation is expressed as a percentage of that change, typically calculated as (V_no-load − V_full-load) / V_full-load × 100%. This captures how much the output sags under load due to the transformer’s internal impedance. The other options describe different ideas: the ratio of voltages under load is the turns ratio, not regulation; efficiency is about losses, not how voltage changes with load; and the winding’s impedance when hot is a property that affects regulation but isn’t itself the definition of regulation.

Voltage regulation is about how much the secondary voltage changes as the transformer goes from no-load to full-load, with the primary voltage held fixed. When there’s no load, there’s almost no current, so the voltage on the secondary is near its rated value. Once a load is connected, current flows through the winding’s own resistance and leakage reactance, causing a voltage drop and a lower secondary voltage than at no-load. The regulation is expressed as a percentage of that change, typically calculated as (V_no-load − V_full-load) / V_full-load × 100%. This captures how much the output sags under load due to the transformer’s internal impedance.

The other options describe different ideas: the ratio of voltages under load is the turns ratio, not regulation; efficiency is about losses, not how voltage changes with load; and the winding’s impedance when hot is a property that affects regulation but isn’t itself the definition of regulation.