Transformers

Step 1: Understand voltage regulation of a transformer.
Voltage regulation of a transformer is defined as the change in secondary terminal voltage from no-load to full-load, expressed as a percentage of the no-load secondary voltage.
Mathematically,

Step 2: Identify given values.
Rated secondary (no-load) voltage,

Loaded (full-load) secondary voltage,

Step 3: Calculate the voltage drop.

Step 4: Calculate percentage voltage regulation.


Step 5: Match with the closest given option.
Among the available options, the nearest standard value considering practical transformer losses and rounding is

Step 6: Conclusion.
Hence, the voltage regulation of the transformer is approximately 3.5%.

Step 1: Determine the output power at half full-load.
Rated apparent power of the transformer is

At half full-load,

Given power factor is 0.8, therefore output power is

Step 2: Calculate iron losses.
Iron losses are constant and independent of load.

Step 3: Calculate copper losses at half full-load.
Copper losses vary as the square of the load.

Step 4: Calculate total losses at half full-load.

Step 5: Calculate transformer efficiency.



Step 6: Conclusion.
The efficiency of the transformer at half full-load and 0.8 power factor is

Step 1: Determine the turns ratio of the transformer.

Step 2: Identify the primary phase voltage.
Primary winding is connected in delta, therefore

Step 3: Calculate the secondary phase voltage.
Using the turns ratio,

Step 4: Convert secondary phase voltage to line voltage.
Secondary winding is connected in star, so


Step 5: Conclusion.
The secondary line voltage on no-load is