Delta/star transformers, also known as delta-wye transformers, are commonly used in electrical power distribution systems. They are designed to handle both balanced and unbalanced loads effectively. Let's understand why the correct answer is option 'C' by discussing the operation of delta/star transformers in both scenarios.

Delta Connection:
In a delta connection, the primary and secondary windings are connected in a triangular shape. This configuration allows the transformer to handle unbalanced loads efficiently. The delta connection provides three independent paths for current flow, which makes it suitable for unbalanced loads. Each winding carries a current proportional to the load connected to it, irrespective of the load imbalances.

Star Connection:
In a star connection, the primary and secondary windings are connected in a star shape. This configuration is beneficial for handling balanced loads. The star connection provides a neutral point, which allows the load to be divided equally between the three phases. In a balanced load scenario, the current flowing through each phase remains the same, resulting in a balanced distribution of power.

Operation with Balanced Load:
When a balanced load is connected to a delta/star transformer, the delta primary winding receives a balanced three-phase supply. The balanced currents flowing through the primary winding induce balanced voltages in the secondary winding. In the star secondary winding, the load is divided equally between the three phases, ensuring a balanced distribution of power.

Operation with Unbalanced Load:
When an unbalanced load is connected to a delta/star transformer, the delta primary winding receives unbalanced currents. These unbalanced currents induce unbalanced voltages in the secondary winding. The star secondary winding allows the unbalanced load to be distributed among the three phases, mitigating the effects of the load imbalance. The neutral point in the star connection helps in compensating for the unbalanced currents and voltages.

Conclusion:

Delta/star transformers are designed to handle both balanced and unbalanced loads effectively. The delta connection allows for efficient operation with unbalanced loads, while the star connection facilitates balanced load distribution. This versatility makes delta/star transformers suitable for a wide range of applications, providing reliable and stable power distribution in electrical systems.