Correct Answer : Option (D) : Both (A) and (B)
Explanation : Parallel operation of single-phase transformer is done to increase the load capacity and reliability of the supply. It is done by adding another transformer in parallel simultaneously, given the continuous supply and frequent maintenance can be done evenly.
Some conditions must be fulfilled before the parallel operation of a transformer is given below.
The ratio of primary and secondary voltage ratings must be identical. It means the same transformation ratio for the transformer.
Both transformers must have the same polarity.
The X/R ratio must be the same.
