When power transformers with different voltage ratios are connected in parallel, the difference will appear as circulating current between transformers in the case of no load. At load condition, the power transformers will be differently loaded due to the difference in voltage ratio.
Assume two power transformers with different voltage ratios ( the same primary voltage and different secondary voltage). In this case the circulating current can be obtained from the following equation
Where:
- K1, K2 : Transformation ratios of transformers 1, and 2 respectively.
- Z1%, Z2% : Percentage impedances of transformers 1, and 2 respectively.
- IS1, IS2 : Rated secondary current of transformers 1, and 2 respectively.
