Paralleling Transformers | Unequal Turns Ratios | Part Four

Paralleling Transformers | Unequal Turns Ratios | Part Four Sometimes there is a need for paralleling transformers to increase substation capacity or have the capability of de-energizing one transformer to perform routine maintenance while the remaining transformer is serving the load. It is very important to ensure paralleled transformers have the same turns rations. Having different ratios will lead to voltage mismatch, causing circulating current flow in the parallel loop. Circulating currents could lead to overheating the transformers. This video shows an example calculation of circulating currents, using two methods. One method is detailed while the other method is an approximation. Both methods yield similar results especially when transformer X/R ratios are equal. It is worth noting that the circulating current will take place before the transformers are even serving the load.