What are connections used in power transformers. If we change the connection DYn 11 to DYn1 what are the effects. Why we generally used DYn11 connections.

 

Hi,
The connections as mentioned by yourself applies to three-phase power transformers. This is known as the Vector Group of the transformer. This represents the electrical phase angle difference between the primary winding & the secondary winding. To the best of my knowledge, this Vector Group cannot be changed by the user. This is as per the design consideration while designing the transformer.

For transformers to be connected & run in parallel the Vector group of the transformers will have to be the same. Parallel operation of transformers having different Vector Groups is furnished in "J&P Transformer Hand Book". Some modes of operation are clearly not permitted. Kindly refer the above book regarding for operation of Dyn1 with Dyn11.(Actually there will be a lot of circulating current flow between the transformers with different Vector Groups.)

Regarding the point of wide use of Dyn11 transformers, this is the same as to why we are having say 3.3KV & not 3.7Kv. A certain Vector Group was taken as a standard for parallel operation of the transformers.

Hope this clarifies.