Power Supplied by V-V Bank Transformer

 

Open-delta or V-V Connection of a Transformer

A V-V connection uses two single-phase transformers to produce a three-phase output. 

Here is one possible connection with $0^o$ phase displacement:

Power Supplied by V-V Bank Transformer

The main advantage of a V-V is a reduction in equipment cost and physical construction space for applications where the power demand is relatively light.

Why do V-V Bank Connection?

Picture a delta-delta connected three-phase transformer, then picture one of the three-phase windings removed. That is a V-V-connected transformer. 

This connection saves money on the transformer since it has one less phase winding but at the cost of degrading the KVA rating and creating a phase imbalance.

It may happen that due to some reason, one of the transformers is removed; like maintenance, damage, faults, etc. In such a case, the second delta is broken and the connection resembles a V.

 Hence this sort of connection is also known as a V-V connection or Open-delta connection.