The Δ–Δ connection is the most flexible of the various connection forms. One of the advantages of this connection is that if one transformer becomes damaged or is removed from service, the remaining two can be operated in what is known as the open-Δ or V connection, as shown in Figure 3.44.
(Note that three-phase four wire means a three-phase system made up of four wires.)
Assume that a balanced three-phase load with unity power factor is served by all three transformers of a Δ–Δ bank. The taking out of one of the transformers from the service ...