Next, we solve for IS.
The student should note from the previous examples that a transformer that "steps-up" voltage,
"steps-down" the current proportionally.
Three-Phase Transformer Connections
So far, our discussion has dealt with the operation of single-phase transformers. Three-phase
transformer operation is identical except that three single-phase windings are used. These
windings may be connected in wye, delta, or any combination of the two.
In the delta connection, all three phases are connected in series to form a closed loop
Figure 3 Delta Connection
In the wye connection, three common ends of each phase are connected together at a common
terminal (marked "N" for neutral), and the other three ends are connected to a three-phase line