Transformers
TRANSFORMER THEORY
Figure 4 Wye Connection
Combinations of Delta and Wye Transformer Connections
A three-phase transformer may have three separate but identical single-phase (1f) transformers
or a single 3f unit containing three-phase windings. The transformer windings may be connected
to form a 3f bank in any of four different ways (Figure 5).
Figure 5 shows the voltages and currents in terms of applied line voltage (V) and line current (I),
Figure 5 3f Transformer Connections
where the turns ratio (a) is equal to one. Voltage and current ratings of the individual
transformers depend on the connections (Figure 5) and are indicated by Table 1 for convenience
of calculations.
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