Combinations of Delta and Wye Transformer Connections:
The three-phase transformer might have three separate but identical single-phase (1ø) transformers or a single 3ø unit holding three-phase windings. The transformer windings might be connected to form a 3ø bank within any of four various ways.
![1391_Combinations of Delta and Wye Transformer Connections.png](https://www.expertsmind.com/CMSImages/1391_Combinations%20of%20Delta%20and%20Wye%20Transformer%20Connections.png)
Figure: Transformer Connections
Figure displays the voltages and currents in terms of applied line voltage (V) and line current (I), where the turns ratio (a) is equal to one. Current and voltage ratings of the individual transformers depend on the connections that were show in figure and are denoted by Table 1 for convenience of calculations.
![1601_Combinations of Delta and Wye Transformer Connections1.png](https://www.expertsmind.com/CMSImages/1601_Combinations%20of%20Delta%20and%20Wye%20Transformer%20Connections1.png)
*a = N1/N2; √3= 1.73
Example: If line voltage is 440 V to a 3ø transformer bank, find the voltage across each primary winding for all four types of transformer connections.
?-? : primary voltage = V = 440 volts
Y-Y: primary voltage = V/√3 =440/1.73 =254.3 volts
Y- ? : primary voltage = V/√3 = 440/1.73 =254.3 volts
?-Y: primary voltage = V = 440 volts