Delta connection (/_\)
In a balanced circuit, when the generators are connected in delta, the voltage between any two lines is equal to that of a single phase.
The line voltage and the voltage across any winding are in phase, but the line current is 30° or 150° out of phase with the current in any of the other windings.
In the delta-connected generator, the line current from any one of the windings is found by multiplying the phase current by the square root of 3, which is 1.73.
Wye connection (Y)
In the wye connection, the current in the line is in phase with the current in the winding. The voltage between any two lines is not equal to the voltage of a single phase, but is equal to the vector sum of the two windings between the lines.
The current in line A of is the current flowing through the winding L1; that in line B is the current flowing through the winding L2; and the current flowing in line C is that of the winding L3.
Therefore, the current in any line is in phase with the current in the winding that it feeds. Since the line voltage is the vector sum of the voltages across any two coils, the line voltage EL and the voltage across the winding Ef are 30° out of phase.
The line voltage may be found by multiplying the voltage of any winding Ef by 1.73.
Delta and wye summarized
The properties of delta connections may be summarized as follows: The three windings of the delta connection form a closed loop. The sum of the three equal voltages, which are 120° out of phase, is zero.
Thus, the circulating current in the closed loop formed by the windings is zero. The magnitude of any line current is equal to the square root of 3 (1.73) times the magnitude of any phase current.
Properties of the wye connection do not form a closed loop. The magnitude of the voltage between any two lines equals the magnitude of any phase voltage times the square root of 3, that is, EL-L = sqrt 3 X Ef