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
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