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The phasor diagram shows the 120
The phase-to-phase voltage in a balanced three-phase wye system is 1.732 times the
phase-to-neutral voltage. The center point of the wye is tied together and is typically
grounded. Table 1.1 shows the common voltages used in the United States for wye-
connected systems.
Phase to Ground Voltage
120 volts
277 volts
2,400 volts
7,200 volts
7,620 volts
Usually a wye-connected service will have four wires: three wires for the phases and
one for the neutral. The three-phase wires connect to the three phases (as shown in
Figure 1.1). The neutral wire is typically tied to the ground or center point of the wye.
In many industrial applications the facility will be fed with a four-wire wye
but only three wires will be run to individual loads. The load is then often referred to
as a delta-connected load but the service to the facility is still a wye service; it
contains four wires if you trace the circuit back to its source (usually a transformer).
In this type of connection the phase to ground voltage will be the phase-to-ground
voltage indicated in Table 1, even though a neutral or ground wire is not physically
present at the load. The transformer is the best place to determine the circuit
connection type because this is a location where the voltage reference to ground can
be conclusively identified.
Electro Industries/GaugeTech
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angular separation between the phase voltages.
Table 1: Common Phase Voltages on Wye Services
1: Three Phase Power Measurement
Phase to Phase Voltage
208 volts
480 volts
4,160 volts
12,470 volts
13,200 volts
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