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1.1.2
Delta Connection
EPM 6010 MULTI-FUNCTION POWER METERING SYSTEM – USER GUIDE
The following table indicates the common voltages used in the United States for wye
connected systems.
Table 1–1: Common Phase Voltages on Wye Services
Phase-to-Ground Voltage
120 volts
277 volts
2400 volts
7200 volts
7620 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. The neutral wire is
typically tied to the ground or center point of the wye (refer to the Three-Phase Wye
Winding diagram above).
In many industrial applications the facility will be fed with a four-wire wye service but only
three wires will be run to individual loads. The load is then often referred to as a
deltaconnected 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
the table above, 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.
Delta connected services may be fed with either three wires or four wires. In a three-phase
delta service the load windings are connected from phase-to-phase rather than from
phase-to-ground. The following figure shows the physical load connections for a delta
service.
CHAPTER 1: THREE-PHASE POWER MEASUREMENT
Phase-to-Phase Voltage
208 volts
480 volts
4160 volts
12470 volts
13200 volts
1–3
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