Electro Industries/GaugeTech
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Doc# E166703 1-4
1: Three-Phase Power Measurement
1.1.2: Delta Connection
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. Figure 1.3 shows the physical load connections for a delta
service.
Figure 1.3: Three-phase Delta Winding Relationship
In this example of a delta service, three wires will transmit the power to the load. In a
true delta service, the phase-to-ground voltage will usually not be balanced because
the ground is not at the center of the delta.
Figure 1.4 shows the phasor relationships between voltage and current on a three-
phase delta circuit.
In many delta services, one corner of the delta is grounded. This means the phase to
ground voltage will be zero for one phase and will be full phase-to-phase voltage for
the other two phases. This is done for protective purposes.
V
C
Phase 1
Phase 3
Phase 2
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