11
Introduction to Power Delivery Configurations
Figure 1 presents most common power delivery
configurations. ATPOL II is able to measure voltage,
current, power, power factor, and more for all of these
systems. Figure 1A presents the normal single-phase and
split-phase service as found in a residential service. In
North America, V
1N
and V
2N
are 120V and are 180
degrees out of phase with each other. When heavier
loads are encountered, V
12
(240V) is used by delivering
both hot voltages to the load. Neutral provides the current
return path. If the load is balanced, there will be relatively
little neutral current. Refer to figures
3
various ways to connect to single-phase and split-phase
power service.
Figure 1B presents normal three-
phase “wye” power
service. Voltages are usually measured from phase-to-
neutral. Neutral provides the current return path. If the
load is balanced, there will be relatively little neutral
current. Refer to
for how to connect to a three-
phase wye power service.
Figure 1C presents normal three-phase delta service. Voltages are usually measured from phase-to-
phase. In North America, service is usually supplied as 120V, 240V, 480V, 600V, 4160V, or 12,500V.
In most of the world, phase-to-phase service is usually supplied as 381V, 5,716V, or 11,431V. ATP
has voltage probes for direct connect to all of these services. Refer to
delta power service. When there is no access to measuring one of the currents,
figure 8
presents the 2
current approach for measuring power. This approach is also useful for measurement of an open delta
circuit as described in Connections to an Open Delta Circuit (2PT/3CT)
figure 10
. Although phase-to-
phase is the normal voltage measurement mode for this service, ATPOL II can be set to phase-to-
neutral (even though the neutral is not connected). In this case, the measured voltages will be phase-
to-metering-neutral (such as V
1N
V
1N
= 277V for a 480V service) and all other measurements will also
be correct.
Figure 1D presents three-phase
. In this configuration, a neutral is supplied from
a point midway between two phases. This is handy when 240V delta is supplied. V
2N
and V
3N
supply
conventional 120V single-phase power and V
1N
provides 208V, if needed. In this configuration,
depending on what you are measuring, you may choose to measure in phase-to-phase mode or in
phase-to-neutral mode.
Figure 1E presents
grounded delta service
. This configuration is actually not very common. It can be
attractive to use if an electrically isolated three-wire delta service is available and there is a need to
provide the power a long distance away at a private facility (such as a saw mill). By grounding one of
the phases at the source, the cost of supplying one of the phases to the remote site is saved. A motor
at that site would be connected to phase 1, phase 2, and earth ground. There is increased danger in
this configuration over normal isolated delta service since the reference to ground is intentionally an
excellent conductive path. Nevertheless, ATPOL II will provide the desired measurements in this
configuration.
Содержание ATPOL II
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