Valhalla 2300, Operation Manual

Page: 112 / 115

APPLICATION NOTE AN108
MEASURING SINGLE-PHASE THREE-WIRE POWER
WITH THE 2300
108-1. General
This application note describes the
connections required to measure a single-
phase three-wire connected load with the
2300.
108-2. Single-Phase Three-Wire Systems
This system consists of two 120Vrms
(nominal) lines and a common grounded
neutral conductor. The two 120Vrms lines
are phase shifted 180 degrees. This system is
sometimes called "splitphase 120/240V".
120Vrms is measured between either line and
neutral, and 240Vrms line to line. Figure 1
details the line voltage relationships.
Single-phase three-wire power is available
in most every residential structure in the
United States.
Lighting fixtures and wall
outlets are powered from one line and neutral.
Major appliances e.g. electric clothes dryers,
electric ovens and air-conditioners are
commonly powered from 240VAC using
single-phase three-wire power.
108-3. 2300 Connections
Single-phase three-wire systems may be
looked upon as two single-phase power
measurements. The total single-phase three-
wire power is the sum of the individual phase
powers. Figure 2 details the connections to
the 2300. Channels A and C are used to
measure the individual phase powers. The
individual phase powers are displayed by
pressing the
∅
A and
∅
C display selection
push-buttons.
The total single-phase three-wire power is
displayed by pressing the 3
∅
3-wire display
selection push-button. The voltage and
current displays will be blanked in this mode.
108-4. Measuring Neutral Current
Some applications require the measurement of
neutral current as well as total power and line
currents. This is easily accomplished with the
2300. These connections are shown in Figure
3. The neutral current is passed through the
∅
B current shunt. The neutral current is
displayed by pressing the
∅
B display
selection push-button.
)
If this method is used with a Model 2301,
only one line may be measured at a time.