Operating Instructions 43
The WattNode meter measures the displacement or fundamental power factor, which does not
include harmonics.
Integer power factor registers are reported in units of 0.01, so 85 equals a power factor of 0.85.
PowerFactorA, PowerFactorB, PowerFactorC
These are the power factor values for each phase.
PowerFactorAvg
This is the average power factor, computed as
PowerSum
/
ApparentPowerSum
.
Reactive Power
Reactive power is also known as VARs. Inductive loads, like motors, generate positive reactive
power, while capacitive loads generate negative reactive power. Reactive power transfers no net
energy to the load and generally is not metered by the utility. Loads with high reactive power rela-
tive to the real power will tend to have lower power factors. The integer reactive power registers
are scaled by
The WattNode meter only measures the fundamental reactive power, not including harmonics.
To scale the integer
PowerReacA
,
PowerReacB
,
PowerReacC
, or
PowerReacSum
to VARs,
use the following equation:
PowerReac(VAR) = PowerReacSum • PowerIntScale
For example, if
PowerIntScale
(
1609
) is 100, and the integer
PowerReacSum
(
1343
) reports
1500, then the reactive power sum is 1500 * 100 = 150,000 VAR (or 150 kVAR).
PowerReacA, PowerReacB, PowerReacC
These are the per-phase reactive power measurements.
PowerReacSum
The
PowerReacSum
is the sum of the reactive power of active phases. This can include negative
values, so if one phase is negative, it will reduce the reported
PowerReacSum
.
Apparent Power
Apparent power (VA) can be described three ways:
●
The RMS voltage multiplied by the RMS current.
●
The square root of the real power squared plus the reactive power squared.
●
The absolute value or magnitude of the complex power.
The WattNode meter’s measurement of apparent power includes real, but not reactive harmonic
apparent power content.
Apparent power is always a positive quantity. The integer apparent power registers are scaled by
.
PowerAppA, PowerAppB, PowerAppC
These are the per-phase apparent power measurements.
PowerAppSum
The
PowerAppSum
is the sum of apparent power for active phases.
