74 Rockwell Automation Publication 1426-UM001J-EN-P - August 2019
Chapter 4 Metering
The PowerMonitor 5000 unit calculates phase angles of voltage and current, and
checks the phase angles against three distinct ranges of system power factor:
• Range 1: lagging 97% to leading 89%. This range is for very high lagging or
significantly leading power factors. Examples of loads in this range include
data centers, over-excited synchronous motors, and circuits with power
factor correction.
• Range 2: lagging 85% to leading 98%. This range includes most industrial
circuits that range from lagging to slightly leading power factors, including
circuits feeding AC variable-frequency drives.
• Range 3: lagging 52% to lagging 95%. This range exhibits lower lagging
power factors. Examples include lightly loaded motor circuits and DC
SCR drives.
The power monitor displays wiring diagnostic status results for all three power
factor ranges when a command is issued. You decide which power factor range
applies based on your knowledge of the circuit and its load characteristics. You
can expect more reliable wiring diagnostic results when the circuit is operating in
a normal condition, that is, not especially lightly loaded.
Figure 29
illustrates the part power factor plays in wiring diagnostics. The PF
ranges show the I1 phase angle limits for each range. The phasor diagram shows
the fundamental voltage and currents in a three-phase, 4-wire system operating
with a lagging power factor of roughly 85%. In this example, ranges 2 and 3
wiring diagnostic can return good results, but range 1 can incorrectly indicate
that all currents are inverted and displaced by a phase, as shown by the –I1, -I2,
and –I3 phasors.
Figure 29 - Power Factors and Wiring Diagnostics
In addition to wiring diagnostics on command, the PowerMonitor 5000 unit
updates voltage and current magnitude and phase angle data continually. These
values are used by FactoryTalk® EnergyMetrix™ RT software to display a system
phasor diagram.
IMPORTANT If insufficient current is available, the wiring diagnostics status shows input
level low.
To Next Page
Loading...
