Rockwell Automation 1404-M4_M5_M6_M8 Powermonitor 3000 User Manual, Firmware rev. 3.0 or LATER - Manual (Page 31)

Publication 1404-UM001F-EN-P - November 2009 31
Powermonitor 3000 Unit Operations Chapter 3
•
Frequency Averaging – like the RMS result averaging, the default
setting provides for a smoother response by averaging the
frequency of each of the last eight cycles. You may select no
averaging to return the frequency of only the last cycle
Refer to Advanced Device Configuration on page 50 for more
information.
Symmetrical Component Analysis Results
The power monitor calculates sequence voltages and currents for use
in symmetrical component analysis, a method of mathematically
transforming a set of unbalanced three-phase vectors into three sets of
balanced vectors. The positive sequence components are a set of
vectors that rotate the same direction as the original power vectors,
and represent that portion of the applied voltage or current capable of
doing work. Negative sequence components rotate opposite to the
original vectors, and represent the portion of the applied power that
results in losses due to unbalance. The percent Unbalance value is the
ratio between the negative and positive current sequence in a
three-phase system and is the most accurate measurement of current
unbalance because it takes into account the magnitude of the
individual currents and the relative phase displacement. The zero
sequence component is a single vector that does not rotate, and
represents ground or neutral current or voltage. The component
analysis results returned include the following:
•
Positive Sequence Current
•
Negative Sequence Current
•
% Current Unbalance
•
Positive Sequence Voltage
•
Negative Sequence Voltage
•
% Voltage Unbalance
•
L4 current, which is the zero-sequence current on a wye system
when neutral current is connected to the I4 current input or in
delta systems when an external zero sequence transformer is
connected to the I4 input
The Voltage, Current, and Frequency Metering table on page 32
summarizes the voltage and current metering information provided by
the power monitor.