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2857-570/024-001
Functions
32
Product manual | Version: 2.0.0
3-Phase Power Measurement Module, 1 A
Figure 14: RMS Calculation (Example – Not to Scale)
The current and voltage RMS values are calculated for each period and refreshed every
two periods (2T). In a 50 Hz power system, this corresponds to refresh rate of 40 ms.
The product is designed for measurements with a Current Transformer, so high currents
can be measured. The transformation ratios are parameterized and then taken into ac-
count when the measured values are calculated.
The
arithmetic mean value
for the phase current and voltage is calculated on the basis
of the RMS values. The observation interval for which the mean value should be calcu-
lated can be set with the Interface Configuration Software or parameters 21, 22 and 23.
For more detailed information, see Parameter.
The min. and max. RMS values
for the current and voltage are also determined over a
configurable time interval.
A reset interval can be set with parameters 24, 25 and 26. This interval can be activated
with parameter 2 (bits 8 to 10).
Peak current and voltage values can also be recorded, for one selectable phase (L1 or L2
or L3). The observation interval can be set according to number of half-waves (Interface
Configuration Software or parameters 11, 12 and 13).
Arithmetic mean, min/max values and the peak value are not available for the neutral
conductor current.
Calculation of line voltages U
Lx–Ly
is performed on the basis of the phase voltages and the
corresponding phase angles.
Calculation of Power
Individual, synchronous sampling values for current and voltage are used for calculating
active power (P). Phase shifts between the currents and voltages are taken into account
in the power calculation. Positive values occur when the power is “exhausted” by a load,
i.e., the current has a phase shift of −90° to +90° relative to the voltage (operation under