56 Function Description
WAGO-I/O-SYSTEM 750 XTR
750-495/040-00x 3-Phase Power Measurement Module 690 V
Manual
Version 1.2.0
4.4
Measurement Errors
The measurement accuracy of the I/O module is described in section “Device
Description” > “Technical Data” > “Measurement Accuracy.” However, the values
indicated only apply if the following conditions are met:
1.
The measurement signals must be within the permitted limits.
At 120 % of the nominal input signals for voltage and current, the
measurement errors increase by 0.10 % for the voltage and 0.15 % for the
current.
The ZC limit (also known as sag level) is
- 30 V
RMS
if a voltage ≤
120 V
RMS
is parameterized for the “Secondary
Voltage” setting
- 60 V
RMS
if a voltage > 120 V
RMS
is parameterized for the “Secondary
Voltage” setting
If the voltage signal is below the ZC limit, no frequency measurement is
possible. The I/O module then outputs the measured value 0 for the
frequency.
A ZC limit underrun is signaled by the “D” LED. If the nominal values of the
I/O module are exceeded, input overloading occurs (see figure).
Figure 12: Input Limiting (Clipping)
In the event of input overloading of the current or voltage measurement
inputs, the I/O module cannot digitize these values and limits the measured
values to the maximum measurable range (clipping of the current or voltage
measured values). As a result, the RMS value that is output is erroneous.
The more the input (and, thus, the reference points for RMS calculation) is
overdriven, the greater the measuring error is. This can also damage the
I/O module.
If the topology is configured as a “3-Wire Wye/Delta“, the line-to-line