38
Function Description
WAGO-I/O-SYSTEM 750
750-494 3-Phase Power Measurement Module
Manual
Version 1.2.0
Limits
The I/O module also offers limit monitoring. Limits for undervoltage, overvoltage
and overcurrent can be set for each phase (WAGO-I/O-
CHECK
or Register 36-38,
parameters 23-31). Signaling is carried out in the process image (PI).
Pos: 75 /Serie 750 ( WAGO-I/O-SYST EM)/F unktionsbeschr eibung/Funkti onsbeschrei bung 750-0494 - Messfehl er und M essgenauig kei t @ 24\mod_1446714888787_21.docx @ 194992 @ 2 @ 1
4.4
Measuring Errors and Accuracy
The measuring errors of the I/O module are specified in the table below. The
values already take into account the errors caused by the connection method
(single-ended 0.1%) and the calibration tolerance (0.1%). They apply to the entire
temperature range of 0 to 55 °C and to frequencies of 45 to 65 Hz. Outside this
frequency range, the error is max. 2%.
Table 16: AC Measuring Errors
AC Measuring Errors 750-494 and
750-494/000-001
750-494/025-000 and
750-494/025-001
Voltage
<= 0.3 % of full-scale
value
<= 0.5 % of full-scale
value
Current
<= 0.5 % of full-scale
value
<= 0.5 % of full-scale
value
Active power
<= 0.5 %
<= 0.5 %
Phase angle
+/- 0.3°
+/- 0.3°
Frequency
0.01 Hz
0.01 Hz
The harmonics components are determined on the basis of a number of individual
values measured within the current curve shapes for voltage and current.
Calculation is performed to yield the components included in the actual base
frequency (45 to 65 Hz) and their integer harmonics. The accuracy of the
calculation results is typically within a range of around 1%.
"Leakage effect" with the harmonics analysis!
Harmonics components in the actual curve shapes for measured voltages and
currents with non-integer multiples of the base frequency can affect the accuracy
of the calculation results for "neighboring harmonics" (so-called "leakage effect“).
The measuring accuracy of the I/O module falls when an RMS voltage falls below
45 V. This state is called ZC limit and is displayed via the "D" LED (SAG LED).
The following conditions can also degrade the measuring accuracy of the I/O
module:
1.
If only one or two phases of the three-phase supply network are connected,
higher measuring errors can occur in the voltage measurement (+0.1%).
2.
In AC networks only:
If all phases fall below the ZC limit, accurate measurement of phase angle,
