WAGO-I/O-SYSTEM 750 XTR
Function Description 51
750-495/040-00x 3-Phase Power Measurement Module 690 V
Manual
Version 1.2.0
Calculation of energy
Time-based integration of power yields the level of energy for each phase. The
I/O module provides the values for active, reactive and apparent energy. Values
for the individual phases and a total value are provided both for active and
reactive energy; only the fundamental components are included in the measured
value for the reactive energy. A distinction can also be drawn between drawing
and supply of active energy and capacitive and inductive reactive energy (see
figure below).
Figure 10: Allocation of Active and Reactive Energy in the 4 Quadrants
The values of all energy meters are saved in the I/O module. These operate
internally with the resolutions mWh / mVARh / mVAh and are reset when 1 billion
kWh (kVARh, kVAh) is reached.
The representation of the energy values can be scaled by a factor in the process
image (PI). This factor can be set by the user in accordance with the application
being used (WAGO-I/O-
CHECK
or register 35) and can be changed at any time.
The 2 examples below illustrate the information required for this:
Example 1:
- 750-495, meter for the active energy import, L1 (UInt32 in the PI)
- Scaling (WAGO-I/O-
CHECK
, register 35): 0 (1 mWh)
- Maximum meter value in the PI: 4 294 967 295 mWh = ~4 295 kWh
A counter overflow can occur for the counter shown in the PI even though the
internal meter has not yet reached the overflow threshold. This is signaled in
the PI by the flag “Range limiting for process value x.” The user must select
scaling of the measured value in accordance with the application being used.
Example 2:
- 750-495/000-001, meter for total reactive energy (Int32 in the PI)
- Scaling (WAGO-I/O-
CHECK
, register 35): 6 (5 kVARh)
- Maximum meter value in the PI: +10 737 418 235 kVARh (two’s complement)
An overflow of the internal meter can occur here, as it can only count to a
maximum of 1 billion kVARh. The meter shown in the PI can, however, continue
to count substantially higher on account of the scaling that has been set.
