96 Connect Devices
WAGO-I/O-SYSTEM 750 XTR
750-495/040-00x 3-Phase Power Measurement Module 690 V
Manual
Version 1.2.0
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7.4
Current Measurement
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Do not confuse the current and voltage connections
When connecting, be sure not to confuse the current and voltage paths, since
direct connection of the line voltages to the low-impedance current inputs will
destroy the I/O module.
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7.4.1
Current Transformers
Always use current transformers
For measuring current, it is essential to use current transformers.
For line voltages U
LN
≤
400 V, current transformers with basic insulation are
required. For line voltages U
LN
> 400 V, current transformers with reinforced
insulation are required.
Otherwise, touch-proof protection from the system may no longer be given in the
event of a fault. This can cause electric shock or burns. Furthermore, current
measurement without a current transformer can lead to a short circuit in the
power network and destruction of the I/O module.
The current transformers must be able to delivery secondary current of 1 A
RMS
or
5 A
RMS
. The primary current I
pn
must be at least as large as the currents that are
to be measured.
The normal permissible overload level of 1.2 × I
pn
presents no problems for the
I/O module but may lead to measurement inaccuracies.
For correct display of measured values, the appropriate current transformer ratio
must be parameterized.
The properties of the current transformers used directly affect the measurement
accuracy that can be achieved.
When connecting current transformers, pay attention to the direction of current,
since otherwise incorrect signs for the power values may be output. See the
figure below:
Figure 20: Connection of the Current Transformers