Wiring
3.3 Current transformer selection data
Analog input module AI Energy Meter 480VAC/CT HF (6ES7134-6PA00-0CU0)
28 Manual, 07/2018, A5E42674880-AA
Maximum length of the connection cable
To avoid overloading or damaging the current transformer, the burden Z
n
specified on the
data sheet of the current transformer (in VA) must not be exceeded. To prevent this being
exceeded, the entire burden resistance (consisting of the resistance of the connection cable
and the internal resistance of the AI Energy Meter HF (see figure below) must be below a
certain resistance value (depending on Z
n
and I
max
).
Figure 3-2 Maximum length of the connection cable
The maximum value of the resistance of the connection cable is obtained with the following
formula:
R
L
Cable resistance in ohms I
max
Secondary current of the current trans-
Z
n
Rated burden current transformer in VA R
burden
Resistance of the AI Energy Meter HF
Figure 3-3 Maximum value for the resistance of the connection cable
Based on the maximum cable resistance in ohms, you then calculate the maximum length of
the connection cable. To do this, check the data sheet of the connection cable you are using.
Note
The length of the connection cable (outwards and return) must not exceed the value of
200
meters.
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