Siemens simatic et200sp Manual page 24

Wiring
3.3 Current transformer selection data
Checking the ratio of burden load and power loss
The rated burden of the transformer must be 1.5 to 2 times greater than the power loss in the
connection circuit to ensure that the transformer is not overloaded and that the current
limitation is ensured during a short-circuit.
At a maximum secondary current of 4 A the power loss in the connection circuit is calculated
in accordance with the following formula for a connection cable (outgoing and incoming line)
with a length of 10 m and a cross-section of 1.0 mm
Meter of 25 mΩ:
The ratio of the rated burden and the power loss in the connection circuit thus amounts to:
The required ratio of rated burden and power loss in the connection circuit lies within the
required range. The transformer is dimensioned sufficiently large.
See also
Technical specifications (Page 92)
24
and a burden resistance of the Energy
2
Analog input module AI Energy Meter 480VAC ST (6ES7134-6PA20-0BD0)
Manual, 12/2015, A5E36061895-AA