Siemens SIMATIC ET 200AL, System Manual

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Switching of loads
C.2 Switching of inductive loads
Digital I/O module F-DI 4+F-DQ 2x24VDC/2A, 4xM12 (6ES7146-5FF00-0BA0)
Equipment Manual, V1.0, 05/2021, A5E51082342-AA
87
C.2 Switching of inductive loads
The diagram below shows the maximum permitted inductive load and switching frequency
allowed using only the internal suppression circuits of the F-DI 4/F-DQ 2 Fail-Safe module
digital outputs. You should equip larger or more frequently switched inductive loads with
external suppression circuits to avoid early failure of the F-DI 4/F-DQ 2 Fail-Safe module
digital output switch. External suppression conducts the load current at a voltage less than
the internal suppression threshold to avoid overloading the internal suppression.
Figure C-1 Switching of inductive loads for the F-DI 4/F-DQ 2 Fail-Safe module depending on the load current and
switching frequency
WARNING
Unsuppressed inductive loads can lead to failures.
The following failures can result:
•
Unsuppressed inductive loads can lead to early "stuck-on'" failures of the fail-safe module
digital outputs.
• Unsuppressed inductive load switching generates an EMI hazard to the PLC system and
correct processing of the safety function.
Death or serious personal injury and damage to machines and equipment may result if
proper precautions are not taken.
You should use suppressor circuits with inductive loads to limit the voltage rise when a
control output turns off and to limit the electrical noise generated when switching inductive
loads.