Safe Functional Extra Low Voltage For Fail-Safe Modules - Siemens SIMATIC ET 200S Installation And Operating Manual

Wiring and Fitting Modules

4.2 Safe Functional Extra Low Voltage for Fail-Safe Modules

4.2 Safe Functional Extra Low Voltage for Fail-Safe Modules
4.2
Safe functional extra low voltage
Warning
Fail-safe modules must be operated with safe functional extra low voltage. This means that
these modules, even in the event of a fault, can only have a maximum voltage of U
following applies for all fail-safe modules:
U
m
You can find additional information about safe functional extra low voltage, for example, in
the data sheets of the applicable power supplies.
All components of the system that are capable of supplying electrical energy in any form
must satisfy this requirement.
Each additional circuit (24 VDC) implemented must have a safe functional extra low voltage.
Refer to the relevant data specification sheets or contact the manufacturer for information.
Note, too, that sensors and actuators having an external power supply can be connected to
F-modules. Here, pay attention to the supply voltage from safe functional extra-low voltage.
The process signal of a 24 VDC digital module must not exceed a fault voltage of U
event of a fault.
Warning
All power sources, for example internal 24 V DC load voltage power supplies, external 24 V
DC load voltage power supplies, 5 V DC bus voltage must be electrically connected
externally. This prevents voltage additions in the individual voltage sources that would cause
the fault voltage U
Ensure that there is sufficient line cross section for the electrical connection, in accordance
with the ET 200S configuration guidelines (see
4-2
< 60.0 V
to be exceeded even if there are voltage differences.
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ET 200S Distributed I/O System
ET 200S Distributed I/O System - Fail-Safe Modules
Hardware Installation and Operating Manual, 07/2005, A5E00103686-04
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