Wiring; Safe Functional Extra Low Voltage For Fail-Safe Modules - Siemens SIMATIC Operating Instructions Manual

Wiring

In order to prevent danger to humans or the environment, you must not under any
circumstances override safety functions or implement measures that cause safety functions
to be bypassed or result in the bypassing of safety functions. The manufacturer is not liable
for the consequences of such manipulations or for damage resulting from a failure to heed
this warning.
Overview
This chapter presents the specific characteristics involved in wiring fail-safe modules.
Generally applicable information about wiring both ET 200pro with fail-safe modules and
ET 200pro with standard modules can be found in the
manual.
4.1

Safe Functional Extra Low Voltage for Fail-Safe Modules

Safe Functional Extra Low Voltage
Fail-safe modules must be operated with safe functional extra low voltage (SELV, PELV).
This means that only a maximum voltage U
the event of a fault. The following applies to all fail-safe modules:
U
m
You can find additional information about safe functional extra low voltage, for example, in
the data sheets for the applicable power supplies.
All components of the system that are capable of supplying electrical energy in any form
must meet this requirement.
Each additional power circuit (24 V DC) installed in the system must be operated with safe
functional extra low voltage (SELV, PELV). Refer to the relevant data sheets or contact the
manufacturer for information.
Note, too, that sensors and actuators with an external power supply can be connected to F-
modules. In this context, bear in mind the supply voltage from safe functional extra low
voltage. The process signal of a 24 V DC digital module must not exceed a fault voltage U
even in the event of a fault.
ET 200pro Distributed I/O System - Fail-Safe Modules
Operating Instructions, 05/2007, A5E00394073-02
WARNING
WARNING
< 60.0 V
ET 200pro Distributed I/O Device
can ever be applied to these modules, even in
m
4
,
m
27