Wiring
6.2 Additional rules and regulations for the operation of the ET 200SP with fail-safe modules
Distributed I/O system
88 System Manual, 09/2019, A5E03576849-AJ
6.2 Additional rules and regulations for the operation of the ET 200SP
with fail-safe modules
6.2.1 Safety extra-low voltage (SELV, PELV) for failsafe modules and failsafe motor
starters
The failsafe modules must be operated with safety extra-low voltage (SELV, PELV).
You can find more information on safety extra-low voltage (SELV, PELV) in the data sheets
of the applicable power supplies, for example.
The fail-safe modules operate with the 24 V DC rated voltage. The tolerance range is
19.2 V DC to 28.8 V DC.
The fail-safe motor starters operate with the 24 V DC rated voltage. The tolerance range is
20.4 V DC to 28.8 V DC.
Within the overvoltage range from 32 V DC to 36 V DC, the F-modules react in a fail-safe
manner and the inputs and outputs are passivated. For overvoltages greater than 36 V DC,
the F-modules are permanently de-energized.
Use a power supply unit that does not exceed U
m
= 36 V DC even in the event of a fault.
For more on this, refer to the information in the data sheet on overvoltage protection in the
case of an internal error. Or implement appropriate measures to limit the voltage, e.g. use
of an overvoltage protector.
All system components that can supply electrical energy in any form whatsoever must fulfill
this condition.
Each additional circuit (24 V DC) used in the system must have a safety extra-low voltage
(SELV, PELV). Refer to the relevant data sheets or contact the manufacturer.
Sensors and actuators with an external power supply can also be connected to F-modules.
Make sure that power is supplied to these components from safety extra-low voltage
(SELV, PELV) as well. The process signal of a 24 V DC digital module may not exceed a
fault voltage U
m
in the event of a fault.
Even when a fault occurs, the permissible potential difference between the supply of the
interface module (bus voltage) and the load voltage must not be exceeded.
An external direct electrical connection is one way to meet this requirement. This also
prevents potential differences from causing voltage additions at the individual voltage
sources, which would cause the fault voltage U
m
to be exceeded.
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