Siemens Simatic CFU, Commissioning Manual

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A.7.2 Overview of Contents
PROFIBUS PA
PROFIBUS PA is the PROFIBUS for Process-Automation (PA) and is based on
IEC 61784-1:2002 Ed1 CP 3/2 for transmission technology and protocol and on the PA profile.
PROFIBUS PA = PROFIBUS DP communication protocol
+
synchronous transmission technology
+
Power supply of the PA field devices
Connectable field devices
You can connect all field devices that are suitable for PROFIBUS PA to the CFU.
● Measuring transducers, valves, actuators etc.
● For use in the chemicals industry and process engineering
● With field device feed via the data cable
● Also for applications in the potentially explosive area (ignition protection type Ex [ic])
A.7.3 Intrinsic safety
Intrinsic safety
The basis for the intrinsic safety type of ignition protection consists in the necessity for a specific
amount of ignition energy for ignition to take place in a potentially explosive atmosphere. In an
intrinsically safe power circuit this minimum ignition energy is not present, neither in normal
operation nor in case of fault. The intrinsic safety of a power circuit is achieved by limiting
current and voltage so as to avoid sparks and high temperatures as possible sources of ignition.
This limits the intrinsic safety type of ignition protection to relatively low output power circuits.
Spark ignition
So-called spark ignition is excluded because sparks that can normally occur owing to short
circuit or ground fault during operation when a power circuit is opened or closed are excluded
because current and voltage are limited as well as owing to the avoidance of major
inductivities.
Heat ignition
In normal operation and in case of failure heat ignition is not possible because excessive
heating of the equipment and leads in the intrinsically safe power circuit is excluded.
Appendix
A.7 CFU PA: Basics for PROFIBUS PA
SIMATIC CFU
190
Commissioning Manual, 08/2019, A5E39252870-AD