Siemens SIMATIC ET 200AL, System Manual

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Connecting
5.1 Rules and regulations for operation
Distributed I/O system
System Manual, 08/2021, A5E31861578-AJ
33
24 V DC supply
Below there is a description of what you need to pay attention to with 24 V DC supply:
•
For buildings:
If there is a danger due to overvoltages, you must take lightning protection measures for
external lightning protection (e.g. lighting protection elements).
• With 24 V DC supply lines and signal lines:
If there is a danger due to overvoltages, you must take lightning protection measures for
internal lightning protection (e.g. lightning protection elements. You will find additional
information in the Designing interference-free controllers
( https://support.industry.siemens.com/cs/ww/en/view/59193566 ) function manual).
• For 24 V DC supply:
Ensure that there is a safe (electrical) separation of low voltage (SELV/PELV) according to
IEC 61010-2-201 or IEC 60950-1.
You must secure all feeding supply voltages with a UL/IEC approved fuse 24 V DC/4 A
(trigger characteristic type B or C).
• Continuous operation of fail-safe modules with more than 28.8 V DC can result in personal
injury and equipment damage.
WARNING
Continuous operation of fail-safe modules with more than 28.8 V DC can result in
personal injury and equipment damage.
Certain transients from certain source impedances (for example according to
EN 61000-4-2, 61000- 4 4 and 61000-4- 5), as specified in the "Electromagnetic
compatibility" section, can act on this voltage without interrupting operation or causing
damage.
Operate the fail-safe module within the voltage parameters specified in the technical
specifications. This will avoid unacceptable temperature increases and heat damage that
will cause the module to lose its functionality.
Requirements for power supplies in the event of a power interruption
To ensure compliance with IEC 61131-2, use only power supply units/power supplies with a
power failure bridging time of at least 20 ms. Observe the relevant requirement in your
product standards (e.g. 30 ms for "burners" according to EN 298) with regard to possible
voltage interruptions. You can find the latest information on power supply components on
the Internet.