Siemens SIRIUS 3SK1 Equipment Manual page 24

Safety instructions
2.1 General safety notes
Safe functional extra-low voltage
The 3SK1 safety relays with a supply voltage of 24 V DC must be operated with safe functional
extra-low voltage (SELV, PELV). This means these modules must only be subjected to a voltage
of Um even in the event of a fault. The following applies for these 3SK1 safety relays: Um <
60.0 V.
You can find more detailed information about safe functional extra-low voltage in the data
sheets of the power supplies to be used.
When performing the light test: Ensure safe state
As a result of light tests performed at the semiconductor outputs, the level changes to the ON
state for up to 2.5 ms. Users are responsible for ensuring that this does not result in any actuator
changing to the active state.
Protection against electrostatic charge
When handling and installing 3SK1 safety relays, ensure that the components are protected
from being electrostatically charged. Changes to the system configuration and wiring are only
permissible while the supply voltage is switched off.
Connection of 3SK1 safety relays is only permissible when the power supply units (PELV and
SELV) are switched off.
Noise immunity / grounding
The following must be grounded in accordance with the regulations to ensure noise immunity
of the 3SK1 safety relays:
• PELV / SELV power supply units
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WARNING
WARNING
CAUTION
CAUTION
(please also note the documentation for the respective power supply unit in this regard).
SIRIUS 3SK1 Safety Relays and 3RQ1 Positively-Driven Coupling Relays
Equipment Manual, 05/2021, A5E02526190021A/RS-AE/005