Siemens SIRIUS 3SK1 Equipment Manual page 122

System configuration
6.3 System configuration rules
Ensuring electrical safety and safety function
The normally closed contact of 3RQ12. is designed for a voltage of 24 V DC. If higher voltages
occur, electrical safety cannot be ensured due to the voltage clearance distances. If the 3RQ12.
is integrated in a system with a device connector, the feedback circuit is routed via the device
connector; connection of external voltage is not necessary and not permitted. Connecting
external voltage can bypass the safety function.
Supply voltage must only be fed in on the basic unit
The supply voltage of 24 V DC must only be fed in on the basic unit, otherwise the safety
function is bypassed.
Note
If expansion units are controlled via the 3ZY12 device connector, additional feeding of the
control supply voltage (A1/A2) at one of the output expansions leads to a fault in the system
configuration.
Power supply by means of the 3SK1230 power supply
• When device connectors are used, only one 3SK1230 power supply is permitted in each
system.
• The 3SK1230 power supply must always be located on the extreme left.
• If a 3SK1230 power supply is used, an additional (external) 24 V DC connection is not
permitted (this also applies to the cascading input, as well as to non-floating sensors).
24 V DC supply voltage from an external power supply unit
• It is only permitted to connect a voltage of 24 V DC to the terminals on the basic unit.
• It is not permitted to supply 24 V DC to an expansion component or 3RM1 Failsafe motor
starter.
122
WARNING
WARNING
SIRIUS 3SK1 Safety Relays and 3RQ1 Positively-Driven Coupling Relays
Equipment Manual, 05/2021, A5E02526190021A/RS-AE/005