1.6.5.3 Stop category 1 (SS1)
This example depicts the prerequisites and wiring for an emergency stop that fulfills the requirements
according to
IEC 60204-1:2016 stop category 1 (a controlled stop with power available to the machine actuators to
achieve the stop and then removal of power when the stop is achieved)
ISO 13849-1:2015 PLe, Cat. 3
IEC 61508:2010 SIL3
IEC 61800-5-2:2017 SS1 (Safe stop 1)
When the Emergency Stop Device (such as a push button or a light curtain) signals the execution of an
emergency stop, two redundant sets of contactors are triggered:
K1/K2 gives immediately the signal to the Master PLC/IPC Digital Input. When the Digital Input is
logical 0, the Master PLC/IPC shall request “quick stop” via EtherCAT Controlword 0x6040.
K3/K4 are triggered after a configurable time delay. During the time delay, the machine can be
gracefully controlled to a stop before the activation of the SOMANET Node STO-SBC function.
1.6.5.3.1 Prerequisites
SOMANET Node Safety
Safety Relay
Emergency stop device
Power supply (PELV)
Reset/Start switch
Note
It is necessary to use a momentary switch for Reset/Start function to fulfill the requirement
regarding emergency stop “The reset of the emergency stop command shall not restart the
machinery.”
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