F1
Fuse
S1
Switch: Start/stop
S2
Pushbutton: Reset
S3
Pushbutton: EMERGENCY OFF
S4
Pushbutton: Monitored start (safety relay)
Q1
Motor starter protector
Q11
3RW55 Failsafe soft starter
Q21
Contactor
K
Safety relay
M1
Motor
P1
Indicator light
PE
Protective conductor
When the EMERGENCY OFF (S3) pushbutton is pressed, the signals at the digital inputs DI and
F‑DI are canceled simultaneously. The 3RW55 Failsafe soft starter executes the "Safe Torque Off"
(STO) safety function, which however is not shown in the display of the 3RW5 HMI High Feature.
After EMERGENCY OFF (S3) has been reset, the safety relay (K) must also be reset with the
Monitored Start pushbutton (safety relay) (S4). If an ON command is still applied at the start/stop
switch (S1), a restart is initiated via the 3RW55 Failsafe soft starter.
A.4.4
EMERGENCY STOP shutdown to SIL 3 STO with a 3RW55 Failsafe soft starter in
conjunction with bus communication and a safety control
Together with an additional motor contactor connected between the 3RW55 Failsafe soft starter
and motor, two-channel STO applications can be implemented with the 3RW55 Failsafe soft
starter up to integrity level SILCL 3 according to IEC 62061 and PL e / Cat. 4 according to
EN ISO 13849‑1 (two-channel shutdown using the 3RW55 Failsafe soft starter in one of the two
channels). The safe signaling output (F‑RQ) of the 3RW55 Failsafe soft starter and the auxiliary
contacts of the contactor are monitored by a higher-level safety relay with SIL ≥ 2 (e.g. safety
control). The control commands at the failsafe digital input F‑DI of the 3RW55 Failsafe soft
starter and at the contactor come from 2 failsafe outputs of the higher-level safety relay.
Note that the EMERGENCY STOP shutdown must only be performed via the safe outputs (Q1 and
Q2) of a safety control. Both the shutdown of the contactor and the safety-related shutoff (STO)
of the 3RW55 Failsafe soft starter via the failsafe digital input F‑DI must be performed via a
dedicated safe output (F‑DQ) of a safety control.
The feedback signals of the mirror contact of the contactor and of the failsafe signaling output
(F‑RQ) of the 3RW55 Failsafe soft starter must be made via safe inputs of the safety control. As
an alternative to control via the control inputs (DI), functional switching by the 3RW55 Failsafe
soft starter can also be performed via a suitable 3RW5 communication module (e.g. PROFINET).
Note the requirements in chapter 3RW55 Failsafe soft starter (Page 343).
Example circuits
A.4 3RW55 Failsafe soft starter
SIRIUS 3RW55 and 3RW55 Failsafe Soft Starters
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Equipment Manual, 02/2022, A5E35630887002A/RS-AF/006
