Appendix: Safe torque off (STO) 401
STO inputs have been energized, and any of the drive reactions have been reset.
Drive event can be parametrized according to the table below.
If the operation delay between the inputs is excessive or only one STO input is de-
energized, an event is always considered a fault (STO1 LOST or STO2 LOST). This
event cannot be changed. De-energizing of only one STO input is not considered
normal operation since the safety integrity level would decrease if only one channel is
used.
STO status indications
When both STO inputs are energized, the STO function is in the standby state and
the drive operates normally. If either of the STO inputs or both are de-energized, the
STO function is executed in a safe manner and corresponding reaction is updated
according to the table below.
Parameter Selection values Explanation
3025 STO
OPERATION
(1) ONLY FAULT Drive event on successful STO operation is fault
SAFE TORQUE OFF. The fault bit is updated.
(2) ALARM&FAULT Drive event on successful STO operation is alarm
SAFE TORQUE OFF when stopped and fault SAFE
TORQUE OFF when running. Fault and alarm bits
are updated.
(3) NO & FAULT Drive event on successful STO operation is no alarm
when stopped and fault SAFE TORQUE OFF when
running. The fault bit is updated.
Default:
(4) ONLY ALARM
Drive event on successful STO operation is alarm
SAFE TORQUE OFF. The alarm bit is updated. Start
command must be toggled to continue running the
drive.
STO event Fault name Description Status
Fault 0044 SAFE TORQUE
OFF
STO functions correctly and the
fault must be reset before starting.
0307 FAULT WORD 3
bit 4
Fault 0045 STO1 LOST STO input channel 1 has not de-
energized, but channel 2 has.
Opening contacts on channel 1
might have been damaged or there
is a short circuit.
0307 FAULT WORD 3
bit 5
Fault 0046 STO2 LOST STO input channel 2 has not de-
energized, but channel 1 has.
Opening contacts on channel 2
might have been damaged or there
is a short circuit.
0307 FAULT WORD 3
bit 6
Alarm 2035 SAFE TORQUE
OFF
STO functions correctly. 0309 ALARM WORD 2
bit 13
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