Siemens SINAMICS S120 Function Manual page 73

● When the "Safe Torque Off" function is selected, the following applies:
– The motor cannot be started accidentally.
– The pulse suppression safely disconnects the torque-generating energy supply to the
– The power unit and motor are not electrically isolated.
● The selection/deselection of the STO function also acknowledges the safety faults when
the Basic Functions are used. The standard acknowledgment mechanism must also be
performed.
● Extended acknowledgement:
The selection/deselection of STO can also acknowledge the safety messages of the
extended safety functions. This requires that the extended message acknowledgement is
configured (p9507.0 = 1).
If in addition to the "Extended Functions", the "Basic Functions via terminals" are also
enabled, in addition to selection/deselection of STO via PROFIsafe or TM54F,
acknowledgement is also possible by selection/deselection of STO via terminals.
● The status of the "Safe Torque Off" function is displayed using parameters (r9772, r9872,
r9773 and r9774).
● Effect on the "Setpoint speed limit effective" (r9733[0...2]):
For STO (≙ STOP A), a setpoint of 0 is specified in r9733[0...2].
Unplanned motor motion
After the energy feed has been disconnected (STO active) the motor can undesirably move
(e.g. the motor can coast down), therefore presenting risk to persons.
• Take suitable measures to prevent undesirable movement, e.g. by using a brake with
Danger due to short, limited movements
If two power transistors simultaneously fail in the power unit (one in the upper and one in
the lower inverter bridge), then this can cause cause brief, limited movement.
The maximum movement can be:
• Synchronous rotary motors: Max. movement = 180° / no. of pole pairs
• Synchronous linear motors: Max. movement = pole width
Safety Integrated
Function Manual, 12/2018, 6SL3097-5AR00-0BP1
motor.
WARNING
safety-relevant monitoring. For additional information, see Chapter "Safe Brake Control
(SBC) (Page 78)".
WARNING
Description of Safety Integrated functions
4.1 Safety Integrated basic functions
71