Safe Torque Off (Sto) - Siemens SINAMICS S120 Function Manual

10.4

Safe Torque Off (STO)

In conjunction with a machine function or in the event of a fault, the "Safe Torque Off" (STO)
function is used to safely disconnect the torque-generating energy supply to the motor.
A restart is prevented by the two-channel pulse suppression. The switching on inhibited
prevents an automatic restart after deselection of STO.
The two-channel pulse suppression function integrated in the Motor Modules / Power
Modules is the basis for this function.
Functional features of "Safe Torque Off"
● The function is completely integrated in the drive. It can be selected via terminals, TM54F
or PROFIsafe from an external source.
● The function is drive-specific, i.e. it is available for each drive and must be individually
commissioned.
● The function must be enabled via parameter.
● 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 "Speed setpoint limit effective" (r9733[0...2]):
For STO (≙ STOP A), a setpoint of 0 is specified in r9733[0...2].
Drive functions
Function Manual, 11/2017, 6SL3097-4AB00-0BP5
motor.
Safety Integrated Basic Functions
10.4 Safe Torque Off (STO)
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