Functional features of "Safe Torque Off"
● The function is completely integrated in the drive. It can be selected via terminals 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
motor.
– 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 acknowledgment:
The selection/deselection of STO can also acknowledge the safety messages of the
extended safety functions. This means that you must configure the extended message
acknowledgment (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 (Page 338),
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 "Setpoint speed limit effective" (r9733[0...2]):
For STO (≙ STOP A), a setpoint of 0 is specified in r9733[0...2].
WARNING
Unexpected machine motion when STO is active
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
safety-relevant monitoring. You can find additional information in Chapter "SBC (Basic/
Extended) (Page 109)".
WARNING
Unexpected motor movement as a result of defective power transistors
Undesirable motor motion
1)
can occur if 2 power transistor simultaneously become defective
(breakdown of the depletion layer). This can result in accidents leading to death or severe
injury.
● Take suitable measures to prevent undesirable movement, e.g. by using a brake with
safety-relevant monitoring. You can find additional information in Chapter "SBC (Basic/
Extended) (Page 109)".
Safety functions integrated in the drive
4.4 STO (Basic/Extended)
Safety Integrated (with SINAMICS S120)
106 Commissioning Manual, 02/2020, A5E46305916B AB
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