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

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Safety Integrated basic functions

9.4 Safe Torque Off (STO)

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 feed to the motor.

When the function is selected, the drive unit is in a "safe status". The switching on inhibited

function prevents the drive unit from being restarted.

The two-channel pulse suppression function integrated in the Motor Modules / Power

Modules is a basis for this function.

Functional features of "Safe Torque Off"

● This function is integrated in the drive; this means that a higher-level controller is not

● The function is drive-specific, i.e. it is available for each drive and must be individually

● The function must be enabled using parameters.

● When the "Safe Torque Off" function is selected, the following applies:

● Extended acknowledgement:

Unwanted motor motion

Appropriate measures must be taken to ensure that the motor does not undesirably move

once the energy feed has been disconnected, e.g. against coasting down or for a

hanging/suspended axis, the "Safe Brake Control" (SBC) function should be enabled, see

also Section "Safe Brake Control (SBC) (Page 582)".

commissioned.

– 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.

If STO is selected/deselected (and p9307.0/p9507.0 = 1 are set), then the safety

messages are withdrawn automatically.

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.

Function Manual, (FH1), 01/2013, 6SL3097-4AB00-0BP3

Drive functions