Safe Torque Off (Sto) - Siemens SINUMERIK 840D sl Function Manual

Safety Functions integrated in the drive

5.3 Safe Torque Off (STO)

Limited motion
If two power transistors in the power unit fail at the same time (one in the upper bridge and
one in the lower bridge of the inverter), this can cause brief, limited movement. The maximum
movement can be:
● Synchronous rotary motors: Max. movement = 180° / pole pair number
● Synchronous linear motors: Max. movement = pole width
"Automatic restart" function
The "automatic restart" function may not be used together with the safety functions STO/SBC
and SS1. The reason for this is that EN 60204-1 Chapter 9.2.5.4.2 does not permit this (merely
de-selecting a safety shutdown function must not cause the machine to restart).
Note
Deactivating all components, e.g. using p0105, with activated Safety functions is not permitted.
5.3 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 power feed to the motor.
After selecting the function, the drive device is in a "Safe state". 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 the basis for this function.
Functional features of Safe Torque Off
● This function is integrated in the drive, i.e. a higher-level control is not required.
● The function is drive specific. This means that each drive has the function and it must be
individually commissioned.
● The function must be enabled using a parameter.
● When the Safe Torque Off function is selected, the following applies:
– The motor cannot be started accidentally.
– The safety-related pulse suppression safely disconnects the torque-generating energy
– the power unit and motor are not electrically isolated.
58
WARNING
CAUTION
supply to the motor.
Function Manual, 12/2017, 6FC5397-4BP40-6BA1
Safety Integrated