Residual Risk; Safety Integrated Basic Function; Safe Torque Off (Sto) - Siemens SINAMICS V90 Operating Instructions Manual

9.3.6

Residual risk

The fault analysis enables the machine manufacturer to determine the residual risk at this
machine with regard to the drive unit. The following residual risks are known:
Personal injury or device damage due to the intrinsic potential of hardware faults
Due to the intrinsic potential of hardware faults, electrical systems are subject to additional
residual risk, which can be expressed by means of the PFH value.
• Take into account the residual risks when designing your machine and where necessary
Personal injury or device damage resulting from the simultaneous failure of two power
transistors in the inverter
Simultaneous failure of two power transistors (one in the upper and the other offset in the
lower inverter bridge) in the drive may cause brief movement of the drive which can result
in a personal injury or device damage. The movement depends on the number of poles of
the motor. For a synchronous rotary motor, the maximum movement is 180 °/Number of
pole pairs.
• Take suitable measures to prevent unexpected drive movement, for example, by using a
9.4

Safety Integrated basic function

9.4.1

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 and de-energize 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 units 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
required.
● The function is drive-specific, i.e. it is available for each drive and must be individually
commissioned.
SINAMICS V90, SIMOTICS S-1FL6
Operating Instructions, 04/2020, A5E37208830-008
WARNING
apply suitable countermeasures.
WARNING
brake equipped with safety monitoring.
Safety Integrated function
9.4 Safety Integrated basic function
243