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

8.3.5

Response time

Response time means the time from the control via terminals until the response actually
occurs. The worst response time for the STO function is 5 ms. The response time of fault
reaction functions is 2 s.
8.3.6

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:
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.
Simultaneous failure of two power transistors (one in the upper and the other offset in the
lower inverter bridge) in the inverter may cause brief movement of the drive, depending on
the number of poles of the motor.
Maximum value of this movement:
Synchronous rotary motors: Max. movement = 180° / no. of pole pairs
8.4

Safety Integrated basic functions

8.4.1

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 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
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, 09/2015, A5E36037884
WARNING
WARNING
Safety Integrated function
8.4 Safety Integrated basic functions
243