Siemens SINAMICS V90 Operating Instructions Manual page 254

Safety Integrated function
8.4 Safety Integrated basic functions
● 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 feed to the
– The power unit and motor are not electrically isolated.
● By selecting/deselecting STO, the safety messages are also automatically withdrawn.
The STO function can be used wherever the drive naturally reaches a standstill due to load
torque or friction in a sufficiently short time or when "coasting down" of the drive will not have
any relevance for safety.
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.
If two power transistors simultaneously fail in the power unit (one in the upper and one in
the lower bridge), then this can cause brief momentary movement.
The maximum movement can be:
Synchronous rotary motors: Max. movement = 180 ° / No. of pole pairs
Synchronous linear motors: Max. movement = pole width
Note
Closing delay of the holding brake
The closing signal (low level) of the holding brake is output 30 ms after the STO is triggered.
Preconditions for using the STO function
When use the STO function, the following preconditions should be fulfilled:
● Each monitoring channel (STO1 and STO2) triggers safe pulse suppression with its
switch off signal path.
● If a motor holding brake is connected and configured, the connected brake is not safe
because there is no safety function for brake, such as safe brake.
Behaviors of the STO function
Terminal
STO1
High level
Low level
254
motor.
WARNING
CAUTION
State
STO2
High level Safe
Low level Safe
The servo motor can normally run when you power on the servo
drive.
The servo drive starts up normally but the servo motor cannot
run.
Operating Instructions, 09/2016, A5E36037884-002
Action
SINAMICS V90, SIMOTICS S-1FL6