
Safety engineering
Safety functions
Safe stop 2
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EDS94AYAF EN 1.0
1.3.5
Safe stop 2
S
afe
S
top
2
/ SS2
This function corresponds to a "Stop 2" according to EN 60204.
This function serves to monitor the reaching of speed n = 0 within an adjustable stopping
time (C15305). The reached position must be kept active by the controller.
For speed n = 0, a tolerance window (C15310) can be parameterised. For the tolerance
window Delta p=0 (C15311), a relative position is defined by which the drive may move in
the SOS state.
If the monitored limits are exceeded, an error stop will be caused. The power supply of the
motor is immediately safely interrupted (STO). The motor cannot create a torque and thus
no dangerous movements of the drive can occur. Additional measures, e.g. mechanical
brakes are needed against movements caused by external force.
The higher−prior stop function SS1/STO is executed when the SS2 stop request and
SS1/STO occur at the same time. After the SS1/STO request has been cancelled and
acknowledged accordingly (see restart behaviour), a direct STO transition to the SS2/STO
state can be achieved without cancelling the SS2 request.
Deceleration ramp monitoring can be parameterised. Depending on the parameterised
stopping time, a monitoring ramp is calculated. (
Note!
The position of the motor is saved when the SOS state is entered. In the SOS
state, relative position changes are added and compared to the permissible
value in the parameter "Tolerance window Delta p=0". When the SOS state is
quit, the maximum relative position change is displayed in code C15312.
When the SOS state is requested again, the maximum value of the last
position changes is reset to zero.
Example: The states "SS2 active" and "SOS active" are interrupted by a STO
request. When the STO request is reset, an immediate transition to the SOS
state takes place. This causes a reset of the current position deviation to p=0.
After the safe operational stop is interrupted by the STO, the motor may have
a different position due to an external torque.