Siemens SINUMERIK 840D sl Function Manual page 121

The shutdown speed for the pulse cancellation is generally reached faster than the delay time
for the pulse cancellation.
● Effect:
The drive is braked along the OFF3 ramp under closed-loop speed control and brought to
a safe standstill.
● Alarm message for an internally initiated STOP B:
The alarm message "STOP B initiated" is displayed.
● Alarm message for an internally initiated STOP B:
An unintentional restart is prevented using a STOP B. The error can only be acknowledged
from the drive and control using a power on.
SGA "STOP A/B is active"
This signal indicates that STOP A/B is active.
0 signal: STOP A/B is not active
1 signal: STOP A/B is active
Figure 7-6
It is possible that the stop for the NCK becomes effective one safety monitoring clock cycle
earlier than for the drive. This means that braking along the current limit can become effective
before the OFF3 ramp of the drive becomes effective.
In order to reduce the level of stress of the mechanical system of the machine (if required) the
braking torque can be reduced. To realize this, bit 4 "Torque limiting active in motoring/
regenerating mode" can be set in parameter p1400 and parameter p1521 "Torque limit lower/
regenerative" can be set to the required lower torque. In this case, it should be noted that the
braking distance (stopping distance) of the axis is extended, and that the torque limiting is not
only effective for STOP B, but that generally, the dynamic response of the axis changes.
Safety Integrated
Function Manual, 12/2017, 6FC5397-4BP40-6BA1
Transition from STOP B to STOP A
Safety functions integrated in the system/drive
7.3 Safe Stops A-F
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