Siemens SINUMERIK 840D sl Function Manual page 119

the pulses are cancelled via the internal switch-off signal path of the NCK monitoring channel
● Effect:
The drive coasts to a standstill if no external braking mechanism such as an armature short-
circuit and/or holding brake is used. The axis-specific alarm results in a mode group stop,
i.e. as the result of the error in one axis, all axes and spindles in a mode group are stopped.
Safe standstill becomes effective at the end of STOP A.
● Alarm message for an internally initiated STOP A:
The alarm message "STOP A initiated" is displayed.
● Acknowledgment for an internally initiated STOP A:
An unintentional restart is prevented with a STOP A. The error can only be acknowledged
from the drive and control using a power on.
SGA "STOP A/B active"
This signal indicates that STOP A/B is active.
0 signal:
1 signal:
Potentially hazardous motion
If the safe standstill function or "STOP A" is activated, then the motor can no longer generate
any torque. This is the reason that potentially hazardous motion can occur, e.g. for the
following:
● When an external force acts on the drive axes
● Vertical and inclined axes without weight equalization
● Axes that are moving (coasting down)
● Direct drives with low friction and low self-locking
● Cogging torques (depending on the motor type, bearing design and friction characteristics,
Possible hazards must be clearly identified using a risk analysis that must be carried out by
the manufacturer. With an assessment, based on this risk analysis, it should be defined as
to which additional measures are required, e.g. external brakes.
SGE deselect external STOP A
"Pulse cancellation" can be requested and executed using this SGE.
The safety functions currently active (SG/SBH/SN/SE) are not influenced by this SGE, unless
function "Deactivate SBH/SG monitoring during an external STOP A" is enabled.
If one of the currently active limits is violated, an appropriate alarm is initiated. The associated
shutdown response cannot be activated because the pulses have already been cancelled. As
soon as the stop request is cancelled via the SGE "deselect ext. STOP A" any pending
shutdown responses become active.
If a stop request is active, SGA "STOP A/B active" is set in the same way as it would be for
an internally initiated STOP A.
Safety Integrated
Function Manual, 12/2017, 6FC5397-4BP40-6BA1
STOP A/B is not active
STOP A/B is active.
WARNING
up to half a pole pitch in a direction that cannot be predicted)
Safety functions integrated in the system/drive
7.3 Safe Stops A-F
119