Safe Speed Monitor (Ssm) - Siemens SINAMICS S120 Function Manual

5.7

Safe Speed Monitor (SSM)

General description
The "Safe Speed Monitor" function is used for reliably detecting when a velocity limit value
has been undershot (p9346/p9546) (e.g. for standstill detection) in both directions. A fail-safe
output signal is available for further processing.
The function is activated automatically as soon as the Extended Functions are enabled with
p9301.0 = p9501.0 = 1.
NOTICE
If 0 is entered for p9368/p9568, the velocity limit of the SSM function (p9346/p9546) is also
used as a shutdown limit for the SBR function (safe acceleration monitoring), if the
shutdown speed of SBR is set to 0 (also refer to Chapter "Safe Brake Ramp").
In this case, the effects of safe acceleration monitoring are therefore restricted if a relatively
high SSM/SBR velocity limit is set when using the SS1 and SS2 stop functions.
STOP F (indicated by fault C01711/C30711) only results in a follow-up response (STOP B /
STOP A) if at least one of the Safety functions SOS or SLS is active or has been selected.
If only the SSM function is active, a STOP F crosswise comparison error does not result in
a follow-up response STOP B / STOP A.
If SSM is to be used as a safety function, at least one of the SOS or SLS functions must be
active/selected (e.g. by selecting a high SLS level).
Functional features of "Safe Speed Monitor"
The parameter p9346/p9546 "SI Motion SSM (SGA n < nx) velocity limit n_x (CU)" is used to
set the velocity limit. The abbreviation "SGA n < nx" indicates the safety function required for
determining an output signal when a parameterizable velocity limit has been undershot.
If the velocity limit for the "Safe Speed Monitor" feedback signal (n < n_x) is undershot, the
"SSM feedback signal active" signal (SGA n < n_x) is set. When the set threshold value has
been undershot, the "Safe Acceleration Monitor" (SBR) function is also deactivated (see
p9368/p9568). If p9368 = p9568 = 0, then p9346/p9546 applies (SSM feedback signal) - also
as safe acceleration monitoring for SBR.
The hysteresis for the SSM output signal is set in parameter p9347/p9547 "SI Motion SSM
velocity hysteresis n_x". If the maximum permissible velocity tolerance is overshot (i.e. one
channel displays a velocity less than p9546 - p9547, while the other channel displays a
velocity greater than p9546), a STOP F is issued. As an additional function, parameters
p9347/p9547 are used to define the maximum tolerance of the velocity actual values
between the two channels.
Safety Integrated
Function Manual, (FHS), 11/2009, 6SL3097-4AR00-0BP0
WARNING
Safety Integrated Extended Functions
5.7 Safe Speed Monitor (SSM)
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