Siemens SINAMICS S120 Function Manual page 165

Safe motion monitoring
The properties of the actual value acquisition determine not only the encoders used, but also
the values for safe motion monitoring that can be achieved in the best case.
● Safe maximum speed (r9730)
The maximum speed (load side) that is permissible due to the acquisition of actual values
for safe motion monitoring functions is indicated in r9730. This parameter shows the load
velocity up to which the safety-relevant encoder actual values (redundant coarse encoder
position) can still be correctly sensed as a result of the particular encoder
parameterization.
The actual value acquisition clock (p9511) determines the frequency at which the actual
values are acquired. The longer the clock cycle, the higher the "safe maximum velocity."
On the other hand, a longer actual value acquisition clock cycle places a greater load on
the Control Unit. You must consider this circumstance when setting the optimum for your
application.
For SINAMICS S120M, only the values 2 and 0 ms are allowed for the actual value
acquisition cycle clock (p9511). In both cases, the frequency converter calculates with an
actual value acquisition cycle clock of 2 ms regardless of the PROFIBUS DP/PN cycle
clock.
● Safe positioning accuracy (r9731)
This positioning accuracy can be achieved in the best case by acquiring the actual
values. If a 2-encoder system is used, the accuracy of the poorer encoder is indicated
based on the number of encoder pulses.
Safety Integrated
Function Manual, 12/2018, 6SL3097-5AR00-0BP1
Description of Safety Integrated functions
4.2 Safety Integrated Extended Functions
163