Figure 4-17
Time response of the safety function SSM (Safe Speed Monitor)
4.11.1.1
Signal characteristic (with encoder)
Functional features of "Safe Speed Monitor" with encoder
A hysteresis can be configured for the SSM function using (p9547). In this way, a more stable
signal characteristic of SSM can be achieved at velocities close to the velocity limit (p9546).
The following diagram shows the characteristic of the safe output signal SSM when the
hysteresis is active:
Q
W
W
[
Q S
660RXWSXWVLJQDO
+\VWHUHVLVS
+\VWHUHVLVS
Q
[ S
Figure 4-18
Safe output signal for SSM with hysteresis
4.11.1.2
Differences in operation without encoder
In operation, safety function SSM makes a distinction without encoder as a result of the
following features:
● Due to the less precise speed sensing, "Safe Speed Monitor without encoder" requires a
higher hysteresis (p9547) and, where applicable, a filter time (p9545) compared with the
function with encoder.
● For Safe Speed Monitor without encoder, after pulse suppression the drive is unable to
determine the current speed. For this operating state, the additional setting "Feedback
signal SSM for pulse inhibit" is available (see below)
Safety functions integrated in the drive
4.11 SSM
Safety Integrated (with SINAMICS S120)
Commissioning Manual, 02/2020, A5E46305916B AB
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