Technical data

Safety Integrated Functions
8.5 Safety Integrated Extended Functions
Function Manual
388 Function Manual, 06/2012, 6SL3097-4AB10-0BP4
Differences between Safe Speed Monitor with and without encoder
● For Safe Speed Monitor without encoder, after pulse suppression the drive is unable to
determine the current speed. Two responses can be selected for this operating state with
parameters p9309.0/p9509.0:
– p9309.0 = p9509.0 = 1
The status signal (SSM feedback signal) shows "0" (factory setting).
– p9309.0 = p9509.0 = 0
The status signal (SSM feedback signal) is frozen. "Safe Torque Off" (STO) is
selected internally.
● Due to the less precise speed recognition, "Safe Speed Monitor without encoder" requires
a larger hysteresis (p9347/p9547) and, where applicable, a filter time (p9345/p9545)
compared with the function with encoder.
Sequence diagram
The diagram below shows the signal characteristic for the case p9309.0 = p9509.0 = 0.
The speed remains below the limits of p9346/p9546 throughout the entire observation
period. The SSM feedback signal therefore remains r9722.15 = 1. Following the command
for pulse suppression, the motor speed drops. The internal STO is set when the speed drops
below the zero speed detection level.
The SSM monitoring remains active. The motor speed continues to be below the speed limit
p9346/p9546. The SSM feedback signal remains as 1, i.e. it is frozen.
To restart the motor safely, the STO must be selected manually and deselected once more.
After the STO has been deselected, a 5 second time window is opened. If the pulse enable
takes place within this time window, the motor starts. If the pulse enable does not take place
within this 5 second time window, the internal STO becomes active once more.