Siemens SINAMICS G120 Operating Instructions Manual page 236

Functions
9.10 Fail-safe function Safe Torque Off (STO)
Filter to suppress short signals
The converter normally responds immediately to signal changes at its fail-safe inputs. This is
not required in the following cases:
1. When you interconnect a fail-safe input of the converter with an electromechanical
2. Several control modules test their fail-safe outputs using bit pattern tests (on/off tests), in
If the fail-safe input signals too many signal changes within a certain time, then the converter
responds with a fault.
Figure 9-34
234
sensor, contact bounce may result in signal changes occurring, to which the converter
responds.
order to identify faults due to either short-circuit or cross-circuit faults. When you
interconnect a fail-safe input of the converter with a fail-safe output of a control module,
the converter responds to these test signals.
A signal change during a bit pattern test usually lasts:
– On test: 1 ms
– Off test: 4 ms
Converter response to a bit pattern test
SINAMICS G120C frequency converter
Operating Instructions, 03/2012, FW V4.5, A5E02999804B AB