Siemens SINAMICS G120C Operating Instructions Manual page 265

Debounce time
In the following cases, an immediate converter response to signal changes of the failsafe
digital inputs is not desirable:
• If a failsafe digital input of the converter is interconnected with an electromechanical sensor,
brief signal changes can occur due to contact bounce.
• In order to identify faults due to short-circuit or cross faults, several control modules test their
failsafe digital outputs with "bit pattern tests" (on/off test). If a failsafe digital input of the
converter is interconnected with a failsafe digital output of an open-loop control module,
then the converter responds with a bit pattern test.
The typical duration of the signal change within a bit pattern test:
– On test: 1 ms
– Off test: 4 ms
Too many signal changes within a specific time result in a converter fault.
Figure 8-29
You must set the debounce time to ignore temporary signal changes.
Figure 8-30
The debounce time extends the response time of the safety function.
Further information
Debounce times for standard and safety functions
The debounce time p0724 for "standard" digital inputs has no influence over the failsafe
input signals. Conversely, the same applies: The F-DI debounce time does not affect the
signals of the "standard" inputs.
If you use an input as a standard input, set the debounce time using parameter p0724 .
SINAMICS G120C Converters
Operating Instructions, 02/2023, FW V4.7 SP14, A5E34263257B AK
Converter response to a bit pattern test
Filter to suppress brief signals
Advanced commissioning
8.16 Safe Torque Off (STO) safety function
263