Siemens SINAMICS G120 Operating Instructions Manual page 253

Figure 6-28
Filter to suppress short signals
In the following cases, an immediate inverter response to signal changes of the fail-safe digital
inputs is not desirable:
● If a fail-safe digital input of the inverter is interconnected with an electromechanical sensor,
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 fail-safe digital outputs with "bit pattern tests" (bright/dark test). If a fail-safe digital
input of the inverter is interconnected with a fail-safe digital output of an open-loop control
module, then the inverter 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
If the fail-safe digital input responds to many signal changes within a certain time, then the
inverter responds with a fault.
Figure 6-29
A filter in the inverter suppresses brief signals as a result of the bit pattern test or contact
bounce.
Converter with the CU250S-2 Control Units
Operating Instructions, 04/2018, FW V4.7 SP10, A5E31759476B AG
Simultaneity monitoring with discrepancy time
Inverter response to a bit pattern test
Advanced commissioning
6.17 Safe Torque Off (STO) safety function
251