Advanced commissioning
6.11 Safe Torque Off (STO) safety function
Converter with the control units CU240D-2
Operating Instructions, 04/2018, FW V4.9 SP10, A5E34262100B AF
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Figure 6-20 Simultaneity monitoring with discrepancy time
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 6-21 Inverter response to a bit pattern test
A filter in the inverter suppresses brief signals as a result of the bit pattern test or contact
bounce.
