Siemens SINAMICS G220 - Page 189

NOTICE
Reduced relay lifetime due to dark pulses
The self-test of the failsafe digital output with dark pulses can lead to a connected relay short-
circuiting. A relay is designed only for a limited number of switching operations, so the dark
pulses in this situation reduce the lifetime of the relay.
• Set the dark pulses to be so short that the relay does not switch in the self-test.
Description
The failsafe digital output is suitable for connecting the following devices:
• relay
• valve
• Sourcing/sinking failsafe input
Table 7-29 Achievable category according to EN ISO 13849‑1 and SIL according to IEC61508 and
IEC62061
Category SIL Dark pulses Result
Cat 3 SIL 2 Without activa‐
ted converter-in‐
ternal dark pul‐
ses
The converter self-test detects errors in the circuits of the fail‐
safe digital output.
No cross-circuit detection
The failsafe digital output must switch from Low to High at
least once a year.
SIL 3 The converter self-test detects errors in the circuits of the fail‐
safe digital output.
No cross-circuit detection
The failsafe digital output must switch from Low to High at
least once in three months.
Cat 4 SIL 2 or
SIL 3
With activated
converter-inter‐
nal dark pulses
The converter self-test detects errors in the circuits of the fail‐
safe digital output.
The converter outputs dark pulses as soon as the failsafe digital
output is in the High state.
The self-test detects a cross circuit.
No requirement for regular switching of the failsafe digital
output
Connecting
7.2Interfaces for the controller
SINAMICS G220 converter
Operating Instructions, 04/2024, FW V6.2, A5E51781573B AB 187