Functional Safety
Circuit with OSSD (SIL 3)
Fig. 32: Wiring with OSSD
Fig. 32: Wiring with OSSD
Circuit without OSSD (SIL 3)
The following figure shows a circuit without OSSD safety device, whilst only safety di-
rected command devices with forcibly opened contacts in two-channel design are used.
SIL 3 (according to DIN EN ISO 13849-1) is achieved. It is also possible to cascade sev-
eral different safe emergency stop devices, position switches or door locks to one safety
circuit.
Fig. 33: Wiring without OSSD
Drive
Emergency stop
switching device
1
2 - n
Emergency stop
switching device
Fig. 33: Wiring without OSSD
Note
The safety relay as well as the emergency stop device have to be certificated as safety
devices of at least level SIL 3 to obtain safety level SIL 3 according to DIN EN ISO
13849-1.
Note
In order to obtain the safety level SIL 3 according to DIN EN ISO 13849-1, the circuit
and the layout have been dimensioned according to IEC 60664-1:2008-01. Supporting
material according to IEC 60249 covered by a nonaging protective coat of lacquer ac-
cording to IEC 60664-3:2003-09 have been used. The conformity of standard have been
tested and approved by the TÜV-Nord CERT.
52 Drive Amplifier SD4B - Hardware Description
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