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Entry type: FAQ, Entry ID: 109483115, Entry date: 06/28/2017
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IEC 62061 / ISO 13849-1 – Notes on applicationt Which safety integrity is reachable by using two circuit breakers?

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This FAQ content information for which safety integrity is reachable by using two circuit breakers.




QUESTION:

Which safety integrity is reachable by using two circuit breakers?



ANSWER:

Circuit breakers do not have „mirror contacts“ (as contacts mechanically linked with power contacts) used by the main contactors, but have instead of auxiliary contacts as feedback signal which can be used  for diagnostic means. Due to the missing characteristic „positively driven contacts“ of the auxiliary contacts of the circuit breaker (a kind of „ monitoring of the status of the contacts“), a dynamic monitoring of those contacts is necessary for diagnostics.

Dynamic monitoring means that when applying the command “ON” the feedback “ON” is expected after a defined time frame, respectively following the command „OFF“ the feedback “OFF” is expected; it is also necessary to monitor by the F-program separately and dynamically the feedback (status of the contacts) „ON“ and „OFF“ of both circuit breakers when switching including also operational switching. It’s irrelevant whether the electrical signals of the
auxiliary contacts are evaluated by using non-safety-related (“standard”) or safety-related digital (“failsafe”) input cards. The generation of the “operation-OFF” or “operation-ON” command can be realized via non-safety-related („standard“) digital outputs.

Evaluation with HFT = 1 acc. to EN 62061 respectively with category 3 acc. to EN ISO 13849-1, as dual channel architecture:
SIL 3 acc. to EN 62061 respectively PL e acc. to EN ISO 13849-1 can be claimed.

Both circuit breakers are simultaneously switched via safety-related outputs (F-output) and are dynamically monitored by the safety-related software (F-program). This monitoring is also necessary while operational switching.

This approach allows claiming for each circuit breaker at least a diagnostic coverage DC ………


See additional   Registrierung notwendig  IEC62061_ISO3849_Leistungsschalter_V10-EN.pdf (53,9 KB) 

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