APPENDIX C
Curtis AC F2-A, F4-A, F6-A Motor Controllers – FOS 4.5 – April 2022 Return to TOC
pg. 256
EN1175-1:1998+A1:2010 species that traction and hydraulic electronic control systems must
use Designated Architecture 1 or greater. is design employs input, logic, and output circuits
that are monitored and tested by independent circuits and soware to ensure a high level of safety
performance (up to PL=D).
Mean Time To Dangerous Failure (MTTFd) is related to the expected reliability of the safety
related parts used in the controller. Only failures that can result in a dangerous situation are
included in the calculation.
Diagnostic Coverage (DC) is a measure of the eectiveness of the control system’s self-test and
monitoring measures to detect failures and provide a safe shutdown.
Common Cause Faults (CCF) are so named because some faults within a controller can aect
several systems. EN13849 provides a checklist of design techniques that should be followed to achieve
sucient mitigation of CCFs. e CCF value is a pass/fail criterion.
Performance Level (PL) categorizes the quality or eectiveness of a safety channel to reduce the
potential risk caused by dangerous faults within the system with “A” being the lowest and “E” being
the highest achievable performance.
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