Terms And Abbreviations - ABB ACS580 Series Hardware Manual

• The STO is a type A safety component as defined in IEC 61508-2.
• Relevant failure modes:
• The STO trips spuriously (safe failure)
• The STO does not activate when requested
• A fault exclusion on the failure mode "short circuit on printed circuit board"
has been made (EN 13849-2, table D.5). The analysis is based on an
assumption that one failure occurs at one time. No accumulated failures
have been analyzed.
• STO response times:
• STO reaction time (shortest detectable break): 1 ms
• STO response time: 2 ms (typical), 5 ms (maximum)
• Fault detection time: Channels in different states for longer than 200 ms
• Fault reaction time: Fault detection time + 10 ms.
• Indication delays:
• STO fault indication (parameter 31.22) delay: < 500 ms
• STO warning indication (parameter 31.22) delay: < 1000 ms.
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Terms and abbreviations

Term or Reference
abbreviation
Cat. EN ISO 13849-1
CCF EN ISO 13849-1
DC EN ISO 13849-1
HFT IEC 61508
MTTF D EN ISO 13849-1
PFD avg IEC 61508
Description
Classification of the safety-related parts of a control
system in respect of their resistance to faults and their
subsequent behavior in the fault condition, and which is
achieved by the structural arrangement of the parts, fault
detection and/or by their reliability. The categories are:
B, 1, 2, 3 and 4.
Common cause failure (%)
Diagnostic coverage (%)
Hardware fault tolerance
Mean time to dangerous failure: (Total number of life
units) / (Number of dangerous, undetected failures)
during a particular measurement interval under stated
conditions
Average probability of dangerous failure on demand,
that is, mean unavailability of a safety-related system to
perform the specified safety function when a demand
occurs
The Safe torque off function 427