Terms And Abbreviations - ABB ACS880-37LC-0390A-7 Hardware Manual

232 The Safe torque off function
• The following temperature profile is used in safety value calculations:
• 670 on/off cycles per year with ΔT = 71.66 °C
• 1340 on/off cycles per year with ΔT = 61.66 °C
• 30 on/off cycles per year with ΔT = 10.0 °C
• 32 °C board temperature at 2.0% of time
• 60 °C board temperature at 1.5% of time
• 85 °C board temperature at 2.3% of time.
• The STO is a type B 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), 25 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

Terms and abbreviations

￭
Term or abbre- Reference
viation
Cat. EN ISO 13849-1
CCF EN ISO 13849-1
DC EN ISO 13849-1
HFT IEC 61508
MTTF EN ISO 13849-1
D
PFD IEC 61508
avg
PFH 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
Average frequency of dangerous failures per hour, that is, average
frequency of a dangerous failure of a safety related system to perform
the specified safety function over a given period of time