ABB ACS880-107

• The STO is a type A (frames R1i…R7i) or type B (frame R8i and multiples) 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:
- Frames R1i…R7i: 7 ms (typical), 10 ms (maximum)
- Frame R8i and multiples: 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.
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Terms and abbreviations
DescriptionReferenceTerm or
abbreviation
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.
EN ISO 13849-1Cat.
Common cause failure (%)EN ISO 13849-1CCF
Diagnostic coverage (%)EN ISO 13849-1DC
Hardware fault toleranceIEC 61508HFT
Mean time to dangerous failure: (Total number of life units) /
(Number of dangerous, undetected failures) during a particular
measurement interval under stated conditions
EN ISO 13849-1MTTF
D
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
IEC 61508PFD
avg
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
IEC 61508PFH
Average frequency of dangerous failures per hour for the
diagnostic function of STO
IEC/EN 62061PFH
diag
Performance level. Levels a…e correspond to SILEN ISO 13849-1PL
Periodic test performed to detect failures in a safety-related
system so that, if necessary, a repair can restore the system to
an "as new" condition or as close as practical to this condition
IEC 61508, IEC 62061Proof test
Systematic capability (1…3)IEC 61508SC
Safe failure fraction (%)IEC 61508SFF
Safety integrity level (1…3)IEC 61508SIL
Safe torque offIEC/EN 61800-5-2STO
The Safe torque off function 209