• 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 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
￭ Terms and abbreviations
DescriptionReferenceTerm or ab-
breviation
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 coverageEN ISO 13849-1DC
Hardware fault toleranceIEC 61508HFT
Mean time to dangerous failure: (Total number of life units)
/ (Number of dangerous, undetected failures) during a partic-
ular measurement interval under stated conditions
EN ISO 13849-1MTTF
D
The Safe torque off function 363
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