• 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 beenmade (EN 13849-2, table D.5). The analysis is based on an assumption that onefailure occurs at one time. No accumulated failures have been analyzed.• 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• STO fault indication (parameter 31.22) delay: < 500 ms• STO warning indication (parameter 31.22) delay: < 1000 msAbbreviationsDescriptionReferenceAbbr.Classification of the safety-related parts of a control system in respectof their resistance to faults and their subsequent behavior in the faultcondition, and which is achieved by the structural arrangement of theparts, 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 13849-1CCFDiagnostic coverageEN ISO 13849-1DCFailure in time: 1E-9 hoursIEC 61508FITHardware fault toleranceIEC 61508HFTMean time to dangerous failure: (The total number of life units) / (thenumber of dangerous, undetected failures) during a particular meas-urement interval under stated conditionsEN ISO 13849-1MTTFDAverage probability of dangerous failure on demandIEC 61508PFDavgAverage frequency of Probability of dangerous failures per hourIEC 61508PFHPerformance level. Levels a…e correspond to SILEN ISO 13849-1PLSystematic capabilityIEC 61508SCSafe failure fraction (%)IEC 61508SFFSafety integrity level (1…3)IEC 61508SILMaximum SIL (level 1…3) that can be claimed for a safety functionor subsystemIEC/EN 62061SILCLSafe stop 1IEC/EN 61800-5-2SS1Safe torque offIEC/EN 61800-5-2STO262 The Safe torque off function
