The Safe torque off function 169 Abbreviations Declaration of conformitySee Electrical planning instructions for ACS880 multidrive cabinets and modules(3AUA0000102324 [English]).Abbr. Reference DescriptionCat. EN ISO 13849-1 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.CCF EN ISO 13849-1 Common cause failure (%)DC EN ISO 13849-1 Diagnostic coverageFIT IEC 61508 Failure in time: 1E-9 hoursHFT IEC 61508 Hardware fault toleranceMTTF D EN ISO 13849-1 Mean time to dangerous failure: (The total number of life units) / (thenumber of dangerous, undetected failures) during a particularmeasurement interval under stated conditionsPFD avg IEC 61508 Average probability of dangerous failure on demandPFH IEC 61508 Average frequency of dangerous failures per hourPL EN ISO 13849-1 Performance level. Levels a…e correspond to SILSC IEC 61508 Systematic capabilitySFF IEC 61508 Safe failure fraction (%)SIL IEC 61508 Safety integrity level (1…3)SILCL IEC/EN 62061 Maximum SIL (level 1…3) that can be claimed for a safety function orsubsystemSS1 IEC/EN 61800-5-2 Safe stop 1STO IEC/EN 61800-5-2 Safe torque offT1 IEC 61508-6 Proof test interval. T1 is a parameter used to define the probabilisticfailure rate (PFH or PFD) for the safety function or subsystem.Performing a proof test at a maximum interval of T1 is required to keepthe SIL capability valid. The same interval must be followed to keep thePL capability (EN ISO 13849) valid. Note that any T1 values givencannot be regarded as a guarantee or warranty.See also section Maintenance (page 167).
