Abbreviations - ABB ACS880-04 Hardware Manual

282 The Safe torque off function
• STO warning indication (parameter 31.22) delay: < 1000 ms
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Abbreviations

Abbr. Reference
Cat. EN ISO 13849-1
CCF EN ISO 13849-1
DC EN ISO 13849-1
HFT IEC 61508
MTTF D EN ISO 13849-1
PFD avg IEC 61508
PFH IEC 61508
PL EN ISO 13849-1
SC IEC 61508
SFF IEC 61508
SIL IEC 61508
SILCL IEC/EN 62061
STO IEC/EN 61800-5-2
T 1 IEC 61508-6
T M EN ISO 13849-1
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 partic-
ular 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
Performance level. Levels a...e correspond to SIL
Systematic capability
Safe failure fraction (%)
Safety integrity level (1...3)
Maximum SIL (level 1...3) that can be claimed for a safety
function or subsystem
Safe torque off
Proof test interval. T 1 is a parameter used to define the
probabilistic failure rate (PFH or PFD) for the safety function
or subsystem. Performing a proof test at a maximum interval
of T 1 is required to keep the SIL capability valid. The same
interval must be followed to keep the PL capability (EN ISO
13849) valid.
See also section Maintenance.
Mission time: the period of time covering the intended use
of the safety function/device. After the mission time elapses,
the safety device must be replaced. Note that any T M values
given cannot be regarded as a guarantee or warranty.