Danfoss VLT FC 102 Series Design Manual page 18

Introduction to VLT® HVAC D...
Safe Torque Off Technical Data
2 2
The following values are associated to the different types
of safety levels:
Reaction time for T37
•
Maximum reaction time: 20 ms
Reaction time = delay between de-energizing the STO
input and switching off the output bridge.
Data for EN ISO 13849-1
•
Performance Level "d"
•
MTTF
14,000 years
•
DC (Diagnostic Coverage): 90%
•
Category 3
•
Lifetime 20 years
Data for EN IEC 62061, EN IEC 61508, EN IEC 61800-5-2
•
SIL 2 Capability, SILCL 2
•
PFH (Probability of dangerous Failure per Hour) =
1E-10/h
•
SFF (Safe Failure Fraction) > 99%
•
HFT (Hardware Fault Tolerance) = 0
(1001 architecture)
•
Lifetime 20 years
Data for EN IEC 61508 low demand
•
PFDavg for 1-year proof test: 1E-10
•
PFDavg for 3-year proof test: 1E-10
•
PFDavg for 5-year proof test: 1E-10
No maintenance of the STO functionality is needed.
Take security measures, e.g., only skilled personnel must be
able to access and install in closed cabinets.
SISTEMA Data
Danfoss provides functional safety data via a data library
for use with the SISTEMA calculation tool from IFA
(Institute for Occupational Safety and Health of the
German Social Accident Insurance), as well as data for
manual calculation. The library is complete and continually
extended.
16
(Mean Time To Dangerous Failure):
d
Danfoss A/S © Rev. 06/2014 All rights reserved.
Design Guide
Abbrev.
Cat.
FIT
HFT
MTTFd
PFH
PFD
PL
SFF
SIL
STO
SS1
Table 2.2 Abbreviations Related to Functional Safety
2.6.1 Terminal 37 Safe Torque Off Function
The FC 102 is available with Safe Torque Off functionality
via control terminal 37. Safe Torque Off disables the
control voltage of the power semiconductors of the
adjustable frequency drive output stage which in turn
prevents generating the voltage required to rotate the
motor. When the Safe Torque Off (T37) is activated, the
adjustable frequency drive issues an alarm, trips the unit,
and coasts the motor to a stop. Manual restart is required.
The Safe Torque Off function can be used for stopping the
adjustable frequency drive in emergency stop situations. In
the normal operating mode when Safe Torque Off is not
required, use the adjustable frequency drive's regular stop
function instead. When automatic restart is used – the
requirements according to ISO 12100-2 paragraph 5.3.2.5
must be fulfilled.
Ref. Description
EN ISO Category, level "B, 1-4"
13849-1
Failure In Time: 1E-9 hours
IEC 61508 Hardware Fault Tolerance: HFT = n
means that n+1 faults could cause a
loss of the safety function
EN ISO Mean Time To Failure - dangerous. Unit:
13849-1 years
IEC 61508 Probability of Dangerous Failures per
Hour. This value shall be considered if
the safety device is operated in high
demand (more often than once per
year) or continuous mode of operation,
where the frequency of demands for
operation made on a safety-related
system is greater than one per year
IEC 61508 Average probability of failure on
demand, value used for low demand
operation
EN ISO Discrete level used to specify the ability
13849-1 of safety related parts of control
systems to perform a safety function
under foreseeable conditions. Levels a-e
IEC 61508 Safe Failure Fraction [%]; Percentage
part of safe failures and dangerous
detected failures of a safety function or
a subsystem related to all failures
IEC 61508 Safety Integrity Level
EN Safe Torque Off
61800-5-2
EN 61800 Safe Stop 1
-5-2
MG11BC22