Terminal 37 Safe Torque Off Function; Abbreviations Related To Functional Safety - Danfoss VLT CDS 303 Operating Instructions Manual

Safety Instructions and Gen...
WARNING
2 2
After installation of Safe Torque Off (STO), a commis-
sioning test as specified in section Safe Torque Off
Commissioning Test in the Design Guide must be
performed. A passed commissioning test is mandatory
after first installation and after each change to the safety
installation.
Safe Torque Off Technical Data
The following values are associated to the different types
of safety levels:
Reaction time for T37
•
Maximum reaction time: 10 ms
Reaction time = delay between de-energizing the STO
input and switching off the frequency converter output
bridge.
Data for EN ISO 13849-1
•
Performance Level "d"
•
MTTF
years
•
DC (Diagnostic Coverage): 99%
•
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)=7e-10FIT=7e-19/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 one-year proof test: 3, 07E-14
•
PFDavg for three year proof tests: 9, 20E-14
•
PFDavg for five year proof tests: 1, 53E-13
No maintenance of the STO functionality is needed.
Take the necessary security measures, e.g. installation in a
closed cabinet that is only accessible for skilled personnel.
SISTEMA Data
Functional safety data is available via a data library for use
with the SISTEMA calculation tool from the IFA (Institute
for Occupational Safety and Health of the German Social
Accident Insurance), and data for manual calculation. The
library is permanently completed and extended.
8
(Mean Time To Dangerous Failure): 24816
d
Danfoss A/S © Rev. 2013-07-03 All rights reserved.
®
VLT Compressor Drives CDS 302/CDS 303
Abbrev.
Cat.
FIT
HFT
MTTFd
PFH
PL
SFF
SIL
STO
SS1
Table 2.1 Abbreviations Related to Functional Safety
The PFD
Failure probability in the event of a request of the safety
function.

2.2.1 Terminal 37 Safe Torque Off Function

The frequency converter is available with Safe Torque Off
functionality via control terminal 37. Safe Torque Off
disables the control voltage of the power semiconductors
of the frequency converter output stage. This in turn
prevents generating the voltage required to rotate the
motor. When the Safe Torque Off (T37) is activated, the
frequency converter 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 as an emergency
stop for the frequency converter. In normal operating
mode when Safe Torque Off is not required, use the
regular stop function instead. When automatic restart is
used, ensure the requirements of ISO 12100-2 paragraph
5.3.2.5 are fulfilled.
Ref. Description
EN 954-1 Category, level "B, 1-4"
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. Consider the PFH value when the
safety device is operated in high
demand (more often than once per
year); or operated in continuous mode,
where the frequency of demands for
operation made on a safety-related
system is greater than one per year.
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 Torque Off 1
-5-2
value (Probability of Failure on Demand)
avg
MG34M422