1 PKZM0-…/XTPR…BC1NL, PKZM0-…-T/XTPT…BC1NL motor-protective circuit-breakers
1.4 Safety analysis
PKZM0-…/XTPR…BC1NL, PKZM0-…-T/XTPT…BC1NL
01/22 MN03402003Z-DE/EN
www.eaton.com
29
1.4 Safety analysis
The following safety functions were determined for
PKZM0-…/XTPR…BC1NL and PKZM0-…-T/XTPT…BC1NL:
“Switching off motor in case of overload via thermal release to avoid thermal
overheating of motor.”
Following characteristics for functional safety for PKZM0-…/XTPR…BC1NL
and PKZM0-…-T/XTPT…BC1NL were determined due to field data from
experience and operational reliability and lifespan tests. The calculation was
carried out i.a. according EN 61508-2 / 7.4.4ff (Path 2
H
), for the architecture
1oo1 consisting of Typ A subsystems and a Hardware Fault Tolerance (HFT)
of 0 and according IEC 62061 and EN ISO 13849.
EN IEC 61508 / EN IEC 62061 –
Operation mode with high or continuous demand (> 1/year)
EN IEC 61508 / EN IEC 62061 –
Operation mode with low demand (
≤
1/year)
User must check if relevant regulations and standards e.g. according
EN 50156 require a shorter test interval.
Safety integrity level / SIL Claim Limit
SIL 1 / SIL CL 1
Safe Failure Fraction (SFF)
25 %
Common Cause Failure (CCF)
not relevant because single channel system
Diagnostic Coverage (DC)
0 %
Frequency of dangerous failure per hour (PFH
D
)
20.06 x 10
-9
Safety integrity level / SIL Claim Limit
SIL 1 / SIL CL 1
Requirement for SIL 1 according to EN IEC 61508
≥
10
-2
up to < 10
-1
Test interval
1 year
Safe Failure Fraction (SFF)
25 %
Common Cause Failure (CCF)
not relevant because single channel system
Diagnostic Coverage (DC)
0 %
Average probability of a dangerous failure when
safety function is on demand (PFD
avg
)
• At an interval for the repeat test T1 of
12 month: PFD
avg
= 0.879 x 10
-4
• At an interval for the repeat test T1 of
36 month: PFD
avg
= 2.63 x 10
-4
