BECKHOFF TwinSAFE - Manual (Page 43)

Circuit examples
Application Guide TwinSAFE 41
If only PFH values are available for EL1904 and EL6900, the following estimation applies:
ܯܶܶܨ
ௗ
ሺELxxxxሻ ൌ
ሺ1 െ ܦܥሺܧܮݔݔݔሻሻ
ܲܨܪሺܧܮݔݔݔሻ
Hence:
ܯܶܶܨ
ௗ
ሺEL1904ሻ ൌ
൫1 െ ܦܥሺܧܮ1904ሻ൯
ܲܨܪሺܧܮ1904ሻ
ൌ
ሺ1 െ 0.99ሻ
1.11E െ 09 ଵ
୦
כ 8760 ୦
୷
ൌ
0.01
9.72E െ 06 ଵ
୷
ൌ 1028.8y
ܯܶܶܨ
ௗ
ሺEL6900ሻ ൌ
ሺ1 െ ܦܥሺܧܮ6900ሻሻ
ܲܨܪሺܧܮ6900ሻ
ൌ
ሺ1 െ 0.99ሻ
1.03E െ 09 ଵ
୦
כ 8760 ୦
୷
ൌ
0.01
9.02E െ 06
ଵ
୷
ൌ 1108.6y
ܯܶܶܨ
ௗ
ሺEL2904ሻ ൌ
ሺ1 െ ܦܥሺܧܮ2904ሻሻ
ܲܨܪሺܧܮ2904ሻ
ൌ
ሺ1 െ 0.99ሻ
1.25E െ 09 ଵ
୦
כ 8760 ୦
୷
ൌ
0.01
1.1E െ 05 ଵ
୷
ൌ 913.2y
MTTF
d tot =
ଵ
భ
రఱలలమ.భ೤
ା
భ
భబమఴ.ఴ೤
ା
భ
భభబఴ.ల೤
ା
భ
వభయ.మ೤
ା
భ
ఱవయలబళ.య೤
ା
భ
రఱలలమభబ.బ೤
ା
భ
భబమఴ.ఴ೤
ൌ 252.1ݕ
DC
avgs =
వవ%
రఱలలమ.భ
ା
వవ%
భబమఴ.ఴ
ା
వవ%
భభబఴ.ల
ା
వవ%
వభయ.మ
ା
వబ%
ఱవయలబళ.య
ା
వబ%
ఱవయలబళ.య
ା
వబ%
రఱలలమభబ.బ
ା
వవ%
భబమఴ.ఴ
భ
రఱలలమ.భ
ା
భ
భబమఴ.ఴ
ା
భ
భభబఴ.ల
ା
భ
వభయ.మ
ା
భ
ఱవయలబళ.య
ା
భ
ఱవయలబళ.య
ା
భ
రఱలలమభబ.బ
ା
భ
భబమఴ.ఴ
ൌ 98.99%
MTTF
d
Designation for each channel Range for each channel
low 3 years ≤ MTTF
d
< 10 years
medium 10 years ≤ MTTF
d
< 30 years
high 30 years ≤ MTTF
d
≤ 100 years
DC
avg
Designation Range
none DC < 60 %
low 60 % ≤ DC < 90 %
medium 90 % ≤ DC < 99 %
high 99 % ≤ DC