11
PSD1206
- PSD1210
- SIL 3 - SIL 2 Switching Power Supply 24 Vdc
G.M. International ISM0076-7
The probability of this system to fail is calculated as follows, considering 5 %
β
common cause factor, between the two power supply units PSD12xx:
(
)
(
)
(
)
2
_ System
_ PSD12xx
_ PSD12xx
2
(
)
(
)
(
)
1
1
2
2
AVG
AVG
AVG
DU
DU
TI
x years
TI
x years
TI
x years
PFD
PFD
PFD
TI
TI
β
β
β λ
β λ
=
=
=
= ⋅
+
−
⋅
=
⎛
⎞
= ⋅
⋅
+
−
⋅
⋅
⎜
⎟
⎝
⎠
where
= Dangerous Undetected failure rate of PSD12xx; = Proof Test
Interval.
DU
λ
T I
NE loads
For 2 power supply units in parallel architecture driving NE loads, it’s possible to calculate the system probability to fail for different
values by using previous
TI
_ System
(
)
AVG
TI
x years
PFD
=
equation and replacing
_ PSD12xx
(
)
AVG
TI
x years
PFD
=
or
DU
λ
with values in NE loads tables (pag.11)
In following table, it’s reported the
_System
(
)
AVG
TI
x years
PFD
=
with determination of SIL supposing module contibutes 10% of total SIF
ND loads
For 2 power supply units in parallel architecture driving ND loads, it’s possible to calculate the system probability to fail for different values
by using previous
TI
_ System
(
)
AVG
TI
x years
PFD
=
equation and replacing
_ PSD12xx
(
)
AVG
TI
x years
PFD
=
or
DU
λ
with values in ND loads tables (pag.12)
In following table, it’s reported the
_System
(
)
AVG
TI
x years
PFD
=
with determination of SIL supposing module contributes 10% of total SIF
T[Proof] = 1 year
PFDavg = 3.03 E-05
Valid for
SIL 3
See Note 1 in the section Notes
T[Proof] = 3 years
PFDavg = 9.34 E-05
Valid for
SIL 3
See Note 1 in the section Notes
T[Proof] = 6 years
PFDavg = 1.90 E-04
Valid for
SIL 2
See Note 2 in the section Notes
T[Proof] = 10 years
PFDavg = 3.41 E-04
Valid for
SIL 2
See Note 2 in the section Notes
T[Proof] = 1 year
PFDavg = 8.09 E-05
Valid for
SIL 2
See Note 2 in the section Notes
T[Proof] = 5 years
PFDavg = 4.65 E-04
Valid for
SIL 2
See Note 2 in the section Notes
T[Proof] = 9 years
PFDavg = 9.40 E-04
Valid for
SIL 2
See Note 2 in the section Notes
T[Proof] = 10 years
PFDavg = 1.10 E-03
See Note 3 and Note 4
in the section Notes
In following table, it’s reported the
_System
(
)
AVG
TI
x years
PFD
=
with determination of SIL supposing module contibutes 20% of total SIF
T[Proof] = 1 year
PFDavg = 3.03 E-05
Valid for
SIL 3
See Note 6 in the section Notes
T[Proof] = 3 years
PFDavg = 9.34 E-05
Valid for
SIL 3
See Note 6 in the section Notes
T[Proof] = 6 years
PFDavg = 1.90 E-04
Valid for
SIL 3
See Note 6 in the section Notes
T[Proof] = 10 years
PFDavg = 3.41 E-04
Valid for
SIL 2
See Note 7 in the section Notes
In following table, it’s reported the
_ System
(
)
AVG
TI
x years
PFD
=
with determination of SIL supposing module contibutes 20% of total SIF
T[Proof] = 1 years
PFDavg = 8.09 E-05
Valid for
SIL 2
See Note 6 in the section Notes
T[Proof] = 10 years
PFDavg = 1.10 E-03
Valid for
SIL 2
See Note 6 in the section Notes
PSD1206, PSD1210 Isolated Power Supply, 3 units in parallel
For 3 power supply units in parallel architecture, it’s possible to calculate the system probability to fail for different values by using the following equation:
TI
(
)
(
)
3
_System
(
)
1
2
4
DU
AVG
DU
TI
x years
TI
TI
PFD
β λ
β λ
=
−
⋅
⋅
≅ ⋅
⋅
+
NE Loads
T[Proof] = 1 year
PFDavg = 2.99 E-05
Valid for
SIL 3
See Note 1 in the section Notes
T[Proof] = 3 years
PFDavg = 8.96 E-05
Valid for
SIL 3
See Note 1 in the section Notes
T[Proof] = 10 years
PFDavg = 2.99 E-04
Valid for
SIL 2
See Note 2 in the section Notes
Where
β
= 5 %; = Dangerous Undetected failure rate of PSD12xx; = Proof Test Interval
DU
λ
TI
In following table, it’s reported the
_System
(
)
AVG
TI
x years
PFD
=
, with determination of SIL supposing module contributes 10% of total SIF
Use previous
_ System
(
)
AVG
TI
x years
PFD
=
equation and replace
DU
λ
with value 134.80 FIT
