Excelsys XS1000-24, Manual, Page: 9 / 10

powerMod 0.958 failures per million hours
4slot powerPac 0.92 failures per million hours
6slot powerPac 0.946 failures per million hours
The figures for the powerPac excludes fans.
Example:
What is the MTBF of UX4DD00
UX4 FPMH = 0.92
XgD FPMH = 0.286
Total FPMH = 1.49
MTBF = 670,000 hours at 40°C
Xsolo MTBF
Xsolo has an MTBF of 550,000 hours at 40°C and full load
based on the Telecordia SR-332 (fans excluded).
MTBF and Temperature
Reliability and MTBF are highly dependent on operating tem-
perature. The figures above are given at 40°C. For each 10°C
decrease, the MTBF increases by a factor of approximately 2.
Conversely, however, for each 10°C increase, the MTBF
reduces by a similar factor. Therefore, when comparing manu-
facturer's quoted MTBF figures, look at the temperature infor-
mation provided. Contact Excelsys for detailed analysis of MTBF
for your specific application conditions.
Section 7.2
Safety Approvals
UltiMod and Xsolo carry dual safety certification,
UL/EN60950 2nd Edition for Industrial Applications and
UL/EN60601-1 2nd and 3rd Edition for Medical Applications,
meeting the stringent creepage and clearance requirements,
4KVAC isolation and <300uA leakage current. The Xgen series
also carries full safety approvals. Refer to individual Xgen
Datasheets for the relevant safety approvals carried by each
model.
UltiMod, Xsolo and Xgen are designed to meet MIL810G and
are also compliant with SEMI F47 for voltage dips and interrup-
tions as well as being compliant with all relevant EMC emission
and immunity standards (Eee individual datasheets for details).
Safety Approvals
Low Voltage Directive (LVD) 2006/95/EC
The LVD applies to equipment with an AC input voltage of
between 50V and 1000V or a DC input voltage between 75V and
1500V. The XSolo series is CE marked to show compliance with
the LVD.The relevant European standard for UltiMod, Xsolo and
Xgen models is EN60950 (Information technology). The 2nd
Edition of this standard in now published and all relevant
Excelsys power supplies are certified to the latest edition as well
as the 1st Edition.
The relevant European standard for UltiMod, Xsolo and Xgen
models is EN60601-1 (Medical Devices Directive). The 3rd
Edition of this standard is published and all Excelsys medically
approved power supplies are certified to this latest edition as
well as the 2nd Edition. With appropriate packaging, the UltiMod,
Xsolo and Xgen models can also meet the requirements of
EN61010-1 for industrial scientific measuring equipment and
process control.
UltiMod, Xsolo and Xgen models are certified to comply with the
requirements of IEC950, EN60950, UL60950 (1st and 2nd
Editions), and CSA 22.2 no. 234 and IEC1010, when correctly
installed in a limited access environment.
The UltiMod, Xsolo and Xgen series are certified to comply with
the requirements of IEC601-1, EN60601-1, UL60601-1 (2nd and
Section 7.1
Reliabilty
The 'bath-tub' curve shows how the failure rate of a power supply
develops over time. It is made up of three separate stages.
Immediately after production, some units fail due to defective
components or production errors. To ensure that these early fail-
ures do not happen while in the possession of the user, Excelsys
carries out a burn-in on each unit, designed to ensure that all
these early failures are detected at Excelsys. After this period,
the power supplies fail very rarely, and the failure rate during this
period is fairly constant. The reciprocal of this failure rate is the
MTBF (Mean Time Between Failures).
At some time, as the unit approaches its end of life, the first signs
of wear appear and failures become more frequent. Generally
'lifetime' is defined as that time where the failure rate increases to
five times the statistical rate from the flat portion of the curve.
In summary, the MTBF is a measurement of how many devices
fail in a period of time (i.e. a measure of reliability), before signs
of wear set in. On the other hand, the lifetime is the time after
which the units fail due to wear appearing.
The MTBF may be calculated mathematically as follows:
MTBF = Total x t / Failure , where
Total is the total number of power supplies operated simultane-
ously.
Failure is the number of failures.
t is the observation period.
MTBF may be established in two ways, by actual statistics on
the hours of operation of a large population of units, or by cal-
culation from a known standard such as Telecordia SR-332 and
MIL-HDBK-217 and its revisions.
Determining MTBF by Calculation
MTBF, when calculated in accordance with Telecordia, MIL-
HDBK-217 and other reliability tables involves the summation of
the failure rates of each individual component at its operating
temperature. The failure rate of each component is determined
by multiplying a base failure rate for that component by its oper-
ating stress level.
The result is FPMH, the failure rate per million operating
hours for that component.
Then FPMH for an assembly is simply the sum of the individual
component FPMH.
Total FPMH = FPMH1 + FPMH2 + ………….. +FPMHn
MTBF (hours) = 1,000,000
FPMH
In this manner, MTBF can be calculated at any temperature.
Section 7 Reliabilty, Safety, EMI and Technical Resources
8 www.excelsys.com