230 VAC at 50, 60 or 400 Hz single phase. The power supply can also operate from a 24 VDC storage battery in the battery standby mode.

Pages 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10 - 11 - 12

MIL-PRF-49080D

6.5.6

Night Vision Imaging System (NVIS) Compatibility. NVIS use image intensifier

tubes to produce an enhanced image of a scene in light conditions too low for normal navigation.

Sporulation. Sporulation is the formation of minute unicellular reproductive or

6.5.7

dormant bodies, called spores.

6.5.8

Tubular germination. Tubular germination is partial growth by the production of

hyphae, which are tubular shaped fungal filaments. Tubular germination constitutes restricted

individual spore growth not proceeding to colonization.

6.6

Subject term (key word) listing.

Battery Standby

Single Phase

Changes from previous issue. Marginal notations are not used in this revision to

6.7

identify changes with respect to the previous issue due to the extent of the changes.

6.8

Reliability requirement and test method. The original reliability requirement for the

power supplies covered by this specification was for an upper MTBF of 5,000 hours, or stated

another way, a 0.0002 constant failure rate (λ, or "lambda", the reciprocal of the upper MTBF).

This was erroneously translated to "90% probability of providing 5,000 hours of failure-free

operation" in 2002 in an effort to comply with then DoD policies regarding changing the way

reliability requirements were stated. The proper translation should have been "90% probability of

500 hours of failure free operation", since 500 hours represented the lower MTBF for λ = 0.0002

with a 90% probability.

Also in 2002, DoD policy required reliability requirements to avoid prescribing any specific

test method in favor of allowing offerors to propose a test method that would be subject to technical

evaluation and ranking of various proposals for a "best value" determination. In practice, this

policy worked well for developing systems and major end items, but provided no benefit in re-

procurement of sustainment items such as the PP-6224()/U and PP-2953()/U power supplies.

The test method described in this specification is based on test method models from the now-

cancelled MIL-STD-781D and the current Revision A of MIL-HDBK-781, using an accelerated

aging calculation based on the Arrhenius Acceleration Model (see section 8.7.5 of MIL-HDBK-338

for further information). In brief, testing at 65�C provides a 2.83 acceleration factor for devices

intended to operate at 50�C (3.12), reducing the total hours on test from 5,000 to 1,766.8 hours. By

increasing the duty cycle from four hours per 12-hour period to four hours for each 6-hour period,

another acceleration factor of 2 was obtained, reducing the total hours to 883.4 hours.

Custodian:

Preparing activity:

Army � CR

(Project 6130-2010-002)

NOTE: The activities listed above were interested in this document as of the date of this

document. Since organizations and responsibilities can change, you should verify the currency

of the information above using ASSIST Online database at https://assist.daps.dla.mil/online/.