MIL-DTL-24765A(NAVY)
For UPS with the same input and output parameters (AC, DC, voltage, phases, etc.), when the load exceeds the
limits specified above for a, b, or c; it shall automatically transfer to the UPS by-pass. For UPS with the different
input and output parameters, when the load exceeds the limits specified above for a, b, or c; the UPS shall
automatically shut down. For all UPS that exceed the load limit specified in d, above; the UPS shall automatically
shut down. For instances where the UPS is in automatic by-pass, when the load current drops to a level equal to or
less than full-rated, the load shall automatically be transferred to the UPS without disturbance to the load. For
instances where the UPS shut down, manual restart shall be required. None of these operations shall cause fuses or
circuit breakers to activate or produce voltage transients in the load exceeding 6 percent. These events shall be
indicated locally and provision shall be made for remote indication.
3.2.6 Display and control. For UPS rated 5kW and greater, the UPS shall track and display its performance. It
shall also provide operational instructions and alarm functions. The operator shall be able to control the UPS from
the local, front mounted panel or, when specified (see 6.2), from a remote location via a computer. If the UPS rating
is less than 5kW, the panel requirement may be in other forms such as push-buttons and switches and shall not
require remote operation capability.
3.2.7 Modes of operation. The UPS shall operate automatically with two modes of operation as follows:
a.
Automatic. The power to the load is provided by the UPS.
b. By-pass. For AC output, the UPS is disconnected from input power and by-passed with the load directly
supplied from the incoming AC line or alternate source. For DC output, the UPS is disconnected from input power
and the load. The DC load may be supplied power from an alternate source if available.
3.2.8 Transfer time. Power source transfer shall be automatic, shall be accomplished within 1 millisecond, and
shall not produce voltage transients in the output of the UPS greater than 6 percent.
3.2.9 Battery charging. Battery charging shall be automatically regulated to provide output voltage and current
as necessary to keep the battery bank fully charged. Battery temperature shall be taken into consideration to avoid
damage during charging. There shall not be any reverse current flow from the battery bank when the UPS is
disconnected from the input power.
3.2.10 Battery bank. The batteries shall be maintenance-free and shall be provided by UPS manufacturer. If
lithium batteries are selected for use, NAVSEA S9310-AQ-SAF-010 shall be complied with for battery safety.
Batteries shall be selected to provide a minimum of 10-year life.
3.2.10.1 Battery configuration. For small UPS (less than 5kW), batteries may be housed in a common
enclosure with the UPS. For all other UPS, batteries shall be supplied on racks in accordance with
MIL-STD-2003-2.
3.2.11 Leakage current. The rms leakage current caused by the electromagnetic interference (EMI) filter
capacitor from each input power line to the ship's ground shall not cause a fundamental 60-Hz current greater than
30 milliamperes per line. This requirement applies to the output when the UPS supplies a 60-Hz output.
3.3 Design and construction.
3.3.1 General. Design and construction shall be in accordance with the requirements of MIL-E-917, except as
otherwise specified herein.
3.3.2 Electrical construction. The UPS shall use solid-state circuitry and devices to the maximum extent
possible.
3.3.3 Mechanical design. UPS rated 5kVA and greater shall provide front access for maintenance.
3.3.3.1 Size and weight. The weight and volume of the UPS shall be minimized to the maximum extent
possible.
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