MIL-DTL-24765A(NAVY)
3. REQUIREMENTS
3.1 First article. When specified (see 6.2), a sample shall be subjected to first article inspection in accordance
with 4.2.
3.2 Performance.
3.2.1 Input voltage and frequency. The rated input voltage and frequency shall be in accordance with
MIL-STD-1399, Section 300, Type I power and the following:
a.
For UPS rated 5kVA and above - 440 V, 60 Hz, three-phase.
b. For UPS rated 1kVA and above but below 5kVA - 440 V, 60 Hz, three-phase or 115 V, 60 Hz, single-
phase."
3.2.1.1 Input power perturbations. When the UPS is supplying any load from no-load to rated-load, the UPS
shall withstand, without damage or blowing fuses, the following conditions of input power:
a.
A loss of input power for any time duration.
b. Departures, excursions, transients, and emergency conditions of input voltage or frequency or combinations
of these conditions in accordance with MIL-STD-1399, Section 300.
Upon return of the input voltage and frequency to the specified range (see 3.2.1), the UPS shall operate and supply
the load with the same output as that prior to the input power changes.
3.2.1.2 Input voltage spikes. The UPS shall tolerate voltage spikes in accordance with MIL-STD-1399, Section
300, without damage or interruption of UPS operation. Joule content of the spike shall not be greater than would be
encountered by interrupting the magnetizing current of an input transformer sized to supply the total kilovolt-ampere
(kVA) requirements of the UPS.
3.2.1.3 Input current harmonics. When the input power to the UPS is as specified in 3.2.1 and with the UPS
supplying any load from no-load to rated load, the harmonic distortion of the input current waveform for single and
multi-phase UPS shall be in accordance with MIL-STD-1399, Section 300 for user equipment.
3.2.1.4 Input current balance. When a three-phase UPS (see 3.2.1) is supplying any load from 15 to 100
percent rated-load, it shall comply with the input current balance for user equipment in accordance with
MIL-STD-1399, Section 300.
3.2.1.5 Starting time. The UPS shall accept any load from no-load to rated-load and operate in compliance
with all requirements specified herein not greater than 5 seconds after energization (start up).
3.2.1.5.1 Starting without input power present. The UPS may be started without the input power present if the
battery is fully charged. For these conditions, the output voltage of the UPS shall be linearly ramped up to the rated
output voltage level in 5±1 seconds to avoid load surges of not greater than 200 percent of rated load.
3.2.1.6 Input power system grounding. The UPS shall meet all requirements specified herein when connected
to an ungrounded or high-resistance grounded ship's input power system in accordance with MIL-STD-1399,
Section 300.
3.2.2 Output. The UPS output shall be as specified (see 6.2) and shall be selected from the following:
a. AC. The rated AC output voltage and frequency of the UPS shall be 115-volt, 60-Hz, single-phase; 440-
volt, 60-Hz, three-phase; or as specified (see 6.2).
DC. The rated DC output voltage of the UPS shall be as specified (see 6.2).
b.
3.2.2.1 Voltage regulation (AC output). The average of the line-to-line rms values of the output voltage shall
be maintained at the UPS output terminals within ±3 percent of the rated output voltage under the following variable
conditions and any combination thereof:
a.
A load variation from no-load to 125 percent load.
b.
Load power factor (p.f.) varying between 0.7 lagging and 0.9 leading with rated output.
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