MIL-DTL-26517B
held at 200 V and 400 Hz. Operation shall be satisfactory and output voltage and rectifier temperature shall not
exceed the maximum allowable values for overload as specified in the acquisition document (see 6.2).
4.5.8.3 Short circuit. The power supply shall demonstrate its ability to deliver no less than 500 percent
rated-load current under short-circuit conditions with an input voltage and frequency of 200 V and 400 Hz. The
duration of the fault shall be 1 second (see 3.5.7). This test shall be repeated 3 times, and the power supply shall be
allowed to return to ambient temperature before each short-circuit application. No damage shall occur as a result of
this test.
4.5.9 Radio interference (see Table I). Conducted and radiated interference shall be measured at no load, half
load, and full load using the test procedures and applicable test instruments specified in MIL-STD-461 (see 3.7).
Either the current probe or the stabilization network procedures shall be used to measure conducted interference on
the direct-current power lines. Measured interference shall be within the applicable limits of MIL-STD-461.
4.5.10 Ripple voltage (see Table I). The ripple in the DC output voltage of the power supply shall be measured
at no load, one-fourth, one-half, three-fourths, and full-rated resistive loads. Voltage shall be measured with a
4-microfarad (µF) capacitor in series with a peak-reading voltmeter. Peak voltage readings shall be taken with a
digital multimeter. The higher of the two readings shall not exceed 1.5 V (see 3.5.13).
4.5.11 Endurance (see Table I). The power supply shall be operated for 500 hours under the operating
conditions specified in the acquisition document (see 6.2). If a motor is used, the power to the unit shall be
interrupted once every 24 hours so that the motor shaft comes to rest. After the shaft has been at rest for 5 minutes,
the power shall be restored and the endurance test continued. If the motor fails to start after one of the power
interruptions, the power supply shall be considered to have failed the endurance test. Thermocouples shall be used to
monitor the temperatures of the transformer, the rectifier, fan-motor case, and bearings (if a motor is used) for
indication of maximum temperatures. Upon completion of this test, the power supply shall satisfactorily withstand
the test specified in 4.5.2.
4.5.11.1 Additional endurance. If a motor is used, and upon completion of the 500-hour test specified in 4.5.11,
the power supply shall be subjected to an additional l,000 hours of operation. During this portion of the test, the
transformer and rectifier elements may be electrically disconnected with only the fan motor being energized. The
power to the motor shall be interrupted once every 24 hours, as specified in 4.5.11. The ambient temperature shall
be such that the motor bearings will be maintained at the maximum stabilized temperature reached during the
500-hour test. There shall be no evidence of bearing deterioration and no damage to the fan-motor assembly at the
conclusion of this test.
4.5.12 Environmental (see Table I). The power supply shall be subjected to the following tests in accordance
with the specified procedures of MIL-STD-810.
4.5.12.1 Low temperature (see Table I). The power supply shall be subjected to low temperature in accordance
with procedure II, except that the 72-hour exposure shall be at -65° C (see 3.5) and the 24-hour exposure shall be at
-59° C (see 3.5). A source of 200 V, 3-phase and 400 Hz power shall be connected and the power supply operated
at no-load during the final hour of the test. Operation shall be satisfactory and no damage shall occur as a result of
this test.
4.5.12.2 Humidity (see Table I). The power supply shall be subjected to humidity (see 3.5) in accordance with
procedure I. At the end of the test, the power supply shall show no signs of excessive corrosion and shall
satisfactorily withstand the following tests in the order listed:
Voltage regulation (at an ambient temperature of 25° C) (see 4.5.2)
a.
b.
Efficiency (see 4.5.5)
c.
Ripple voltage (see 4.5.10)
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