MIL-DTL-26517B
4.5.3.1.4 At zero-output current and 380 Hz. The input voltage shall be varied gradually from 190 to 210 V
and returned. The load shall not be adjusted and data need be recorded only at minimum and maximum input
voltage conditions. This test shall be conducted on Type I only.
4.5.3.1.5 At 50-percent rated output current. The test specified in 4.5.3.1.4 shall be repeated (Type I only).
4.5.3.l.6 At 100-percent rated output current. The test specified in 4.5.3.1.4 shall be repeated (Type I only).
4.5.3.2 At 25° ± 15° C with the frequency of 420 Hz. The tests specified in 4.5.3.1 through 4.5.3.1.6 shall be
repeated.
4.5.3.3 Voltage regulation at low temperature. The tests specified in 4.5.3.1 and 4.5.3.2 shall be repeated at an
ambient temperature of - 65° C. The unit shall have been stabilized by at least 4 hours of continuous operation at this
temperature at full load.
4.5.3.4 Voltage regulation at maximum temperature. The tests specified in 4.5.3.1 and 4.5.3.2 shall be repeated
at an ambient temperature of 71° C for class A units, 125° C for class B and class C units. The units shall have been
stabilized by at least 4 hours of continuous operation at these temperatures at full load.
4.5.4 Insulation (see Table I). A potential of l,500 V rms commercial frequency shall be applied for 1 minute
between the input terminals short-circuited together and the output terminals short-circuited together. The test shall
be repeated with the 1,500 V applied between the metal enclosure and all terminals short-circuited together. The
electromagnetic-interference filter capacitors shall be disconnected during this test. There shall be no insulation
breakdown as a result of this test (see 3.5.14).
4.5.5 Efficiency (see Table I). With the input adjusted at 200 V and 400 Hz, the full-load efficiency of the
power supply shall be measured after an initial 30-minute warm-up period. The load shall be reduced to 50-percent
resistive and the efficiency measured again. The efficiency shall be not less than that shown in the acquisition
document (see 3.5.12 and 6.2).
4.5.6 Frequency influence (see Table I). The output voltage of the power supply shall be measured at no load
and minimum specified load with the input maintained at 210 V and 420 Hz. Full resistive load shall then be
connected and the output voltage measured at an input of 195 V and 380 Hz and again at 195 V and 420 Hz (see
3.5.3). During this test, the DC output voltage shall remain within the limits specified in 3.5.10.
4.5.7 Parallel operation (see Table I).
4.5.7.1 Two power supplies. Two power supplies shall be connected to a common load and the load varied
from no load to the combined rated load in 25 percent increments. Load division shall be as specified in 3.5.11. The
output voltage during parallel operation shall remain within the limits shown on the acquisition document (see 6.2).
4.5.7.2 Three power supplies. Three power supplies shall be connected to a common load and the load
adjusted to two-thirds of the combined rating of the 3 units (see 3.5.11.2). One unit shall be de-energized and the
output voltage of the remaining units shall remain within the limits shown in the acquisition document (see 6.2).
4.5.8 Overload (see Table I).
4.5.8.1 Resistive load of 150 percent. The power supply shall be operated for 7 hours, during which time a
resistive load of 150 percent is cycled for 5 minutes on and 15 minutes off, the input voltage and frequency being
held at 200 V and 400 Hz. Operation shall be satisfactory and the output voltage and rectifier temperature shall not
exceed the maximum allowable values for overload as specified in the acquisition document (see 6.2).
4.5.8.2 Resistive load of 250 percent. The power supply shall be operated for 7 hours during which time a
resistive load of 250 percent is cycled for 1 minute on and 18 minutes off, the input voltage and frequency being
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