MIL-PRF-26611F
Hz and returned to 5 Hz in 20-minute intervals at an applied acceleration of ± 20g. After
completion of testing in three axes, the output voltage shall be measured in accordance with
4.6.4. The generator, not operating, shall be subjected to 350°F for a minimum of 1 hour. The
generator shall be removed from the oven and immediately vibrated (while operating) for 15
minutes. During the 15 minutes, the vibration frequency shall be cycled between 5 and 2,000 Hz
one or two times, and the output voltage measured at this higher temperature in accordance with
4.6.4. The generator, not operating, then shall be subjected to 350°F for a minimum of 1 hour
and the test repeated. No output voltage measurement shall be less than 20.0. The generator shall
be subjected to the dielectric strength test in 4.6.5.
TABLE III. Vibration schedule.
Number of resonances
0
1
2
3
4
Total vibration time at
--
30
60
90
120
resonance (min)(see note)
Cycling time (hr)
3
2.5
2
1.5
1
Note: 30 minutes at each resonance
4.6.8 Operation. The generator output shall be connected to a non-standard load consisting of
three 20-ohm, Y-connected resistances. The generator temperature shall be 250° ± 10°F and the
drive shaft rotated between 4,200 and 4,300 rpm for 500 to 520 hours. The generator temperature
then shall be lowered to 75° ± 10°F and the drive shaft rotated at 4,200 ± 100 rpm for 500 to 520
hours. After the generator has cooled, the output voltages shall be checked as specified in 4.6.4.
The three voltages shall be 21 ± 1.
4.6.9 Oil soak. The generator shall be immersed in oil conforming to MIL-PRF-7808 or MIL-
PRF-23699 at 350° ± 10°F and operated for 24 hours at 4,200 ±100 rpm. The oil temperature
then shall be lowered to -50° ± 10°F and the generator operated for a minimum of 30 minutes.
No damage or malfunction of the generator shall result from this test.
4.6.10 High temperature operation. The generator shall be subjected to 350° ± 10°F for a
minimum of 3 hours. At this higher temperature, the voltage test specified in 4.6.4 shall be
conducted and no output voltage shall be less than 17. The generator temperature then shall be
raised to 455° ± 10°F and maintained for 4 hours while rotating the drive shaft at 4,200 ± 100
rpm with no electrical load on the generator. After the generator has cooled to 75° ± 10°F, the
output voltages shall be checked according to 4.6.4, and the 3 voltages shall be 21 ± 2. The
generator shall then be subjected to the dielectric strength test in 4.6.5.
4.6.11 Altitude - high temperature. The generator shall be placed in a chamber maintained at
300° ± 10°F at an absolute pressure of 0.82 inch Hg (80,000 ft). The output shall be connected to
the standard load and the drive shaft rotated at 4,200 ± 100 rpm for 20 hours. There shall be no
damage to the generator as a result of this test.
4.6.12 Overspeed and reverse operation. The generator shall be connected to the standard load
and the drive shaft rotated at 4,200 ± 10 rpm. The output voltages then shall be measured. With
the standard load still connected, the generator first shall be rotated at 5,000 rpm for 5 minutes,
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