MIL-PRF-27G
(2)
For transformers and inductors weighing more than 10 pounds - The sequence of vibration
shall be as follows: First vertically, and then horizontally in two mutually perpendicular
directions. Two machines may be used (one vibrating horizontally and one vibrating vertically),
or a single machine may be used which provides for both vertical and horizontal table motion,
or a vertical vibrating machine, at the option of the supplier.
e.
Examinations after vibration - Transformers and inductors shall be examined for evidence of leakage
and physical damage.
4.7.16.2 Vibration, high frequency (when specified). Transformers and inductors shall be tested in accordance
with method 204 of MIL-STD-202. The following details and exception shall apply:
a.
Mounting of specimens - As specified in 4.7.16.1d.
b.
Test-condition - D, unless otherwise specified.
Examinations after vibration - As specified in 4.7.16.1e.
c.
4.7.17 Shock (see 3.19). Transformers and inductors shall be tested in accordance with 4.7.17.1, or when
specified (see 3.1), in accordance with 4.7.17.2. The mounting of specimens shall be as specified in 4.7.16.1.
4.7.17.1 Specified pulse. Transformers and inductors shall be tested in accordance with method 213 of MIL-STD-
202. The following details and exceptions shall apply:
a.
Test conditon - I, unless otherwise specified.
b.
Examinations after shock - Transformers and inductors shall be examined for evidence of leakage and
physical damage.
4.7.17.2 High-impact. Transformers and inductors shall be tested in accordance with method 207 of MIL-STD-
202. The following detail and exception shall apply:
a.
Mounting fixtures - Figure "Standard mounting fixtures for electrical controller parts" of method 207.
Examinations after shock - As specified in 4.7.17.1b.
b.
4.7.18 Winding continuity (see 3.20). All windings of transformers and inductors shall be tested for electrical
continuity by any suitable means.
4.7.19 Immersion (grades 4 and 5) (see 3.21). Transformers and inductors shall be tested in accordance with
method 104 of MIL-STD-202. The following detail and exception shall apply:
a.
Test condition - B (for qualification inspection for grade 4); A (for qualification inspection for grade 5).
b.
After final cycle - Transformers and inductors shall be washed under running tap water and dried.
After the drying period, transformers and inductors shall be examined for evidence of leakage and
other visible damage.
4.7.20 Moisture resistance (see 3.22). Transformers and inductors shall be tested in accordance with method 106
of MIL-STD-202. The following details and exceptions shall apply:
a.
Mounting - On racks.
b.
Initial measurements - Not applicable.
c.
Conditioning - The 24-hour initial drying period prior to the first cycle may be omitted.
Polarization - Unless otherwise specified (see 3.1), polarization is applicable. The polarizing
d.
voltage shall be applied during steps 1 to 6 inclusive, between all windings not connected directly to
the core or case, and the core or case. When the dielectric withstanding test voltage is less than
100 volts rms, a 50-volt dc polarizing voltage may be used. The polarizing voltage shall be positive
with respect to the core and the case.
e.
Loading voltage - Not applicable.
f.
Final examinations:
(1) Grade 4 - Upon completion of step 6 of the final cycle, transformers or inductors shall be removed
from the humidity chamber and shall be conditioned for a maximum of 8 hours at standard
inspection conditions (see 4.3). After this conditioning period, dielectric withstanding voltage (at
reduced voltage), induced voltage, and insulation resistance shall be measured at any
temperature above 20°C and at ambient room humidity, but rejections shall be based on
measurements made at 25°C +10°C, -5°C and at a relative humidity not greater than 80 percent.
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