MIL-DTL-27500H
4.3.3.1 Dielectric withstand-component wires. The finished cable shall be tested in accordance with
MIL-STD-2223, method 3005 , except that immersion is not required. Each conductor, in turn, shall be tested against all others tied
together with the (inner) shield (if any). The test voltage shall be 1,500 V rms for 600-volt rated basic wire and 2,500 V rms for
1,000 volt rated basic wire. The time of electrification shall not be less than 15 and not more than 30 seconds.
4.3.3 2 Dielectric withstand-inner jacket. The inner jacket of a double shielded cable shall be subjected to a dry dielectric test.
A potential of 500 V rms shall be applied to the inner shield with the outer shield grounded. The time of electrification shall not be
less than 15 and not more than 30 seconds.
4.3.3.3 Impulse dielectric test (for unshielded/unjacketed cable configuration. The impulse dielectric test shall be performed in
accordance with MIL-STD-2223, method 3002. The test voltage shall be 6 kV (peak).
4.3.4 Jacket flaws. One-hundred percent of all finished shielded and jacketed cable shall be tested in accordance with MIL-
STD-2223, method 3001 or 3008, with a minimum potential voltage of 1500 volts AC between the electrode and the cable shield..
4.3.5 Braid angle and shield coverage. The braid angle and the percent coverage of the braid shall be determined by the
following formula.
1. Tan α = 2 Π (D + 2d1) P/C
2. If "F" is less than 1, coverage is determined by K = 100 (2F-F2)
3. If "F" is greater than 1, then K= 100%
Where:
K = percent coverage
= Epd2/sin α
F
P
= picks per inch of cable length
α = angle of braid with axis of cable
E
= number of strands per carrier
d1 = diameter of one of the round shield strands or thickness of flattened strand
d2 = diameter of one of the round shield strands or width of flattened strands
D
= diameter of cable under shield, nominal
D
= Gb ( for cables with no fillers, cable factor from column G of table IV)
D
= Ab (for cables with fillers to round, use cable factor A of table IV)
C
= number of carriers
n
= number of basic wires (see table IV)
b
= basic wire diameter
Slide the test specimen of braid over a mandrel which has a diameter equal to the nominal diameter (D) of the braid ( if no
mandrel exists then take care to ensure the braid diameter is formed as close to the nominal diameter as possible.) Determine the
quantity P by counting the number of picks over a given length of braid. Determine n/C by counting the number of ends on a single
carrier. Determine C by counting the number of carriers on the braid. Find the value of d1 and d2 by measuring the strands with a
micrometer. These will be equivalent for round strands. Calculate the braid angle α using equation 1. Using the braid angle,
calculate the value of F Depending on the value of F, calculate the value the shield coverage using either equation 2 or 3.
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