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MIL-PRF-27 Transformers And Inductors \(Audio, Power, And High-Power Pulse\), General Specification ForThis specification covers the general requirements for power transformers, power inductors, audio transformers, audio inductors, high power pulse transformers, charging inductors, saturable transformers and saturable inductors for use in electronic and communication equipment. This specification covers transformers and inductors weighing 300 pounds or less or having root-mean-square \(rms\) test-voltage ratings 0f 50,000 volts or less, and also high-power pulse transformers where the peak pulse power is greater than 5 watts. Transformer and inductor assemblies incorporating any other active or passive components do not come within the scope of this specification.

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MIL-PRF-27G

TABLE V. Qualification inspection - Continued.

Inspection

Grade

Requirement

Method

paragraph

Group III - Continued

Visual and mechanical examination

(external) (post test) - - - - - - - - - - - -

3.24

4.7.1.1.1

Electrical characteristics (final) - - - - - -

3.14

4.7.12

Flammability (2 sample units) - - - - - -

3.25

4.7.22

Visual and mechanical examination

(internal) (3 sample units) - - - - - - -

3.1, 3.3 to 3.3.3.2 incl., 3.4.5, 3.4.6, 3.4.8,

4.7.1.2

and 3.32

Group IV

Life (2 samples) - - - - - - - - - - - - - - - -

3.26

4.7.23

Dielectric withstanding voltage:

At reduced voltage - - - - - - - - - - - -

3.11

4.7.9

Insulation resistance - - - - - - - - - - - -

3.13c

4.7.11

Induced voltage - - - - - - - - - - - - - - -

3.12

4.7.10

Visual and mechanical examination

(external) (post test) - - - - - - - - - - -

3.24

4.7.1.1.1

Electrical characteristics - - - - - - - - -

3.14

4.7.12

Group V

Fungus 3/ - - - - - - - - - - - - - - - - - - - - -

3.27

4.7.24

Printed circuit type transformers and inductors only, or when specified (see 3.1).

Solderable type terminals only: If the soldering iron method (4.7.2.2) of the solderability test is performed,

then the resistance to soldering heat test (4.7.6.2) need not be performed.

Test shall not be performed if the manufacturer provides certification that all external materials are fungus

resistant.

Substitute Bond Strength for SMD type devices.

All subsequent tests for SMD units are to be performed with units mounted on test substrates per 4.3.3.

Tests are not required for T level units provided Thermal shock was performed during group II testing.

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