INCH - POUND
MIL-PRF-27F
25 June 1999
SUPERSEDING
MIL-T-27E
4 April 1985
PERFORMANCE SPECIFICATION
TRANSFORMERS AND INDUCTORS
(AUDIO, POWER, AND HIGH-POWER PULSE),
GENERAL SPECIFICATION FOR
This specification is approved for use by all Departments and Agencies of the Department of Defense.
1. SCOPE
1.1 Scope. This 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.
1.2 Classification. Transformers covered by this specification are classified according to product levels (see
1.2.1).
1.2.1 Product level . This specification makes provisions for three product levels: level C, for high reliability
commercial/industrial type applications; level M, for general purpose military applications; and level T, for high
reliability critical military applications. These product levels are coded into the part or identifying number (PIN) (see
3.1). Examples of the PIN’s are shown below.
M27/1-01C - denotes the C level part with a C code on the end of the PIN.
M27/1-01 - denotes the M level part. (NOTE: This PIN system that was in use in MIL-T-27E and
previous revisions of MIL-T-27.)
M27/1-01T - denotes the T level part with a T code on the end of the PIN.
1.2.2 Dash number. The dash number which uniquely identifies the transformer or inductor.
1.2.3 Grade. The grade is identified by a single digit denoting metal encased, encapsulated, or open-type
construction, and the ability of the transformers or inductors to withstand the environmental tests of table I.
1.2.3.1 Grade 4. Grade 4 units are sealed, metal encased with either separately fabricated headers or
terminals or both. This grade does not include units which are encapsulated in a metal shell with an opening in
either end or side of the shell, or with insulated lead wires extending through the metal shell.
Beneficial comments (recommendations, additions, deletions) and any pertinent data which may be of
use in improving this document should be addressed to: Defense Supply Center Columbus ATTN:
DSCC-VAM, 3990 East Broad Street, Columbus, OH 43213-1199, by using the Standardization
Document Improvement Proposal (DD Form 1426) appearing at the end of this document or by letter.
AMSC/NA FSC 5950
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.
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