INCH - POUND
MIL-PRF-27G
19 May 2014
SUPERSEDING
MIL-PRF-27F
25 June 1999
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.
