MIL-PRF-55629E
6.1.1 Derating. Circuit breakers should continuously carry normal load current; however, the value chosen should
be the lowest rating that will not open the circuit breaker inadvertently. The following factors should be considered in
selecting the proper current rating and time delay curve of a circuit breaker:
a.
The average (steady state) conditions of the load.
b.
The initial start-up current and duration of the current of the equipment to be protected.
c.
Transient overloads and their duration.
d.
Comparison of the time delay characteristics of the circuit breaker with the time current characteristics
(including starting or overload surges) of the equipment, component, or wire.
6.2 Acquisition requirements. Acquisition documents must specify the following:
a.
Title, number, and date of the specification.
b.
Assist online database should be cited in the solicitation, and if required, the specific issue of individual
documents referenced (see 2.2).
c.
Packaging requirements (see 5.1).
6.3 Qualification. With respect to products requiring qualification, awards will be made only for products which are,
at the time of award of contract, qualified for inclusion in Qualified Products List QPL No. 55629 whether or not such
products have actually been so listed by that date. The attention of the contractors is called to these requirements,
and manufacturers are urged to arrange to have the products that they propose to offer to the Federal Government
tested for qualification in order that they may be eligible to be awarded contracts or orders for the products covered
by this specification. Information pertaining to qualification of products may be obtained from the Defense Supply
Center Columbus, ATTN: DLA Land and Maritime-VQH, 3990 E. Broad Street, Columbus, OH 43218, online at
6.3.1 Provisions Governing Qualification. Copies of SD-6, "Provisions Governing Qualification" may be obtained
upon application to Defense Printing Service Detachment Office, Standardization Document Order Desk, Building 4D
(Customer Service), 700 Robbins Avenue, Philadelphia, PA 19111-5094.
6.4 Intermetallic contact. The finishing of metallic areas to be placed in intimate contact by assembly presents a
special problem since intermetallic contact of dissimilar metals results in electrolytic couples that promote corrosion
through galvanic action. To provide the required corrosion protection, intermetallic couples should be selected to
meet the performance requirements of this specification.
6.5 Material and finishes. Pure tin finishes may result in tin whisker growth. The use of alloys with tin content
greater than 97 percent, by mass, may exhibit tin whisker growth problems after manufacture. Tin whiskers may
occur anytime from a day to years after manufacture and can develop under typical operating conditions, on products
that use such materials. Conformal coatings applied over the top of a whisker-prone surface will not prevent the
formation of tin whiskers. Alloys of 3 percent lead, by mass, have been shown to inhibit the growth of tin whiskers.
For additional information on this matter, refer to ASTM-B545 (Standard Specification for Electrodeposited Coatings
of Tin).
6.6 Definitions.
6.6.1 Auxiliary contacts (see 1.1 and 3.5.8.2). Auxiliary contacts are those mechanically interlocked with and
operated by the main contacts of the circuit breaker and intended for use in monitoring circuits for signaling electrical
interlocking or other purposes.
6.6.2 Line terminal (see 3.5.8.1). The terminal attached to the isolated stationary main contact of the circuit
breaker with the breaker in the open or tripped position is considered the line terminal. If both main contacts of a
circuit are isolated, only one terminal is to be designated the line terminal.
6.6.3 Multipole circuit breaker (see 3.5.4). A multipole circuit breaker has two or more poles controlled by a single
actuating member.
6.6.4 Overtravel (see 4.8.9). Overtravel is the distance between the normal operating "on" and "off" positions of
the actuating lever and the extreme positions to which the lever may be moved in either direction.
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