MIL-PRF-39019 Circuit Breakers, Magnetic, Low-Power Sealed, Trip-Free General Specification ForThis specification covers the requirements and test procedures for single and multipole, trip-free, sealed, low-power, magnetic circuit breakers with current ratings of 0.050 amperes to 20.0 amperes inclusive, up to and including 240 volts, 60 hertz \(Hz\) and 400 Hz alternating current \(ac\), and 50 volts direct current \(dc\) \(see 6.1 and 6.7\). These circuit breakers may also include auxiliary contacts \(see 6.6.1\) and terminals for monitoring circuits. Designers are CAUTIONED that these circuit breakers may contain a pure tin finish on some of the component parts \(see 6.5\).

Pages 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10 - 11 - 12

MIL-PRF-39019F

3.3.1 Metals. Metals shall be of a corrosion-resistant type or shall be suitably plated or treated to resist corrosion

(see 3.21). Cadmium and zinc plating shall not be used.

3.3.1.1 Dissimilar metals. When dissimilar metals are used in intimate contact with each other, protection against

electrolysis and corrosion shall be provided. The use of dissimilar metals in contact, which tend toward active

electrolytic corrosion (particularly brass, copper, or steel used in contact with aluminum or aluminum alloy), is not

acceptable. However, metal plating or metal spraying of dissimilar base metals to provide similar or suitable abutting

surfaces is permitted. The use of dissimilar metals separated by a suitable insulating material is also permitted.

Dissimilar metals are defined in 6.4.

3.3.2 Fungus resistance. Materials used shall be non-nutrient to fungus growth.

3.3.3 Solder and soldering flux. The solder and solder flux shall be of such a quality as to enable the circuit

breaker to meet the performance requirements of this specification.

3.4 Interface and physical dimensions. Circuit breakers shall be of the interface and physical dimensions specified

(see 3.1).

3.4.1 Trip-free feature. Circuit breakers shall be so designed that the circuit cannot be maintained closed by

physically holding the lever in the closed position when any pole is carrying overload currents which would normally

automatically trip the breaker to the open position.

3.4.2 Trip indication. Circuit breakers shall be so designed that when the circuit breaker contacts open

automatically on overload, the actuating lever shall indicate the operation by moving to the "off" ("trip") position.

3.4.3 Attitude. Circuit breakers shall be constructed to trip within maximum and minimum limits of the specified trip

times (see 3.9 and 3.13) when mounted on a vertical panel (normal mounting means) (see 4.8.6).

3.4.4 Actuating lever. The exposed portion of the actuating lever shall have a smooth, nonglare, metallic finish

and shall be insulated from all current-carrying parts. Multipole circuit breakers (see 6.6.3) shall be configured so that

it will be impossible by any manipulation of the actuating lever to close less than the total number of contacts. The

actuating lever shall point in the direction of the mounting bushing keyway when the circuit breaker is in the "closed "

("on") position. The actuator shall not work to an intermediate position, give a false trip indication, or be removable

from the circuit breaker.

3.4.5 Panel seal. The panel seal shall effectively seal the circuit breaker to the mounting panel.

3.4.6 Mounting hardware. Mounting hardware shall be as specified (see 3.1). Circuit breakers shall be furnished

with a nonturn device. Each circuit breaker shall be furnished with a tab or plate which fits over the mounting bushing

and into the keyway slot. The tab or plate shall be marked with "on" on the side where the keyway slot is located and

"off" on the side opposite the keyway slot. For direct Government procurement, the hardware shall be assembled in

proper order as specified (see 3.1).

3.4.7 Threaded parts. Screw threads on removable threaded parts shall be in accordance with FED-STD-H28.

Threading of nonmetallic parts shall not be permitted.