NPFC - MIL-PRF-55629
CIRCUIT BREAKERS, MAGNETIC, UNSEALED OR PANEL SEAL,TRIP-FREE, GENERAL SPECIFICATION FOR
|Publication Date:||19 May 2020|
This specification covers the requirements and test procedures for single and multipole, trip-free, unsealed, magnetic circuit breakers with current ratings of 0.2 amperes to 100 amperes inclusive, up to and including 240 volts, 400 Hertz, 480 volts, 60 Hertz alternating current (ac) and 125 volts direct current (dc), (see 6.1). These circuit breakers may also include auxiliary contacts (see 6.6.1) for monitoring circuits. A voltage sensitive pole is also available in a four pole device. Panel seal mounts are available in 0.2 amperes through 50 amperes. Designers are WARNED that these circuit breakers may contain a pure tin finish on some of the component parts (see 6.5).
Calibration of these circuit breakers will be affected if mounted in other than the vertical plane.
Circuit breakers covered by specification sheet 1 through sheet 12 and sheet 20 through sheet 22 are intended primarily for use in the protection of electronic circuits, and should be used where... View More
Circuit breakers covered by specification sheet 1 through sheet 12 and sheet 20 through sheet 22 are intended primarily for use in the protection of electronic circuits, and should be used where moderate but unprolonged starting overloads may be expected and where the optional speed of response provided can be matched to the characteristics of the equipment to be protected. These circuit breakers are military unique in that they must operate satisfactorily under the following demanding conditions: Endurance testing of 10,000 mechanically performed make and break operations, 6,000 of them while energized to 100% of rated current, and they must meet stringent salt atmosphere (corrosion) testing. These circuit breakers should not be used in circuits, such as primary power circuits of electric systems, whose rupture current potential is greater than the interrupting capacity of the breaker, unless the circuit is properly protected by other means. Circuit breakers covered by specification sheet 13 through sheet 19 are physically larger than the other breakers covered by this specification; however, they offer higher current ratings and interrupt capacities, and may be used in primary power circuits providing their interrupting capacity is not exceeded. Many of the specification sheets now include high-inrush features that provide tolerance for short duration of high inrush or transient currents without decreasing steady-state protection.
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.View Less