MIL-PRF-23419H
4.7.4.2 For group B, the inspection shall be done only at +20°C to +35°C (room ambient temperature).
The test current shall be as specified (see 3.1). The current shall be maintained for 30 minutes after the
temperature of each fuse has stabilized. Stabilization shall be considered to have occurred when no
individual fuse temperature rise reading of 4 consecutive readings taken at 5 minute intervals exceeds the
average reading of these 4 readings by more than 2°C and no indication of increasing temperature rise is
observed. This average temperature rise reading shall be deemed to be the temperature rise of the fuse.
4.7.4.3 When two or more fuses are tested in series, the fuseholders shall be located so that there will
be a spacing, as specified in table VII, between any two fuses under test. The wire connecting the
fuseholders together and connecting the fuseholders to the ammeter and the source of supply shall be as
specified in table VII, (unless otherwise specified). The length of wire between fuseholders shall be as
specified in table VII. The temperature of the fuse case or body and of the terminals shall be measured
by thermocouples (wire size 28 to 32 AWG).
TABLE VII. Current-carrying capacity test set-up.
Fuse current rating
Spacing (mm)
Wire size
Length (mm)
8 AWG
2 feet (609.6)
> 15 amperes
> 6 inches (152.4)
(unless otherwise specified)
14 AWG
6 inches (152.4)
≤ 15 amperes
> 1 inch (25.4)
4.7.5 Terminal strength (see 3.9). Unless otherwise specified, terminals shall be tested in accordance
with method 211 of MIL-STD-202, test condition A or E, as applicable. Forces shall be as specified (see
3.1) and shall be applied to individual terminals as follows:
a. Plug or lead type terminals.
(1) Along terminal axis.
(2) Perpendicular to terminal axis.
b. Ferrule type terminals. Torque.
4.7.6 Overcurrent.
4.7.6.1 Overload interrupt (see 3.10.1). Fuses shall be subjected to the percentage of rated current
and voltage specified (see 3.1); for qualification (group II) and group C inspection (subgroup 2) the
sample fuses shall be apportioned and submitted to the tests as specified (see 3.1), at -55°C to -60°C, at
+20°C to +25°C (room ambient temperature) and at maximum rated temperature. The tolerance at the
maximum rated temperature shall be -0°C, +5°C. The fuses shall be maintained at the test temperature
for a minimum of 30 minutes, prior to the actual application of the test current. For qualification and group
C inspections, the power supply shall have an open-circuit voltage of not less than that of the specified
voltage rating of the fuse under test. For group B, the inspection shall be done only at room ambient
temperature and the power supply may be of any value which is not less than 6 volts. For the
qualification and group C inspections, the fuses shall be left in the circuit for 1 minute after opening
without any indication of the circuit reclosing. Opening time measurements shall be made with an
oscillograph for periods shorter than 1 second; a synchronous timer may be used for measurements
longer than 1 second; a sSop watch is suitable for measurements of longer than 10 seconds.
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