MIL-PRF-15160K
4.7.5.1 Overload test voltage. For qualification, group C, and first article tests, half of the test samples shall be
tested with a power supply having an open circuit voltage within 5 percent of the specified voltage rating for the fuse
under test. No times shall be recorded but the fuses shall be examined to determine that they have opened the
circuit. The power supply voltage of the other half of the samples and for group B tests may be of any value which is
not less than 6 volts.
4.7.5.2 Overload test currents.
4.7.5.2.1 135 percent tests. For 135 percent rated current tests at either rated or reduced voltage, the current
tolerance shall be zero to plus 10 percent.
4.7.5.2.2 150, 200, and 300 percent tests. For fuses not greater than .406 inch (10.3124 mm) diameter, when
tested at either rated or reduced voltage, the current tolerance shall be plus or minus 3 percent. For fuses greater
than .406 inch (10.3124 mm) diameter, when tested at either rated or reduced voltage, the test shall be conducted on
a preset circuit or the current may be adjusted to the required test current at a uniform rate not exceeding 3 seconds.
4.7.5.2.3 500 percent tests. For 500 percent rated current tests at rated voltage, the current tolerance shall be
zero to minus 5 percent; for reduced voltage tests, the test shall be conducted on a preset circuit adjusted to the
required test current using a copper bar in the circuit. The copper bar shall then be replaced with the test fuse, the
circuit turning on and readjusted to the required test current at a uniform rate not exceeding 3 seconds.
4.7.6 Short circuit interrupt. Fuses shall meet the requirements specified in 3.11.
4.7.6.1 AC tests. Fuses shall be subjected to ac short circuit tests at the current and voltage specified (see 3.1).
The tolerance on the short circuit current shall be zero to plus 20 percent. The tolerance on the voltage shall be zero
to plus 10 percent. The ac tests shall be conducted using a supply of adequate capacity such as an ac generator and
transformer bank, and shall be on a single phase basis. The current shall be applied within plus or minus 10 degrees
of the voltage wave zero point. For characteristic A fuses tested at 450 volts, for characteristic BR fuses and for
characteristic C fuses, the power factor shall be as specified (see 3.1). For other fuses, the power factor shall be
0.45 to 0.50 for current ratings not less than 100 amperes, or 0.85 to 0.95 power factor for current ratings not greater
than 100 amperes. Fuses shall remain in the energized circuit for not less than 30 seconds after interruption without
any indication of reclosing. Short circuit currents shall be determined by means of an oscillograph. Test circuits shall
be calibrated for the specified current with the fuseholder short circuited.
4.7.6.2 DC tests. Fuses shall be subjected to dc short circuit tests when specified (see 3.1). The current and
voltage shall be as specified (see 3.1). The tolerance on the short circuit current shall be zero to plus 20 percent.
The tolerance on the voltage shall be as follows.
1 volt dc to 100 volts dc; zero to plus 15 percent.
Over 100 volts dc, zero to plus 5 percent.
The dc test shall be made using a source of power with the rate of current rise for the test circuit adjusted for not less
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than 2.92 x 10 amperes per second. The current rate of rise may be lower if the test station limitations preclude
obtaining the stated value. Fuses shall remain in the energized circuit for not less than 30 seconds after interruption
without any indication of reclosing. Short circuit currents shall be determined by means of an oscillograph. Test
circuits shall be calibrated for the specified current with the fuseholder short circuited.
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