MIL-PRF-39003/10D
Surge current: Capacitors shall be tested as specified herein. The following details shall apply:
a. Temperature: 10 cycles minimum at -55°C (-5°C/+0°C) and 10 cycles minimum at +85°C (+5°C/-
0°C).
b. Voltage: Apply rated voltage ±2 percent for 4 ± 1 seconds. Maximum voltage (including transients)
shall not exceed 130% of +85°C rated voltage. Minimum voltage shall not be less than +85°C rated
voltage. Discharge the capacitors for 4 ± 1 seconds to a voltage below 1 percent of rated voltage.
c.
Series resistance: The total dc resistance (excluding the capacitor) including the wiring, fuse,
fixturing and output impedance of the regulated power supply to each test position during the
charging cycle shall be 1.0 ohm maximum.
d. Energy storage bank. The energy storage bank shall consist of a single or multiple electrolytic
capacitor, of the ultra low impedance type. The capacitor/capacitors shall have a minimum
capacitance value of 20,000 µF, and have a working voltage equal to or higher than the rated dc
voltage of the capacitors under test.
e. Power supply. The power supply shall be capable of supplying the specified rated dc voltage for the
capacitors under test, at a minimum current level of 15 amps.
f.
Each capacitor under test shall have a 1 to 5 ampere fuse connected in series. Total resistance
between the energy source and each capacitor under test (including the fuse) shall be 1.0 ohm
maximum (see application note of MIL-PRF-39003/10). Test equipment (including ohm resistance)
shall be designed and adjusted so that instantaneous current available to each capacitor under test
shall be 10 amperes minimum, ringing (overshoot) of the applied surge voltage (as measured at the
terminals of the capacitor(s) under test) shall not exceed 1.30 times (50 V and less and 1.20 for 75
V) the 85°C working voltage of the capacitor. Peak current to any group of capacitors under test
shall be achieved in less than 100 microseconds.
g. Surge current test set up (typical or equivalent). See figure 2.
h. Capacitors shall be placed in the chamber at the specified temperature, in such a position with
respect to the air stream that there is substantially no obstruction to the flow of air across and
around the capacitors. They shall be soaked for a minimum of 1/2 hour or until all capacitors have
stabilized to the chamber temperature. The first temperature to be tested shall be -55°C.
The test sequence shall consist of 10 cycles at -55°C and 10 cycles at +85°C. A cycle shall be of
closing the switch and allowing the capacitors under test to charge and discharge through 1.0 ohm
maximum.
Failure criteria. Any blown fuse or out of spec (DCL at +25°C) conditions or visible indications of
i.
damage shall reject the capacitor.
k.
System check. System shall be checked at the beginning of each 8 hour shift. The necessary
minimum level of resistance (R) and inductance (L) are achieved when the peak surge current level
of a single CSS13 style capacitor (330 µF at 6 WV dc) is at least 18 amperes when tested at 6 WV
dc. A dc resistance measurement shall be used for calibration purposes.
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