Degrees C depending upon the resistance value. They are not capable for application when the alternating current \(ac\) characteristics are of critical importance; however, provisions have been made to minimize the inductance.

Pages 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10 - 11 - 12 - 13 - 14 - 15 - 16

MIL-PRF-18546G

4.7.8 Low temperature operation (see 3.12). Resistors shall be mounted as specified in 4.7.11.1.

Following a measurement of resistance (see 4.7.2), rated voltage from an ac supply at commercial line

frequency and waveform (see 3.5) shall be applied until thermal stability has been reached. The potential

shall then be removed and within 8 seconds to 12 seconds, the resistors shall be subjected to an air

temperature of -55�C +0�C, -5�C for a period of not less than 15 minutes or more than 30 minutes.

Resistance (see 4.7.2) shall again be measured not less than 2 hours after final exposure. Resistors

shall then be inspected for evidence of mechanical damage.

4.7.9 Short time overload (see 3.13). Resistors shall be mounted as specified in 4.7.11.1. One of the

resistor terminals shall be grounded to the resistor housing during the test. Following a measurement of

resistance (see 4.7.2), a test potential from an ac supply at commercial line frequency and waveform

which will result in five times the rated wattage (see 3.1), but not to exceed the specified voltage used for

the dielectric withstanding voltage test (atmospheric pressure) (see 3.1), shall be applied to the resistors

for 5 seconds. Resistors (see 4.7.2) shall be measured after the resistors have stabilized at room

temperature. Resistors shall then be inspected for evidence of arcing, burning, and charring.

4.7.10 Moisture resistance (see 3.14). Resistors shall be tested in accordance with method 106 of

MIL-STD-202. The following details and exceptions shall apply:

a. Mounting: Resistors under load shall be mounted as specified in 4.7.11.1. Resistors under

polarization shall be mounted as specified in 4.7.6.1a.

b. Initial measurements: Resistors shall be measured as specified in 4.7.2.

c. Load and polarization: One half of the resistors shall be subjected to load and the remaining half

to polarization.

(1) Load: During the first 2 hours of each of steps 1 and 4, the rated dc continuous working

voltage (see 3.5), derated in accordance with figure 1 to the temperature attained at the end of

the two hour period, shall be applied to the resistors. The negative terminals shall be

electrically grounded to the mounting surface.

(2) Polarization: During steps 1 to 6 inclusive, a potential of 100 volts dc shall be applied with the

positive side connected to the terminals tied together, and the negative side connected to the

mounting plate.

d. Final measurements and inspection: At the end of the final cycle, the resistors shall be removed

from the chamber, conditioned at room ambient conditions, and the dc resistance and insulation

resistance shall be measured as specified in 4.7.2 and 4.7.7, respectively, within 30 minutes �15

minutes of removal from the chamber. The resistors shall not be wiped or forced air dried prior to

these measurements. Resistors shall then be inspected for evidence of breaking, cracking,

loosening of terminals and corrosion. (The subsequent 4 hours to 24 hours conditioning period

and measurements do not apply).