MIL-DTL-18396E
4.7.5 Temperature rise (see 3.5.4.7). The temperature rise of the switch stationary contacts, bolted connections and
terminal studs energized during the electrical endurance tests shall be determined by means of thermocouples of
small wire gage (28-32 AWG). The temperature sensitive elements shall be placed on the current carrying parts
where they first emerge from the switch body. Temperature measurements shall be taken prior to, during, and
immediately following the electrical endurance test. The temperature rise measurements during the electrical
endurance test shall be taken after the first 50,000 cycles of operation, while the switches are in the 65°C (149°F)
ambient temperature. The contacts hall be the same as those that were used for the overload and endurance tests,
and shall be energized at the "carry" rating at any convenient voltage within the switch rating. Temperature
measurements shall be taken at half hour intervals until three successive measurements are within plus or minus
1°C. Switch wiring shall be size 16 for 5 amperes or less and size 14 in excess of 5 amperes (20 amperes
maximum). The cable length from load on sup-ply to the switch shall be 3 feet plus 1 inch, minus 0 inch. If
enclosures or covers are provided as part of the switch, the test shall be made with the enclosures or covers properly
mounted to the switch.
4.7.6 Overload. The switches shall be operated for 50 operations to interrupt 150 percent of the maximum rated
current at the voltage for that rating. The circuit shall provide for "on-off" switching and one operation shall consist of
throwing the switch from the "off" position to the "on" position and returning to the "off" position. "Two pairs of
contacts shall be used for each electrical rating subsequently tested in the electrical endurance test and shall be the
same ones used for the endurance and overload tests. The test rate shall be two operations per minute and the duty
cycle shall be 50 percent on and 50 percent off. The wiring for the test shall be the same as for the endurance test.
4.7.7 Endurance (see 3.5.4.9).
4.7.7.1 Electrical. The contacts tested shall be used to determine the suitability of the switch to make, break, and
carry each of the current/voltage ratings specified for the switch. The a.c. tests shall be conducted at a 0.75 to 0.80
lagging power factor (p.f.). The contacts shall be distributed uniformly over the entire length of the switch.
Nonshorting contacts shall be used for interrupting ratings and shorting contacts shall be used for the maximum
carrying rating. The switch shall be subjected to 100,000 cycles of operation. The first 50,000 cycles of operation
shall be performed with the switches exposed to an ambient temperature of 65 ± 3°C. The last 50,000 cycles of
operation shall be performed at room ambient conditions. A cycle of operation is defined as one electrical make and
break of each contact. The cycling rate shall be a minimum of 6 cycles of operation per minute, with a minimum of a
50 percent duty cycle. Switches shall be monitored to determine when any loaded contacts fail to open or close in
proper sequence.
4.7.7.2 Mechanical. The switch shall be operated without electrical load for 10,000 cycles of operation. A cycle of
operation is defined as a complete rotation of the switch shaft through all switch positions. Where the switch has
removable stops, the stops shall be removed and a cycle of operation shall be the full 360 degrees. Where the
switch has nonremovable stops, the rotation of the shaft from the fully counterclockwise position to the fully clockwise
position and rturn shall constitute two cycles of operation. The cycling rate shall be at any convenient speed.
4.7.8 Contact resistance (see 3.5.4.10). Contact resistance of each pole subjected to the electrical endurance test
and each pole subjected to the mechanical endurance test shall be determined in accordance with method 307 of
MIL-STD-202. The following details shall apply:
(a) Test leads shall be connected by a method suitable for the switch terminals.
(b) Contact resistance as indicated by the millivolt drop shall be measured after the electrical endurance tests
using the load applied during the test.
(c) Contact resistance as indicated by the millivolt drop shall be measured after the mechanical endurance test,
using a 100 milliampere test current and an open circuit test voltage of 2 to 4 volts.
(d) Ten separate measurements shall be taken for (b) and ten for (c) with one operation of the switch between
measurements. The average value of the measurements shall be calculated.
4.7.9 Vibration (see 3.5.4.11). Switches shall be tested in accordance with type I requirements of MIL-STD-167-1.
The following shall apply:
(a) Method of mounting Switches shall be mounted to a rigid metal panel in a normal manner using associated
mounting hardware. Switches having means for rear support shall be so supported during the test.
(b) Switch positions One sample switch shall be tested in one switch position, and a second sample switch in
any other switch position. For momentary action (spring return) switches, the switch shall be tested in the
"rest" position.
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