MIL-DTL-19648E
Following is a listing of operate time ratings and applicable life test cycles:
N.O.T. rating (seconds)
Cycles of operation
Up to 60
5,000
Above 60 to 80
4,000
Above 80 to 120
2,200
Above 120 to 160
1,600
Above 160 to 180
1,500
Above 180 to 300
1,000
The relay operation cycling shall be such that the heater voltage shall be removed immediately after the
relay contacts operate (open or close) as applicable. Every operation cycle of the contacts shall be
monitored for failure to close (normally open relay) or failure to open (normally closed relay), as
applicable. A failure to open or a failure to close for each cycle shall be considered a "miss." The test
equipment used for continuous monitoring of the contacts shall have an automatic cutoff when a "miss"
occurs or it shall record the number and time of occurrence of each "miss." The test equipment shall also
count and record the number of cycles the relay is energized. The first 50 percent of the test cycles shall
be performed at the maximum ambient temperature rating of the applicable temperature class (see
1.2.2.2 and 3.1). A periodic test of normal operate time after each 20 percent of the life test shall be
conducted after stabilizing the relay at room temperature of 25°C ±5°C for at least 1 hour, and the test
results recorded. The remaining 50 percent of the life test shall be conducted at room temperature
ambient of 25°C ±5°C. During and at the end of test specified in 4.7.16.1, the relay shall meet N.O.T.
tolerance requirements of 3.6.2.1.2.
4.7.16.2 Life test with heater power recycled immediately after contact operation (for accelerated
contact life test. The relay contacts shall be loaded with rated resistive current and voltage. Heater
voltage shall be rated voltage. The additional contact life cycles and applicable normal operate time
range are:
N.O.T. rating (seconds)
Additional cycles
Total life test cycles
Up to 60
20,000
25,000
Above 60 to 80
11,000
15,000
Above 80 to 120
8,800
11,000
Above 120 to 160
4,800
6,400
Above 160 to 180
4,000
5,500
Above 180 to 300
3,000
4,000
For the first cycle, the relay shall be operated for normal operate time (N.O.T.) plus N.O.T. tolerance.
Successive heater energizing time(s) shall be decreased until the cycling time is as short as practicable
consistent with the contacts completely making and breaking, or breaking and making the load (as
applicable) for each operation. At the end of the additional cycling test, the relay shall be subjected to
25°C ambient temperature for at least 1 hour. Normal operate time shall be measured at the end of the
1-hour period followed by contact resistance (or contact voltage drop), insulation resistance, and dielectric
withstanding voltage as specified in 4.7.3.2, 4.7.3.1, 4.7.6, and 4.7.5, respectively.
4.7.16.3 Heater life test. Before heater life test, conduct normal operate time test (see 4.7.3.2) on
three relays following which the three relays shall be placed in an ambient temperature of maximum rated
(see 3.1) with the heater energized with nominal voltage for a period of 200 hours. At the end of this
period with the relay at 25°C, normal operate time test (see 4.7.3.2) shall be conducted. The relays shall
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