MIL-PRF-11767 Relay Assembly: Gun-Firing, Waterproof, 24 Volt DcThis specification covers one type of waterproof gun-firing relay assembly with a nominal rating of 24 volts \(V\) direct current \(dc\) for use in the main gun and machine gun circuits of military combat vehicles. The assembly consists of relays which control the firing of the main gun by the operation of a time delay circuit and a separate fast-operating, fast-release relay which controls the firing of the machine gun \(see 6.1\).

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MIL-PRF-11767G(AT)

4.9.1 Endurance.

4.9.1.1 Main gun relay. To determine conformance to 3.5.3, the main gun relay assembly

shall be subjected to 50 000 cycles of operation at 24 Vdc. Cycling shall consist of making and

breaking a 45 A dc load in an inductive circuit with the time constant ratio L/R (time required for

the current to reach 63.2% of its steady state value) not less than 0.026 second. On time shall be

0.3 + 0.2 second. Off time shall be 5.7 + 0.2 seconds. The 50 000 cycles of operation shall be

conducted at the following temperatures:

Number of cycles

Temperatures

77 + 15�F

20 000

-65 + 5�F

15 000

160 + 5�F

15 000

The relay assembly shall then be subjected to the tests specified in 4.10.1 and 4.10.7.

4.9.1.2 Machine gun relay. To determine conformance to 3.5.3, the machine gun relay

shall be subjected to the test specified in 4.9.1.1, except that the following values shall be

substituted. Cycling shall consist of making and breaking a 20 A dc inductive load. On time shall

be 4 + 0.1 seconds. Off time shall be 8 + 0.1 seconds. The machine gun relay shall then be

subjected to the test specified in 4.10.4 through 4.10.7.

4.10 Operating verification.

4.10.1 Time delay. To determine conformance to 3.6.1, the relay assembly shall be

subjected to test potentials of 18, 24, and 30 Vdc. The time delay shall be measured with an

oscilloscope or other time interval measuring equipment, accurate to within three percent. These

tests shall be repeated with the relay assembly mounted in the direction of each of its three major

axes.

4.10.2 Operating current. To determine conformance to 3.6.2, the following procedure

shall be followed:

a. Connect 29 + 0.0, - 0.5 Vdc between pins B and G of the relay assembly.

b. Energize main gun relay by applying 29 Vdc between pins C and G of the relay

assembly.

c. Determine the coil current.

4.10.3 Dielectric strength. To determine conformance to 3.6.3, relay assembly shall be

subjected to a voltage of 500 V root mean square (rms) at a frequency of 60 Hz from a voltage

source of a minimum rating of 0.5 kilovolt-amperes (kV-A). The voltage shall be applied as

follows: