MIL-PRF-17773C(SH)
3.4.30.3 Chassis leakage current protection. All electrical parts capable of electrical conduction shall be at
ground potential in accordance with MIL-STD-1310 and shall limit leakage current for personnel safety in
accordance with MIL-STD-1399-300.
3.4.30.4 Operational source-to-source impedance. The source-to-source impedance shall be no less than 1.3
megohms at 68 °F (20 °C) with a minimum load of 25 amps and 0.5 megohm at 122 °F (50 °C). If specified (see
6.2), a higher source-to-source impedance may be required.
3.4.30.5 Source-to-source leakage current for maintenance. When specified (see 6.2), leakage current to the
non-energized side of the ABT shall be controlled by air gap isolation between sources to allow for safe load center
maintenance.
3.4.31 Electrical bonding. Electrical bonding shall be in accordance with MIL-STD-1310.
3.4.32 Mechanical hazards. Suitable protection shall be provided to prevent contact with moving mechanical
parts such as gears, fans, and belts when the equipment is operating. Sharp projections on cabinets, doors, and
similar parts shall be avoided. Rack-mounted equipment shall maintain the center of gravity as low as possible to
minimize tipping over. Door or hinged covers shall be rounded at the corners, provided with stops to hold them
open, and shall be removable. ABT design shall include provisions to prevent accidental pulling out of drawers or
rack mounted equipment components, which would cause equipment damage or injury. Equipment power switches,
if used, shall be located so that accidental contact shall not place the equipment in operation, secure the equipment,
or change its mode of operation.
3.4.33 Component heat removal. If forced air-cooling is used, the unit shall generate no more than the
structureborne or airborne noise acceptance criteria as specified in MIL-STD-740-2. The unit shall be capable of
operating normally for a period of at least 24 hours at rated load, in 122 °F (50 °C) ambient air, with a loss of one-
third, minimum, of the active cooling capacity, and support the rated load for a minimum of 6 hours, in 82 °F
(28 °C) ambient air, with a loss of all (100 percent) of the active cooling capacity.
3.4.34 Transfer positions. Switches shall be two-way or three-way as specified by configuration type (see
3.4.35 Current ratings. The continuous duty current ratings (see 1.2.5) for switches shall be in accordance with
3.4.36 Line phases. Switches shall operate in three-phase circuits.
3.4.37 Compatibility with shipboard ground fault detector circuits. When specified (see 6.2), an ABT
connected to both power sources and to the loads shall:
a.
Have a source-to-source impedance as high as possible, but no less than 0.5 megohm at 122 °F (50 °C).
b.
Have a minimum line-to-ground impedance of at least 10 megohms.
c. Not cause a low-impedance to a ground fault condition detected on one source to be imposed on,
transferred to, or reflected on the other source.
3.4.38 Endurance and overload. Switches shall meet endurance and overload requirements when tested in
3.4.39 Short-circuit withstandability. Unless otherwise specified (see 6.2) switches shall meet the short-circuit
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