MIL-W-80040E
3.4.2 Current rating.
The power source shall be rated at 100 percent
duty cycle in accordance with NEMA EW 1 for class I machines (NEMA Class
I(100)). The power source shall be capable of operating under 100 percent
load in an maximum ambient temperature of not less than 110°F. The power
source shall be capable of delivering 50 Percent overload for 2 minutes fol-
lowing its normal operation at 100 percent duty cycle in 110°F ambient tem-
perature.
3.403 Polarity. The size 500 and 750 ampere power sources shall be of sin-
gle polarity design. When specified (see 6.2), the size 1000 and 1500 ampere
power sources shall be of dual polarity design. The power sources shall pro-
vide 1000 and 1500 ampere output, respectively, when operated in the single
polarity mode, and shall provide not less than 500 ampere output in each po-
larity when operated in the dual polarity mode.
3.4.4 Voltmeter and ammeter. A DC, analog or digital voltmeter and am-
meter shall be provided to measure the welding power output of the power
source. The instruments shall be weather-tight, located on the front of the
unit. The instruments shall be at least 2-1/2 inches in height and at least 3
percent accurate at full scale.
3.4.5 Pilot light. An "on-off" pilot light with a protective cover shall
be provided on the front of the unit panel with the voltmeter and ammeter.
The protective cover shall not protrude over 1 inch from the face of the en-
closure. The light shall be visible in daylight from a distance of 10 feet.
3.4.6 Automatic overload protection. The primary line voltage feeding the
main transformer and main control circuits of the power source shall be auto-
matically removed in event of an overload. All protective devices shall be
readily accessible for replacement or resetting.
3.4.7 Enclosure. The power source components shall be securely mounted
within a rigid, all weather, metal enclosure conforming to the requirements of
NEMA EW 1. The ventilation openings shall permit positioning multiple power
sources adjacent to each other. Access to the primary and secondary termi-
nals, transformer taps, and diode bridges shall be provided. Access openings
shall easily removable for inspection, cleaning, and servicing. After wiring
the unit, all internal components and connections shall be sprayed with air
drying epoxy or varnish or two-part urethane or similar q aterial and dried ac-
cording to the supplier's recommended drying practice. The terminal board
front with the links in standard positions shall be sprayed with a suitable
material to prevent corrosion.
3.4.8 Heaters. When specified (see 6.2), heaters shall be mounted inside
the power enclosure with the necessary controls to allow heating only
when the power source is "off" at the front panel and the primary power is on
to minimize moisture inside the enclosure. Heaters may be furnished when not
specified provided the heater system is part of the manufacturer's standard
design.
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