output at an ambient temperature of 44 degrees C 112 degrees F in full
sunlight with expected life in excess of 10 years.
2.2.1.1
Transformer
Transformer shall conform to UL 506.
2.2.1.2
Rectifiers
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NOTE: Below about 500 volt-amperes of dc rating
output, single phase selenium rectifiers cost less
to acquire and operate than silicon rectifiers.
Above 1000 volt-amperes silicon rectifiers are more
economical for both single phase and three phase.
Silicon rectifiers are more economical to repair.
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Rectifying elements shall be [silicon diodes] [selenium cells] connected to
provide full-wave rectification. Silicon diodes shall be protected by
selenium surge cells or varistors against over-voltage surges and by
current-limiting devices against over-current surges.
2.2.1.3
Meters
Meters shall be accurate to within plus or minus 2 percent of full scale at
27 degrees C 80 degrees F, and shall possess temperature stability above
and below 27 degrees C 80 degrees F and shall possess temperature stability
above and below 27 degrees C 80 degrees F of at least 1 percent per 5
degrees C 10 degrees F. Separate meters shall be 63.5 mm 2-1/2 inch
nominal size or larger.
2.2.1.4
A [single] [double] [three]-pole, flush-mounted, fully magnetic, properly
rated non-terminal type circuit breaker shall be installed in the primary
circuit of the rectifier supply transformer.
2.2.1.5
Fuses
Cartridge-type fuses with suitable fuse holders shall be provided in each
leg of the dc circuit.
2.2.2
Cabinet Construction
Cabinet shall be constructed of [not lighter than 1.56 mm No. 16 gauge
[steel] [hot dipped galvanized steel] [stainless steel] [aluminum]] [molded
fiberglass reinforced polyester], and shall be provided with a full door.
The enclosure shall have oil-resistant gasket. The door shall be hinged
and have a hasp that will permit the use of a padlock. The cabinet shall
be fitted with screened openings of the proper size to provide for adequate
cooling. Holes, conduit knockouts, or threaded hubs of sufficient size and
number shall be conveniently located.
2.2.2.1
A complete wiring diagram of the power unit showing both the ac supply and
the dc connections to anodes shall be on the inside of the cabinet door.
All components shall be shown and labeled.
SECTION 13112A
Page 16
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