Figure 4-3.--Delta-delta transformer connections.
allows the lamp to operate at higher temperatures,
resulting in higher efficiency. Lamps of 50 watts or less
are of the vacuum type because inert gas would not
increase their luminous output.
The incandescent lamp is further subdivided into
The four sources of electric light used in naval ships
tungsten- and carbon-filament types.
are (1) incandescent, (2) fluorescent, (3) glow, and
tungsten-filament lamps comprise most of those listed
(4) low-pressure sodium lamps.
in this group.
A complete list of lamps used by the Navy is
contained in federal item identification number
sequence in the Illustrated Shipboard Shopping Guide
(ISSG), carried aboard all ships. `This list includes the
electrical characteristics, physical dimensions,
applications, ordering designation, and an outline of
each Navy-type lamp.
The incandescent lamp consists of a tungsten
filament supported by a glass stem (fig. 4-4). The glass
stem is mounted in a suitable base that provides the
necessary electrical connections to the filament. The
filament is enclosed in a transparent, or translucent,
glass bulb from which the air has been evacuated. The
passage of an electric current through the filament
causes it to become incandescent and to emit light.
All Navy-type 115- or 120-volt lamps (up to and
including the 50-watt sizes) are of the vacuum type and
all lamps above 50 watts are gas filled. The use of an
Figure 4-4.--Components of an incandescent lamp.
inert gas, which is a mixture of argon and nitrogen gases,