Satco Products Incandescent Lamps - Manual (Page 3)

THE FILAMENT
Incandescent lamp filaments are made
of tungsten. Tungsten is a metal that
can operate at very high temperatures
without evaporating too quickly and
resulting in early lamp failure.
Incandescent filaments only
convert about 10 percent of the
energy used into visible light, so it
is necessary to use a material
that can withstand extremely
high temperatures. Most
lamps use a coiled
filament design, which
has been found to be
stronger and deliver
better performance.
THE GLASS BULB
The filament inside an
incandescent lamp
must be protected so that
oxygen does not reach it and
cause it to evaporate on con-
tact. Most incandescent lamps
are either vacuum-sealed or
gas-filled. It was discovered in
the early 1900s that the
introduction of gas inside the
bulb, or envelope, created a
pressure against the
filament. This pressure
allowed the filament to
burn hotter and last
longer. Most gas-filled
incandescent lamps today
use a mixture of argon
and nitrogen gases.
Incandescent Basics
The basic design of the incandescent
lamp has not changed much since the
late 1800s, when Thomas Alva Edison
successfully produced the first
operational electric light bulb.
These are the must-know
fundamental facts about
incandescent lamps and
the alternative
choices that are
available today.
Bulb
shapes
The size and shape of a lamp’s
bulb are designated by a letter(s)
and a number. The letter specifies
the shape of the bulb and the
number indicates the maximum
diameter in 1/8-inch increments.
Example: A G40 is a globe shape
which is 5 inches in diameter.
HOW IT WORKS
Just as a piece of metal being
blacksmithed or the molten glass at the
end of a blower’s rod heats to a brilliant
glow, so does the filament of an
incandescent lamp. The difference is
that electricity is used to heat the filament
instead of fire. This phenomenon is known
as incandescence.
THE BASE
Screw-type bases used on incandescent
lamps consist of three components: the
threaded screw section, the glass insulation
ring and the contact disc. The lead wires
which exit the glass bulb of the lamp are
attached to the base at two points. One
wire is soldered to the bottom of the
contact disc and the other to the top
edge of the screw section. The glass ring
acts as an insulation barrier between the
two points. This assembly completes the
circuit and the lamp is electrified once
the base is screwed into a socket and the
contact disc touches the center point of
the socket.
The base itself has nothing to do with the
seal of the bulb; it is a separate part of
the lamp that is attached with cement.
Typically, bases are made from aluminum
or brass. Brass bases tend to perform best
due to their compatibility with most socket
materials.
Base Types
A F
G PAR
PS R
S T
B CA
BR HX
Medium
E26
Medium
Skirted
Mogul
E40
Int.
E17
Cand.
E12
S.C. Bay. D.C. Bay.
Mog. End
Prong
Screw Terminal S14S Med. Side Prong