ers almost its full light output throughout its
life (figure 6.10).
In order for this self-cleaning cycle to
occur consistently, the temperature of the
lamp bulb must be a minimum of 500°C.
The use of quartz rather than glass is dic-
tated by this thermal requirement and the
need for strength to resist high internal gas
pressures. Although quartz is no longer the
only material used for the enclosure of these
lamps, the lamps are still sometimes referred
to as “quartz-halogen.”
The high internal pressure may cause an
explosive shattering of the bulb if it develops
a fault and fails. Although this is a rare
occurrence, halogen lamps must be
enclosed because fragments of quartz glass
are hot and can cause burns or start a fire.
The halogen tube is either enclosed in an
outer bulb or used in a luminaire equipped
with a glass cover or fine mesh screen.
The higher the operating temperature of
a filament, the higher the color temperature.
Therefore, halogen lamps have a higher color
temperature than conventional incandescent
lamps. And, greater energy in the blue region
of the spectrum makes them appear
“whiter.” They have longer life and greater
efficacy; they are also more compact, permit-
ting the use of smaller luminaires.
Halogen lamps are available in five con-
figurations: (1) single-ended T; (2) double-
ended T; (3) integral-reflector AR, MR, and
PAR; (4) modified A-lamp CP, MB, and TB;
and (5) modified decorative B and F shapes.
Single-ended halogen lamps have bayo-
net, bipin, miniature screw, mini-candelabra
(“mini-can”), twist-and-lock (TAL), or two-
pin bases in sizes that range from T3 to T24
and wattages from 5 W to 10,000 W.
Double-ended halogen lamps have
recessed single contact (RSC) bases, one atINTERIOR LIGHTING FOR DESIGNERS
Figure 6.9Cool-beam PAR lamp. Since the unwanted
heat is transmitted from the back of the lamp, cool-beam
lamps are to be used only in luminaires designed to allow
the heat to escape.
Figure 6.10Halogen cleaning cycle.