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Starting and operating principles
of Kolorlux and Multi-Vapor lamps are shown in Figure 9.3:
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When the circuit is energised, a
small arc forms between the starting electrode and adjacent main electrode.
-
The arc ionises the fill gas and
metallic vapour.
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When enough ions are present in the
arc tube, the main arc strikes between the two main electrodes (resistance drops
sufficiently).
-
Current to starting electrode stops
as the resistance is higher than that between the main electrodes.
-
Main arc radiates intense
light.
HID lamps require several minutes
to "warm-up" and reach stable operation. During this period the heat from the arc vaporises the
metal(s) in the arc tube and the vapour pressure increases. If switched off, the lamp requires
several minutes cooling before the arc can re-strike.
Figure 9.3. Kolorlux and
Multi-Vapor lamps starting operation.
Note that metal halide lamps
without a starting electrode start in the same manner as Lucalox lamps described later in this
section. Like fluorescent lamps, HID lamps require an external ballast. This supplies sufficient
starting current and voltage to allow the arc to strike and to stabilise after warm-up. In stable
operation the ballast limits the lamp current to control the arc discharge and to prevent the lamp
from self-destructing. The ballast is specific to each lamp type and power rating and is for a
single supply voltage unless provided with input connections (taps) to select an alternative
voltage.
Types of HID Lamps
There are four main ranges of GE HID lamps:
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Kolorlux mercury lamps
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Multi-Vapor and Kolorarc metal
halide lamps
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Lucalox high pressure sodium
lamps
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SOX low pressure sodium
lamps
The first three have similar
general construction and operating principles. SOX lamps are more akin to fluorescent tubes only
without the phosphor coating and using sodium in place of mercury. |
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