Theatre Design & Technology - Summer 1982 - 21

2000

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Figure 3: Operational Characteristics of Incandescent Lamps

Figure 4: Halogen Cyclic Process

Countermeasures: Usually preheating of the electrodes by
two filament transformers. Ignition every half cycle when voltage at the lamp exceeds momentary value "V z ". In the case of
ignition current flow occurs first. The electrode-current averaging time is the duration of the flowing current which is always less than 180°, since a particular voltage must be applied at the lamp in order to achieve periodic reignition. (V z )
Simulated cos .p.

varying current flow duration which in turn also regulates
power consumption PL' Electronic control also allows variation
of the position of the angle of current flow with respect to the
supply voltage--see 0/" 0/2, 0/3' The angle of the current flow is
important with respect to adaptation of the control unit to the
characteristics of the lamp.

N = U x J x K (K = Distortion Factor). A selection of a
particular type of control unit is required. Measures must be
taken to reduce V z in order for an increase of 0/ to be possible
with respect to igniting striae, particularly with respect to electrodes and gas fills.

lamps.

C} Mercury, Natrium, Halogen Metal-Vapor, and Xenon
Lamps: Have practically the same characteristics as fluorescent lamps, but provide no possibility of special electrode preheating. In cases of underloading light arcing punctiformly occurs in a concentrated form at insufficiently heated
electrodes. Localized increases in temperature result in vaporization of the emissive material, with blackening of the bulb
and a reduction in service life occurring if underloading is allowed to go to extremes. 50% possibly still permissable. Electrode-current averaging time must also be available, since
current cannot flow until ignition of gas discharge at V z * A selection of particular control units is required (Fig. 2).
A} Thermal Radiators
Control through variation in power supply UN' Practical only
for use with incandescent lamps. Regulation of UN also results
in reduction of IL, and thus of PL (power consumption) allowing
practically loss-free control, except for the reduced efficiency
1) of the lamp.

0/,: suitable for incandescent lamps
0/2 and 0/3: suitable for incandescent

lamps and discharge

In the case of discharge lamps it is important that the control unit also provide the required reignition voltage Vz per half
cycle. Nearly nondissipative control. Radio transmissions may
cause some interference. Incandescent lamps may generate
noise during control within phase interval. Magnetic fields can
be generated by coiled filament (Fig. 3).
5% Excess Voltage = service life reduced by half, approximately 20% more light current, 12% improved efficiency.
10% Excess Voltage = service life reduced by one-fourth,
approximately 42% more light current, 24% improved efficiency.
5% Undervoltage = doubled service life, approximately
18% less light current, 12% less efficiency.
10% Undervoltage = a fourfold increase in service life, approximately 34% less light current, 22% less efficiency.
Figure 4 shows a simplified illustration of the iodine cyclic
process. This cyclic process prevents blackening of the bulb
by vaporized tungsten and thus a change in color temperature. Vaporized tungsten bonds with iodide to form tungsten
iodide below 1,400°C. Decomposition of the tungsten iodide
occurs near the coiled filament. Tungsten is depositied upon
the coiled filament. Although the tungsten is not deposited
uniformly upon the coiled filament, burnout of the tungsten
coiled filament occurs nonetheless.
Prerequisites for the halogen cyclic process (Fig. 4):

B} Fluorescent Tubes
Control through use of series or drop resistance. Voltage
Un remains constant. Series or drop resistance can be ohmic,
inductive, or capacitive. A variation in series or drop resistance results in a reduction in current strenght IL, and thus in
PL (power consumption). Can be used with respect to practically all types of lamps. Ohmic resistance results in a loss in
power.

1.) Coiled Filament Temperature> 1,400°C
2.) Two Temperature Zones in the Lamp:
a. > 1,400°C
b. < 1,400°C
3.) Lamp Wall Temperature> 250°C

C} Mercury, Natrium, Halogen Metal-Vapor, and Xenon
Lamps
Supply voltage UN remains constant. The electrode-current
averaging time is varied through electronic control thus also

In everyday use iodide is seldom used with the same applying to hydrogen bromide. Conditions in reality are essentially
more complicated than described here. For example, reduced
traces of oxygen are a prerequisite for the functioning of the
halogen cyclic process.

USITT/Summer, 1982

Theatre Design & Technology

19



Table of Contents for the Digital Edition of Theatre Design & Technology - Summer 1982

Contents
Theatre Design & Technology - Summer 1982 - 1
Theatre Design & Technology - Summer 1982 - 2
Theatre Design & Technology - Summer 1982 - 3
Theatre Design & Technology - Summer 1982 - Contents
Theatre Design & Technology - Summer 1982 - 5
Theatre Design & Technology - Summer 1982 - 6
Theatre Design & Technology - Summer 1982 - 7
Theatre Design & Technology - Summer 1982 - 8
Theatre Design & Technology - Summer 1982 - 9
Theatre Design & Technology - Summer 1982 - 10
Theatre Design & Technology - Summer 1982 - 11
Theatre Design & Technology - Summer 1982 - 12
Theatre Design & Technology - Summer 1982 - 13
Theatre Design & Technology - Summer 1982 - 14
Theatre Design & Technology - Summer 1982 - 15
Theatre Design & Technology - Summer 1982 - 16
Theatre Design & Technology - Summer 1982 - 17
Theatre Design & Technology - Summer 1982 - 18
Theatre Design & Technology - Summer 1982 - 19
Theatre Design & Technology - Summer 1982 - 20
Theatre Design & Technology - Summer 1982 - 21
Theatre Design & Technology - Summer 1982 - 22
Theatre Design & Technology - Summer 1982 - 23
Theatre Design & Technology - Summer 1982 - 24
Theatre Design & Technology - Summer 1982 - 25
Theatre Design & Technology - Summer 1982 - 26
Theatre Design & Technology - Summer 1982 - 27
Theatre Design & Technology - Summer 1982 - 28
Theatre Design & Technology - Summer 1982 - 29
Theatre Design & Technology - Summer 1982 - 30
Theatre Design & Technology - Summer 1982 - 31
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Theatre Design & Technology - Summer 1982 - 36
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