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1953-54 Theatre Catalog, 11th Edition, Page 102 (68)

1953-54 Theatre Catalog, 11th Edition
1953-54 Theatre Catalog
1953-54 Theatre Catalog, 11th Edition, Page 102
Page 102

1953-54 Theatre Catalog, 11th Edition, Page 102

4:} ' ELEchomc i dnCONTRQL ,- p UNIT

79Rcuinsss SELECTOR

7131,ch diagram? 51?;

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Fig. 10. Block diagram of dimming system lor lluorescent lamps, The control unit may be placed <1an where and two wires run to the Brightness selector and only three wires to the lamp load.

brightness level and it is recommended that these lamps be seasoned at normal brightness for a short time in order to provide the maximum dimming range for all lamps.


Fluorescent lamps on dimming circuits offer several advantages over filament lamps: higher efficiency over the dimming range7 lower operating costs, and better color control. Filament lamps become increasingly red as they are dimmed; fluorescent lamps change very little 'in color over their entire brightness range. A comparison of efficiencies of lluorescent and filament lamps appears in Table 1; figures are for color of approximately equal chromaticity, with lamps at their normal brightness.

Fig. 11. Comparison of lamp efficiency for the fluorescent. and incandescent lamps over the daunting range for white light.


TABLE I (Typical Lumen: Filters} Lumvnc PI" W ul! Eficicnry Pvr Wan BOG-Wan Rulio 40-well Filament Flrmr/ Color Fluorescent (Typical Filters) Filuml'nl 18 3.5 15 2.2 S 3 1.3 Medium Green . T7 3 26.0 Medium Blue . 27 1.5 18.0 Daylight . . . . . i 49 9 5.4

Figure 11 shows a comparison of the approximate efficiencies of warm white fluorescent and ZOO-watt filament lamps for a wide range of dimming. No consideration is given to the change in color of the filament lamp as it is dimmed.

Figure 11 does not include the losses of the ballasts or control equipment for fluorescent lamps. The total loss will vary depending on the number of lamps in the load. However, with 35 lamps on the control unit there will be a nearly constant loss of 3-1/2 watts per lamp over the dimming range. The individual ballasts will have approximately 10 watts loss


wit .foziffluoreseew

at the highest brightness and four watts at the lowest brightness. Losses of the control equipment for filament lamp dimming will vary considerably with the type of equipment and the total load.

Dimming Control and Ballast Design

The General Electric fluorescent lamp dimming control has three parts each of which may be located remote from the other two. The ballast and 40-watt lamp make up one part, the dimming control unit is the second part and the intensity control is the third part.

The ballast, which would be conventionally located in the lamp fixture, has tw0 functions: to limit the lamp current in the usual way and to supply low potential power to heat the lamp cathodes continuously. Three leads must be brought to the ballast from the dimming control unit. The ballasts are connected in parallel, the maximum number depending on the rating of the dimming control unit.

Two models of the dimming control unit are available. One will control 35 (or less) 40-watt fluorescent lamps, and the other will control eight (or less) 40watt lamps. Both models operate from 236 volt (SO-cycle supply lines. The heart of each unit is a pair of industrial thyratron tubes. The principal difference between the two models is the size of these tubes which determine the maximum number of lamps each unit will control. To protect the thyratron tubes in the control unit during initial operation, a time delay device Hwarms up" the tubes. (T. T. Fig. 3) Both models iarc the same size in physical dimensions and may be racked side by side, or panel mounted side by side. Each model has a completely ellClOSPd terminal box built in and provided with standard knock-outs for leads.

The intensity control is csscntially a variable resistance. Its purpose is to set the time at which the tliyratrons ltfireli and pass current to the fluorescent lamps. The variable resistancc is rather low in value (less than 1000 ohms), hence the remote control lines are not likely to pick up stray signals to affect the brightness level of the fluorescent lamps. Thc intensity control operates at 25 volts or less, and is clcctrically isolated from the 236 volt supply lines. The intensity control may be used with wither model of the dimming control unit.


1953-54 Theatre Catalog, 11th Edition, Page 102