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1948-49 Theatre Catalog, 7th Edition, Page 344 (331)

1948-49 Theatre Catalog, 7th Edition
1948-49 Theatre Catalog
1948-49 Theatre Catalog, 7th Edition, Page 344
Page 344

1948-49 Theatre Catalog, 7th Edition, Page 344

winding, the contact buttons, and the interconnections are all embedded in insulating cement and supported by a metal base plate. The reduction in voltage on the lamps with this type of dimmer is secured by direct transformer action and is not dependent on the load connected to the dimmer. This feature alone makes the Autrastat a more desirable unit, as the actual lighting in the theatre may be changed from time to time and it can still be properly controlled by the same dimmer. Because of the transformer action, the actual losses in heat are very low and the operating etiiciency of the lighting circuit is high even at very low intensities. Individual units with maximum rating as high as 8000 watts are available, thereby reducing the number of dimmers that might be required for the control of the auditorium lighting.

The Autrastat dimmer is higher than the resistance type in the initial cost of installation but because of its high operating efficiency, the difference in initial cost is quickly saved by the reduction of power consumed in the circuit.

The reactance type dimmer consists of a magnetic element connected in series with the lamp load. Some controlling device must be provided to regulate the impedance produced by this magnetic element. In the modern type of reactance dimmer installation this is usually an electronic control unit having miniature pilot controls. This means that the reactance type dimmer is essentially for remote control installations.

With this type of dimmer the amount of reduction of the voltage applied to the lighting load depends on the load connected to the dimmer, somewhat in the same manner as the resistance dimmer. However, a regulating characteristic is included in the control element, permitting a wide range of variation in the connected load with equal dimming results. As the reduction in voltage is obtained by reactance voltage drop, little loss occurs in the magnetic unit in the form of heat. The system operates at high efficiency closely approaching the efficiency of the Autrastat type dimmer. Reactive units of large capacity can be manufactured, reducing the number of units required in any installation to a minimum. Individual loads of 14,000 Watts can easily be controlled by one .unit with the miniature pilot device.

Because of the auxiliary devices required with this system, the reactance type dimmer is the highest in initial cost, but on the other hand, there are no moving contacts carrying the heavy lighting current, therefore maintenance on this type of installation is minimized. The electronic tubes used in this circuit have been selected for long useful life. to reduce tube replacement costs to a minimum.

Selection And Location

The type of dimmer equipment best suited for any particular installation can be determined by considering the various factors involved. First of all, a comparison should be made between the relative cost of the various units. This should include a balance between the Initial installation cost and the operat 1948-49 THEATRE CATALOG

ABOVE is a wiring diagram for resistance type dimmers ot the single phase. three wire service, two wire branch circuit type. The dimer is connected in the neutral return of the branch circuit. For lump loads of more than 3600 watts. resistance dimers are connected mechanically but are electrically independent, und the load must be divided so that each dimmer plate carries its portion of the total load.

ing cost, which is greatly affected by the efiiciency of the various types of dimmer equipment.

The next consideration is the character of presentation for which the theatre is designed. If limited solely to motion picture presentations, the simplest type of equipment is obviously adequate.

However, in some community theatres provision is made for the possible use of the theatre by local organizations for meetings, benefit shows for charitable organizations, and presentation of amateur theatrical productions. These obviously require some form of stage lighting and additional dimmer equipment to

BELOW is a wiring diagram of an autrastut dimmer oi the three phase, tour wire service, two wire branch circuit type. Note-circuit breakers are ahead at nutrastat dimers in addition to the branch circuit protection. This dimmer, known throughout the electrical industry as an autotranstormer, has been a tavorite with theatremen because ot its provisions at flexible and efficient lighting at low cost.
1948-49 Theatre Catalog, 7th Edition, Page 344