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1954-55 Theatre Catalog, 12th Edition, Page 309 (273)

1954-55 Theatre Catalog, 12th Edition
1954-55 Theatre Catalog
1954-55 Theatre Catalog, 12th Edition, Page 309
Page 309

1954-55 Theatre Catalog, 12th Edition, Page 309

a Todayls Rectifier for Tomorrowls Arc

An Analysis of the Design, Construction and Operation of a Selenium Rectiiier Developed With Features for the Future

BRIEF: It is only natural that when there is a great demand for more light on the screen of a motion picture theatre . . . as there is today as a result of the acceptance of the wide screen . . . that all of the equipment designed to furnish that light be adapted . . . and improved to meet this demand . . . This article describes a new selenium rectifier which includes many of the features in its design . . . and operation . . . necessary in the modern projection booth.

The author . . . who has spent many years in this phase of motion picture operation . . . gives a detailed description of the various parts of this rectifier . . . and discusses why each of the features were designed as they were.

This article should be of great assistance to the theatre operator who has been seeking more information about the selenium type of rectifier . . . which appears to be increasing in popularity.

Obviously, the new enlarged picture requires more total light supplied by a source of direct current which has a greater output than the arc lamp power wpply of the past. Foreseeing the now proven need and lack of sufiicient source for such units, American Selectifier division designed two types of selenium rectifiers to meet todayls requirements, with an eye to the even larger lamps of the future.

Starting with the assumption that a tremendous safety factor and far lower than present ripple-content power supplies would be required in the future, it was decided that the exhibitor must be protected by built-in features in the rectifier he buys now to meet the expected demands of tomorrow.

The former copper-oxide and magnesium-copper-sulphate rectifiers in use since 1933, when the writer saw the General Electric unit in a Lynn, Mass, theatre, did an eiiicient job under old standards, and most can be rebuilt by replacing the stacks with selenium stacks and thereby have more output than when they were new. However, we are getting ahead of ourselves. First, what is a iiinetal" rectifier, and why should it be used instead of other types of direct current power supplies 7

Why Metal Rectifiers

Consisting essentially of a cabinet housing a line transformer, a series of selenium rectifier stacks, a forced cooling system and some means of controling the output, the system seems extremely simple, and, in its installation, operation, and maintenance, it actually

THIS selenium rectifier is so constructed that it can lurnish a clear llickerless picture ior slandIn'd lilms and the wide screen h'lm systems.



President, Norpal Sales Company .tlmerican Selecti/icr Uiu.

is. The Selectifier is so constructed, but with ramifications to assure uninterrupted efficient performance.

Important Features of Rectifiers

Our engineers knew the conditions which an arc rectifier must meet-high room temperature, abrupt changes in load, accidental overloads, and corrosive atmosphere. Our engineers knew, too, that the power supply must be easy to install, operate, and maintain. Here are some of the features which are engi

neered into Selectiiiers to make sure that they will meet these demands:

Custom-built selenium stacks assembled by hand from pre-tested selenium plates. This extra operation makes it possible to match the resistance characteristics of the plates in each stack. The result is a stack which runs cooler, which can stand a greater overload, and one which has no uweak spotly where failure can start.

An exclusive corrosion-prooiing process. Each stack is given a multiple coat of a special corrosion-resistant enamel, applied by our own process, and then sprayed with moisture and fungus-proof varnish.
1954-55 Theatre Catalog, 12th Edition, Page 309