File:Motion picture electricity (1914) (14780932491).jpg

Identifier: motionpictureele00hall (find matches)
Title: Motion picture electricity
Year: 1914 (1910s)
Authors: Hallberg, Josef Henrik, 1874-
Subjects: Motion picture theaters Electric lighting
Publisher: New York city, The Moving picture world
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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ey shaped insulated coupling which en-tirely separates the a. c. from the d. c. system, and thiscoupling can also serve as a pulley where the d. c. machinehas to be used as a generator driven by any other motor,or by an engine of any kind. This is an important pointin all Hallberg A. C. to D. C. Economizers and is con-sidered to be of advantage to the exhibitor, as it reallygives him the opportunity of putting in a small engine,by means of which the generator can be driven in anemergency, if the electric power should fail, or if the out-fit should be installed at a point where the proper kindof alternating current is not available. The construction of the generator is along the mostmodern lines, and the arrangement of the brushes andconnections is similar to the Hallberg D. C. Economizer,and the same general instructions hold good for thed. c. end of the a. c. to d. c. outfit. The d. c. end of thismachine is so designed that a short circuit may be put on 202 MOTION PICTURE ELECTRICITY
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bo MOTION PICTURE ELECTRICITY 203 it without injury to the generator—in fact, the currentwill drop down to zero if the carbons are put togetherand held that way for a few moments. This is a point ofadvantage because it protects the machine from shortcircuits or overload, and also permits the operation ofthe motion picture arc without a large rheostat in serieswith the arc. Wherever possible, it is desirable to operate the Hall-berg A. C. to D. C. Economizer on either two or three-phase circuits rather than single phase, and althoughmade for either no or 220 volts the latter is preferable.The economizer is also made for single phase no or 220volts, but the investment is greater for the single phasecurrent than for two or three-phase systems. HallbergA. C. to D. C. Economizers are made in several sizes. Inview of the fact that these machines are installed by ex-hibitors who appreciate the value of a picture whichstands out in great relief where the delicate shadows inthe half-tones an

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