File:Motion picture electricity (1914) (14803878623).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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used. Fig. 3 gives a diagrammatical illustration of an elec-tric generator and a 2-wire distribution system in its sim-plest form operating a motor, incandescent lamps andarc lamps. The illustration indicates the names of theprincipal parts of the system and how connections aremade. We have already learned that the further the currenthas to be transmitted, the greater the drop of voltage inthe wires, therefore it takes larger wires to carry a givenquantity of amperes a long distance, and this is also oneof the reasons why the field rheostat for the generator isnecessary at the power house in order to raise the voltageof the generator to overcome the line losses, and it is oneof the duties of the dynamo attendant to keep the voltageat the proper amount at all times by means of the fieldrheostat. The battery is only suitable for small and inter-mittent work. 26 MOTION PICTURE ELECTRICITY DIRECT CURRENT 2 WIRE ELECTRIC SYSTEM RHEOSTAT SHUNTFIELD WINDING \ ^ARMATURE —COMMUTATOR BRUSHES
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Fig-3 MOTION PICTURE ELECTRICITY 27 Where large current supply is required, it be-comes necessary to make the electricity by a dyna-mo electric machine driven by an engine or similarpower. THREE-WIRE SYSTEM FOR DIRECTCURRENT The 2-wire direct current distributing system is used,as a general rule, in small plants and in isolated plantswhere the distance from the electric generator to thepoint where the current is used is not very great. In abuilding, for instance, the distance would never be overa few hundred feet, and in a small town the distance fromthe power .station to the furthest consumer might not beover one mile. In such places the 2-wire system may beinstalled and used, although the cost for copper wire isgreat as compared with the 3-wire system, which is gen-erally used where a large amount of power is requiredand where the distance may be several miles, as is thecase in the larger towns and cities. The 2-wire system may be either no or 220 volts, butonly one of these voltage

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