Motion picture projection : an elementary text book (1928)

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668 MOTION PICTURE PROJECTION Comparative power costs under the conditions shown are illustrated by the relative heights of the blocks, Fig. 279. No. 1 is that corresponding to the 75 volt machine, No. 2 the 110 volt machine, No. 3 the Transverter, No. 4 the 220 volt machine if a motor generator and No. 5 the 220 volts if taken directly from a 220 volt D.C. supply line. While we see that increasing the voltage of such constant voltage machines tends to improve the stability of the arcs, it results in increased cost for power with no possibility of getting ideal results at the arcs. To overcome these difficulties and at the same time be able to get from one machine simultaneously two such arcs of equal amperes and light value, the arcs must be connected in series and we must use a constant current machine. With this equipment only the desired results can be accomplished. There is no power waste in ballast — power bills are therefore reduced to a minimum. Being in series, the amperes in both arcs are identical and in dissolving there is no change in light intensity. The source, being a constant current machine, the amperes and light do not decrease if the arc length increases from 55 to 60 or even 70 volts, so that the arc is not lost or even noticeably changed. The Transverter, a description of which follows, is such a machine. In fact, it is the pioneer in this class of equipment. The first units were sold and installed in theatres in 1915, and from all reports these early machines as well as the later ones are giving their users entire satisfaction. Therefore, a detailed description of the Transverter, with the