Moving Picture World (Jul - Aug 1918)

July 6, 1918 THE MOVING PICTURE WORLD 69 z ^g^_g_g> *c° g^gig^E; ^> *> ^i^S-Lii^-^-^-^ ^ '^L^ 'J^HHZSH^Z^igA Projection Department Conducted by F. H. RICHARDSON rvy ■ — -> ■ ---^ — ■ ' — ■ ■ — Si Manufacturers' Notice. IT IS an established rule of tbls department that no apparatus or other goods will be endorsed cr recommended editorially until the excellence of such articles bas been demonstrated to Its editor. Important Notice. Owing to the mass of matter awaiting publication, it is Impossible to reply through the department in less than two to three weeks. In order to give prompt service, those sending four cents, stamps (less than actual cost), will receive carbon copy of the department reply, by mall, without delay. Special replies by mall on matters which cannot be replied to in the department, one dollar. Both the first and second set of questions are now ready and printed In neat booklet form, the second half being seventy-six in number. Either booklet may be had by remitting 25 cents, money or stamps, to the editor, or both for 40 cents. Cannot use Canadian stamps. Every live, progressive operator should get a copy of these questions. You may be surprised at the number you cannot answer without a lot of •tudy. The Wagner Converter. The purpose of my visit to St. Louis was primarily to examine the Wagner Converter and set before our readers such details with regard to it and its performance as may seem desirable. The Wagner Converter is well known to the motion picture fraternity, having been on the market for four or five years. It is a compact apparatus, having a very satisfactory electrical efficiency, as has been proven by former tests published in this department at the time of my last visit to the plant. The Wagner Company's outfit is a current rectifying device of the converter type. As between the regular motor-generator set and the converter the difference consists in the following : The motor-generator is nothing more nor less than a D. C. generator of suitable amperage capacity and voltage range driven by an alternating current motor designed to work at the line voltage and frequence of the supply circuit. The converter, on the other hand, consists of one machine only, which 'in general has the performance of a standard D. C. generator. It has a commutator, and the brushes on the commutator end have exactly the same function as the brushes on a D. C. generator. In addition to the commutator, however, there are two or more slip-rings mounted on the shaft on the opposite end from the commutator. These rings will be seen at the left in the illustration and the commutator at the right. The slip-rings are connected to a small, stationary A. C. transformer, the primary side of which is connected to the A. C. line. The impressed A. C. voltage and the resultant direct current voltage bear a fixed relation to each other ; for instance, if 50 volts A. C. be Impressed at the slip-rings then the D. C. commutator will deliver 75 50 Ampere Wagner Converter Installed at the Victoria Theater, Watertown, Mass. Duplex Resistance. volts. If more than 75 volts D. C. is required an A. C. voltage larger than 50 volts must be impressed on the slip-rings. This is accomplished by providing the A. C. transformer with special, higher voltage taps. In other words, the machine is, by means of the transformer, which is an integral part thereof, adjustable either for the purpose of obtaining a higher direct current voltage at the lamp or to compensate for fluctuations in line voltage. This is accomplished by means of a change In tap connections in the transformer, the coils and connections of which are seen just above and to the left of the converter. The switch leading to the alternating current supply is the two-pole, single-throw switch immediately above the transformer. In addition to this switch a four-pole switch will be seen to the right of the two-pole switch just mentioned. This four-pole, double-throw switch is marked "Start" on one side, the other side is marked "Running." In order to start the converter throw the fourpole, double-throw switch into position marked "Start." Leave the switch closed in this position until converter has reached approximately normal speed, which will occur in ten to fifteen seconds. Then throw the switch into the position marked "Running." The machine will now be ready to deliver D. C. current on the commutator end. One peculiarity of the machine is that the polarity of the brushes on the D. C. side cannot be predetermined. Sometimes the top brush is positive and sometimes negative, and this makes necessary an additional two-pole, doublethrow switch in order to change polarity. This switch is shown in the upper righthand corner of the switchboard. If it should happen that the converter has picked up with wrong polarity all that is necessary is to throw the double-throw switch in the opposite position. In order to obtain a steady arc it has been found essential that a certain amount of resistance be introduced between the arc and the D. C. supply. For this reason a certain amount of resistance is connected into the D. C. line. This resistance is shown in the right, lower corner, just above the converter. It is inclosed in a pressed steel, ventilated case. In cases where two arcs are to be fed from the same converter, and where it is desired to gradually increase the • brilliancy of one and decrease the brilliancy of the other a duplex resistance, or as the Wagner Company term it, "Duplex Arc Regulator," is used. This resistance makes it possible to gradually decrease the brilliancy of the arc in use, and to gradually increase the brilliancy of the arc to be used It is by this operation that the act of change-over is accomplished The cutting out of resistance on one arc and cutting it in on the other is accomplished by simply moving this handle from one extreme position into the other extreme position. The arc of the idle machine is thus gradually developed to full brilliancy, and the arc of the running machine gradually extinguished. The manufacturer claims a machine efficiency of from ,0 to 75 per cent when operating on 220 volts A. C. supply. This however does nof include the resistance loss. The Wagner machine is niechan.call, £ ^'con^^tTr ^ =ur;^ HpiS-a-^in =5 ^xv^;^2 ,,V-rrn^"o?\ber"nverter. This arrangement is known as "Emergency gineering department. Film Indicator. The J K E Company, Seattle, Washington, have submitted working mode! of thefr indicator, designed to warn the operator when ,to preDare Ms second machine for the change-over. The operation of he devkes quite clearly .mown in the Illustration, except a. to the