Motion Picture News (Sept-Oct 1916)

2572 ACCESSORY NEWS SECTION Vol. 14. No. 16 Apparatus for Dissolving One Picture Into Another Good Eflfect Obtained by an Alternating Current Motor Driving a Direct Current Dynamo at Low Pressure, Thus Providing the Means for Warming Up the Arc of a Second Machine While the First Is Still Running— Complete Description of " The White Light Converter " DYNAAIO-ELECTRIC alternating to direct current transforming devices, such as motor generator sets, rotary converters, etc., have always been close competitors of the rectifier which I have illustrated in this series, and many operators claim for them the advantages of better quality (whiter) light and greater freedom from interruptions in service. The device is nothing more than an alternating current motor driving a direct current dynamo at low pressure, i. e., voltage, One important advantage of the motor-generator or the rotaryconverter is the ability to provide a single machine, whose characteristics will permit of the second arc to be started and warmed up without interfering with tlie continuous projection of a picture, whicli is so desirable in those houses which successfully dissolve one picture into another. r Plate •• B " When one picture is to immediately follow another on the program it becomes necessary, in order to avoid a delay of several minutes, to have a second machine ready to start at the instant the first stops. By means of the motor-generator or rotary-converter the delay may be cut down to a few seconds. It is generally considered necessary, however, to warm up the second arc for from 3 to 5 minutes before showing the next reel, thus giving the arc time to steady itself. Moreover, in the better class of theatres, it is coming to be the accepted method of operation to " dissolve " one picture into another, thus eliminating all delay and giving a more artistic touch to the projection. This calls for the use of ballast resistance when the second arc is struck, and while the two are operating in parallel, as well as extra switching equipment, rheostats, etc., the arrangement of which vary with different types of apparatus. That which I shall illustrate this week, is known as the " White Light Converter," manufactured by the Wagner Electric Manufacturing Company of St. Louis, Mo. Mr. G. V. Bain, whose acquaintance I made while in the above named city, was of great assistance to me in collecting data on the White Light Converter, which, briefly described, consists of the converter itself, a small transformer, and one or more resistances for controlling the amount of current at the arc. The transformer is of the core type, the core being constructed of specially laminated iron very securely belted to prevent any possible noise. The coils are thoroughly impregnated and are of a high overload capacity. Suitable taps are brought from the windings to provide connections that will take care of any possible variations in the line voltage. The converter consists of the usual armature and field, but with special windings for both A. C. and D. C. current. There are alternating current slip rings on one end of the armature and a direct current commutator on the other, the whole being mounted on one shaft and carried on two bronze bearings. The latter are of the usual ring oiling type, but with a very large oil reservoir. The frame is cast in one piece and is quite similar to the ordinary types of motor frames. It will be noted from this description of the converter that it is an extremely compact machine, inasmuch as it performs the duty of both generator and motor, but unlike the motor-generator, it (the converter) has only two bearings, one shaft, one armature and one set of windings, making it extremely efficient. The resistance may be any one of three types, namely, adjustable, non-adjustable or so-called "Duplex" arc resistance which allows of the operation of two arcs from one convertor by the manipulation of but one lever. These resistances are of the ventilated enclosed type, and are very substantially constructed and mounted upon a heavy slate base. They meet all requirements of the underwriters and fire prevention bureaus. The Converter equipment is built for single, two or three phase circuits and for frequencies of 25, 50 and 60 cycles. Standard transformers are for a line voltage of 220, but are furnished for 110 to 550 volts. The capacities of the converters range from 25 to 100 amperes, there being four sizes. It is also possible to overload the converter far beyond its rated capacity, it being possible to pull as high as 70 amperes from a 50 ampere converter for a period of approximately three minutes, thus giving ample time and capacity to allow the operator to warm up the second arc while the first is yet in operation. As the equipment is practically noiseless it may be mounted in the operating room, unless this conflicts with local laws, when it may be installed in any part of the theatre, for as the only thing necessary for the operator to have under his control is the resistance, particularly the " Duplex " arc resistance, this can be placed in the operating room while the converter itself may be placed in a room adjoining, care being taken that this room be dry and well ventilated and that the equipment be so mounted that no damage can result from accidental contact with other objects. In installing the resistance it is advisable, where two machines are used, to have the resistance placed between the two machines where the operator can get at i: without changing his position. It is not necessary to have the pole changing switch convenient, as it will only be used when Plate " B " Starting up the converter. The position marked " starting " on the main switch is for this purpose only, and it should not be left in starting position any longer than is necessarj to bring the converter to the proper speed. It should be left in runtiitig position or open. (Continued on page 2575) <