Motion Picture News (Jan-Feb 1922)

January 21, 1922 647 NEW THEATRE Construction & Equipment PROJECTION Department c * m e b * I P. M. ABBOTT --------- TECHNICAL EDITOR Proper Care and Operation of the Motor-Generator Equipment Common Troubles Eliminated Thru Attention to Simple Precautions The electrical equipment supplying power to the projection machines, spot lights, flood lights and stereopticon lamp may be reasonably styled the heart of a modern motion picture theatre. An attractive entrance, pleasing interior decorations, ample ventilation and good music are all desirable and necessary but all of these count for little if poor projection is permitted. The patron of the theatre wishes to see and has the right to expect good, clear snappy pictures with a minimum of flicker and of uniform brilliancy except of course where the obvious artistic effect in the film produces less intense lighting of the screen. To produce the desired results it is not only necessary to have installed the proper type of motor-generator equipment and control but this apparatus must be given a reasonable amount of care and inspection to assure that it will function continuously and correctly. The care of this electrical equipment usually falls upon the shoulders of the projectionist who should acquaint himself ■with the apparatus by studying the instruction in the form of tags, leaflets, etc., supplied with the equipment by the manufacturers. The motor generator should be installed in a clean well ventilated room with sufficient space around it so that all parts may jbe inspected readily. The question of sufficient ventilation is one which most persons especially architects and contractors fail to appreciate. If the temperature in ithe motor generator room can be kept ifrom rising appreciably above that of the outdoor air, considerable more capacity can be obtained from the equipment without causing its temperature to reach a danjgerous value. In this connection it is well to mention that most persons do not realize what constitutes a dangerous temperature for the parts of a motor or generator. |Modern electric machines are designed and constructed of materials which does not Ibecome damaged unless the temperature ^exceeds 90 deg. C. or 194 deg. F. This ipermits a temperature rise of 50 deg. F. 'above a surrounding air temperature of 40 deg. C. or 104 deg. F. Obviously, therefore, if the air temperature in the motor Efficient Service Very often considerable trouble is experienced in obtaining efficient service from the motor generator set. This may be caused through a defective apparatus. However, in the great majority of cases it is traced to lack of proper care and operation. This article, prepared by Mr. A. M. Candy, Engineering Department of the Westinghouse Electric and Mfg. Co., will be found very helpful in securing good results from the projection control equipment. The care and procedure or installation and operation as outlined in this article should save the projectionist much time and worry and the exhibitor considerable expense. While motorgenerators as a rule are sturdy, reliable machines, they demand considerable attention as does any machine doing heavy constant service. — Tech. Ed. generator room is allowed to increase much above 100 deg. F. the capacity which can be obtained from the equipment will be proportionally less. Each time the motor generator is started up the operator should inspect the bearings to make sure that the oil rings are revolv Motion Picture Tau/pment TWO LIGHT Schematic Connections Motion Picture Motion Picture Machine No 1 Machine No.X Fig f. ing and carrying oil upon the shaft journals. If these rings fail to roll on the shaft or if the oil level in the bearing housing is too low, the bearing and journal will become overheated and burn out the babbitt, thereby putting the set out of commission. The motor generator must be protected from water which may come through open windows, faulty ventilators or other sources. If water gets into the windings or. on the commutator a burned out machine will result. Oil should not be allowed to collect inside the frames of the machines nor on the windings as it will cause the insulation on the windings or rubber covering on leads and cross connections to gradually disintegrate, grounding the winding to the frame of the machine, which will result in burning out the windings. The commutator should be wiped off carefully occasionally with a clean piece of canvas cloth. If the commutator needs a little lubrication a piece of paraffin rubbed lightly across the commutator surface will suffice. Do not put oil on the commutator as it will cause the binder in the mica between commutator bars to disintegrate. It will also collect between the bars especially where the mica is undercut and will collect carbon dust which may short circuit the commutator and cause the generator to “ buck over ” or flash across from one set of brushes to the other. Whenever it becomes necessary to insert new brushes they should be ground in to fit the surface of the commutator. To do this properly only one brush should be ground in at a time and the rest should be pulled out of the holders so they do not rest on the commutator. A piece of number oo sand paper should be placed on the commutator with sand sides toward the brush. The brush should be pressed down against the sand paper which should then be pulled along under the brush in the direction of rotation of commutator. The sand paper must be kept against the commutator so that the edges of the brush surface will not be beveled off. Emery cloth must not be ( Continued on page 656)