The Works Of Messrs. Schneider And Co.

TRANSFORMERS; PARIS ELECTRIC LIGHTING. 121 diminishing the liquid résistance progressively, and when the normal speed is obtained a special arrangement places the armature coils in short circuit. The complété series of three-phase motors made by Messrs. Schneider and Co. range from rwth of 1 horse- power to 120 horse-power; the efficiencyand power factors are high. For instance, the 3 horse-power machine has an efficiency of 80 per cent., and as power factor, 75 per cent in füll load, with a slip of from 4 to 5 per cent. Single-Phase Transformers.—The single-phase trans- formers built by Messrs. Schneider and Co. are on the Ganz system ; they are of the cased-in type, with closed magnetic circuit formée! of tvvo piles of sheets E-shaped, joined together, with the horizontal arms placed opposite each other between four wrought-iron uprights. The primary and secondary coils, one above the other, are lodged in the recesses thus formed. In the manufacture of the primary coils, high concluctivity copper wire is used generally; while for the secondary ones, flat copper bands are used, as with these a better utilisation of the space available is insured. As the coils in this type of transformers are in direct contact with the metallic parts of the magnetic circuit, their perfect insulation is of great importance, and requires all the care and attention of the manufacturera. The minute attention given by Messrs. Schneider and Co. in the choice of the insulating material and in the préparation of the coils, has enabled them to obtain an insulation which can sustain without inconvenience, a current of 15,000 volts. The transformer rests on porcelain insulators, in which are enclosed the lower ends of the uprights. The coils, placed vertically, are protected by a sheet-iron cover, which envelopes thê transformers and facilitâtes ventilation in the same time, by forming a conduit for the ambient air. A cast-iron plate placed at the top of the transformer carries the terminals and the lifting rings. Of these transformers, eight types are built from 500 watts to 25 kilowatts. The efficiency varies from 90 per cent, for the small, to 97 per cent, for the large, type. For those of 1 to 25 kilowatts, the total potential fall, from no load to füll load, is not above 2 per cent, on non-inductive circuits, and 5 per cent, on inductive circuits. Three-Phase Transformers.—Messrs. Schneider and Co. make 11 types of three-phase transformers, varying in power from 2 to 100 kilowatts. They are formed of laminated columns, square in section, with angles rounded off and placed at the angles of an équilatéral triangle, their ends being united by V-shaped pieces. The primary and •secondai’y circuits, star-connected, consist of concentric coils which envelope the columns, leaving free spaces to facilitate ventilation and insulation. The primary and secondary coils are manufacturée! in the same way as for the single- phase transformers, and can resist a tension of 15,000 volts without inconvenience. Tw.o cast-iron plates, on which rest four holding-down bolts, render the whole machine secure ; the lower plate is fitted with stands, and the top one is provided with a lifting ring. The primary and secondary terminals, mounted on porcelain insulators, are fixed on the lower V-shaped piece under the coils. A perforated plate, which rests on the uprights, envelopes the transformer ; three openings in the envelope, which are closed when the transformer is working, give free access to the coils and terminals. Trials made with a 7-5-kilowatt transformer have shown an efficiency of 97.5 per cent, in füll load, and a total potential drop of 2 per cent, between no load and füll load on a non-inductive circuit. Three-Phase Alternators.—The three-phase alternators and motors built by Messrs. Schneider and Co. are of the Ganz system. They are fitted with a revolving armature and fixed coils, and are therefore without movable contact The revolving part is of cast steel keyed on the shaft and is made with laminated polar projections. The exciting coil, the centre o£ which is on the axis of the shaft, generates the current which goes through two distinct armatures ; the total number of turns in the winding of these is in the ratio of 1 to .86. As the right-hand polar projections extend beyonel the left-hand ones over one- fourth the angular space between two neighbouring poles, there i'esults in the armatures a difference of 90 deg. in the succession of currents ; these, grouped according to Scott’s system, give the difference of 120 deg. at the dynamo terminals. The part of the armature coils opposite the revolving mass is formed of laminated segments, fitted together in a cast-iron shell; this shell complétés the magnetic circuit, and is embodied in the frame. The inductor coil is supplied by an exciting tetrapolar dynamo, placed on the end of the shaft opposite the pulley. The alternator shaft carries the armature and commutator ; the inductor poles, fitted with branches, the fields of which are inelined on the génératrices of the armature drum, are set in a cast-iron shell fixed to the frame. This type of alternator can yield simultaneously single-phase and three- phase alternating currents. In alternating the coils in a suitable way, two-phase currents can also be obtained, without modifying the general system of manufacture. (See Figs. 347 to 349, Plate LXXIX.) Messrs. Schneider and Co. build six machines of this type, from 42 to 280 kilowatts; their efficiency varies between 90 and 91 per cent. Paris Electric Lighting.—One of the most important contracta for electric lighting hitherto completed by Messrs. Schneider and Co., was that for the Sector on the left bank of the Seine, forming an important part of the Paris Municipal electric lighting scheme. The concession for the great work was granted on December 11, 1890. The area included in the concession comprised the whole of the left bank of the Seine within the Municipal limits, and the Iles de la Cité and St. Louis. The distance from the station to the end of the concession was about 7 miles, and it was decided to generate high-tension currents (3,000 volts), reducing them by transformers before distribution. The generating station is at Grenelle, near the Point du Jour Viaduct. The works occupy an area of 13,000 square metres, and the company (Compagnie du Secteur de la Rive Gauche) possesses a coal wharf on the Seine. The leading