ELECTRIC LIGHTING AT THE PARIS EXHIBITION—THE OERLIKON WORKS

Scientific American Supplement, No. 711, August 17, 1889, by Various, is part of the HackerNoon Books Series. You can jump to any chapter in this book here. ELECTRIC LIGHTING AT THE PARIS EXHIBITION—THE OERLIKON WORKS.

ELECTRIC LIGHTING AT THE PARIS EXHIBITION—THE OERLIKON WORKS.

Immediately on entering the Machinery Hall by the galerie leading from the central dome, and occupying a prominent position at the commencement of the Swiss section, is a very important plant of dynamos, motors, and steam engines, put down by the Oerlikon Works, of Zurich. During the time the machinery is kept running in the hall, power is supplied electrically to drive the whole of the main shafting in the Swiss section and part of that in the Belgian section, amounting in all to some 200 ft., a large number of machines of various industries deriving their power from these lines of shafting, while during the evening a portion of the upper and lower galleries adjoining this section is lit by some twenty-five arc lamps run from this exhibit. Steam is supplied from the Roser boilers in the motive power court. The whole of the generating plant is illustrated in one view, and a separate view is given of the motor employed to drive the main shafting, this latter view showing the details of connection to the same. On the extreme right hand side of the first view is a direct coupled engine and dynamo of 20 horse power, a separate cut of which is given in Fig. 3. The engine is of the vertical single cylinder type, standing 5 ft. high, and fitted, as are the other two engines exhibited, with centrifugal governor gear on the fly wheel, acting directly on the throw of the cutoff valve eccentric. The two standards, supporting the cylinder and forming the guide bars, together with the entire field magnets and pole pieces of the dynamo, and the bed plate common to both, are cast in one piece.

The winding is compound, and in such a direction that the two opposite horizontal poles have the same polarity; it follows from this that there will be two consequent poles in the iron, these being opposite in name to the horizontal poles and at right angles to them, viz., above and below the armature. Opposite sections of the commutator are connected together internally as in most four-pole machines, so that only two brushes are necessary, at 90 deg. apart.

The section of iron in the field is 60 square inches and rectangular in form, and the whole machine measures 4 ft. 3 in. in length, and 2 ft. in height, without including the height of the bed plate. The armature is 17 in. in length and the same in diameter, measured over the winding, and develops at the machine terminals 70 volts and 200 amperes at 480 revolutions. The moving parts of the engine are well balanced, and run remarkably well and without noise at this high rate of speed.

This dynamo serves to develop power to run a motor in an adjoining inclosure, containing some fine specimens of lathes and machine tools constructed by the Oerlikon Works. These are driven by the motor through the medium of a countershaft, and the power and speed are controlled from the switch board seen at the left of the exhibit, and in Fig. 11. The resistance, R1, serves to vary the intensity of the shunt field of the dynamo, the volts being indicated by the voltmeter V1, and a resistance separate from the switch board is inserted in the main circuit of the two machines. The ammeter, A2, is directly connected to the dynamo, and therefore indicates the current, whatever circuit this machine is running.

A larger combined engine and dynamo, seen in the center of the stand, serves to run the lighting of the galleries. The engine is a 60 horse power compound, running at 350 revolutions, and fitted with a governor on the fly wheel, like that described above.

The dynamo is a two-pole machine, the upper pole and yoke being cast in one, and the lower pole, yoke, and combined bed plate forming a separate casting. The two vertical cores, over which the field bobbins are slipped, are of wrought iron, and are turned with a shoulder at either end, the yokes being recessed to fit them exactly. The cores are then bolted to the yokes vertically from the top and horizontally below. The field of this machine is shunt-wound, and in order to maintain the potential constant a hand-regulated resistance—R2 on the switch board—is added in circuit with the shunt field. The voltmeter, V2, immediately above this resistance, serves to indicate the difference of potential at the machine terminals. Both voltmeters are fitted with keys, so that they are only put in circuit when the readings are taken.

The main terminals of this machine are fitted on substantial insulating bases, fixed one at each end of the top yoke. These connect to the external circuit by a heavy cable—the machine being capable of developing 500 amperes—and to the shunt circuit, and regulating resistance by small wires; while the two connections to the brushes are by four covered wires in parallel on each side. This mode of connection is more flexible than a short length of heavy cable, and looks well, the wires being held neatly together by vulcanized fiber bridges. The dynamo is a low tension machine, the field being regulated to give 65 volts when running the lamp circuits.

The illustration, Fig. 10, represents the automatic re-regulator—C.E.L. Brown's patent. Motion is imparted to the cores of two electro-magnets at the ends by the pulleys, W W1. The cores have a projection opposite to the spindle, a b, which latter is screw-threaded. By a relay one or other electro-magnet is put in action, and the rotating core, which is magnetized, causes rotation of the spindle by attraction, resulting in the movement of the contact along the resistance stops. The relay is acted upon directly by the potential of the dynamo, and the variable resistance is included in the shunt field of the machine, so that changes in the potential, resulting from changes in load or speed, are compensated for.

The arrangements of the lamp circuits and the lamp itself may now be described. The lamps are all run in parallel circuit, but are divided into groups of five, each group being controlled by a separate switch on the board—Figs. 11 and 11a. These switches are not in direct communication with the dynamo, but make that connection through a large central switch, S2, which therefore carries the whole current. The returns from each group are brought to the connections seen between the two resistances, where the circuits may be disconnected if desired, and the main current then passes through the ammeter, A3, to the other terminal of the machine. One of the smaller switches at the top, Fig. 11a, is directly connected with one terminal of the 20 horse power dynamo before mentioned, and the other side of the switch to the motor in the machine tool exhibit. Also one of the switches in connection with the central switch, S2, is connected to the same motor, and therefore the latter may be run by either machine, or, in fact, any combination of machines, lamps, and motor be made as required.

The form of switch made by the Oerlikon Works is illustrated in Fig. 7. Two thick semicircular bands of copper are screwed at one end to opposite sides of a square block which is turned round by the switch handle. The block has a projection at each corner, and two strong, flat, stationary springs are attached to the framework of the switch and press on opposite sides of the block. The ends of the springs engage in the projections and prevent the switch being turned round the wrong way, while the pressure of the springs on opposite sides forces the copper bands to take up a position exactly in line with the terminal contacts when the switch is closed, or at right angles to them when it is opened.

Further, each lamp has its own separate adjustable resistance, fuse, and switch. These are of special construction, combined in one, and are illustrated in Figs. 4 and 4a; the other figures, 4b and 4c, showing some of the details of the same. The wires, W W, lead from and to one lamp. The current enters at one wire, passes through the fuse, f—Figs. 4c and 4a—down the center of the cylinder to a divided contact, into which a switch arm can be shot. When this is so, a connection is made to the upright brass rod, T, which serves to grip the band, R, passing round the body of the cylinder. The current then passes through all the turns of wire above the band, and out at the other terminal. The resistance can be varied by raising or lowering the band. Fig. 4b shows the manner of tightening the band against the wires on the cylinder. The upright rod, T, is seen in section, and is fixed in one position to the frame of the apparatus. Abutting against this, and working in the block to which the two ends of the band are screwed, is a thumb screw, S, by turning which the band may be loosened for adjusting, and tightened when the right position is found. The cylinder is covered with asbestos sheet, and the wire, which is of nickel, and measures altogether from 3 to 4 ohms, is wound helically round this. The switch arm, to which the handle is attached below, does not itself make and break the circuit, but carries a spring, as shown, which, when the arm is at the end of its movement, pulls over the contact lever with a rapid action, shooting the same between the divided contact piece, and making a perfect contact. The switchboard forms one side of a closed wooden case or cupboard, with sufficient room for a man to enter and adjust the resistances or switches for each lamp. These are screwed to the inside of the case in rows, to the number of twenty-five. The greatest care has been taken in the fixing of the connections to the inside of this case, and no leading wires of different potential are allowed to cross each other.

The Oerlikon lamp, which is designed to work with constant potential, is shown partly in section in Fig. 8. There is only one solenoid, A, through which all the current passes, and whose action is to strike the arc and maintain the current constant. The soft iron core, C, is suspended from the inside of the tube, T, in which it has an up and down movement checked by an air piston in the tube. An end elevation of the brake wheels and solenoid is given in Fig. 9, where it will be seen that the spindle carrying these wheels also carries between them a pinion engaging with the rack rod, R. The top carbon attached to the rack rod falls by its own weight, and is therefore in contact with the lower carbon before the lamp is switched in circuit. When this is done the core is instantly magnetized, and attracted to the soft iron brake wheels, which it holds firmly. The air cushion in the tube prevents the core being drawn up until it has fairly gripped the sides of the wheels. The subsequent raising of the core therefore turns the wheels, raises the rack rod, and strikes the arc. The feed is operated by the weakening of the magnetic field of the coil, which causes the core to lose its grip of the wheels, and allows the top carbon to descend. The catch, L, Fig. 8, has a lateral play, and serves to engage in the teeth of the rack rod, so as to prevent its falling when being trimmed. Each carbon when in position is held against two rectangular guide bars by the pressure of a wire spring—see figure. In this way the carbon is pressed against two parallel knife edges, and is therefore always in true alignment. The action of the lamp is very simple, the working parts are few and solidly constructed, and the regulation, as exhibited by the lamps running in the galleries, is exceptionally steady.

The transmission of power plant consists of two 250 horse power dynamos—C.E.L. Brown's patent—the generator being driven by a vertical compound condensing engine of the same power, running at 180 revolutions. The dynamo generator is a four-pole 600 volt direct current machine, series wound, and may be distinguished in the engraving next to the switch board; while the motor receiver connected to it, and erected in another portion of the Swiss section, is of exactly the same size and type. The field, which is hexagonal in shape, is cast in two pieces, bolted together horizontally, the cross-sectional area of iron being 170 square inches. The armature is cylindrical, and built up of flat rings stamped out of soft sheet iron, eight notches in the same being provided to fit over the arms of the spider keyed to the shaft. The spider is in halves, which are bolted together longitudinally after the rings are in position. It is Gramme wound, and measures over the winding 7 in. radial depth, 37 in. outside diameter, and 22 in. in length. The current is collected by four brushes. The fitting and mechanical build of the dynamos leaves nothing to be desired. All the working parts of the dynamos and engines are turned up to gauge and template, so as to be interchangeable. As an instance of this, the armature of the generator was built in the works, while the field magnets were being erected in the exhibition, and, on arrival, fitted in position perfectly, and ran at once without trouble.

The energy taken off on the motor shaft is close on 200 horse power, but varies according to the machines at work; the speed of the motor does not, however, vary more than 3 per cent., and the brushes need no adjustment. About 6 ft. of shafting is coupled on in line with the motor shaft, and an extra plummer block fixed at the end. This shafting carries at its extremity an additional 2 ft. pulley, the power being delivered by belting from these pulleys to two large pulleys on the main shaft.

The machines run by this transmission consist of the looms of Rieter & Co., of Winterthur; the large flour mill and lift of A. Millot & Co.; the flour milling machinery of Frederick Wegmann & Co., of Zurich; the brick and tile making machines of the Rorschach foundries; and the looms of Messrs. Houget & Teston, of Verviers, in the Belgian section. A 15 horse power two-pole Oerlikon dynamo is also run by a belt from the main shaft, and generates power to drive a motor of similar type in the Swiss section of the upper gallery. This runs a length of countershafting supplying power to three silk-weaving machines constructed by Benninger Frères; six weaving machines from the Ruti works, near Zurich; and one knitting machine exhibited by Edward Dubied & Co., of Couvet.

The dynamo and motor are connected to the main cable by switches of the type shown in Fig. 5. These are specially designed to destroy the extra current on breaking circuit by the formation of an arc which gradually increases the resistance till the break occurs, rendering it less sudden. One wire passes through the handle and makes contact with the springs, and the other is attached to the clamp in which the carbon rod is held. The current is made to enter at the carbon rod, so that the arcs formed cause consumption of the carbon. A magnetic cut-out—Fig. 6—is also provided to each machine; this consists of an electro-magnet, through which the main current passes, provided with side pole pieces. A flat soft iron plate armature is hinged so as to come up against the pole pieces when attracted. When the current is not sufficiently strong to cause the plate to be attracted, a hole in the center of the latter engages over a small projection in the top of a weighted arm hinged in the center of the board, and keeps it upright. If now the current exceeds the limits of safety to the machine, due to a too heavy load being thrown on, the armature is attracted and releases the vertical arm, which falls over and enters with considerable force between the two spring contacts below. These contacts are connected to the field terminals, which are, therefore, short-circuited, and prevent the dynamo generating any current. A retractile spring can be adjusted to cause cut-off at any required current. These details are indicated in our illustrations mounted on their respective switch boards.

Since the erection of plant by these works at Solothurn for transmitting 50 horse power five miles distant, which attracted so much interest some time ago, several important works have been carried out. Among these we may mention a 280 horse power transmission at 1½ kilom. distance to a cotton mill at Derendingen in Switzerland, a 250 horse power transmission at ½ kilom. distance, carried out for Gaetano Rossi at Piovene in Italy, and a 300 horse transmission at 6 kilom. distance installed for Giovanni Rossi, in which the power is given off at two different stations.—The Engineer.

About HackerNoon Book Series: We bring you the most important technical, scientific, and insightful public domain books.

This book is part of the public domain. Various (2004). Scientific American Supplement, No. 711, August 17, 1889. Urbana, Illinois: Project Gutenberg. Retrieved https://www.gutenberg.org/cache/epub/16972/pg16972-images.html

This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at www.gutenberg.org, located at https://www.gutenberg.org/policy/license.html.