Electrical machinery

“ The current for power purposes is generated in a large stationary armature about ten feet in diameter and of the same depth as the revolving ring. The revolutions of the ring send out currents of alternating polarity, and each of the ten machines will furnish electrical energy equal to 5000 horse-power, so that when the work that is now under way is completed 50,000 horse-power can be furnished in the form of electricity. About 35,000 horse-power is now actually delivered to the various industrial enterprises. ”

“ CHAPTER LIII.—THE ELECTRICAL MACHINE, AND HOW TO MAKE IT. In our chapter on the Leyden Jar we assumed that those of our readers who were likely to experiment in frictional electricity would be in possession of an electrical machine to start with. Many, however, may be desirous of building an electrical machine of their own. ”

“ Every one knows that when by means of an ordinary electrical machine electricity has been generated in sufficient quantity and under suitable conditions to prevent its dispersion, a spark of intense brilliancy and greater or less length, according to the amount of electricity thus collected, can be obtained when some body, not similarly electrified, is brought near to what is called the conductor of the machine. ”

“ In the electrical machines already described sparks occur whenever the carrier comes in contact with a conductor at a different potential from its own.
Now we have shewn that whenever this occurs there is a loss of energy, and therefore the whole work employed in turning the machine is not converted into electrification in an available form, but part is spent in producing the heat and noise of electric sparks. I have therefore thought it desirable to shew how an electrical machine may be constructed which is not subject to this loss of efficiency. ”

“ The electrical machines in common use are composed of a hollow glass cylinder, or circular plate of glass, turning on an axis, and rubbing against two or more leather rubbers covered with silk, the electricity being collected by sharp points fixed in a metal rod standing on a glass pillar. ”

“ Replace it, and let the cylinder be again wiped; the machine is fit for use.
4. Sometimes the electric matter will not be well collected, because the machine is not sufficiently supplied with it from the earth; which happens, when the table upon which the electrical machine is placed and to which the chain or wire of the rubber is connected, is very dry, and consequently a bad conductor. In this case, the best method is to connect the chain or wire of the rubber with some moist ground, or with the iron-work of a water-pump, if convenient. ”

“ Observations of Faraday and Henry—Magneto-Electric Machines of Pixii and of Saxton—Hjorth’s Dynamo of 1855—Wilde’s Machine of 1866—Siemens’ of 1867—Gramme’s of 1870—Tesla’s Polyphase Currents.
In the last thirty-five years of the Nineteenth Century there has grown up into the full stature of mechanical majority this stalwart son of electrical lineage. As the means for furnishing electrical power it stands to-day the great fountain head of electrical generation, and in its peculiar field ranks as of equal importance with the steam engine. ”

“ On account of this very low electrical pressure all danger from the current is eliminated and the apparatus may be handled with the same freedom as any ordinary metal-working machine. In the distribution of the electrical appliances the current is usually generated by a machine conveniently located with reference to the source of power, and the current carried by wires to the welders, where the transformation takes place, each welder being provided with its own converter, proportioned so as to supply the character of current best suited to the special work of the machine. ”

“ If the needle can be soldered to a metal stand, or the cork covered with tinfoil, the wire is not needed. On rubbing the paper and placing it on the tray, the electricity passes up the wire into the needle, thence into the wire cross, and escapes by the bent portions of the wires, each of which should be filed to a point. In escaping it electrifies the surrounding air, and this, according to the law that “like electricities repel each other,” has a reacting force on the wire arms. Accordingly the windmill begins to turn, and may attain a tolerable rate of speed if the tray is strongly charged. ”

“ The Plate Electrical Machine. Fig. 7 also shows an old form of machine. Such machines are made of circular plates of glass or ebonite, two rubbing pads being usually employed, one on each side of the plate. One operator is seen on an insulated stool (Fig. 7) , the electricity passing through him before entering the earth by way of the body of the man at the right.
Fig. 8.
11. The Toepler-Holtz Machine, in one form, is shown in Fig. 8. The electricity is produced by the principle of induction, and not by mere friction. This machine, used in connection with condensers, produces large sparks. ”

“ The rays were very powerful, so powerful that they required triple power generators, but the special field of electrical force was the worst problem. The field could not be made sufficiently strong if a single layer of the force was used, but the invention of a method to back up the first with two other layers of equal voltage, thus getting nearly three times the effect without exceeding the capacity of the insulation, had made the new machine possible. ”

“ To begin with, you all know that a piece of machinery is usually made to work by revolving a wheel which is part of the machine, either by means of a steam-engine or by water-power, or, as a sewing-machine, by foot-power. Now, when we work a piece of machinery by electricity we do just the same thing by using, instead of the steam-engine or water or foot power, an electric-engine called an "electromotor," which operates in the same way—namely, by turning the wheel of the machine it is applied to. ”

“ As, however, an understanding of the how and the why of the dynamo-electric machine or generator is the very A B C of electrical engineering, an exposition of the fundamental principles of the mechanical production of electric currents demands an important place in the current science of the day. It will be our endeavor to expound these principles in the plainest terms, while at the same time sacrificing nothing in point of scientific accuracy or of essential detail. ”

“ Fig. 175. The Leyden jar and brass wire discharger.
Thirty-sixth Experiment.
The jar is silently discharged if the balls are removed from the discharger and points used instead; so, also, the whole of the electricity produced by an electrical machine in full action may be readily drawn off by a pointed conductor, such as a needle, placed at the end of a brass wire. Electricity passes much more rapidly through points than rounded surfaces, hence the reason why all parts of electrical apparatus are free from sharp points and rough asperities. ”

“ Having described the electrical machine, we are now to consider some of the phenomena attending its operation. When the prime conductor receives electricity from the cylinder, it is said to be electrified by communication, and it then acts in every respect like the cylinder itself, except that the latter, when touched by a conductor communicating with the earth, gives a considerable number of sparks before it is discharged; whereas the conductor discharges itself by a single spark. ”

“ As designed for power work and generally for lighting service, the brushes of each machine are set at the neutral point in order to get the best results for operating alternately either as a generator or motor. ”

“ When but one of the machines is running, the idle machine is brought up to speed with the main switch open, and the voltage regulated by means of the rheostat and voltmeter until the voltages of the machines are the same. Then the main switch is thrown in and the load on the machines (which is ascertained by the ammeters) is equalized by means of the rheostats. Should there be any great difference in voltages, the higher one will run the other as a motor without changing the direction of rotation. ”

“ We cannot walk across a dry carpet, or run the hand along a piece of furniture, without producing some slight electrification which has the effect of setting up potential differences between different points of space, and, as the merest trace of such a potential difference suffices to start the cumulative process, machines of the Wimshurst type generally start without the necessity of previous electrical excitation. ”

“ He showed that all substances could be electrified by friction, but that to electrify conductors they must be insulated or supported on non-conductors. Various improvements were made in the electrical machine, and thereby experimentalists were provided with the means of generating strong electrification ”

“ The men who have made electricity the handmaid of industry are nearly as widespread as the subtle force with which they have had to deal. The United Kingdom was the birth-place of the monarch of modern machinery—the steam-engine,—and also of the leading inventions in metallurgy which supply the framework of all our manufacturing machinery; but the pioneers and engineers of electricity have been of different nations and tongues. ”

“ Thus in paper-making machinery, where the band of paper passes at high speed over hot metal rolls, it may become electrified to the extent of sparking and igniting itself. To avoid this danger it is necessary to fix spiked combs, which draw off the charge as soon as generated. In all these cases the electricity produced by friction is only an inconvenient by-product of some other operation; but if we wish to produce electricity for experimental work we may use special appliances based on the principle of electrification by friction. ”

“ Collecting Ring.
In some kinds of generators instead of the commutator a pair of
collecting rings of metal, insulated from the machine and from each
other, are carried on the armature shaft. A brush, q. v., presses on
each, and the circuit terminals connect to these two brushes. Such rings
are employed often on alternating current generators, where the current
does not have to be changed or commuted. Collecting rings with their
brushes are used also where a current has to be communicated to a
revolving coil or circuit as in the magnetic car wheel, the cut of which
is repeated here. ”

“ The machine gets charged after a few turns of the handle, and the operator feels that, as the charging progresses, it gets harder to turn the handle. In large machines the manual work becomes so heavy that it is convenient to use an electric motor for working the machine. ”

“ The framework of the machine is now complete, and we have to provide the glass plate from which the electricity is to be produced. As we cannot make this we must apply to an electrician for it. This is 10 inches in diameter. If the maker is good at, and has appliances for, working in brass on a small scale, he can make the axle himself by taking a [Pg 5] piece of brass rod 1⁄4 inch in diameter and 3 inches long and fastening the glass plate in the center. ”

“ Their powers may be enormously increased by covering them with amalgam, as sold in the electrical shops, but a far better plan is to cover the cushions with tinfoil, which can be glued right round the rubbers and over the backs. ”

“ If the electrical stand be kept clean and dry, a man standing on it when such clouds are passing low, might be electrified and afford sparks, the rod drawing fire to him from a cloud. If any danger to the man should be apprehended (though I think there would be none) let him stand on the floor of his box, and now and then bring near to the rod, the loop of a wire that has one end fastened to the leads, he holding it by a wax handle; so the sparks, if the rod is electrified, will strike from the rod to the wire, and not affect him. ”

“ At the plant or plants where the power transmitted by continuous current is received, a number of motors must be connected in series to operate at the high-line voltage. These motors may all be located in a single room, may be connected to machinery in different parts of a building, or may be in use at points miles apart. ”

“ Of the feasibility of economically distributing the electric current there is a growing confidence among electricians, and the advantages of so transmitting power have been frequently urged of late, not only for moving light machinery, but for doing all the work now done in our factories by the steam-engine. ”

“ The tray will consequently speedily lose its electricity. It will be found to be impossible to get a spark from the tray as long as the needle is on it, as the electricity vastly prefers to escape by the point. The escape of the electricity may be rendered still more evident by means of the following piece of apparatus.
Take two pieces of thin wire about two inches long, and bend each at right angles about an eighth of an inch from each end, both the bent portions being in the same direction. ”

“ A machine at Niagara receives mechanical power, and generates electricity. Call this the generator. Let there be Wires to another electric machine in New York, which will receive electricity, and give out mechanical work. Now this machine, which may be called the motor, produces a back electromotive force, and the mechanical power given out is proportional to the back electromotive force multiplied into the current. ”

“ The machine well illustrates how mechanical work may be changed into electricity, and electricity caused to do work. The power required to drive the machine at a given speed is much less when no current is being drawn from it, than when the current is flowing. If the current from one machine is sent through the armature of another, the latter revolves, and may be made to do work. Thus power may be conveyed to a distance by electricity, with only the loss caused by the resistance of the conducting wires. ”