CHAPTER V.

THE DYNAMO AND ITS APPLICATIONS. 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. Until about 1865 the voltaic battery, which generated electricity by chemical decomposition, was practically the only means for producing electricity for industrial and commercial purposes. It was through its agency that the telegraph, the electric light, and many other discoveries in electricity were made and rendered possible. Its cost and limited amount of current, however, restricted the limits of its practical application, and although its current could furnish beautiful laboratory experiments, its mechanical work was more in the nature of illustration than utilization. But with the advent of the dynamo electricity has taken a new and very much larger place in the commercial activities of the world. It runs and warms our cars, it furnishes our light, it plates our metals, it runs our elevators, it electrocutes our criminals; and a thousand other things it performs for us with secrecy and dispatch in its silent and forceful way. But what is a dynamo? To the average mind the most satisfactory answer would be--that it is simply a machine which converts mechanical power into electricity. Attach a dynamo to a steam engine, and the power of the steam engine will, through the dynamo, become transformed or converted into a powerful electric current. Any other source of mechanical power, such as a water wheel, gas engine, wind wheel, or even a horse or man, will serve to operate the dynamo; its primary and sole function being to take power and convert it into electricity. The stepping stone to the dynamo in its development was the _magneto-electrical machine_. This is a machine founded upon the general principle observed by Faraday in 1831 and 1832, and also by Prof. Henry about the same time, that when a magnet is made to approach a helix of insulated wire it causes a current of electricity to flow in the helix as long as the magnet advances. If the magnet is passed through the helix, the current is reversed as soon as the magnet passes the middle point. The principle is the same if the magnet be made to approach and recede from the poles of an electro-magnet having a helix wound around a soft iron core. Likewise the same result occurs if the electro-magnet with its helix is made to approach and recede from a permanent magnet, the current in the helix flowing in one direction when it approaches the permanent magnet, and in the opposite direction when leaving the said magnet. The movement of the two elements in relation to each other requires some force to overcome the repellent and attractive actions, and this force is converted into electrical energy. This is the principle of the magneto-electric machine. [Illustration: FIG. 17.--PIXII MAGNETO-ELECTRIC MACHINE, 1832.] Saxton in the United States and Pixii in France were the first to produce organized devices of this class for generating electricity from magnetism. Pixii’s machine (1832) consisted of a permanent horse-shoe magnet which was caused to revolve in proximity to an armature upon which was wound a coil of insulated wire. On March 30, 1852, Sonnenberg and Rechten obtained a United States patent, No. 8,843, for an electrical machine for killing whales, and on August 19, 1856, Shepard obtained U. S. Pat. No. 15,596 for the machine which came to be known as the “Alliance” machine. Both of these machines had permanent field magnets, and were early types of magneto-electric machines. The efficiency of these magneto-electric machines was necessarily limited to the strength of the inducing field magnets, which, being permanent magnets, were a positive and fixed factor. It was an easy step to substitute electro-magnets for permanent magnets, as the field or inducing magnets, and also to excite the (electro) field magnet by voltaic batteries, but the important step which resulted in the machine which is called the “dynamo” (from the Greek “Δυναμις”--power) was yet to come. [Illustration: FIG. 18.--HJORTH’S DYNAMO ELECTRIC MACHINE.] [Illustration: FIG. 19.--HJORTH’S DYNAMO ELECTRIC MACHINE, PLAN VIEW.] This step consisted in taking the current induced in the revolving helix or armature (by the field magnets) and sending it back through the coils of the field magnets which produced it, thereby increasing the energy of the field magnet coils, and they in turn with an increased efficiency and reciprocal action induce still stronger currents in the armature coils, and so a building up process, or principle of mutual and reciprocal excitation, is carried on until the maximum efficiency is reached. This principle was the discovery of Soren Hjorth, of Copenhagen, and is fully described in his British patent, No. 806 of 1855, for “An Improved Magneto-Electric Battery.” As the prototype of the dynamo, it is worthy of illustration. In the illustration, Figs. 18 and 19, _a_ is a revolving wheel bearing the armature coils, _C_ permanent magnets, _d_ electro-magnets (field magnets), and _g_ the commutator. Quoting from his specifications, he says: “The permanent magnets acting on the armatures brought in succession between their poles, induce a current in the coils of the armatures, which current, after having been caused by the commutator to flow in one direction, passes round the electro-magnets (field magnets), charging the same and acting on the armatures. By the mutual action between the electro-magnets and the armatures an accelerating force is obtained, which in result produces electricity greater in quantity and intensity than has heretofore been obtained by similar means.” Although the principle of the dynamo was clearly embodied in the Hjorth patent, its value was not appreciated until some time later. Eleven years later Wilde (U. S. Pat. No. 59,738, Nov. 13, 1866), employed a small machine with permanent magnets to excite the coil-wound field magnets of a larger machine. But Siemens (British Pat. No. 261 of 1867), taking up the principle employed by Hjorth, dispensed with his superfluous permanent magnets, having found that the residual magnetism, which always remained in iron which has once been magnetized, was sufficient as a basis to start the building up process. Farmer, Wheatstone and Varley also recognized this fact about the same time. Siemens’ patent also was the first embodiment of what is known as the bobbin armature. Gramme and D’Ivernois (British Pat. 1,668 of 1870, and U. S. Pat. No. 120,057, of Oct. 17, 1871), were the first to bring out the continuously wound ring armature. Active development now began in various types and by various inventors, including Weston, Brush, Edison, Thomson and Houston, Westinghouse, and others, who have brought the dynamo to its present high efficiency. The revolving coils of the dynamo are called the armature, and the fixed electro-magnets are called the field magnets, and these latter may be two or more in number. When two are used they are arranged on opposite sides of the armature, and form what is known as the bipolar machine. A larger number constitutes the multipolar machine. The field magnets in the multipolar machine usually are arranged in radial position around the entire circumference of the revolving armature, and are held in a fixed circular frame. To give a clear idea of the principles of the dynamo, the bipolar machine is best suited for illustration, and is here given in Figs. 20 and 21, in which Fig. 20 represents the dynamo complete, and Fig. 21 a detail of the end of the armature and commutator. This armature consists of coils or bobbins of insulated wire, each section having its terminals connected with separate insulated plates on the hub, which plates are known as the commutator. When any section of the armature approaches the pole of a field magnet, the current induced in that section of the armature coils by the field magnet, is taken off from a corresponding plate of the commutator by flat springs, seen in Fig. 20, and known as brushes. The field magnets A and B, Fig. 20, are shown with only a few turns of wire about them for clearer illustrations of the connections, which are made as follows: The wire _a_ is extended in coils around the field magnet B, and thence around field magnet A, and thence to the upper brush on the commutator, thence through the wire coils or bobbins of the rotary armature C, and thence by the lower brush to the wire _b_. The terminals of the wires _a_ and _b_ extend to the point of utilization of the current, whether this be electric lights, motors, or other applications. In this illustration, the circuit, it will be seen, passes through both the coils of the field magnets and the coils of the armature, involving the principle of mutual excitation. [Illustration: FIG. 20.--BIPOLAR DYNAMO.] There are two principal kinds of dynamos--those producing the alternating currents, and those producing the continuous current. In the first the current alternates in direction, or is composed of an infinite number of impulses of opposite polarity: one polarity when a section of the armature coil is approaching a north field magnet pole or receding from a south pole, and the other polarity when receding from a north field magnet pole and approaching a south pole. In the continuous current machine, the commutator and brushes are so arranged as to take up all the impulses of the same polarity and conduct them away by one brush, and gathering all the impulses of the opposite polarity and conducting them away by another brush. Thus the current of each brush, in the continuous current machine, is always of the same polarity, and the polarity of one being always positive, and that of the other negative, the current flows continuously in the same direction. A third species of dynamo is the pulsatory, in which the current flow is invariable in direction, but proceeds in waves. [Illustration: FIG. 21.--ARMATURE OF BIPOLAR DYNAMO.] A change in the character of the current generated by the dynamo is made by what is known as the “transformer,” in which the principle of the induction coil is made available. In this way, for instance, the high potential currents generated by the powerful water wheels at Niagara Falls are taken twenty miles to Buffalo, and are there transformed into other currents of lower potential, suited to incandescent lighting and other various uses. A similar scheme is in process of fulfillment in the establishment of a water power electric plant near Conowingo, Maryland, on the Susquehanna River, to furnish electrical power to Baltimore, Wilmington and Philadelphia. An important development in electrical generation and transmission is to be found in what is known as the _polyphase_, _multiphase_, or _rotating_ current, pioneer patents for which were granted to Tesla May 1, 1888, Nos. 381,968, 381,969, 382,279, 382,280, 382,281 and 382,282. Realizing the possibilities of the dynamo, the Legislature of New York in 1888 passed a law, which went into effect in 1889, in that State, substituting death by electricity for the hangman’s noose. The criminal is strapped in the chair, seen in Fig. 22, one terminal of the wire from the dynamo is strapped upon his forehead, and the other to anklets on his legs, and like a flash of lightning the deadly energy of the dynamo performs its work. Not the least of the applications of the dynamo is its use in electro-metallurgy for plating metals, and also for promoting chemical reactions. The electric furnace, stimulated into higher heat by the dynamo than can be otherwise obtained, has brought about many valuable discoveries, and made great advances in various arts. The metal aluminum, and the hard abrasive or polishing and grinding material known as “carborundum” are the products of the electric furnace, and so is the product known as “calcium carbide,” which, when immersed in water, gives off acetylene gas and is a product now universally used for that purpose, and rapidly increasing in commercial importance. [Illustration: FIG. 22.--ELECTROCUTION CHAIR.] In Fig. 23 is seen the Acheson electric furnace for producing carborundum. The electric current traverses the furnace through a series of horizontal electrodes at each end, and highly heats a central core of carbon, which is disposed in a mass of silicious and carbonaceous material, and which latter is converted by the heat into silicide of carbon, or carborundum. In Fig. 24 is shown a continuous electric furnace constructed as a revolving wheel, under the Bradley patents. Rim sections 5 are placed on the wheel on one side and filled with a mixture of carbon and lime, through which the electric current is passed from the dynamo _g_. The heat of the current fuses the mass and converts it into calcium carbide, and as the wheel slowly revolves the rim sections 5 are removed from the opposite side, and the mass of calcium carbide, seen at _x_, is broken off. The electrolytic production of copper through the agency of the dynamo amounts to 150,000 tons annually, and the commercial reduction of aluminum by the electric furnace has grown from eighty-three pounds in 1883 to 5,200,000 pounds in 1898, and its cost has been reduced to about 33 cents per pound. [Illustration: FIG. 23.--PART SECTIONAL VIEW OF CARBORUNDUM FURNACE.] The storage battery, holding in reserve its stored up electric energy, also owes its practical value entirely to the dynamo which charges it, and thus makes available a portable source of supply. [Illustration: FIG. 24.--BRADLEY ELECTRIC FURNACE FOR PRODUCING CALCIUM CARBIDE.] To contemplate the dynamo with its clumsy, enormous spools, it suggests to the imagination of the average observer the gigantic toy of some Brobdingnagian boy--but the dynamo is no toy. It is the most compact, business-like, and dangerous of all utilitarian devices. To touch its brushes may be instant death, for the dynamo is the prison house of the lightning, and resents intrusion. Hidden away from public gaze in some sequestered power house, and working night and day like some tireless, dumb, and mighty genii, it sends its magnetic thrills of force silently through the many miles of wire extending like radii from some great nerve center through the conduits in our streets, and stretching from pole to pole like giant cobwebs through the air. Responding to its force, thousands of little incandescent threads leap into radiant brightness and shed their mellow and genial light in our offices, our stores, hotels, and homes. Brilliant arc lamps, rivaling the sun in power, make night into day, and produce along our streets coruscations, silhouettes, and dancing shadows in spectacular and unceasing pageants. From the towering lighthouses of our coasts its beams are thrown seaward, and a beacon for the mariner shines beyond all other lights. The great search light of our ships is in itself but a hollow mockery until the dynamo whispers in its ear the word “light!” and then its beam, reaching for miles along the horizon, discovers a stealthy enemy, or signals the safe return to port. The mighty force of the dynamo entering the electric motors on the street cars turns the wheels and transports its load with scarcely a passenger inside realizing how it is all done. The same energy turns the electric fan, and with kindly service soothes the weary sufferer, and at another place remorselessly takes the life of the condemned criminal. The dynamo is one of the great factors of modern civilization, and its potential name, like that of “dynamite,” rightly defines its character. [Illustration: FIG. 25.--MODERN MULTIPOLAR DYNAMO.]