Part 1

Produced by Chris Curnow, Paul Marshall and the Online Distributed Proofreading Team at http://www.pgdp.net (This file was produced from images generously made available by The Internet Archive)

Transcriber’s Notes:

Underscores “_” before and after a word or phrase indicate _italics_ in the original text. Carat symbol “^” designates a superscript. Small capitals have been converted to SOLID capitals. Illustrations have been moved so they do not break up paragraphs. Typographical errors have been silently corrected but other variations in spelling and punctuation remain unaltered.

HISTORY OF THE TRANSFORMER.

BY F. UPPENBORN,

EDITOR OF THE “CENTRALBLATT FÜR ELEKTROTECHNIK,” AND CHIEF OF THE ELECTRO-TECHNICAL TESTING STATION IN MUNICH.

_TRANSLATED FROM THE GERMAN._

E. & F. N. SPON, 125, STRAND, LONDON. NEW YORK: 12, CORTLANDT STREET. 1889.

PREFACE.

As of late the employment of alternating current transformers has largely increased and become of great importance, indeed as they are called upon to play a striking part in electric lighting from central stations, the author has thought a short notice of the development of this invention would possess some interest. This task appeared to be so much the more pressing, as many distorted versions of the invention and its priority have found place in the technical journals.

The author has not let the reading of the large number of patents discourage him, and hopes that the following plain and concise statement of these researches will contribute towards the forming of a correct judgment as to the services rendered by the several inventors.

THE AUTHOR.

HISTORY OF THE TRANSFORMER.

As we wish to write of those discoveries which led up to the invention of the transformer, we must go back to a time, old as compared with the modern development of electrotechnics. For the starting-point of our observations we shall take Faraday, who, like Newton in mechanics, led the way in the domain of electricity, and whose name stands in the most intimate relations with all inventions for the mechanical production of the electric current, and therefore with the later development of electrotechnics.

[Sidenote: Faraday, 1831.]

The most important discovery for which we have to thank Faraday is that of induction. This discovery was made by him in the year 1831, and intimated to the philosophical world in a paper read on the 24th November, 1831, appearing in the Transactions of the Philosophical Society in the year 1832.

Faraday’s first induction apparatus consisted of two coils of wire, the one being slid over the other. As he was passing the current from a battery through one of these, he made the discovery that each time the circuit of the coil was opened or closed an electromotive force was created in the second coil, which caused a short gush of current or induction current to flow, provided the circuit of this coil was closed, as might be through a galvanometer. The peculiarity of this induced current was, that it only flowed in the second coil during the time the current in the first coil took to reach its normal strength after closing the circuit, or on breaking the circuit during the time the current took to decrease from its normal strength to zero.

This discovery undoubtedly belongs to the domain of the transformer, induction being the physical precedent upon which the transformer is based; indeed, a transformer is in principle an induction apparatus.

Fig. 1 represents the arrangement of this fundamental experiment. The primary coil is connected with the battery, the secondary with the galvanometer. The primary coil, in order to obtain the best effect, is placed inside the secondary, and on opening and closing its circuit the needle of the galvanometer is thrown to the one or the other side respectively.

The arrangement, as in Fig. 2, made by Faraday showed itself to be an especially effective combination for the production of these induction phenomena. There were wound round an iron ring two separate wires of about the same length. The one coil was brought into connection with a battery, and to the ends of the other a pair of electrodes were attached. The current from the battery being sent through the primary coil, lines of force were produced which ran almost altogether in the iron core. As the core possessed only a very small magnetic resistance, the intensity of magnetisation was very great, and on closing the primary circuit a strong inductive effect on the secondary coil was produced. Faraday obtained with this apparatus the first sparks of induction. The apparatus is all the more interesting as, although not completely without poles, it at least forms a closed magnetic circuit. It has much likeness to the non-polar transformer of Zipernowsky, Déri, and Bláthy, but it may be easily shown to be not entirely poleless. Poles mean, in electrical as well as magnetic circuits, those points between which the greatest difference of potential exists. A current without difference of potential can only flow in an electrical or magnetic circuit when the loss of potential in each part of the length of the circuit, viz., the product of resistance and current, is equal to the gain of potential, that is the magneto-or electromotive force; therefore a current without difference of potential requires that the resistance and magneto-or electromotive force in each part of the length be the same. Now the magnetic resistance of a symmetrical iron ring is constant in all parts of the length of its magnetic circuit. In the case in question only one half of the ring was excited, therefore poles must have been formed at both ends of the exciting coil. The ratio of transformation of this apparatus of Faraday’s was equal to unity, so it had therefore no claim to the designation of “transformer.”

The induction apparatus of Faraday in its simplicity was in a certain measure the embryo out of which all dynamos and transformers have developed. We have seen how the first induction current was discovered by making and breaking the current from a battery in the primary coil. This method was at first adhered to, until Faraday remarked that when the secondary was quickly drawn out of or put into the primary coil, induced currents were also produced without requiring to break the circuit, the wires of the secondary coil cutting the lines of force in the magnetic field of the primary coil. He then replaced the primary coil and battery by a permanent magnet, which was likewise dipped into the induction coil, Fig. 3.

[Sidenote: Henry and Page, 1836.]

From this, and from the later development of this invention, it follows that the question was not of a transformer in the present sense of the word, but of a secondary generator. Transformers as at present understood were first known in Europe as the Ruhmkorff’s induction coil. Before we take up this invention we shall mention a much earlier and like invention, which had already been made in the United States in the year 1838. This was the induction coil of Professor Page, and was the outcome of another invention by Professor Henry, whose apparatus was only a single induction coil. The first public notice of Professor Page’s apparatus appeared in the Silliman-Journal of 12th May, 1836, under the title, “Methods and trials of obtaining physiological phenomena and sparks from a heat engine by means of Professor Henry’s apparatus.” In May, 1837, Sturgeon published, in the “Annals of Electricity,” in London, a description of the apparatus of Henry and Page.

[Sidenote: Callan, 1837.]

Callan, an English student of physics in Minnoth, showed first, in the year 1837, that if high tension was wanted, it was necessary to employ thick wire for the primary and thin for the secondary coil. Before this time wires indeed of different lengths, but of equal cross sections, had always been employed. His apparatus was not so bad as those before known, but still stood far behind that of Professor Page.

[Sidenote: Page, 1838.]

The arrangement of Professor Page’s apparatus, which is shown in Fig. 4, was as follows:—Two coils of wire well insulated from one another were wound on to a bundle of iron wires. A self-acting contact-breaker was put into the primary circuit, and consisted of a double lever E, having on one of its arms two parts bent downwards, so as to dip into two mercury cups. The movement of the part H, as compared with that of E, was so small that it remained always in the mercury. At M, however, when the lever was set in motion contact was broken and made. To prevent oxidation Page poured in a layer of alcohol over the quicksilver.

The continuation of the lever in the other direction of the axis, which was borne by two pillars K, was bent backwards, and on its end carried a cylindrical piece of iron standing before the end of the bundle of iron wires. If the primary coil were now placed in connection with a source of current, the iron core became magnetised, attracted the cylindrical piece of iron to itself, and by raising the lever E broke the contact at M. The iron core then lost its magnetism, released the iron armature, and the play began anew. A counter-weight F, which could be shifted along another lever O, allowed the play of the contact-breaker to be regulated. It will be found that this interruptor was very like that constructed many years afterwards by Léon Foucault. The effects which Page produced by means of this instrument were much more intense than those produced by Ruhmkorff with his, as Page succeeded with only a single Grove element in inducing in the secondary circuit such a high electromotive force as produced sparks 4½ inches in length through a vacuum tube—a result that Ruhmkorff, although his invention created such a great and well-deserved attention, did not attain. In the year 1850 Page built a much larger apparatus.

In order to give some idea of the magnitude of the electro-magnetic forces which came into play here, suffice it to say, that the exciting coils could hold suspended in the air in their interior an iron core weighing 520 kg. The primary or magnetising coil was of square copper wire, with a side measuring ¼ inch, and a battery of 50 to 100 Grove elements was employed, the immersed area of the surface of the plates being 100 square inches. This apparatus gave sparks of great length. When, with maximum currrent strength, the primary circuit was broken, sparks of 8 inch length were received.

[Sidenote: Ruhmkorff, 1848.]

Ruhmkorff constructed, in the year 1848, the so-called spark-inducer named after him, the object of which was also to convert currents of low tension into hose of very high tension. With this coil and like coils of larger dimensions effects were produced, but only such as were afforded by the common forms of frictional electrical machines. All things considered, it is not a little surprising that while the invention of the Rhumkorff coil was still in its infancy, the wonderful output of Page’s apparatus was still, even in the year 1851, quite unknown in Europe.

Fig. 5 represents the earlier form of the Ruhmkorff apparatus. It consisted of a bobbin of good insulating material; thoroughly dried wood, or better, hard rubber. The two end pieces of the bobbin were usually made of grooved glass discs, and were bound down to the bedplate of the apparatus by two wires. Inside the coil was the already often-mentioned bundle of iron wires. The primary or inducing wire was next wound upon the bobbin. As this wire had to carry currents of comparatively great strength, it consisted of only one or a few layers of thick wire. The circuit of this coil was completed as far as two terminals on the bedplate, first passing through an interruptor like what has already been described. Over the primary coil, and after a sufficient layer of insulation had been added, the secondary wire was wound. As this wire was destined for very small currents, it was of as fine wire as it was possible to wind. In order to obtain high potential it was necessary that the secondary should possess many turns. In the earlier coils a length of between 8 and 10 kilometres was used; in the coils now made this length has been increased to between 50 and 70 kilometres. The ends of the secondary coil were connected to terminals insulated on glass pillars. It was not nearly sufficient insulation for the secondary wire to be covered with silk, but every layer was well soaked with dissolved shellac, and then well dried as it should be. A condenser in connection with the primary coil was placed under or in the bedplate, which was usually a box. This condenser was, and is still, often made thus:—On both sides of a strip of paraffined paper, several metres long and of convenient breadth, tinfoil is stuck, at the same time leaving a sufficient margin of paper for insulation. The whole is then folded together suitably. The effect of the coil is substantially enhanced when the sheets of tinfoil are each connected to the circuit of the primary coil in such a way that the condenser is in shunt to the interruptor.

In Fig. 6 is shown a newer form of Ruhmkorff’s coil, with an interruptor like the mercury contact-breaker which we have before described. According as the movable weight is raised or lowered, the oscillations of the lever, and consequently the induced currents, follow one another more slowly or more rapidly.

[Sidenote: C. T. and E. B. Bright, 1855.]

We find a further development or modification of the invention of Page and Ruhmkorff, patented by the brothers C. T. and E. B. Bright on 21st October, 1852, and No. 2103 in the year 1855. In the latter of these patents the inventors state what follows concerning the nature of their inventions.

“A section of an induction coil made after this manner is shown in fig. 7, having a very strong effect. The primary wire, of which only a part is shown, is wound on an iron core, and outside is surrounded by an iron cylinder. Both of these are metallically connected by the flanges of the bobbin, which also are of iron. The secondary coil may also be surrounded by an iron tube, and if the resistance of the circuit be extraordinarily great with still more primary coils, or it may be also contained in the same tube as the primary. In cases where it is found necessary to increase the quantity of the electro-magnetic effects, we find that the forms shown in Figs. 8 and 9 are very effectual, and may by varied on the same principle. The iron core in the middle is wound with the primary wire, and is surrounded by the other iron cores, which are fixed into the large flanges of the middle core, and carry the secondary coils. Should still greater effects be required, more primary or secondary coils connected in series with the others may be added outside, in order to produce a greater extension of the poles and a more extensive induction.”

This patent is interesting also for the fact that in it we find a disposition of parts, viz. the arrangement of several induction coils in ranks, and connected with one another in parallel, which nearly 30 years later was taken up and practically used by Gaulard.

[Sidenote: Harrison, 1857.]

Among the patents of the year 1857 there is an English one by Harrison, claiming as its object the passing of a primary current through one or more induction coils, and the connection of the secondary coils with the carbons of an arc lamp. There is nothing remarkable in the description.

[Sidenote: Jablochkoff, 1878.]

The last attempt to use induction coils for industrial purposes is met with in the year 1878. In this year Jablochkoff took out a German patent, which was also carried out in practice. He required currents of very high tension to feed his kaolin lamp; at that time such currents could only be produced by induction coils. He writes as follows in his patent:—

“Die Herstellung einer elektrischen Beleuchtung nach meinen System begreift eine Serie von Induktionsrollen in sich, wovon die inneren Drähte in eine elektrische Leitung eingeschaltet sind.”

Jablochkoff used intermittent direct currents as well as alternating currents. The arrangement shown in Fig. 10 was for the former. He states concerning this:—

“In diesem Falle sind die Induktionsrollen mit Unterbrecher und Kondensator ausgestattet, oder man kann auch, wie die Zeichnung nachweist, einen und denselben Unterbrecher für alle Rollen anwenden. Die Induktionsrollen B^1 B^2 B^3, nach einen beliebigen Prinzipe konstruirt, sind in der Nähe der Lichtherde angebracht.”

Concerning the employment of alternating currents, Jablochkoff says:—

“Diese Disposition weicht von der ersteren nur durch die Weglassung des Unterbrechers und des Kondensators der Rolle ab.”

“Die in Fig. 11 angewendeten Rollen sind in Fig. 12 detailliert gezeichnet. Auf einer kreisförmigen Scheibe C aus weichem Eisen erhebt sich in der Mitte derselben ein hohler Cylinder _b_ aus Holz oder anderem isolirten Materiale; um den unteren Teil des letzteren ist die Hauptspirale _a_ gewickelt, welche aus bandförmigen Kupferstreifen oder anderem Metalle besteht, _a′_ ist die in gleicher Weise zusammengesetzte Induktionsspirale, deren Drahtenden zu den Lichtherden führen. Zwischen den einzelnen Windungen der Spirale sind Streifen aus Papierkarton oder einem anderen isolirenden Material angebracht. Die Spirale a ist in die Hauptleitung, wie Fig. 11 zeigt, eingeschaltet.”

The second claim of this patent is also interesting, and reads as follows:—

“Die Einführung einer Serie von Induktionsrollen in den Umkreis eines beliebigen Elektricitätsgenerators zur Erzeugung einer Serie von Induktionsströmen, welche es gestatten, Lichtherde von verschiedener Intensität durch eine einzige Elektricitätsquelle zu versorgen, was zur vollständigen Teilbarkeit des elektrischen Lichtes führt.”

Jablochkoff’s system as just described was to be seen working in the Paris Exhibition of the year 1878. A proper industrial application of this system does not appear to have taken place.

[Sidenote: C. T. & E. B. Bright, 1878.]

In the year 1878 the brothers Bright had also made further progress in the use of induction coils for electric lighting purposes, and in the same year they took out the English patent No. 4212, in which they described the use of alternating currents for working secondary apparatus or induction coils placed at various points where light was required. We shall here quote some very interesting sentences from this patent, which again show that the brothers Bright knew already in the year 1878 the properties of transformers suiting them for electric lighting purposes; indeed they then anticipated the principles contained in the later patent of Gaulard. Here is an abstract from the description:—

“At each point where electric light is used, the electric lamps or groups of such lamps are fed by the secondary coil or coils of an induction apparatus placed there. The primary coils of all the induction apparatus are in the common circuit of one main lead, which is in connection with a battery or a magneto-electric machine placed in some suitable situation. The size and length of the primary and secondary coils of each induction apparatus is determined according to the number of lamps at each point, where the secondary current shall supply the electric lighting.”

[Sidenote: E. Edwards & A. Normandy, 1878.]

The employment of induction coils for the distribution of light, heat, and power was patented in England in the same year by Edmund Edwards and Alphonse Normandy. Among other matter in this patent there is as follows:—

“At or near every point where it is required that a light shall be produced, we arrange a coil (or series of coils) of insulated metallic wire or ribbon (preferably surrounding a bar or wires of soft iron), through which coil or coils the current from the principal wire first described can be passed when desired, or cut off by means of a key or lever. Round, or adjacent to, each coil of insulated wire described, we form one or more secondary coils of insulated metallic wire, or ribbon, arranged so that the passage of the rapidly intermittent current of electricity, as described, through the primary coil or coils, generates a corresponding current of electricity in each of the secondary coils.”

[Sidenote: Strumbo, 1878.]

In the same year, Strumbo had also constructed a secondary generator like that of Gaulard, and a description of it was contained in the newspaper ‘Le Monde,’ of 24th October, 1878. It is of note in this apparatus, which we have illustrated in Fig. 13, that the primary and secondary wires were wound side by side, and that both coils had the same relative position to the iron core.

[Sidenote: Harrison, 1878.]

Harrison also, in the same year, took out a patent having the same object as his of the year 1857. Both patents proposed the connection of induction coils in series. This is especially clearly mentioned in the latter of these, as there he says that both induction coils are put in circuit at intervals along the main lead, or primary circuit, so that one or more coils are near the places where lamps are to be fed.

[Sidenote: Meritens, 1878.]

We find in Meritens’ English patent, No. 5257, of the year 1878, the series connection of primary coils in the dynamo-circuit also described.

Meritens intended to employ, in place of the many separately insulated circuits of the alternating dynamos of that time, only a single circuit, fed from one large or several smaller dynamos. A large number of induction coils connected in series, were to have been distributed in the different districts of a city. Besides this, Meritens made a combination of the secondary coils, so that he was in a position to produce currents and potentials of various dimensions.

[Sidenote: Fuller, 1878.]

We now come to an inventor, who, in his time, exercised a great influence upon electric lighting by means of transformers, and whose system was in every way a great advance on those of his foregoers. This man was named Jim Billings Fuller. He began to study electric lighting in his laboratory at Brooklyn in the year 1874, giving his whole energy for this object. Fuller’s system of current distribution was first patented in America in the year 1878. The patent No. is 210,317, of 26th November, 1878. His apparatus is represented in Fig. 14. It consisted of an induction coil on which an electric lamp was mounted, to all appearances a Jablochkoff candle. The induction coil, to which we shall return later on, was built in the form of two horseshoe magnets joined together, and having consequent poles at the small coils in the middle, after the manner of the magnets of a Gramme machine. The four large coils are the primary or exciting, the four small coils on the poles of the double magnets are the secondary coils.