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Title: History of the Transformer
Author: Uppenborn, F.
Language: English
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Copyright Status: Not copyrighted in the United States. If you live elsewhere check the laws of your country before downloading this ebook. See comments about copyright issues at end of book.

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  Underscores “_” before and after a word or phrase indicate _italics_
    in the original text.
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    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._

                             [Illustration]

                 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.

[Illustration: FIG. 1.]

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.

[Illustration: FIG. 2.]

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.

[Illustration: 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.

[Illustration: FIG. 4.]

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.

[Illustration: FIG. 5.]

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.

[Illustration: FIG. 6.]

[Illustration: FIG. 7.]

[Illustration: FIG. 8.]

“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.”

[Illustration: FIG. 9.]

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.”

[Illustration: FIG. 10.]

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.”

[Illustration: FIG. 11.]

[Illustration: FIG. 12.]

     “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.”

[Illustration: FIG. 13.]

[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.

[Illustration: FIG. 14.]

The lever MN was of iron, and served to weaken the effects of
induction, inasmuch as it formed a magnetic short circuit. Here we
find for the first time the employment of a regulating device. Fig. 15
illustrates the method of connection.[1] As already mentioned, Fuller
succeeded in setting aside many of the defects which were adhered to in
the many very badly constructed transformers of his predecessors. While
he was busy carrying his invention into practice, he became a sacrifice
to his over-great activity, and on the 15th February, 1879, he was
taken away by illness. Only a few hours before his death, he called his
foreman to himself, and explained to him the principles of his system.
After ending his explanations, he asked him if he had understood all
that he had said, and, on receiving an answer from him that he had, he
smiled contentedly, and a few moments later he ended a useful life,
which had given so much promise of good results.

[Sidenote: E. H. Gordon, 1880.]

In the year 1880 Edward Henry Gordon took out the English patent No.
41,826. Gordon had constructed an electric lamp based on the fact that
when a current of sufficient electromotive force was passed over the
space between two balls of platinum or platinum iridium, the balls were
rendered glowing white. These balls were suspended by thin platinum
wire, or the supports were of platinum, serving also to carry the
current. For the production of overspringing sparks, it is well known
that a great difference of potential is necessary, so Gordon was
obliged to have recourse to induction coils, which he intended to
excite by means of magneto-electric machines, or alternating current
dynamos. In his patent he describes how this idea should be carried
out, and he actually did feed two lamps of 50 c.p., or one of 100 c.p.
The apparatus is described as follows:—“The primary consists of a
bundle of iron wire 1·3 inch diameter, and 18 inches long. Three layers
of insulated wire 0·08 inch in diameter are wound on it. The secondary
is wound on an insulating tube, and consists of about two-thirds of a
mile of wire 0·0075 inch diameter, covered four times with silk. It
is wound in 60 discs.” “There are three binding screws, one at each
end and one in the centre, so that the whole coil, or either half
separately, can be used for one lamp.”

[Illustration: FIG. 15.]

We do not find in Gordon’s patent the slightest indication which
would justify us in ascribing to him the invention of a system of
distribution by transformers as known at the present day, but, on
the contrary, it is clearly shown that the fundamental conditions of
such a system of distribution were unknown to him, for he laid the
chief weight upon connecting the induction coils in series, and on the
production of high electromotive force necessary for his lamp. Over and
above this, he was of opinion, as he stated prominently, that the more
advantageous kind of dynamo was one such as that of de Meritens, having
many coils of thin wire, which were connected to separately insulated
leads.

Let us look back upon the inventions which were made in the domain of
electric lighting by transformers from the time of Faraday’s discovery
of induction up to the year 1880. There we see that three distinct
characteristics were possessed by all the systems invented up to that
year. These three characteristics lay in the construction, the ratio of
transformation, and the method of employing the transformers. Single
transformers, with two or more poles, were used. The ratio was either
1:1, in which case the induction coil is really not a transformer, or
it was from a low to a high electromotive force; but nowhere do we
find that currents of high electromotive force were converted into
those of low electromotive force. The idea in the use of transformers
was that of division, not that of distribution of electric energy. The
difference between division and distribution of electrical energy is,
in the main, as follows. By a division of electrical energy it is meant
that a fixed amount of produced energy is divided into pre-determined
parts of a certain number and size, while it remains indifferent, as
far as the total energy is concerned, in what manner and how many of
these parts are usefully employed. By distribution of electrical energy
it is meant, on the other hand, that the energy produced is variable
according to the variable requirements of consumption, the maximum
requirement being pre-determined from the number and size of the local
requirements, which also vary relatively to one another. Of the last
of these systems there is no indication in any of the inventions of
induction coils up to this date.

If we seek for the cause of these characteristics, we find that the
reason why transformers with two or more poles were constructed
is, that the electricians of those days either did not know or did
not understand the principles on which a proper transformer should
be constructed. With them the idea of a magnetic pole acting on a
wire near it was always present, while they entirely overlooked the
fact that the electro-magnetic force, not the pole, produced the
electromotive force in the wire. On account of this they were of
opinion that free poles in a transformer were not only not a drawback,
but, on the other hand, a distinct advantage.

We find that Fuller especially held this view. He sought not only to
have in his apparatus two simple poles, but double poles, and indeed he
patented this arrangement of his transformer. The first claim of his
patent reads thus:—

       “The double electro-magnet herein described, the main
      coils of which are included in the circuit of a main
      conductor from a generator of alternating electric
      currents, producing in said magnet consequent
      magnetic poles, as shown, and around which poles are
      coiled helices of wire for receiving the currents
      induced by the polar changes, said helices being
      included in the local circuit with the lamp.”

We must bear in mind that, as far as the ratio and idea of employment
of a transformer are concerned, the problem at that time was quite
another to what it is now. At present the transformer serves principally
to render possible the carrying of the current to a great distance
economically. The electricians of those days were not so far advanced
as to be able to run arc lamps independently of one another on the same
circuit, and this they held to be quite impossible, whether the lamps
were connected in parallel or series. That apparatus was thought to be
good which allowed separately insulated currents to be led from one
source of current, each separate circuit going to feed a single lamp.
The chief reason for this view lay in the fact that the extinguishing
of all the lamps in one circuit could easily take place through the
fault of one of them. At that time, when an arc lamp was cut out of
circuit, it was replaced by a fixed resistance, instead of which it was
thought that induction coils would have suited well. It may be casually
mentioned that owing to this fact too sanguine hopes of the solution
of the problem of independent working of lamps were aroused, through
a want of sufficient knowledge of the laws of induction. There have
also been apparatus other than induction coils used for the purpose of
making the points of consumption independent of one another. We can
only now recall the patent of Jablochkoff, No. 1638, which is based
on the principle of connecting condensers into branches of a quickly
alternating main current, from which arc lamps, &c., were fed; also
a like arrangement by Avernarius (Figs. 16 and 17), with the use of
secondary batteries, which were to be employed for either parallel or
series connection.[2]

[Illustration: FIG. 16.]

[Illustration: FIG. 17.]

There were no transformers in those days which, in the present sense
of the word “transformer,” convert high electromotive force to low
to suit the consumers. On the contrary the apparatus, which was then
used in electric lighting plant, was such as converted low into high
electromotive force, or such that the ratio was 1:1, or nearly so,
according as it was determined by the connection in series of the
primary coils, and the difference of potential at the consumption
devices; for example, the induction coils of B. Ruhmkorff, Jablochkoff,
and Gordon.

When, however, the term high electromotive force is met with in
descriptions of the apparatus of that time, it must be taken to mean
a great difference of potential between the terminals of the dynamo,
not between the primary terminals of the transformers. Take, for
instance, 100 transformers connected in series, run with a difference
of potential at the dynamo of 1000 volts, although it was not known at
that time how to produce so high an electromotive force, still this
would give across the primary terminals of each transformer the modest
difference of potential of 10 volts. In this way the difference of
potential at the generator was determined by the number of transformers
in series. This system had plainly the great disadvantage, that no
matter how tortuous a path the lead must follow, it had to pass through
the primary coils of all the transformers, and the principles of a
proper system of distribution were not present.

With the invention of the incandescent lamp the activity of inventors
was given quite another direction. The systems of electric lighting
up to this time were not sufficiently advanced to permit even of a
_division_[3] of the electric light, that is, the ability to feed even
a small number of lamps from one generator. We shall only mention this
invention so far as it helps to further the history of the transformer.

Gramme made the earliest arc lamp that could be employed alone; then
followed Jablochkoff, as the first who carried out practically, and
with good results, the use of arc lamps in series or in parallel arc
with condensers. Siemens and Halske then replaced the Jablochkoff
candles with their differential lamp, which, although not offering
an opportunity for a good division of light, was unexcelled in
construction and manufacture, pointing out the way for further progress
in arc lighting. This class of lighting was brought nearly as far
forward as it is to-day by the introduction of continuous currents for
this use by Brush.

With the invention of the glow lamp quite other aims were placed in
the foreground for the electrical world. The incandescent lamp did
not possess that unsteadiness of light which, with arc lamps, gave
so much trouble to electricians. The prominent qualities of the glow
lamp offered opportunity for the solution of a problem, such as gas
had already solved half-a-century earlier, namely, the distribution of
the electric light, or, more properly, of the electric current. For
this, the already known and generally employed methods of connection
were no longer sufficient. Edison was the first who demonstrated that
the series method of connection was not suitable for glow lamps;
at the same time he showed the advantages of parallel connection,
coming forward with a thoroughly well thought and worked out system
of distribution. By this means the change was made, and, from this
time onward, all inventors were obliged to suit their systems to the
demand, that each point of consumption must remain undisturbed by the
variations of current which take place in the circuit.

Marcell Depréz has laid down in a work of his,[4] the laws which make
it possible to hold the points of consumption of electric energy
independent of one another, and, excepting some inexactnesses which
crept into his representation, these laws have been almost all carried
out in practice since that time.

The system of direct distribution to glow lamps had the one well-known
serious drawback, viz. that it only allowed of limited employment,
because the cost of the leads, with equal loss of energy, increased
with the square of the distance from the source of current.

It was therefore obligatory, in order to carry the current economically
to greater distances, to seek new means and ways, without rendering
inefficient the only practical system of connecting incandescent lamps
in parallel. The experience which had already been gained in the
economical carrying of high tension currents with arc lamps in series,
pointed out that high tension currents should be used, and that in the
secondary circuits of transformers fed by such a current, consuming
devices could be connected as might be desired.

[Sidenote: H. Enuma, 1881.]

Haitzema Enuma, in the year 1881, was the first to go in this
direction, and took out a patent for the feeding of glow lamps by means
of transformers.

He followed the principle of making each secondary circuit and each
point of consumption independent. The means to this purpose which he
thought to employ were not practical, and did not at all differ in
substance from those of his predecessors. His system is remarkable for
his method of connecting the induction coils in the main lead, i.e. in
series, using the secondary currents from these coils to excite other
coils from which tertiary currents were received, and these again were
further used to excite quaternary currents, and so on. This procedure
stands on a level with that of the famed dynamo-electric chain of
Siemens and Halske, of which it has been asked, “To what purpose?”

The peculiarities of the system of Haitzema Enuma become evident from
the following extract from his patent:—

     “Solche (nämlich die bekaunten) Induktionsrollen werden
    in den Hauptstromkreis überall eingeschaltet, wo der
    Strom abgezweigt (!) werden soll; und durch diese
    Einrichtung erhält zuletzt jede elektrische Lampe, oder
    jeder durch Elektrizität in Betrieb gesetzte Apparat
    seinen eigenen Strom.”

Haitzema Enuma had intended, so far as this shows, to connect the
primary, secondary, tertiary, &c., coils in series, and the main lead
being a closed circuit, the ends were taken to earth. The ends of the
circuits of the secondary, tertiary, and further induced currents, were
also connected together, or to earth.

[Sidenote: Gaulard and Gibbs, 1883.]

The first who came forward with an industrial employment of the series
system were Gaulard and Gibbs, who, in the year 1883, placed before the
public an installation of electric lighting in the Royal Aquarium in
London.

[Illustration: FIG. 18.]

There were two such apparatus as shown in Fig. 18, which were connected
in series, and excited with 13 ampères from a Siemens’ alternating
current dynamo. The apparatus had the following construction:—The
induction coils, a section of one of which is shown in Fig. 19, had
three layers of primary wire, and the secondary was wound in four
divisions, the ends of the wires of the divisions being led to a
commutator. Fig. 20 shows this commutator placed in the middle of four
induction coils. The ends of the secondary wires were connected to
eight terminals on the upper plate of the apparatus, from which the
current could be led away from each pair, or combined at will. By aid
of the commutator, the number of coils in circuit could be altered as
desired. On the lower plate there was a second commutator, which served
the same purpose for the primary circuit.

[Illustration: FIG. 19.]

The core of the apparatus consisted of bars of insulated iron, and
by means of a rack could be raised or lowered in the coils for the
regulation of the current. Both of these arrangements had been already
long known.

In the same year another installation for the lighting of some stations
on the Metropolitan Railway was taken in hand and carried out.

[Illustration: FIG. 20.]

The source of current was a Siemens’ alternating current dynamo of type
_W_0, which was excited by a continuous current machine. The potential
was supposed to be 1500 volts and the current 11·3 ampères. The main
lead connecting the transformers in series was of 7 wires of 1·5 mm.
diameter, and was 22·9 kilometres long, having a resistance of 30 ohms.
Three stations were supplied. At Edgeware Road twelve coils, with their
secondary coils in parallel, fed 30 glow lamps; and other four coils,
also in parallel, fed two Jablochkoff candles. In Aldgate two coils
supplied one arc lamp, and twelve more coils 35 glow lamps, each of 20
c.p. and three of 40 c.p. At Notting Hill there were 22 glow lamps and
one arc lamp. In this last installation coils were employed with their
coils arranged after a somewhat different manner. On a pasteboard or
wooden cylinder of about 50 cm. in height a cable was coiled in layers.

The interior of this cable consisted of a 4 mm. copper wire well
insulated with paraffined cotton, and around this, parallel to its
axis, lay 6 cables or cords, each consisting of 12 wires, also
insulated with paraffined cotton (Fig. 21). The wire of 4 mm. formed
the inductor through which the primary current was passed. The six
cables, each of twelve strands, formed the induced portion of the
apparatus, and the ends were connected to a commutator, so that they
could be used either in parallel or series.

[Illustration: FIG. 21.]

The methods of construction and connection used in these attempts
by Gaulard and Gibbs did not differ in principle from those of
their predecessors. Gaulard and Gibbs also employed in these trials
bi-polar induction apparatus. The efficiency of such apparatus can
only be comparatively small, because the effects of magnetisation, and
therefore of induction, are weakened to a great extent by the lines of
force having to pass for the greatest part of their path through air
instead of iron. Taking another view of such apparatus, as they have a
ratio of transformation of 1:1, they must, with the employment of high
potential, be connected in series.

Undoubtedly Messrs. Gaulard and Gibbs have in their time claimed
certain things as new and of their own invention, namely, the
arrangement of several separate induction coils together, the placing
of the coils next to one another, and the winding of the wires
parallel. These claims, however, have been condemned from all sides as
unjustified. The employment of several coils has already been mentioned
as patented by the brothers Bright on 21st October, 1852, and was again
later on discovered by Poggendorf, Ruhmkorff, Foucault, and others. We
have also shown, on page 11, that the placing of the coils next one
another had likewise been invented by the same men 30 years earlier.
The symmetrical arrangement of both coils, the primary and secondary,
had also already been used. (See page 18.)

But when, in spite of all this, we find Mr. J. K. Mackenzie[5]
maintaining that the Fuller transformer was non-polar, and further,
that the following improvements must be ascribed to Messrs. Gaulard and
Gibbs, viz.:—

    1. The reduction of the primary and secondary
    wire-resistance to a minimum.

    2. The attainment of the greatest possible coefficient
    of induction with the lightest apparatus.

    3. The symmetrical arrangement of both coils.

    4. The proportioning of the coils, so that the weight
    of metal in each is the same.

Seeing this, it must be thought that this gentleman either does or
will not, understand the subject. Then if Gaulard has succeeded
with his apparatus in obtaining some advantages as proposed in the
above-mentioned clauses, Nos. 1 and 2, these advantages can be obtained
to a much higher degree with non-polar transformers. This has been
proven by Prof. Ferraris.[6]

The improvements mentioned under Nos. 3 and 4 are only to be
attained with bi-polar transformers after difficult and otherwise
disadvantageous arrangements; for instance, the combination of the
primary and secondary wires in a common cable, or, when the coils
consist of ribbon wire, by the winding of the one inside the other.
With non-polar transformers these improvements are already inherent.
The Fuller transformer was just as much without poles as two horseshoe
magnets are, with their like poles laid together.

In all these systems with series connection of the transformers, the
intensity of the current in the primary circuit must be held constant
in order that it may be possible for the induction apparatus to
maintain the secondary electromotive force constant. Notwithstanding
this, constancy was not attained, but only one cause of the variations
annulled. Another cause of the variations of the difference of
potential at the secondary terminals of the coil still remained; this
was the loss of potential due to resistance and self-induction, which
increased with the load. The electromotive force of the secondary, and
therefore of the primary coils, accordingly increases as the current
in the secondary decreases. When no secondary current is flowing, the
electromotive force in the primary and secondary coils is a maximum. We
have consequently this disproportion that the smaller the output of the
apparatus the greater the energy consumed. With the secondary circuit
open and a constant exciting current, the energy used could be as much
as ten times as great as under full load.

The disadvantages of this system are apparent; for, putting aside the
loss of energy arising from the disproportion between produced and
consumed energy, each change of load on the secondary circuit exerted
a great influence on the primary circuit, and again on the secondary
circuits of the other coils in the main circuit.

All the transformer systems already described were intended, as we see,
for subdividing the current, and as fitting therefor we find the series
method of connection universally brought forward. With this method,
owing to a rise in electromotive force which was dangerous to the
lamps, &c., when only a part of those in the secondary circuit were
extinguished, it was compulsory either to run the induction coil
fully loaded or quite empty. Thus, when the number of lamps or other
devices in use was varied, a regulation of the current strength and
uniform working was either quite impossible, or only partly possible
by unreliable and incomplete mechanical means. On this account no one
succeeded with this method in carrying out a rational distribution
of current by means of induction coils such as are required by the
widespread demands for electric current from a central station.

The first to point out the disadvantages of the series method of
connection was Rankine Kennedy, who had devoted himself wholly to the
study of induction apparatus. These disadvantages he published in an
article in the “Electrical Review” of 9th June, 1883. At the end of
this article we find the interesting statement that transformers,
when not connected in the primary circuit in series, as had been
usual till then, but in parallel, form a self-regulating system of
current distribution. Rankine Kennedy expresses this in the following
words:—“In parallel arc, however, the secondary generator is a
beautiful self-governing system of distribution.” At the same time,
however, his article affords proof that the author then possessed only
a limited comprehension of the physical facts concerned, because he
maintained, for instance, that the introduction of an induced counter
electromotive-force in the circuit of an alternating current dynamo
might constitute a means of regulation without loss of energy; however,
it might be allowed, that he meant by these words one of these elements
which must be present in a really rational system of distribution with
the use of transformers, if it were not the case that at that time he
was not aware both of the properties of transformers suiting them for
such a connection as well as those which make them self-regulating in
a system of distribution. Above all this he had at that time never
thought of a transformer in the sense, the word is used to-day, that
is, as an induction apparatus, which converts high into low tension
currents. This is quite clear, as is seen from the end of the sentence
before cited, as he says, “But what about the size of conductors for
such a system? Prodigious!” Kennedy thought to all appearance that
the parallel connection of transformers made possible self-regulation
in the same manner as the simple direct parallel connection of
incandescent lamps. While at the same time he imagined that on account
of the small resistance of each coil the resistance of the net of
leads must nearly vanish, therefore he concluded that the parallel
connection of such induction apparatus as he had in his mind’s eye was
impracticable.

The apprehension of Kennedy’s ideas, as we have here stated, finds
direct confirmation from the leading article in the “Electrical Review”
of 9th June, 1883. At the end of this leader the editors say, that “Mr.
Kennedy’s apparatus is an induction coil pure and simple.” “Messrs.
Gaulard and Gibbs will scarcely deny, nor can they deny, that the
action of this particular construction of the coil is identical with
that of his.” In this sentence it is distinctly stated that the
construction of Kennedy’s induction apparatus is identical with that of
Gaulard and Gibbs’. Kennedy accepted this statement in silence; if it
had been otherwise, he would have protested in his next appearance in
print.

In order to make possible the connection of transformers in parallel,
the advantages of which it may be said Kennedy had augured, there
was still much wanting. Above all there was wanting the idea of a
transformer as meant at present, and an exact knowledge of its action.
F. Geraldy has expressed himself very suitably upon this point in the
introduction to his report upon the trials made with the system of
Messrs. Gaulard and Gibbs.[7]

    “La distribution de l’électricité comporte la solution
    d’un grand nombre de problèmes. Il ne suffit pas
    de se décider en principe et lorsqu’on a choisi la
    distribution en quantité (en supposant même, que
    l’un des procédés puisse être appliqué d’une façon
    exclusive, ce qui n’est pas certain), lorsqu’on
    a trouvé le moyen de régler le générateur et les
    recepteurs conformément au mode choisi, il reste encore
    à lever quantité de difficultés, a créer et disposer
    beaucoup d’organes auxiliaires.” Geraldy explained
    distinctly that it was not sufficient to determine
    only the method of connection, but there were still
    a considerable number of obstacles to be surmounted
    before the object could be attained.

It has been a costly lesson, before the properties of transformers were
known, which make them form a self-regulating system. Even in the year
1884 do we still find Messrs. Gaulard and Gibbs on the same false track
as previously. It was in the Turin Exhibition where Messrs. Gaulard and
Gibbs carried out their system upon a large scale, and where they also
succeeded in gaining the interest of technical circles, and arousing
general attention.

The transformers installed by Messrs. Gaulard and Gibbs in the Turin
Exhibition were protected by the German patent, No. 28947, and
this time again their transformers were wound with equal primary
and secondary coils. The construction of the apparatus, as already
explained, made it a necessary condition that the transformers be
connected in series, because only by this means could the high tension
current be utilised. It was a necessary corollary of this method of
connection that the converting of the high potential of the primary
circuit into low potential, was performed, not by the ratio of the
number of turns in the coils of the transformers, but in a certain
manner by the subdivision of the electromotive force in the circuit.

[Illustration: FIG. 22.]

The special construction of the transformers used in the Turin
Exhibition differed from the older apparatus in so far that both coils
were formed of stamped out circular copper discs, which were soldered
together by projecting teeth. The insulation was made of stamped-out
paper discs. Both spirals were wound between one another. The building
up of such coils was effected in the following manner (see Fig. 22A):—A
red copper disc was first placed on the core, then insulation, upon
this a black copper disc, then again a red copper disc, and so on. Like
colours of copper discs were then soldered together at the projecting
teeth. In this manner there were produced two spirals running parallel
with one another, there only being one layer of coils. The employment
of such ribbon conductors had some advantages, namely, good use of the
space at disposal for coils, and rapid cooling through the projecting
teeth. They had, also, disadvantages, the chief of which was, that the
conductors were of bare metal, so that a fault in insulation could
easily occur.

[Illustration: FIG. 22A.]

In fact, several faults in the transformers in Turin did arise from
this cause, the action of the coils being disturbed. Further attempts
with similar coils were made, the station houses of Turin, Venaria,
and Lanzo being lit for five consecutive hours. The circuit was about
80 kilometres long, the main lead being of chrombronze wire of 3·7 mm.
diameter. At Turin there were 34 Edison lamps of 16 c.p. each, and a
sun arc lamp; at Lanzo there were nine Bernstein lamps, 16 Swan lamps,
a sun arc lamp, and two Siemens’ arc lamps. In the exhibition itself,
there were nine Bernstein lamps, nine Swan lamps, and a sun arc lamp.
In the Figaro Kiosk nine Swan lamps were fed from a small transformer.

As already related, the trials of Messrs. Gaulard and Gibbs’ system at
Turin had aroused in the widest circles the liveliest interest, and,
consequently, the errors of the system soon became public. Thus we find
in the technical literature of that time influential voices raised
against the system, and pointing out its disadvantages.

Among others, Prof. Colombo read a paper during the course of the
National Exhibition at Turin, the subject being the system of Gaulard
and Gibbs. While doing sufficient justice to the good points of the
system, he also said that although it solved the problem of carrying
the electric current to great distances, it was in no way what it was
represented to be, and what it should be: a system of distribution
allowing the electric current from a distant central station to be led
to meet the demands of any kind of consumer without any one of these
interfering with the supply of current to any other. He characterised
these drawbacks sharply, and very suitably, by the remark, that in the
Gaulard and Gibbs system, each consumer drew properly his supply of
current from his transformer, and not from a common network of leads
always self-regulating, as is the case in every large installation
with continuous currents. Prof. Colombo satisfied himself with this
reference to its disadvantages, mentioning also what should be striven
after to make the system a perfect one, saying that the ideal
electric lead system was one combining the advantages of the Edison
central-station with that of Gaulard and Gibbs.

Prof. Colombo confined himself to these hints, and he must acknowledge
that the means leading to the attainment of this purpose remained still
to be found out.

The reproduction of this lecture by Prof. Colombo is placed before an
article by Depréz in “La Lumière électrique,”[8] in which latter the
system of Gaulard and Gibbs is strongly criticised. Depréz showed that
that system can have no claim to be new. He points also to the wants
of the system, especially that of self-regulation, stating that the
means remain still to be discovered, which would make possible the
self-regulation of a system of distribution with transformers. He also
says that Gaulard’s system of distribution had not solved this problem,
and therefore could not be held to be practically useful.

We find the same view represented in an article by H. Roux,[9] where
he points to the enormous fluctuations which take place when the
resistance in the secondary circuit is altered. Some of the figures
vouching for his opinion we shall now reproduce. They were taken by M.
Pietro Uzel, in Turin, in an observational way.[10]

The observations are only quoted so far that the Watts Δ I at the
secondary terminals are still increasing; were they continued further
the damning fact would reveal itself that as the power put in
increased, the power given out would approach zero.

Taking account of these fluctuations, it is not possible to see how, as
Mr. Roux says with justice, a distribution of current by this system
can be made in an efficient manner. Mr. Gaulard in his reply, virtually
assents to this article, but adds, that these variations could be
prevented, if the cores of the transformers be shifted either by hand
or automatically. Both methods would be expensive, and, besides, the
automatic regulation would be unreliable.

    ───┬───────────────────┬──────────┬───────────────────┬───────────
       │                   │ External │                   │
       │                   │Resistance│                   │
    No.│     Primary       │    of    │     Secondary     │Efficiency.
       │     Circuit.      │Secondary │      Circuit.     │
       │                   │ Circuit. │                   │
    ───┼─────┬─────┬───────┼──────────┼─────┬─────┬───────┼───────────
       │  Δ  │  I  │  I Δ  │    W.    │  Δ  │  I  │  I Δ  │   Δ
    1  │ 23·4│12·13│ 283·84│   1·24   │ 15·0│12·02│ 180·30│  63·52
    2  │ 31·4│12·13│ 380·88│   2·00   │ 24·0│12·00│ 288·00│  75·62
    3  │ 53·0│12·13│ 642·89│   3·80   │ 45·0│11·83│ 532·35│  82·81
    4  │ 70·0│12·13│ 849·10│   5·50   │ 65·0│11·75│ 762·45│  89·80
    5  │ 93·0│12·13│1128·09│   7·53   │ 87·0│11·58│1007·46│  89·31
    6  │107·0│12·13│1297·91│   9·00   │102·0│11·31│1153·62│  88·88
    7  │126·0│12·13│1518·38│  10·60   │119·0│11·13│1324·77│  86·66
    8  │145·0│12·13│1758·85│  12·60   │138·0│10·95│1511·10│  85·35
    9  │159·0│12·13│1928·67│  14·15   │156·0│10·76│1678·66│  87·03
    ───┴─────┴─────┴───────┴──────────┴─────┴─────┴───────┴───────────

It was at once recognised by all those interested in the subject,
that this system made possible a subdivision, but by no means a
distribution of current.

Before proceeding further with the history of the development of the
transformer, let us for a little while take up the question, what
conditions are necessary for a practical and rational system of
current distribution by means of transformers. As we have already
explained in another part of this paper, the method of parallel
connection, i.e., a system in which the difference of potential is
held constant, is alone suitable. Depréz maintained in his time that
the difference of potential between the terminals of the source of
current must be kept constant. Should the distribution be made on this
principle, the resistance of the network of leads must be very small,
in order that with full load only a very small loss of electromotive
force may take place in the leads. In the indirect system of current
distribution, consequently, the tension at the secondary terminals of
the transformers must also be maintained constant.

The question is now before us, “In what manner must the primary
electromotive force vary to effect this?” Consider an iron core,
having on two different parts round it, two rings of wire. This iron
core may now be magnetised by bringing near to it in the line of
its axis a permanent magnet. On drawing the latter quickly away, an
electromotive force will be momentarily produced in both the wire
rings, and the electromotive force will be proportional to the number
of the disappearing lines of force. This number, in consequence of the
dispersion of the lines of force, will be very different at different
parts of the magnetised core. The induced electromotive forces in the
windings of the wire will also be different. The equality of these
electromotive forces, which is so important, can only be attained if
all the windings are in relatively the same position with regard to the
magnetic field. The circuits of both coils being closed, the one having
a current flowing through it, the other through a suitable resistance,
besides the condition mentioned in the last sentence, another must be
fulfilled; this is, the internal resistance must be practically zero,
i.e. the difference of potential between the terminals shall equal to
all intents and purposes the total electromotive force.

We have now to examine how far the already observed constructions
of transformers fulfilled these demands. A transformer in which the
windings lie relatively in the same position to the magnetic field can
quite well be bi-polar. All that is necessary for this is that the
coils be wound on to the core next to one another; this is most simply
managed in a transformer having a ratio of 1:1. This law was first
determined by Maxwell. The apparatus of Strumbo shows such a method of
winding already carried out.

Thus it may be seen that of bi-polar transformers, those which, with
regard to the constancy of the secondary tension, are most suitable,
are quite useless on account of their ratio being 1:1, although they
are destined for the series method of connection.

The connection of proper transformers in parallel can only be made
with such apparatus as, notwithstanding their ratio of transformation,
possess windings having the same relative position to the magnetic
field—this is only the case with non-polar transformers. Besides this
quality of non-polar transformers, their magnetic resistance is so low
that the condition of very low internal resistance is easily fulfilled.

The following conditions of a self-regulating and economical system
of current distribution with transformers result, therefore, from the
foregoing explanations:—

    1. The generator of current must give a great
    difference of potential as constant as possible at the
    terminals of the transformers, and also independent of
    the number fed.

    2. The transformers must convert the current of
    high electromotive force into a current of such
    electromotive force as may be desired. The transformers
    must have a closed magnetic circuit (that is, they
    must be poleless), in order that all the primary and
    secondary turns shall possess, relatively to the
    magnetic field, a like position, also in order that the
    resistances of the primary and secondary coils shall
    be so small that they cause practically no loss of
    electromotive force.

Through the fulfilment of both these conditions, it is rendered
possible to maintain the secondary tension constant by maintaining
the primary tension constant, indifferently whether it is regulated
automatically or by hand. To suit this, the transformers must also be
arranged into distributive stations of the second order, and derived in
parallel from the main leads.

[Sidenote: Zipernowsky, Déri, Bláthy, 1885.]

In May, 1885, a system of current distribution meeting all the
just-mentioned requirements was publicly brought out, giving an
illustration of a truly self-regulating system of current distribution.
This was the system of Zipernowsky, Déri, and Bláthy.

The first two patents concerning this system date from 18th February,
1885, and are entitled, “Improvements in the means for the regulation
of alternating electric currents,” No. 34,649, by Carl Zipernowsky
and Max Déri, of Budapest; “Improvements in the distribution of
alternating currents,” No. 33,951, by Max Déri, of Vienna. The third
patent is dated 6th March, 1885, and is entitled, “Improvements in
induction apparatus for the purpose of transforming electric currents,”
No. 40,414, by Carl Zipernowsky, Max Déri, and Otto Titus Bláthy, of
Budapest.

The system described in these three patents was immediately afterwards
brought forward in the three exhibitions of Budapest, Antwerp, and
London (Inventions Exhibition), arousing in technical circles a general
and well-earned attention.

In the patent documents as well as in the earliest[11] articles in the
journals concerning the system, two special forms of transformers are
described, viz. that consisting of an iron core with the wire outside,
and, secondly, that consisting of copper coils surrounded by iron wire.
The transformers shown in Figs. 24 to 28 belong to the last of these
classes, that in Fig. 23 to the first. The fundamental principle upon
which all these transformers are constructed is that the subdivisions
of the iron core run perpendicularly to the copper wires. Transformers
such as are shown in Fig. 25 having a ring-shaped iron core wound with
copper wire at first employed, later the inventors used in preference
the form represented in Fig. 23.

[Illustration: FIG. 23.]

In all these forms the principle is generally adhered to, that the
magnetic resistance and the exciting power possess for each part of the
length of the magnetic circuit the same value, and thus the formation
of poles with the resulting dispersion of the lines of force is avoided.

[Illustration: FIG. 24.]

This system procured for itself universal recognition, but especially
in the Budapest Exhibition. There several exhibits within a radius
of 1,300 metres were lit from a common central station. The several
circuits were quite independent of one another, and lamps could be
extinguished or lit in any one of them without anywhere producing a
change in the intensity of the light, which could be perceived.

[Illustration: FIG. 25.]

[Illustration: FIG. 26.]

[Illustration: FIG. 27.]

[Illustration: FIG. 28.]

[Illustration: FIG. 29.]

It was, therefore, in the year 1885 that the problem of current
distribution by means of transformers was solved in a truly practical
manner. The ideas which led the inventors to this thoroughly successful
solution were then so unknown to practical and theoretical electricians,
that it was long ere they were understood and appreciated. Even in
February, 1886, such an electrician as Prof. Forbes maintained in
his Cantor Lectures that the parallel connection of transformers was
quite impracticable. He believed, namely, that a connection such as
shown in Fig. 29 was useless, because the difference of potential
at the generator diminished from the machine outwards, but that a
connection such as shown in Fig. 30 must be used. According to him,
in a direct system of distribution each lamp should have a separate
lead, and having regard to the great number of leads which would thus
be necessary, he concluded that the series method of connection was the
right one. One would suppose that Prof. Forbes was not aware of the
weighty disadvantages of this method. However, that was not the case.
He proposed, that with series connection the strength of current should
be kept constant, and that each transformer should have an especial
regulating apparatus—the raising or lowering of the core; which, by the
way, is an arrangement impracticable in a well designed transformer.
Such a regulating apparatus has lately been made automatic.

[Illustration: FIG. 30.]

“This is,” says Prof. Forbes, “the last triumph, which after a series
of troublesome experiments has brought us year after year nearer to the
solution of the difficulties.” “I am not in a position to explain here
the _modus operandi_,” he says further, “but I have seen the apparatus
working very satisfactorily.”

[Illustration: FIG. 31.]

This apparatus has up till now not become known. The assertion that the
troublesome experiments had brought us year after year nearer to the
solution of the difficulties, is quite inappropriate. Just the opposite
is the case; they have taken us year after year further away from the
solution, until at last all was thrown overboard and a new commencement
made.

Profs. Rühlmann[12] and Esson[13] also gave vent to their opinions
against the connection of transformers in parallel. In a like manner
Messrs. Gaulard and Gibbs for some time after the Zipernowsky-Déri
system was known pleaded for their own method of connection, until
at last they were obliged, on account of the unpleasant experiences
at the Grosvenor Gallery in London, to adopt the system of parallel
connection, which they then at once employed at Tours.

There were, up till very lately, still many electricians who did not
perceive the advantages of parallel connection, just for the simple
reason that they were ignorant of the properties of the non-polar
transformer, suiting the parallel system of connection for a rational
system of distribution. Especially the one property of transformers
remained unknown to the literature devoted to the subject up to the
year 1885, namely, that in transformers properly constructed the
relation between the primary electromotive force and that of the
secondary, remains unaltered notwithstanding any variations in the
current taken out; also that if the primary electromotive force be kept
constant the secondary would likewise remain constant, provided the
transformer be connected in parallel.

It had taken 30 years, until at last the way was found leading to the
desired result. We have already superabundantly explained that this
direction was essentially different from that taken by all electricians
until after Gaulard’s time; that not only the methods of connection,
disposition, and regulation of the system, but also the construction of
the transformers themselves had to be quite departed from, and
apparatus constructed which obeyed totally other laws to those of the
earlier forms.

If indeed earlier inventors proposed for other purposes
magnetically-closed induction coils, the fame due to the birth of
proper non-polar transformers, in which the whole of the primary and
secondary turns have a like position relatively to the magnetic-field,
first invented, carried out, and combined into a self-regulating system
of current distribution, belongs undoubtedly to Messrs. Zipernowsky,
Déri, and Bláthy.

It would have been thought that after the direct distribution of
current to glow-lamps had taken up a determined position, it would
not have been difficult to discover a self-regulating system of
distribution with transformers. However, the fact shows this was
not the case, for after the Edison lighting system was long known,
we find such electricians as Haitzema Enuma, Gaulard, and Kennedy,
experimenting with the series system of connection; indeed the last of
these even deters his colleagues from the attempt to run transformers
in parallel, because he openly held the opinion that this method of
connection was impracticable.

We have here the development of current distribution by means
of transformers, as it completed itself in Europe. The American
electricians however, made the matter somewhat easier. They quietly
waited until the invention gave useful results in Europe, and then
simply imported it.

The field to-day belongs to the parallel method of connection, and
after the installation in the alkali works at Aschersleben was
destroyed by flooding, there only remains a single installation with
series connection, as far as we know; this is that which was fitted
up in Tivoli near Rome in the year 1886. This installation however,
serves only to feed an invariable number of street-lamps, and can
therefore have no claim to the designation of an installation for the
distribution of electric currents by means of transformers.


          LONDON: PRINTED BY WILLIAM CLOWES AND SONS, LIMITED,
                   STAMFORD STREET AND CHARING CROSS.



FOOTNOTES:

[1] See also ‘Scientific American,’ 5th April, 1879, p. 212.

[2] Avernarius, Centralblatt für Elektrotechnik, vol. iii. p. 323.

[3] At that time a customary and very characteristic expression.

[4] Comptes Rendues, 1881, p. 872.

[5] The ‘Electrical Engineer,’ 17th Feb., 1888.

[6] La ‘Lumière électrique,’ vol. xvii. p. 145—148, 1885.

[7] La ‘Lumière électrique,’ vol. x. p. 496, 1883.

[8] La ‘Lumière électrique,’ vol. xiv. p. 45.

[9] ‘Electricien,’ 7th March, 1885.

[10] ‘Natura,’ 25th January, 1885, p. 60.

[11] Elektricitätsverteilung aus Centralstationen, System
Zipernowsky-Déri, Centralbl. f. Elektrotechnik Bd. VII. S. 422.

[12] ‘Electrical Review,’ vol. xvii. p. 157.

[13] ‘Elektrotechnische Zeitschrift,’ September, 1885.





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