History of the transformer

•NRLF

HISTORY

THE TRANSFORMER

BY

F.j UPPENBORN,

KDITOti OF 1'HK " CBXTltALBLATT 1'Uli KLI.C TKO TKCHM K."
AM'. CIMICF OK TIIK HI. hX; I'll' i-TKCHMCA I. TK> I'l.Mi hl'ATloX IN MIMCH.

TRANSLATED 1<'1U)M THE (iKH

E. & F. X. SPUN, 125, iSTUAJSJD, LOXDOX.

NEW YOlUv: 12, COKTLANDT S'l'KEKT.
1889.

-t

HISTORY

OF

THE TBANSFOKMEB.

BY

F. UPPENBORN,

EDITOR OF THE " CENTRALBLATT FUR ELECTROTECHNIK,"
AND CHIEF OF THE ELECTRO-TECHNICAL TESTING STATION IN MUNICH.

TRANSLATED FROM THE GERMAN.

E. & F. N. SPON, 125, STEAND, LONDON.

NEW YORK: 12, CORTLANDT STREET.

1889.

TK i
Ut,

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

JM6935

HISTORY OF THE TRANSFORMER,

As we wish to write cf 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 electro-
technics.

The most important discovery for which we have Faraday, 1831.
to thank Faraday is that of induction. This dis-
covery 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

B

HISTORY . OF : THE TRANSFORMER.

force was created in the second coil,
which caused a fehart 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 tranformer is in principle an induction
apparatus.

Fm. 1.

Fig. 1 represents the arrangement of this funda-
mental experiment. The primary coil is connected
with the battery, the secondary with the galvano-

HISTORY OF THE TRANSFORMER. P

meter. 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 combina-

FIG. 2.

tion 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

B 2

HISTORY OF THE TRANSFORMER.

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, Deri, and
Blathy, but it may be easily shown to be not entirely
poleless. Poles mean, in electrical as well as mag-
netic 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 electro-
motive 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 sym-
metrical 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

HISTORY OF THE TRANSFORMER. 0

this apparatus of Faraday's was equal to unity, so it
had therefore no claim to the designation of " trans-
former."

The induction apparatus of Faraday in its sim-
plicity 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 pro-
duced 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 re-
placed the primary coil and
battery by a permanent
magnet, which was likewise
dipped into the induction
coil, Fig. 3.

From this, and from the
later development of this
invention, it follows that the
question was not of a trans-
former in the present sense
of the word, but of a second-
ary generator. Transformers

as at present understood were first known in Europe
as the Kuhmkorff's induction coil. Before we take
up this invention we shall mention a much earlier

6 HISTORY OF THE TRANSFORMER.

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

Henry and 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.

Cailan, 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 em-
ployed. His apparatus was not so bad as those
before known, but still stood far behind that of
Professor Page.

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

HISTORY OF THE TRANSFORMER. 7

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.

FIG. 4.

The continuation of the lever in the other direc-
tion of the axis, which was borne by two pillars K,
was bent backwards, and on its end carried a cylin-
drical 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 cylin-
drical 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

8 HISTORY OF THE TRANSFORMER.

play began anew. A counter-weight F, which could
be shifted along another lever 0, allowed the play of
the contact-breaker to be regulated. It will be
found that this interrupter was very like that con-
structed many years afterwards by Leon Foucault
The effects which Page produced by means of this
instrument were much more intense than those pro-
duced by Kuhmkorff 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 4£ 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
£ 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.

Ruhmkorff, 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

HISTORY OF THE TRANSFORMER. 9

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 Ehumkorff coil was still in its infancy, the won-
derful output of Page's apparatus was still, even in
the year 1851, quite unknown in Europe.

Fig. 5 represents the earlier form of the Euhmkorff
apparatus. It consisted of a bobbin of good insulat-
ing material ; thoroughly dried wood, or better, hard

FIG. 5.

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 con-
sisted 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
interrupter like what has already been described.
Over the primary coil, and after a sufficient layer

10 HISTOKY OF THE TRANSFORMER.

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 interrupter.

In Fig. 6 is shown a newer form of Kuhmkorff's coil,
with an interrupter 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.

HISTOKY OF THE TEANSFOEMEE.

11

We find a further development or modification of c. T. & E. B.
the invention of Page and Kuhmkorff, patented by the Brisht> 1855t
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 con-
cerning the nature of their inventions.

FIG. 6.

"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 sur-
rounded 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

12

HISTORY OF THE TRANSFORMER.

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

FIG. 7.

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.

FIG. 8.

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

HISTORY OF THE TRANSFORMER.

13

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 induc-
tion."

FIG. 9.

III

II I U

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.

Among the patents of the year 1857 there is an Harrison,
English one by Harrison, claiming as its object the 1857>
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.

The last attempt to use induction coils for indus- Jablochkoff,
trial purposes is met with in the year 1878. In this 1878a
year Jablochkoff took out a German patent, which

14

HISTORY OF THE TRANSFORMER.

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 be-
greift eine Serie von Induk-
tionsrollen in sich, wovon
die inneren Drahte in eine
elektrische Leitung einges-
chaltet sind."

Jablochkoff used inter-
mittent direct currents as
well as alternating cur-
rents. The arrangement
shown in Fig. 10 was for
the former. He states con-
cerning this : —

" In diesem Falle sind die
Induktionsrollen mit Unter-
brecher und Kondensator
ausgestattet, oder man kann
auch, wie die Zeichnung
nachweist, einen und den-
selben Unterbrecher fur alle
Kollen anwenden. Die Induktionsrollen B1 B2 B3,
nach einen beliebigen Prinzipe konstruirt, sind in
der Nahe der Lichtherde angebracht."

HISTOKY OF THE TRANSFORMER.

15

Concerning the employment of alternating cur-
rents, Jablochkoff says : —

"Diese Disposition weicht von der ersteren nur
durch die Weglassung des Unterbrechers und des
Kondensators der Kolle ab.

FIG. 12.

"Die in Fig. 11 angewendeten Rollen sind in
Fig. 12 detail! iert gezeichnet. Auf einer kreis-
formigen Scheibe C aus weichem Eiseri 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 bandformigen Kupferstreifen

16 HISTOKY OF THE TRANSFORMER.

oder anderem Metal le besteht. a' 1st die in gleicher
Weise zusammengesetzte Induktionsspirale, deren
Drahtenden zu den Lichtherden ftihren. 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 tbis patent is also interesting,
and reads as follows : —

"Die Einflibrung einer Serie von Induktions-
rollen in den Umkreis eines beliebigen Elektricitats-
generators zur Erzeugung einer Serie von Induk-
tionsstromen. welcbe es gestatten, Lichtberde von
verschiedener Intensitat durch eine einzige Elek-
tricitatsquelle zu versorgen, was zur vollstandigen
Teilbarkeit des elektriscben Lichtes fiibrt."

JablocbkofFs system as just described was to be
seen working in tbe Paris Exhibition of the year
1878. A proper industrial application of tbis system
does not appear to have taken place.

BriTh?i87*' In the ye{ir 1878 the brothers Bright bad also
made further progress in tbe use of induction coils
for electric lighting purposes, and in the same year
they took out tbe 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 tbe
brothers Bright knew already in the year 1878 the
properties of transformers suiting them for electric

HISTORY OF THE TRANSFORMER. 17

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 deter-
mined according to the number of lamps at each
point, where the secondary current shall supply the
electric lighting."

The employment of induction coils for the distri- E. Edwards &
bution 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. Bound,
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

c

18

HISTORY OF THE TRANSFORMER.

Strumbo,

1878.

Harrison,

1878.

described, through the primary coil or coils, generates
a corresponding current of electricity in each of the
secondary coils.

In the same year, Strumbo had also constructed a
secondary generator like that of Gaulard, and a de-
scription 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

FIG. 18.

the primary and secondary wires were wound side
by side, and that both coils had the same relative
position to the iron core.

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

HISTOEY OF THE TRANSFORMER. 19

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.

We find in Meritens' English patent, No. 5257, of Meritens,
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 in-
duction 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.

"We now come to an inventor, who, in his time, Fuller, 1878.
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 Brook-
lyn 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

c 2

20

HISTORY OF THE TRANSFORMER.

FIG, 14.

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 ex-
citing, the four small coils on
the poles of the double mag-
nets are the secondary coils.

The lever MN was of iron,
and served to weaken the
effects of induction, inas-
much as it formed a magnetic
short circuit. Here we find
for the first time the employ-
ment of a regulating device.
Fig. 15 illustrates the method
of connection.* 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 ex-
plained 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 con-

* See also « Scientific American,' 5th April, 1879, p. 212.

HISTORY OF THE TRANSFORMER.

21

tentedly, and a few moments later lie ended a useful
life, which had given so much promise of good results.

In the year 1880 Edward Henry Gordon took out E. H. Goni<

* J 1 OOA

the English patent No. 41,826. Gordon had con-
structed an electric lamp based on the fact that when

1880.

FIG 15.

a current of sufficient electromotive force was passed
over the space between two balls of platinum or plat-
inum 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

22 HISTORY OF THE TRANSFORMER.

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 de-
scribes 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 : — u The
primary consists of a bundle of iron wire 1*3 inch
diameter, and 18 inches long. Three layers of insu-
lated 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

O

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."

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 trans-
formers 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 un-
known 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,

HISTORY OF THE TRANSFOEMER. 23

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 trans-
formers 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 thve 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 electro-
motive force were converted into those of low
electromotive force. The idea in the use of trans-
formers 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 con-
sumption, the maximum requirement being pre-
determined from the number and size of the local

24 HISTORY OF THE TRANSFORMER.

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 under-
stand 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 trans-
former 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 conse-
quent 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

HISTOKY OF THE TRANSFORMER. 25

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 princi-
pally 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 impos-
sible, 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 know-
ledge 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

26

HISTORY OF THE TRANSFORMER.

arrangement by Avernarius (Figs. 16 and 17), with
the use of secondary batteries, which were to be em-
ployed for either parallel or series connection.*

FIG. 16.

FIG. 17.

There were no transformers in those days which,
in the present sense of the word " transformer," con-
vert 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.

* Avernarius, Centralblatt fur Elektrotechnik, vol. iii. p. 323.

HISTORY OF THE TRANSFORMER. 27

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 ter-
minals 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 direc-
tion. The systems of electric lighting up to this
time were not sufficiently advanced to permit even
of a division* of the electric light, that is, the ability
to feed even a small number of lamps from one
generater. We shall only mention this invention
so far as it helps to further the history of the trans-
former.

Gramme made the earliest arc lamp that could be
employed alone; then followed Jablochkoff, as the

* At that time a customary and very characteristic expression.

28 HISTOKY OP THE TKANSFOEMEK.

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 pro-
gress in arc lighting. This class of lighting was
brought nearly as far forward as it is to-day by the in-
troduction of continuous cur rents 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 ad-
vantages 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.

HISTORY OF THE TRANSFORMER. 29

Marcell Deprez has laid down in a work of his,*
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 tbe 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.

Haitzema Enuma, in the year 1881, was the first H. Enuma,
to go in this direction, and took out a patent for the 1J
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

* Comptes Bendues, 1881, p. 872.

30 HISTORY OF THE TRANSFORMER.

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 (namlich die bekaunten) Induktionsrollen
werden in den Hauptstromkreis uberall eingeschaltet,
wo der Strom abgezweigt (!) werden soil ; und durch
diese Einrichtung erhalt zuletzt jede elektrische
Lampe, oder jeder durch Elektrizitat 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.

Gauiard and The first who came forward with an industrial

' employment of the series system were Gauiard and

Gibbs, who, in the year 1883, placed before the public

an installation of electric lighting in the Koyal

Aquarium in London.

There were two such apparatus as shown in Fig. 18,

HISTORY OF THE TRANSFORMER. 31

32

HISTORY OF THE TRANSFORMER.

FIG. 19.

which were connected in series, and excited with
13 amperes from a Siemens' alternating current
dynamo. The apparatus had the following construc-
tion : — 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 com-
mutator. Fig. 20 shows this commutator placed in
the middle of four induction
coils. The ends of the secon-
dary 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 com-
mutator, which served the
same purpose for the primary circuit.

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 Kail-
way was taken in hand and carried out.

The source of current was a Siemens' alternating

HISTORY OF THE TRANSFORMER. 33

FIG 20.

34 HISTORY OF THE TRANSFORMER.

current dynamo of type Wo, which was excited by a
continuous current machine. The potential was
supposed to be 1500 volts and the current 11 • 3
amperes. 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 Edge-
ware 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 aranged 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,
FIG. 21. anc^ 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 con-
nected to a commutator, so that they could be used
either in parallel or series.

The methods of construction and connection used

HISTORY OF THE TRANSFORMER. 35

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 induc-
tion, 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 trans-
formation 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 em-
ployment of several coils has already been mentioned
as patented by the brothers Bright on 21st October,
1852, and was again later on discovered by Poggen-
dorf, 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* maintaining that the Fuller transformer
* The ' Electrical Engineer,' 17th Feb., 1888.

D 2

36 HISTORY OF THE TEANSFORMER.

was non-polar, and further, that the following im-
provements 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 gentle-
man 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 advan-
tages can be obtained to a much higher degree
with non-polar transformers. This has been proven
by Prof. Ferraris.*

The improvements mentioned under Nos. 3 and
4 are only to be attained with bi-polar transformers
after difficult and otherwise disadvantageous arrange-
ments ; 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

* La 'Lumiere electrique," fol. xvii., p. 145-148, 1885.

HISTORY OF THE TRANSFORMER. 37

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 electro-
motive 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

38 HISTOKY OF THE TRANSFORMER.

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 num-
ber 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 re-
quired 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 Eankine Kennedy,
who had devoted himself wholly to the study of in-
duction 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 inter-
esting statement that transformers, when not
connected in the primary circuit in series, as had
been usual till then, but in parallel, form a self-regu-
lating system of current distribution. Kankine
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 com-
prehension of the physical facts concerned, because

HISTORY OF THE TRANSFORMER. 39

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 trans-
formers 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 i*, 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 connec-
tion of transformers made possible self-regulation in
the same manner as the simple direct parallel con-
nection of incandescent lamps. While at the same
time he imagined that on account of the small re-
sistance 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 Keview " of 9th June, 1883.
At the end of this leader the editors say, that " Mr.

40 HISTORY OF THE TRANSFORMER.

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 par-
ticular 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 ap-
pearance in print.

In order to make possible the connection of trans-
formers 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 know-
ledge of its action. F. Geraldy has expressed
himself very suitably upon this point in the intro-
duction to his report upon the trials made with the
system of Messrs. Gaulard and Gibbs.*

"La distribution de 1'e'lectricite comporte la solu-
tion d'un grand nombre de problemes. II ne suffit
pas de se decider en principe et lorsqu'on a choisi la
distribution en quantite (en supposant meme, que
Fun des precedes puisse eire applique d'une facon
exclusive, ce qui n'est pas certain), lorsqu'on a trouve
le moyen de regler le generateur et les recepteurs
conformernent au mode choisi, il reste encore a lever
quantite de difficultes, a creer et disposer beaucoup
d'organes auxiliaires." Geraldy explained distinctly
that it was not sufficient to determine only the
* La * Lumiere electrique,' vol. x. p. 496, 1883.

HISTORY OF THE TKANS FORMER. 41

method of connection, but there were still a consider-
able 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, wfhich 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 Ex-
hibition 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.

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

42 HISTORY OF THE TRANSFORMER.

soldered together by projecting teetb. Tbe insula-
tion was made of stamped-out paper discs. Botb
spirals were wound between one another. The
building up of such coils was effected in the follow-
ing 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

FIG. 22.

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.

HISTORY OF THE TRANSFORMER.

43

In fact, several
faults in the trans-
formers in Turin
did arise from this
cause, the action of
the coils being dis-
turbed. Further
attempts with simi-
lar coils were made,
the station houses
of Turin, Venaria,
and Lanzo being lit
for five consecutive
hours. The circuit
was about 80 kilo-
metres long, the
main lead being of
chrombronze wire
of 3 '7 mm. di-
ameter. 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

44 HISTORY OF THE TRANSFORMER.

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 him-
self with this reference to its disadvantages, mention-
ing also what should be striven after to make the

HISTORY OF THE TRANSFORMER. 45

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 Deprez in " La Lumiere
electrique," * in which latter the system of Gaulard
and Gibbs is strongly criticised. Deprez 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. Koux,f 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 4

The observations are only quoted so far that the

* La ' Lumiere electrique,' vol. xiv. p. 45.

t ' Electricien,' 7th March, 1885.

J 'Natura,' 25th January, 1885, p. 60.

46

HISTORY OF THE TRANSFORMER.

Watts A I at the secondary terminals are still in-
creasing; 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. Eoux 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

External

Resistance

No.

Primary Circuit.

of

Secondary Circuit.

Efficiency.

Secondary

Circuit.

1

2.^4

I
12-13

I A
283-84

w.

1-24

15-0

I
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

variations could be prevented, if the cores of the
transformers be shifted either by hand or auto-
matically. Both methods would be expensive, and,
besides, the automatic regulation would be unreliable.

It was at once recognised by all those interested
in the subject, that this system made possible a sub-
division, 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

HISTORY OF THE TRANSFORMER. 47

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. Deprez 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 electro-
motive force may take place in the leads. In the
indirect system of current distribution, consequently,
the tension at the secondary terminals of the trans-
formers 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 dif-
ferent. The equality of these electromotive forces,

48 HISTORY OF THE TRANSFORMER.

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 resist-
ance 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 use-
less 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, not-
withstanding their ratio of transformation, possess
windings having the same relative position to the
magnetic field — this is only the case with non-polar

HISTORY OF THE TRANSFORMER. 49

transformers. Besides this quality of non-polar trans-
formers, 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 trans-
formers 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.

Throught he 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.

In May, 1885, a system of current distribution
meeting all the just-mentioned requirements was mi

50 HISTOKY OF THE TRANS FOKMER.

publicly brought out, giving an illustration of a
truly self-regulating system of current distribution,
This was the system of Zipernowsky, Deri, and
Blathy.

The first two patents concerning this system date
from 18th February, 1885, and are entitled, "Im^
provements in the means for the regulation of
alternating electric currents," No. 34,649, by Carl
Zipernowsky and Max Deri, of Budapest ; " Improve-
ments in the distribution of alternating currents,"
No. 33,951, by Max Deri, of Vienna. The third
patent is dated 6th March, 1885, and is entitled,
" Improvements in induction apparatus for the pur-
pose of transforming electric currents," No. 40,414,
by Carl Zipernowsky, Max Deri, and Otto Titus
Blathy, 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 *
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

* Elektricitatsverteilung aus Centralstationen, System Ziper-
nowsky-Deri, Centralbl. f. Electrotechnik Bd. VII. S. 422.

HISTORY OF THE TRANSFORMER.

51

upon which all these transformers are constructed is
that the subdivisions of the iron core run perpen-
dicularly 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

FIG. 23.

Copper
wire.

'Copper
wire.

the inventors used in preference the form repre-
sented in Fig. 23.

In all these forms the principle is generally
adhered to, that the magnetic resistance and the

E 2

52

HISTORY OF THE TRANSFORMER.

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.

This system procured for itself universal recogni-
tion, but especially in the Budapest Exhibition.

FIG. 24.

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

HISTORY OF THE TRANSFORMER. 53

FIG. 25.

54 HISTORY OF THE TRANSFORMER.

FIG. 27.

I Copper wire.

HISTORY OF THE TRANSFORMER.

55

any one of them without anywhere producing a
change in the intensity of the light, which could
be perceived.

It was, therefore, in the year 1885 that the prob-
lem of current distribution by means of transformers
was solved in a truly practical manner. The ideas
which led the inventors to this thoroughly success-
ful solution were then so unknown to practical and
theoretical electricians, that it was long ere they

FIG. 29.
Main Conductor1

Main- Conductor

-O-
-O-
O-

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

56

HISTORY OF THE TRANSFORMER.

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. How-
ever, that was not the case. He proposed, that with
series connection the strength of current should be
kept constant, and that each transformer should

FIG. 30.

have an especial regulating apparatus — the raising or
lowering of the core; which, by the way, is an arrange-
ment impracticable in a well designed transformer.
Such a regulating apparatus has lately been made
automatic.

" 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

HISTORY OF THE TRANSFORMER.

57

here the modus operandi" he says further, " but I
have seen the apparatus working very satisfactorily."
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

FIG. 31.

-o-

-o-

-o-

-o-

-Q—

•O-

urn [pi

-

m

]

o

m

] C

m

w

3 C

1

-o-

-0-

-0-

-o-

-0-

-0-

-o-

-o-

-o-

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. Ruhlrnann* and Essonf also gave vent to
their opinions against the connection of transformers

* * Electrical Keview,' vol. xvii. p. 157.

t ' Elektrotecknische Zeitschrift/ September, 1885.

58 HISTORY OP THE TRANSFORMER.

in parallel. In a like manner Messrs. Gaulard and
Gibbs for some time after the Zipernowsky-Deri
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 elec-
tricians 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 con-
structed the relation between the primary electro-
motive force and that of the secondary, remains
unaltered notwithstanding any variations in the
current taken out ; also that if the primary electro-
motive 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 al-
ready 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 trans-

HISTORY OF THE TRANSFORMER. 59

formers 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 pur-
poses 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 systen of current distribution, belongs
undoubtedly to Messrs. Zipernowsky, Deri, and
Blathy.

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 im-
practicable.

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

60 HISTORY OF THE TRANSFORMER.

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 Kome in the year 1886.
This installation however, serves only to feed an in-
variable 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.

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STAMFORD STREET AND CHARING CROSS.

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