“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.