Rhode Island, lighted the parlor of his home at 11 Pearl Street, Salem,
Mass., during July, 1859, with several incandescent lamps having a
strip of platinum for the burner. The novel feature of this lamp was
that the platinum strip was narrower at the terminals than in the
center. Heat is conducted away from the terminals and by making the
burner thin at these points, the greater resistance of the ends of
the burner absorbed more electrical energy thus offsetting the heat
being conducted away. This made a more uniform degree of incandescence
throughout the length of the burner, and Prof. Farmer obtained a patent
on this principle many years later (1882).
[Illustration: FARMER’S INCANDESCENT LAMP, 1859.
This experimental platinum lamp was made by Professor Farmer and
several of them lighted the parlor of his home in Salem, Mass.]
FURTHER ARC LAMP DEVELOPMENTS
During the ten years, 1850 to 1860, several inventors developed arc
lamp mechanisms. Among them was M. J. Roberts, who had invented the
graphite incandescent lamp. In Roberts’ arc lamp, which he patented in
1852, the lower carbon was stationary. The upper carbon fitted snugly
into an iron tube. In the tube was a brass covered iron rod, which
by its weight could push the upper carbon down the tube so the two
carbons normally were in contact. An electro-magnet in series with the
arc was so located that, when energized, it pulled up the iron tube.
This magnet also held the brass covered iron rod from pushing the
upper carbon down the tube so that the two carbons were pulled apart,
striking the arc. When the arc went out, the iron tube dropped back
into its original position, the brass covered iron rod was released,
pushing the upper carbon down the tube until the two carbons again
touched. This closed the circuit again, striking the arc as before.
[Illustration: ROBERTS’ ARC LAMP, 1852.
The arc was controlled by an electro-magnet which held an iron tube to
which the upper carbon was fastened.]
[Illustration: SLATER AND WATSON’S ARC LAMP, 1852.
Clutches were used for the first time in this arc lamp to feed the
carbons.]
In the same year (1852) Slater and Watson obtained an English patent
on an arc lamp in which the upper carbon was movable and held in place
by two clutches actuated by electro-magnets. The lower carbon was
fixed, and normally the two carbons touched each other. When current
was turned on, the electro-magnet lifted the clutches which gripped the
upper carbon, pulling it up and striking the arc. This was the first
time that a clutch was used to allow the carbon to feed as it became
consumed.
Henry Chapman, in 1855, made an arc in which the upper carbon was
allowed to feed by gravity, but held in place by a chain wound around
a wheel. On this wheel was a brake actuated by an electro-magnet. The
lower carbon was pulled down by an electro-magnet working against a
spring. When no current was flowing or when the arc went out, the two
carbons touched. With current on, one electro-magnet set the brake and
held the upper carbon stationary. The other electro-magnet pulled the
lower carbon down, thus striking the arc.
None of these mechanisms regulated the length of the arc. It was not
until 1856 that Joseph Lacassagne and Henry Thiers, Frenchmen, invented
the so-called “differential” method of control, which made the carbons
feed when the arc voltage, and hence length, became too great. This
principle was used in commercial arc lamps several years afterward when
they were operated on series circuits, as it had the added advantage
of preventing the feeding of one arc lamp affecting another on the
same circuit. This differential control consists in principle of two
electro-magnets, one in series with, and opposing the pull of the other
which is in shunt with the arc. The series magnet pulls the carbons
apart and strikes the arc. As the arc increases in length, its voltage
rises, thereby increasing the current flowing through the shunt magnet.
This increases the strength of the shunt magnet and, when the arc
becomes too long, the strength of the shunt becomes greater than that
of the series magnet, thus making the carbons feed.
[Illustration: DIAGRAM OF “DIFFERENTIAL” METHOD OF CONTROL OF AN ARC
LAMP.
This principle, invented by Lacassagne and Thiers, was used in all arc
lamps when they were commercially introduced on a large scale more than
twenty years later.]
The actual method adopted by Lacassagne and Thiers was different from
this, but it had this principle. They used a column of mercury on
which the lower carbon floated. The upper carbon was stationary. The
height of the mercury column was regulated by a valve connected with
a reservoir of mercury. The pull of the series magnet closed the valve
fixing the height of the column. The pull of the shunt magnet tended
to open the valve, and when it overcame the pull of the series magnet
it allowed mercury to flow from the reservoir, raising the height of
the column bringing the carbons nearer together. This reduced the
arc voltage and shunt magnet strength until the valve closed again.
Thus the carbons were always kept the proper distance apart. In first
starting the arc, or if the arc should go out, current would only flow
through the shunt magnet, bringing the two carbons together until they
touched. Current would then flow through the contact of the two carbons
and through the series magnet, shutting the valve. There were no means
of pulling the carbons apart to strike the arc. Current flowing through
the high resistance of the poor contact of the two carbons, heated
their tips to incandescence. The incandescent tips would begin to burn
away, thus after a time starting an arc. The arc, however, once started
was maintained the proper length.
[Illustration: LACASSAGNE AND THIERS’ DIFFERENTIALLY CONTROLLED ARC
LAMP, 1856.
The lower carbon floated on a column of mercury whose height was
“differentially” controlled by series and shunt magnets.]
In 1857, Serrin took out his first patent on an arc lamp, the general
principles of which were the same as in others he made. The mechanism
consisted of two drums, one double the diameter of the other. Both
carbons were movable, the upper one feeding down, and the lower one
feeding up, being connected with chains wound around the drums. The
difference in consumption of the two carbons was therefore compensated
for by the difference in size of the drums, thus maintaining the
location of the arc in a fixed position. A train of wheels controlled
by a pawl and regulated by an electro-magnet, controlled the movement
of the carbons. The weight of the upper carbon and its holder actuates
the train of wheels.
[Illustration: SERRIN’S ARC LAMP, 1857.
This type of arc was not differentially controlled but was the first
commercial lamp later used. Both carbons were movable, held by chains
wound around drums which were controlled by ratchets actuated by an
electro-magnet.]
DEVELOPMENT OF THE DYNAMO, 1840–1860
During the first few years after 1840 the dynamo was only a laboratory
experiment. Woolrich devised a machine which had several pairs of
magnets and double the number of coils in order to make the current
obtained less pulsating. Wheatstone in 1845 patented the use of
electro-magnets in place of permanent magnets. Brett in 1848 suggested
that the current, generated in the coils, be allowed to flow through
a coil surrounding each permanent magnet to further strengthen the
magnets. Pulvermacher in 1849 proposed the use of thin plates of iron
for the bobbins, to reduce the eddy currents generated in the iron.
Sinsteden in 1851 suggested that the current from a permanent magnet
machine be used to excite the field coils of an electro-magnet machine.
In 1855 Soren Hjorth, of Copenhagen, Denmark, patented a dynamo having
both permanent and electro-magnets, the latter being excited by
currents first induced in the bobbins by the permanent magnets. In 1856
Dr. Werner Siemens invented the shuttle wound armature. This consisted
of a single coil of wire wound lengthwise and counter sunk in a long
cylindrical piece of iron. This revolved between the magnet poles which
were shaped to fit the cylindrical armature.
[Illustration: SIEMENS’ DYNAMO, 1856.
This dynamo was an improvement over others on account of the
construction of its “shuttle” armature.]
THE FIRST COMMERCIAL INSTALLATION OF AN ELECTRIC LIGHT
In 1862 a Serrin type of arc lamp was installed in the Dungeness
lighthouse in England. Current was supplied by a dynamo made by the
Alliance Company, which had been originally designed in 1850 by Nollet,
a professor of Physics in the Military School in Brussels. Nollet’s
original design was of a dynamo having several rows of permanent
magnets mounted radially on a stationary frame, with an equal number
of bobbins mounted on a shaft which rotated and had a commutator so
direct current could be obtained. A company was formed to sell hydrogen
gas for illuminating purposes, the gas to be made by the decomposition
of water with current from this machine. Nollet died and the company
failed, but it was reorganized as the Alliance Company a few years
later to exploit the arc lamp.
[Illustration: ALLIANCE DYNAMO, 1862.
This was the dynamo used in the first commercial installation of an arc
light in the Dungeness Lighthouse, England, 1862.]
About the only change made in the dynamo was to substitute collector
rings for the commutator to overcome the difficulties of commutation.
Alternating current was therefore generated in this first commercial
machine. It had a capacity for but one arc light, which probably
consumed less than ten amperes at about 45 volts, hence delivered
in the present terminology not over 450 watts or about two-thirds
of a horsepower. As the bobbins of the armature undoubtedly had a
considerable resistance, the machine had an efficiency of not over 50
per cent and therefore required at least one and a quarter horsepower
to drive it.
FURTHER DYNAMO DEVELOPMENTS
In the summer of 1886 Sir Charles Wheatstone constructed a self-excited
machine on the principle of using the residual magnetism in the field
poles to set up a feeble current in the armature which, passing through
the field coils, gradually strengthened the fields until they built up
to normal strength. It was later found that this idea had been thought
of by an unknown man, being disclosed by a clause in a provisional
1858 English patent taken out by his agent. Wheatstone’s machine was
shown to the Royal Society in London and a paper on it read before the
Society on February 14, 1867. The field coils were shunt wound.
[Illustration: WHEATSTONE’S SELF-EXCITED DYNAMO, 1866.
This machine was the first self-excited dynamo by use of the residual
magnetism in the field poles.]
Dr. Werner Siemens also made a self-excited machine, having series
fields, a paper on which was read before the Academy of Sciences
in Berlin on January 17, 1867. This paper was forwarded to the
Royal Society in London and presented at the same meeting at which
Wheatstone’s dynamo was described. Wheatstone probably preceded Siemens
in this re-discovery of the principle of self-excitation, but both are
given the merit of it. However, S. A. Varley on December 24, 1866,
obtained a provisional English patent on this, which was not published
until July, 1867.
[Illustration: GRAMME’S DYNAMO, 1871.
These were commercially used, their main feature being the “ring” wound
armature.]
[Illustration: GRAMME’S “RING” ARMATURE.
Wire coils, surrounding an iron wire core, were all connected together
in an endless ring, each coil being tapped with a wire connected to a
commutator bar.]
In 1870 Gramme, a Frenchman, patented his well-known ring armature. The
idea had been previously thought of by Elias, a Hollander, in 1842, and
by Pacinnotti, an Italian, as shown by the crude motors (not dynamos)
they had made. Gramme’s armature consisted of an iron wire core coated
with a bituminous compound in order to reduce the eddy currents. This
core was wound with insulated wire coils, all connected together in
series as one single endless coil. Each coil was tapped with a wire
connected to a commutator bar. His first machine, having permanent
magnets for fields, was submitted to the French Academy of Sciences in
1871. Later machines were made with self-excited field coils, which
were used in commercial service. They had, however a high resistance
armature, so that their efficiency did not exceed 50 per cent.
[Illustration: ALTENECK’S DYNAMO WITH “DRUM” WOUND ARMATURE, 1872.
The armature winding was entirely on the surface of the armature core,
a principle now used in all dynamos.]
Von Hefner Alteneck, an engineer with Siemens, invented the drum wound
armature in 1872. The wires of the armature were all on the surface
of the armature core, the wires being tapped at frequent points for
connection with the commutator bars. Thus in the early seventies,
commercial dynamos were available for use in arc lighting, and a few
installations were made in Europe.
RUSSIAN INCANDESCENT LAMP INVENTORS
In 1872 Lodyguine, a Russian scientist, made an incandescent lamp
consisting of a “V” shaped piece of graphite for a burner, which
operated in nitrogen gas. He lighted the Admiralty Dockyard at St.
Petersburg with about two hundred of these lamps. In 1872 the Russian
Academy of Sciences awarded him a prize of 50,000 rubles (a lot of
real money at that time) for his invention. A company with a capital
of 200,000 rubles (then equal to about $100,000) was formed but as
the lamp was so expensive to operate and had such a short life, about
twelve hours, the project failed.
[Illustration: LODYGUINE’S INCANDESCENT LAMP, 1872.
The burner was made of graphite and operated in nitrogen gas.]
[Illustration: KONN’S INCANDESCENT LAMP, 1875.
In this lamp the graphite rods operated in a vacuum.]
Kosloff, another Russian, in 1875 patented a graphite in nitrogen
incandescent lamp, which had several graphite rods for burners, so
arranged that when one failed another was automatically connected.
Konn, also a Russian, made a lamp similar to Kosloff’s except that
the graphite rods operated in a vacuum. Bouliguine, another Russian,
in 1876 made an incandescent lamp having a long graphite rod, only
the upper part of which was in circuit. As this part burned out, the
rod was automatically pushed up so that a fresh portion then was in
circuit. It operated in a vacuum. None of these lamps was commercial as
they blackened rapidly and were too expensive to maintain.
[Illustration: BOULIGUINE’S INCANDESCENT LAMP, 1876.
A long graphite rod, the upper part of which only was in circuit,
operated in vacuum. As this part burned out, the rod was automatically
shoved up, a fresh portion then being in the circuit.]
THE JABLOCHKOFF “CANDLE”
Paul Jablochkoff was a Russian army officer and an engineer. In the
early seventies he came to Paris and developed a novel arc light. This
consisted of a pair of carbons held together side by side and insulated
from each other by a mineral known as kaolin which vaporized as the
carbons were consumed. There was no mechanism, the arc being started
by a thin piece of carbon across the tips of the carbons. Current
burned this bridge, starting the arc. The early carbons were about
five inches long, and the positive carbon was twice as thick as the
negative to compensate for the unequal consumption on direct current.
This, however, did not work satisfactorily. Later the length of the
carbons was increased, the carbon made of equal thickness and burned
on alternating current of about eight or nine amperes at about 45
volts. He made an alternating current generator which had a stationary
exterior armature with interior revolving field poles. Several
“candles,” as they were called, were put in one fixture to permit all
night service and an automatic device was developed, located in each
fixture, so that should one “candle” go out for any reason, another was
switched into service.
[Illustration: JABLOCHKOFF “CANDLE,” 1876.
This simple arc consisted of a pair of carbons held together side by
side and insulated from each other by kaolin. Several boulevards in
Paris were lighted with these arc lights. This arc lamp is in the
collection of the Smithsonian Institution.]
In 1876 many of these “candles” were installed and later several of the
boulevards in Paris were lighted with them. This was the first large
installation of the arc light, and was the beginning of its commercial
introduction. Henry Wilde made some improvements in the candle by
eliminating the kaolin between the carbons which gave Jablochkoff’s arc
its peculiar color. Wilde’s arc was started by allowing the ends of the
carbons to touch each other, a magnet swinging them apart thus striking
the arc.
[Illustration: JABLOCHKOFF’S ALTERNATING CURRENT DYNAMO, 1876.
This dynamo had a stationary exterior armature and internal revolving
field poles. Alternating current was used for the Jablochkoff “candle”
to overcome the difficulties of unequal consumption of the carbons on
direct current.]
COMMERCIAL INTRODUCTION OF THE DIFFERENTIALLY CONTROLLED ARC LAMP
About the same time Lontin, a Frenchman, improved Serrin’s arc lamp
mechanism by the application of series and shunt magnets. This is the
differential principle which was invented by Lacassagne and Thiers in
1855 but which apparently had been forgotten. Several of these lamps
were commercially installed in France beginning with 1876.
ARC LIGHTING IN THE UNITED STATES
[Illustration: WALLACE-FARMER ARC LAMP, 1875.
This “differentially controlled” arc lamp consisted of two slabs of
carbon between which the arc played. In the original lamp the carbon
slabs were mounted on pieces of wood held in place by bolts, adjustment
being made by hitting the upper carbon slab with a hammer. This lamp is
in the collection of the Smithsonian Institution.]
[Illustration: WALLACE-FARMER DYNAMO, 1875.
This was the first commercial dynamo used in the United States for
arc lighting. This dynamo is in the collection of the Smithsonian
Institution.]
About 1875 William Wallace of Ansonia, Connecticut, made an arc light
consisting of two rectangular carbon plates mounted on a wooden frame.
The arc played between the two edges of the plates, which lasted much
longer than rods. When the edges had burned away so that the arc then
became unduly long, the carbon plates were brought closer together by
hitting them with a hammer. Wallace became associated with Moses G.
Farmer, and they improved this crude arc by fastening the upper carbon
plate to a rod which was held by a clutch controlled by a magnet. This
magnet had two coils in one, the inner winding in series with the arc,
and outer one in shunt and opposing the series winding. The arc was
therefore differentially controlled.
[Illustration: WESTON’S ARC LAMP, 1876.
This lamp is in the collection of the Smithsonian Institution.]
They also developed a series wound direct current dynamo. The armature
consisted of a number of bobbins, all connected together in an endless
ring. Each bobbin was also connected to a commutator bar. There were
two sets of bobbins, commutators and field poles, the equivalent of two
machines in one, which could be connected either to separate circuits,
or together in series on one circuit. The Wallace-Farmer system was
commercially used. The arc consumed about 20 amperes at about 35 volts,
but as the carbon plates cooled the arc, the efficiency was poor.
The arc flickered back and forth on the edges of the carbons casting
dancing shadows. The carbons, while lasting about 50 hours, were not
uniform in density, so the arc would flare up and cast off soot and
sparks.
Edward Weston of Newark, New Jersey, also developed an arc lighting
system. His commercial lamp had carbon rods, one above the other, and
the arc was also differentially controlled. An oil dash pot prevented
undue pumping of the carbons. His dynamo had a drum-wound armature, and
had several horizontal field coils on each side of one pair of poles
between which the armature revolved. The system was designed for about
20 amperes, each are taking about 35 volts.
[Illustration: BRUSH’S DYNAMO, 1877.
This dynamo was used for many years for commercial arc lighting.]
[Illustration: DIAGRAM OF BRUSH ARMATURE.
The armature was not a closed circuit. For description of its
operation, see text.]
Charles F. Brush made a very successful arc lighting system in 1878.
His dynamo was unique in that the armature had eight coils, one end of
each pair of opposite coils being connected together and the other ends
connected to a commutator segment. Thus the armature itself was not a
closed circuit. The machine had two pairs of horizontal poles between
which the coils revolved. One end of the one pair of coils in the most
active position was connected, by means of two of the four brushes,
in series with one end of the two pairs of coils in the lesser active
position. The latter two pairs of coils were connected in multiple
with each other by means of the brushes touching adjacent commutator
segments. The outside circuit was connected to the other two brushes,
one of which was connected to the other end of the most active pair
of coils. The other brush was connected to the other end of the two
lesser active pairs of coils. The one pair of coils in the least active
position was out of circuit. The field coils were connected in series
with the outside circuit.
[Illustration: BRUSH’S ARC LAMP, 1877.
The carbons were differentially controlled. This lamp was used for many
years. This lamp is in the collection of the Smithsonian Institution.]
Brush’s arc lamp was also differentially controlled. It was designed
for about 10 amperes at about 45 volts. The carbons were copper
plated to increase their conductivity. Two pairs of carbons were used
for all-night service, each pair lasting about eight hours. A very
simple device was used to automatically switch the arc from one to
the other pair of carbons, when the first pair was consumed. This
device consisted of a triangular-shaped piece of iron connected to the
solenoid controlling the arc. There was a groove on each of the outer
two corners of this triangle, one groove wider than the other. An iron
washer surrounded each upper carbon. The edge of each washer rested
in a groove. The washer in the narrow groove made a comparatively
tight fit about its carbon. The other washer in the wider groove had
a loose fit about its carbon. Pins prevented the washer from falling
below given points. Both pairs of carbons touched each other at the
start. When current was turned on, the solenoid lifted the triangle,
the loose-fitting washer gripped its carbon first, so that current then
only passed through the other pair of carbons which were still touching
each other. The further movement of the solenoid then separated these
carbons, the arc starting between them. When this pair of carbons
became consumed, they could not feed any more so that the solenoid
would then allow the other pair of carbons to touch, transferring the
arc to that pair.
[Illustration: THOMSON-HOUSTON ARC DYNAMO, 1878.
This dynamo was standard for many years. This machine is in the
collection of the Smithsonian Institution.]
Elihu Thomson and Edwin J. Houston in 1878 made a very successful and
complete arc light system. Their dynamo was specially designed to fit
the requirements of the series arc lamp. The Thomson-Houston machine
was a bipolar, having an armature consisting of three coils, one end of
each of the three coils having a common terminal, or “Y” connected, as
it is called. The other end of each coil was connected to a commutator
segment. The machine was to a great extent self-regulating, that is the
current was inherently constant with fluctuating load, as occurs when
the lamps feed or when the number of lamps burning at one time should
change for any reason. This regulation was accomplished by what is
called “armature reaction,” which is the effect the magnetization of
the armature has on the field strength. Close regulation was obtained
by a separate electro-magnet, in series with the circuit, which shifted
the brushes as the load changed. As there were but three commutator
segments, one for each coil, excessive sparking was prevented by an air
blast.