IMPROVEMENTS IN DYNAMO ELECTRIC MACHINES AND ELECTRIC METERS
Year: 1883

page_text: LETTERS PATENT to Sebastian Ziani de Ferranti of N° 5 Stanwick Road,
West Kensington in the County of Middlesex Electrician for an Invention
of "IMPROVEMENTS IN DYNAMO ELECTRIC MACHINES AND ELECTRIC METERS
"
PROVISIONAL SPECIFICATION left by the said Sebastian Ziani de Ferranti
at the Office of the Commissioners of Patents on the 29th December 1883.
SEBASTIAN ZIANI DE FERRANTI of N° 5 Stanwick Road West Kensington in
the County of Middlesex Electrician "IMPROVEMENTS IN DYNAMO ELECTRIC
MACHINES AND ELECTRIC METERS
,,
The object of this invention is first to construct a dynamo electric machine
by which a continuous current may be produced without the use of a commutator.
For this purpose I employ a metallic disc of a good conducting metal such as
copper revolved between two fixed annular poles of an electro magnet. The pole
on one side of the disc being a North pole and on the opposite a South pole. I
connect the outermost ends of the magnet poles so as to form a horse shoe magnet
by projections from them which are made to meet together outside the outer
circumference of the revolving disc. Each annular pole piece of the magnet
I surround on its exterior and preferably also on its interior circumference by
insulated conducting coils through which the magnetizing current is passed.
There may also be a pole piece coming into close proximity with the disc
between the innermost coil of each magnet pole piece and the axis of the disc
whenever an inner coil is used.
When the disc is revolved an electric current is induced in it radially to or from
its periphery and axis.
To carry off the current from the periphery I make contact between the outer
edge of the disc and a fixed metallic casing passing around it by means of a film
of mercury interposed between them and carry off the current from the metallic
casing. Preferably I form the outer circumference of the disc with a T head and
surround this head with a casing of corresponding form.
A small quantity of mercury or other conducting fluid is supplied to the interior
of the casing and distributes itself around the whole of the casings' inner cir-
cumference whenever the disc is revolved. Or in place of this arrangement rubbers
lubricated with mercury may be employed.
1

page_text: From the axis the current can similarly be conveyed away by bosses on the axis
surrounded by fixed metallic casings and with mercury or other conducting liquid
supplied to the intervening space or it might be carried off from the axis by
rubbers bearing upon it as in other dynamo machines.
All parts of the machine with which the mercury used is liable to come into
contact I coat by electro deposition or otherwise with iron or it might be other
metal not affected by mercury.
In order to be able at all times to ascertain the height of the mercury in the
annular chamber surrounding the outer circumference of the disc I employ pairs
of insulated wires-the several pairs opening into the chamber at different distances
from the axis.
The ends of the wires are left bare. When there is sufficient mercury in the
chamber to make an electrical connection between the ends of the wires of any
one or other of the pairs an electric current may pass from one wire to the other
of the pair and the passing of the current may be indicated on a galvanometer or
single wires connected to galvanometers might be used and the circuit completed
through the body of the machine.
Machines constructed as above described may be used not only for the production
of a continuous current but also for obtaining motive power from a continuous
electric current. Or if a continuous current be passed radially through the disc
and the disc be revolved a current may be carried off from the coils of the
electro magnets. In this case the magnet pole pieces or cores would not be
required.
Figure 1 shews a longitudinal section and Figure 2 an end view of a machine
constructed as above described-A B are magnet cores or poles one North the other
South. Around the exterior of each is a coil C of an insulated conductor-and
around the interior another similar coil C. Each coil is preferably formed of a
conducting strip set edgewise that is the broader sides of succeeding coils are
towards one another but it might be of wire or strips of other form. D is the disc
preferably of copper electroplated with iron. E is the chamber surrounding
the T shaped outer circumference of the disc-this chamber is insulated on its
exterior. F is the axis which carries the disc. G G are bosses upon it they lie
in chambers H partly filled with mercury. I I are pipes by which mercury may
be poured from small cisterns or funnels into the chambers H. K is a pipe by
which mercury may be supplied to the chamber E. L L are terminals from which
pairs of insulated wires are led to the space between the magnet poles and by
which the height of mercury in this space can at all times be ascertained. When
the machine is at rest the mercury accumulates at the bottom of the chamber E
but when running the mercury is distributed uniformly around its circumference.
Figure 3 shews a longitudiual vertical section of another form of the machine.
In this form the magnet pole pieces are only surrounded by an outer insulated
conducting coil. The same parts are marked with the same letters of reference as
in Figures 1 and 2 so that it is unnecessary again to describe them. In place of
the space occupied by the coils being cylindrical it may be tapering as shewn at
Figures 4. Figure 5 shews the disc formed without any T head. Figure 6 shews
a longitudinal section and Figure 6ª an end view of another modified form of
the same machine. Figure 7 shews a longitudinal section and Figure 8 an end
view of a further modified form. In this case the iron pole pieces are done away
with and the outer circumference of the disc revolves between two insulated
conducting coils B and C through which a current is made to pass in opposite
directions. The conducting coils are each enclosed in casings X of non magnetic
metal the outer circumference of the disc enters a trough recess between the
casings to allow of a mercury contact being made between them and the disc.
Figure 9 shews a longitudinal section of another form of the machine and
Figure 10 an end view. In this form of machine B and C are two coils of
insulated conducting material through which a current is passed in opposite
directions. E E are metallic troughs for holding mercury. G G is a metallic

page_text: drum the ends of which are flanged outwards and made to enter the troughs E.
The drum G is carried by an axis F by which it can be rotated.
At Figure 11 I have shewn an electric meter acting upon the same principle.
A is the annular magnet core surrounded on its exterior with an insulated
conducting coil B and on its interior by an insulated conducting coil C.
One end of each coil leads to a terminal D the upper end of each terminates in
a cylinder which projects somewhat above the magnet core an annular trough is
thereby formed between these cylinders-into this trough a quantity of mercury
is filled a metallic connection is thereby made between the upper ends of the two
cylinders and a current can be passed from one terminal through both coils to the
other terminal. When a current is so passed radially through the mercury a
rotary motion will be set up and it will revolve in this annular trough. E are
blades carried by arms from an axis F they dip into the mercury and when the
mercury rotates they are carried round with it and rotate the axis.
The axis may have upon it a worm wheel to drive a train of recording gear.
The friction between the mercury and the annular trough will increase as the
square of the speed.
The rotative action induced by the current will also increase as the square of
the current. The two increases will therefore neutralize one another and the actual
rotation of the axis will vary as the current. The amount of current passed
through the meter will therefore be recorded.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Sebastian Ziani de Ferranti in the Patent Office on the 28th June
1884.
SEBASTIAN ZIANI DE FERRANTI of N° 5 Stanwick Road West Kensington
in the County of Middlesex, Electrician "IMPROVEMENTS IN DYNAMO ELECTRIC
MACHINES AND ELECTRIC METERS
"
The object of this invention is first to construct a dynamo electric machine by
which a continuous current may be produced without the use of a commutator.
For this purpose I employ a metallic disc of a good conducting non-magnetic
metal such as copper revolved between two fixed annular poles of an electro
magnet. The pole on one side of the disc being a North pole and on the opposite
a South pole. I connect the outermost ends of the magnet poles so as to form a
horse shoe magnet by projections from them which are made to meet together
outside the outer circumference of the, revolving disc. Each annular pole piece of
the magnet I surround by insulated conducting coils through which the magnetising
current is passed.
When the disc is revolved an electric current is induced in it radially to or from
its periphery and axis.
To carry off the current from the periphery I make contact between the outer
edge of the disc and a fixed metallic casing passing around it by means of a film of
mercury interposed between them and carry off the current from the metallic
casing.
A small quantity of mercury or other conducting fluid is supplied to the interior
of the casing and distributes itself around the whole of the casing's inner circum-
ference whenever the disc is revolved. Or in place of this arrangement rubbers
lubricated with mercury may be employed.
From the axis the current can similarly be conveyed away by bosses on the axis
surrounded by fixed metallic casings and with mercury or other conducting liquid
supplied to the intervening space-or it might be carried off from the axis by
rubbers bearing upon it as in other dynamo machines.
All parts of the machine with which the mercury used is liable to come into
contact I coat by electro deposition or otherwise with iron or it might be other
metal not affected by mercury.
In order to be able at all times to ascertain the height of the mercury in the
annular chamber surrounding the outer circumference of the disc I employ pairs of
insulated wires-the several pairs opening into the chamber at different distances
from the axis.
The ends of the wires are left bare. When there is sufficient mercury in the
chamber to make an electrical connection between the ends of the wires of any one
or other of the pairs an electric current may pass from one wire to the other of the
pair and the passing of the current may be indicated on a galvanometer or bell or
other recording instrument. Or single wires connected to galvanometers might be
used and the circuit completed through the body of the machine.
Machines constructed as above described may be used not only for the production
of a continuous current but also for obtaining motive power from a continuous
electric current. Or if a continuous current be passed radially through the disc
and the disc be revolved a current may be carried off from the coils of the electro
magnets. In this case the magnet pole pieces or cores would not be required.
Figure 1 sheet 1 shews a longitudinal section.
Figure 2 sheet 3 an end view of a machine constructed as above described.

page_text: A B are cylindrical magnet cores or poles facing one another and one North and
the other South. Each of these is surrounded by a cylinder A¹ B¹
The outer cylinder A¹ is in one piece with the rear end of the magnet core A the
other cylinder B¹ is in one piece with the rear end of the magnet core B. The
inner ends of the cylinders A³ B₁ are bolted together by bolts A*.
Around the exterior of each magnet core is a coil C of an insulated conductor.
Each coil is preferably formed of a conducting strip set edgewise that is, the broader
sides of succeeding coils are towards one another, but it might be of wire or strips
of other form.
D is the disc preferably of copper electro plated with iron.
E is the metallic casing surrounding the circumference of the disc. This casing
is insulated on its exterior.
F is the axis which carries the disc; it is mounted in bearings F1 as shown in
Figure 1.
F are belt pulleys by which the axis may be driven.
G G are bosses screwed on to the axis they hold between them the boss of the
disc D. The bosses G also lie in chambers H partly filled with mercury so that
the axis is put into electrical connection with the blocks A and B which form the
body of the machine.
I I are passages by which mercury may be poured from small cisterns or
funnels II¹ into the chambers H.
K is a pipe by which mercury may be supplied to the insulated casing E.
F3 are passages by which lubricating oil may be supplied to the bearings from
oil cups F see Figure 2.
The exciting current to be passed through the two coils C may be obtained by
putting the inner end of each coil in electrical communication with the insulated
casing E and the outer end of each coil in electrical communication with the
blocks A and B respectively; or the exciting current might be conveyed to the
coils through insulated conductors led out through the blocks A and B in the
manner shown at C* Figure 1.
One set of terminals for leading off the current from the machine may be at any
desired points on the exterior of the blocks A and B; the other set of terminals
are carried by insulated blocks E¹ which by insulated rods E are in electrical
connection with the inner insulated casing E.
J J in Figure 2 are gauge glasses by which the height of mercury in the inner
casing E can be ascertained when the machine is standing. They are closed at
their upper ends by screw caps-any excess of mercury can be drawn off from the
bottom of the gauge whilst if more mercury is required it can be supplied through
the pipe K.
At Figures 3 and 4 I have shown how insulated pairs of wires J J may be led
into the interior of the metal casing E.
The two wires in each pair are side by side on the same level they night either
be permanently in connection with an electrical tell-tale so that the height of the
mercury shall at all times be indicated or they might only be coupled to the
tell-tale at times when it is desired to know the mercury level as for example just
before starting the machine.
At Figures 5 and 6 I have shown how the height of mercury in the chamber E
can be ascertained at any time by opening a tap at the end of one or other of a
number of passages leading from the inner casing. These passages should be
formed through the insulating conducting rods which pass from the inner casing E
to the insulated terminal blocks E' at the exterior of the blocks A B.
In place of the spaces occupied by the coils C being cylindrical they might be of
a tapering form as shewn at Figure 1x Sheet 2.
Figures 7 and 8 shew a longitudinal section and end view of a machine similar
to the one shown at Figures 1 and 2 except that the rear ends of the magnet
cores A and B are connected only to a bed plate in place of to a cylinder passing

page_text: all around them. The disc D is also formed with a T shaped head around its
circumference and this head is surrounded by a casing of a corresponding form.
The parts shown in these figures are lettered with the same letters of reference
as in Figure 1 so that it is unnecessary to further describe them.
Figure 9 shows a longitudinal section and Figure 10 an end view of another
modified form. In this case the iron pole pieces are done away with and the outer
circumference of the disc D revolves between two insulated conducting coils B and C
through which a current is made to pass in the same direction. The conducting
coils are each enclosed in casings of non-magnetic metal-the outer circumference
of the disc enters a trough recess between the casings to allow of a mercury contact
being made between them and the disc.
Figure 11 shews a longitudinal section of another form of the machine and
Figure 12 an end view. In this form of machine B and C are two coils of
insulated conducting material through which a current is passed in opposite
directions. E E are metallic troughs for holding mercury. G G is a metallic drum
the ends of which are flanged outwards and made to enter the troughs E. The
drum G is carried by an axis F by which it can be rotated or to which it can give
a revolving motion.
When a current is passed in opposite directions through the two coils and the
drum is rotated a current can be led off from the two troughs E, or if a current
were passed longitudinally through the drum and the axis rotated a current could
be led off from the two coils B and C.
In the several forms of dynamo electrical machines herein before described the
axis is shown to be horizontal but it is not at all essential that it should be so it
might in all the several forms be placed equally well in a vertical position. To
illustrate this I have at Figures 13 and 14 shewn a vertical section and side
elevation of a machine similar to the machine shown at Figures 1 and 2 but with
the axis placed vertically instead of horizontally. The same letters of reference are
used as in Figures 1 and 2.
At Figures 15, 16 and 17 I have shewn one form of an electric meter constructed
according to my Invention and at Figures 18, 19 and 20 another form of the meter.
It is composed of a circular bath of mercury or it might be other conducting liquid
through which the current to be measured is made to pass radially and is also
made to pass through insulated conducting coils surrounding the circumference of
the bath or of a magnet pole piece below or above it and is also composed of
mechanism for recording the rotation of the mercury caused by the passage of the
current.
Figure 15 is a vertical section of the meter.
Figure 16 is a horizontal section through its lower part.
Figure 17 a plan view.
In these figures, A is an annular magnet core surrounded on its exterior with an
insulated conducting coil B. The lower end of the coil is in electrical connection
with a copper ring which is coupled to the terminal C,-the upper end of the coil
is in electrical connection with a cylinder D which stands upwards above the top
of the magnet core.
E is an insulated metallic conductor passing downwards through the centre of
the core A to a terminal F.
The upper end of the conductor E is on a level with the top of the core, and
forms part of the bottom of a trough G, which is to be partly filled with mercury.
The outer rim of the trough is as shown formed by the metallic cylinder D so that
when an electrical current passes from the terminal C through the coil B to the
cylinder D it then passes radially through the mercury to the conductor E, and so
to the terminal F; when a current so passes radially through the mercury and
through the circular ooil B the mercury is thereby caused to revolve within the
trough.
H is an ebonite disc fixed at a short distance above the bottom of the trough G;

page_text: the space between them is entirely filled with the mercury, and the mercury also
rises up a short distance through a hole formed through the centre of the disc. In
this way the greater part of the mercury in the trough is covered over and always
maintained clean.
I is a light spindle passing downwards through the hole in the centre of the disc,
its lower end steps into a jewel bearing in the top of the conductor E-it has also
arms J radiating from it into the space between the bottom of the trough and
the disc.
The upper end of the spindle has a small pinion upon it which when the spindle
is rotated gives motion to a recording train of wheels such as shown in the plan
view Figure 17.
In this way when the mercury is caused to rotate in the trough by the passage
of an electrical current through it, the mercury will carry round with it the radial
arms J and will so revolve the spindle I and cause the pinion which it carries to
give motion to the train of recording wheels. In order to prevent the mercury
from rotating too freely in the trough I provide around the circumference of the
trough a number of pins J¹ which have blades projecting from them in the space
between the bottom of the trough and the disc. The pins can be turned so as to set
these blades at any desired angle and thereby more or less retard the mercury from
rotating in the trough.
The bottom of the trough and of the disc might also have short studs or
projections standing out from them, so as to offer still more impediment to a quick
rotation of the mercury in the trough and so that the resistance offered to the
rotation of the mercury shall become greater and greater as the speed of rotation
increases.
In the meter shewn at Figures 18, 19 and 20 the magnet core is suppressed, and
the coil B is made to surround the mercury bath. In these Figures, G is the bath
of mercury.
E the insulated conductor passing downwards through the centre of the bottom.
of the bath to a terminal F.
B are insulated coils connected at one end to the terminal C, and at the other to
the metal cylinder D, which forms the outer rim of the mercury bath.
J are the radial arms extending from the vertical spindle I.
H is a disc forming a cover for the mercury in the bath.
L is the recording train of wheels which are shewn separately on a larger scale
at Figure 20.
It will be seen both in the construction shewn at Figure 15 and in the
construction shewn at Figure 18 that where the vertical spindle I passes through
the bottom of the chamber which contains the recording train of wheels there is a
tube projecting downwards from the hole through which the spindle passes so that
even if the meter were inverted the mercury would not flow into the chamber
containing the recording wheels.
The mercury bath need not of necessity be a shallow flat bath such as shewn in
the Drawings it might be of other form say for example in the form of a bell. In
place also of employing radial arms extending from the axis into the mercury the
axis night carry a disc either plain or corrugated and this disc might extend
nearly to the circumference of the bath.
Having now described the nature of my said [sic] and in what manner the
same is to be performed 1 would state that I am aware that in dynamo electric
machines for producing a continuous electric current it has before been proposed to
employ a revolving disc of iron magnetized by the passage of an electric current
through a fixed coil of an insulated conductor surrounding its circumference and
that it has also been proposed to encase such disc and coil within a mass of iron
which becomes magnetized by reason of the magnetization of the disc and that it
has also been proposed to carry off the radial electric current set up in the disc
when rotated, by means of contact mechanism applied to its axis and to its

page_text: circumference-My dynamo machines differ essentially from machines constructed
in this manner What I claim is :-
First. The general arrangement and construction of dynamo electric machines
substantially in the ways herein-before described.
Second. In the construction of dynamo electric machines the combination of
a-Two cylindrical magnet pole pieces set face to face and with an insulated
conducting coil wound around the circumference of each pole piece so that one
shall be North the other South when an electric current is passed through
the coils.
b-A disc of copper or such like good conducting or non-magnetic metal mounted
upon an axis concentric with the pole pieces so that it may be revolved
between them, and
c-Means for leading off the radial current set up in the disc from its axis and its
circumference.
Third. In the construction of dynamo electric machines the combination of.
a A disc of copper or such like good conducting and non magnetic metal mounted
upon an axis so that it may be revolved.
6 Two coils of an insulated conductor wound in the same direction and placed one
on either side of the disc near its circumference through which coils an electric
current can be passed, and
c-Means for leading off electric current from the axis and circumference of the
disc.
Fourth. In the construction of dynamo electric machines the combination
substantially as described with reference to Figures 11 and 12 of
a A metallic drum with flanges extending outwards from its ends or it might be a
pair of discs carried by a revolving axis.
b.Fixed coils of an insulated conductor placed at the side of each flange or disc
and through which an electric current can be passed in opposite directions.
c. Means for conveying away an electric current from the circumference of the
two discs.
Fifth. In the construction of dynamo electric machines in which electrical
contact is made between the circumference of a revolving disc and a fixed circular
metallic trough or casing surrounding it the employment of means such as are
herein described by which the height of mercury in the trough or casing may be
readily ascertained.
Sixth. The construction of electric meters substantially in the manner berein
before described.
Seventh. In electric meters the combination of.
a. A bath of mercury (or other conducting liquid) through which the current to be
measured is made to pass radially.
b-A coil of an insulated conductor surrounding the circumference of the bath or an
iron core below or above it and through which the current is also passed.
c, Mechanism for recording the rotation of the mercury set up by the passage of
the current.
In witness whereof I the said Sebastian Ziani de Ferranti have hereunto set
my hand and seal this twenty seventh day of June in the year of our Lord One
thousand eight hundred and eighty four.
a 7
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