Improvements in Dynamo Electric Machines and Motors.
Year: 1886

page_text: Improvements in Dynamo Electric Machines and Motors.
I, HERBERT JOHN ALLISON, of the firm of Allison Brothers, of 52 Chancery
Lane, London, in the County of Middlesex, Patent Agents, do hereby declare the
nature of this invention, which has been communicated to me from abroad by:
William Lawrence Voelker, of Morton, Delaware County, State of Pennsylvania,
United States of America, Electrician, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following:
statement:-
The object of my invention is to improve the efficiency of dynamo electrio.
machines and motors, and also to prevent the injurious heating of the machine
while in use.
The first part of my invention relates to the construction of the body of magnetic
material upon which the coils of wire for the armature of the machine are wound
or carried. It has heretofore been proposed to make this portion of the machine,:
which portion is usually of cylindrical or annular form, from a number of plates
of iron put together to form the armature core or body. The object of this con-
struction is to obtain a subdivision of the mass of iron so as to permit more rapid
changes of magnetic condition and to prevent the flow of induced or Foucault:
currents in the body of iron, and to therefore lessen the heat developed in the
armature.
:
Cylinder or ring armatures have usually been made from a number of thin plates_
of iron in the form of discs or washers, the discs or plates of iron being in some:
cases separated from one another by air spaces or by insulating material such as
mica, paper, &, and in some instances plates of brass have been employed as the
magnetic insulation.
I
In most of the cases mentioned the formation of the heating or Foucault currents.
is but partially prevented, while the results are generally secured at the expense
of efficiency owing to the comparatively large space occupied by the diamagnetic
>
.

page_text: substance, whether it be air or a brass plate. This is especially true of an armature
made up as in one of the previous forms, of a few iron plates alternating with
plates of brass.
In another construction of armature a number of plates of iron have been soldered
together so as to form a solid mass. In this construction the plates are not separate
and the armature is not in fact mechanically subdivided into layers. The result is
as I have found by actual test that the armature heats to a much greater extent
under changes of magnetic condition than does the armature constructed as here-
inafter described from a number of thin sheet iron plates coated as hereinafter set
forth, with a thin film of non-magnetic metal and held together in any suitable way
but so that the various parts shall preserve their mechanical individuality and the
armature shall be in fact a subdivided or laminated armature whose plates or
individual portions are separated by the thin layers of air present when two
separate plates are put into so called contact.
I have discovered that by constructing the armature core or body on which the
electric conductors are placed from a number of thin soft iron discs or plates each
having a film or thin coating of a diamagnetic metal such for instance as tin,
bismuth, zinc, and assembled or held together by any suitable mechanical device,
the formation of the eddy or heating currents may be to a great extent prevented.
By this construction all the advantages of a magnetic subdivision of the core are
secured, while at the same time the magnetic efficiency of the core as an armature
is almost at its maximum owing to the small amount of non-magnetic as compared
with magnetic material.
In carrying out my invention I make use of thin soft iron discs, sheets or annuli,
to which the film or coating of non-magnetic is made to adhere, by electro plating,
by dipping in melted metal, by rolling, or in any other way such as to cause a thin
film of the metal to adhere to the sheet iron plate or disc.
A number of plates thus coated are held together or in contact with one
another upon the armature shaft by suitable clamping devices, so as to form a
cylindrical core or carrier of individual or separate plates magnetically continuous
in the direction of the line of force, but separated from one another in a direction
transverse to those lines and making in fact a series of separate plates whose plane
surfaces lie in contact.
To make a cylinder armature the plates or discs may be punched from thin sheet
iron and placed upon the armature shaft in contact with one another with their
plane surfaces at right angles to the axis of rotation, such discs being held in position
by being keyed to the shaft, or otherwise secured, and kept from lateral displacement
by collars at each end, fastened to the shaft by set screws.
The second part of my invention relates to the construction of the masses of iron
constituting the cores of the field of force magnets, and the pole pieces for said
magnets, between which the armature rotates.
The object is to secure a complete subdivision of the iron and to prevent the
formation of the heat or eddy currents either in the core or in the pole piece.
The object is also to obtain, in spite of such subdivision, a large mass of magnetic
material in a given space.
These objects I attain by building up the cores and pole pieces of the field
magnet for a dynamo electric machine or motor from thin sheet iron plates
mechanically coated or plated with a diamagnetic metal such as zinc, bismuth, &c,
and clamped or held together to form a compact body in which the various
plates maintain their individuality and are divided from one another at their plane
surfaces.
By my invention I secure all the advantages due to a magnetic subdivision of
the core and pole piece, as well as that due to a mechanical subdivision of the
laminated or subdivided structure into separate parts resting in mechanical contact
with one another, but in fact separated by the thin layers of air always present
when two plane surfaces are brought together with any ordinary degree of com-
pression. In a core and pole piece made up in this way there is the highest

page_text: magnetic efficiency, owing to the small amount of diamagnetic material, and the
large amount of magnetic material such as iron, compared with the amount of
diamagnetic substance.
The thin sheet iron plates coated or plated as described may be held or pressed
together to form a compact body, by any suitable means, though it will be sufficient
if they are bound firmly together by the coils of wire wound upon them.
I am aware that it is not new to make the core for a field magnet of a number
of iron plates soldered together to form a solid mass, but I have demonstrated by
actual experiment that in a mass of this kind the heating effects due to changes
of magnetic condition are very much greater than is the case if the plates maintain
their individuality so that the core or pole piece is in fact made up of separate
thin plates resting with their separate plain surfaces in contact with one another
and not as in the case just referred to, forming a practically continuous mass of
metal, discontinuous only in the nature of the material.
In my invention while preserving the feature of the plate of iron having a thin
film of diamagnetic metal mechanically or electrically plated upon its surface, I at
the same time secure a laminated or subdivided state of the body constituting the
core of the pole piece by preserving in each part a mechanical individuality so that
it shall be in fact separated from its neighbors, though the plane surfaces are held
or pressed into contact..
The third part of my invention relates to a means for improving the action or
efficiency of that class of dynamo electric machines in which the current generated
in the armature and carried off to do useful work are set up in lengths of armature
conductor mounted on a suitable carrier, by causing said conductor to move trans-
versely through magnetic lines of force emanating from the pole faces of a suitable
field magnet. The common form of machine in which this principle resides is that
having what is commonly known as a cylindrical or annular armature, though
another form also containing the principle and to which likewise my invention
is obviously applicable is that in which a so called disc armature is employed, or
one in which the wires are arranged radially on a suitable shaft and are caused
to pass between the poles of the field magnets presented to one another and in
close proximity.
My invention consists in the combination with the inductor wire of the armature
of a machine, in which the currents are developed by the passage of the wire
transversely through the magnetic field, of a sheath or envelope of magnetic material,
such for instance as wrought iron encircling said conductor.
This sheath or envelope may be applied or combined with the conductor in
various ways without departing from the invention.
Some of the ways in which this part of my invention may be carried out are
hereinafter described.
I do not claim the application of the magnetic sheath to the conductor wire of
what is known as a pole armature machine, or one in which the conductor is wound
upon a bar or rod of iron whose end is brought into and out of proximity with a
pole piece so as to acquire a magnetic charge and to then discharge, and to thereby
set up currents in the wire wound in planes transverse to its magnetic axis. In
fact the application of the sheath in the manner herein described would be detri-
mental rather than otherwise, inasmuch as it would tend to divert the magnetic
lines of force from the core and in so far as it did so would weaken the action of
the machine.
The armature wire or conductor is preferably provided with the usual insulating
sheath or cover, and the wrapping or sheath of iron is applied to the exterior of
the latter. The wire or conductor thus sheathed is wound or applied directly to
the armature core or carrier without further insulation, and in the proper way to
be carried transversely through the magnetic lines of force emanating from the
field of force pole piece after the manner of the inductor wire in the armature of a
machine having a cylindrical or annular armature, and to thereby, through cutting
of such lines of force by the lengths of conductor transverse to the lines of rotation,

page_text: i
to develope the effective currents that are conveying to the commutator and to the
outside circuit to do useful work.
When the armature conductor thus provided with its sheath is applied to the
iron cylindrical or annular body of a machine such as a Gramme or Siemens
machine, the armature carrier with its conductors. forms a nearly true armature for
the field magnets and an intensely saturated magnetic field is produced for the
conductors to pass through.
The magnetic exposure of the conductor being thus largely increased, and the
effective magnetic lines of force emanating from the field of force pole pieces being
thus brought to bear with greater directness upon said conductor, it is possible to
develope powerful electric currents or mechanical energy with a greater reduced
weight of copper wire and an efficient machine may be produced having a very
low internal resistance and small weight of armature.
The magnetic sheath may be applied to the armature conductor in various ways.
One of the ways is by wrapping the conductor with a spiral of thin iron wires or
with a single iron wire, or it may be formed by covering the conductor with thin
iron washers or beads, or small rings placed thereon side by side, or it may be
constructed of an iron spiral cut to the length of the armature core and slipped
upon the conductor as the latter is being wound upon the core.
The iron sheath might be applied in other ways however.
As will be presently observed, when the conductor sheathed as described is
applied to the armature core or carrier in the manner set forth and shown, the iron
mass of the sheath is subdivided in planes substantially parallel or coincident with
the magnetic lines of force. This feature I find to be of advantage, though I do
not limit myself to this particular form of sheath.
In the accompanying drawings I have shown the various parts of a dynamo
electric machine or motor in which my improvements are embodied.
Fig. 1, is a longitudinal section of the machine, the armature being shown in
cross section, and one of the thin sheet iron plates making up the field magnet cores
and pole pieces, in side elevation.
Fig. 2, is a longitudinal section of the armature showing the armature conductors
in place.
Fig. 3, is a detailed view showing a short length of armature conductor furnished
with an encircling sheath or envelope of iron.
Fig. 4, shows another way of applying the sheath.
Fig. 5, is a plan of the field magnet core and pole piece with the coils broken
away from a portion of the upper side thereof.
A, indicates the armature shaft, and B, a cylindrical armature core or cylinder
on which the wire is applied in the usual way in lengths parallel to the armature
shaft, so as by the rotation of the armature to be carried transversely through the
magnetic lines of force emanating from the pole pieces N, S, of the field of force
magnet. As will be observed the iron on the wire assists in directing the magnetic
lines of force directly and in a natural and proper way for this class of machines,
from the pole pieces to the core on which the wire is applied, and towards the
opposite pole piece.
The core may be constructed in any desired manner as for instance from thin
sheet iron discs b, b, secured together upon the armature shaft.
The discs b, b, are however preferably coated with a film of metal as described
under the first head of improvement, and are secured upon the armature shaft in
the manner before described.
.C, indicates the armature conductor applied in two layers to the exterior of the
armature and connected to the commutator in any desired way. This conductor is
preferably of copper and is preferably furnished with the usual insulating sheath
exterior to which is the iron sheath of my invention.
In Fig. 3, the insulating sheath is indicated at d, and the iron wire sheath
such as, before described is indicated at e. In Fig. 4, the iron sheath is shown aq
consisting of iron beads or rings strung upon the conductor. 5.
J

page_text: I do not limit myself to this particular way of applying the sheath, bub as
before indicated prefer the same, inasmuch as the sheath is subdivided in planes'
substantially coincident with the magnetic lines of force.
The field of force magnet H, is made up from thin sheet iron plates one of which
is indicated at M, in side elevation Fig. 1.
These plates are coated mechanically, electrically, or in any other desired way
with a thin film of a diamagnetic metal such as before specified, and are held or
pressed together in contact with one another to form a compact mass as before
described, which mass consists of separate thin plates both mechanically and
magnetically subdivided.
The core thus formed is secured in position in the frame K, by screws or
otherwise, the ends of the cores resting in slots cut in the frame as indicated in
Fig. 1. The portion of the frame K, in which the cores rest forms the usual
magnetic yoke for the field magnets, and the lower portion of the same is provided,
as is common, with means for holding the whole structure to a foundation.
A similar subdivision of the pole pieces is secured by constructing the core and
pole piece from thin plated iron sheets, and is of great advantage in reducing the
tendency to developement of currents therein, while at the same time but a small
amount of space is taken up by the diamagnetic material, and the magnetic mass
is therefore large.
I also find that the heating of the pole piece is most effectually prevented when
it is made up of several plates pressed together with their plane surfaces in contact
with one another, and from experiments have demonstrated that such heating is
imperfectly avoided if said pole piece is formed of a solid continuous metallic mass
by soldering the thin plates together. In such latter case it would appear that the
beneficial results resulting from the magnetic subdivision produced by the thin
layers of diamagnetic metal are but imperfectly realized. I am aware that it has
been before proposed to make a core and pole piece for a field magnet from tinned
iron plates soldered together, but in such case there is in effect continuous solid
mass of metal and there is not present the mechanical subdivision that exists when
a series of tinned sheet iron plates are simply held together with their plane surfaces
in contact, so that there is a mechanically subdivided armature made of separate
plates or bodies, and so far as my experiments have gone I have demonstrated that
there is a marked difference in efficiency and action.
Having now particularly described and ascertained the nature of my said
Invention, and in what manner the same is to be performed, I declare that what
I claim is:-
1. In a dynamo electric machine or motor a cylindrical armature made up as set
forth from sheet iron plates or dises having an electrical or mechanical plating of
diamagnetic material, as described, and held or secured together upon their shaft
by suitable clamping devices, the whole constituting an armature body made up of
separated or individual plates in contact with one another so that the armature
will be mechanically subdivided or laminated in planes coinciding with the lines of
magnetic force, and magnetically subdivided by films of diamagnetic metal each
united on one side with a disc or plate of iron and having its other side constituting
a plane surface resting in contact with a separate plane surface to make a plane of
subdivision.
2. In a dynamo electric machine or motor; a field of force magnet whose cores
and pole pieces are formed of a number of separate sheet iron plates having
mechanically or electrically plated surfaces plated with a diamagnetic metal, the
whole being held or pressed together with their plane surfaces in contact and
forming a compact mass of separate or individual plates, which mass is both
mechanically and electrically subdivided as described.
3. In a dynamo electric machine or motor a field magnet whose pole pieces are
formed of a series of separate tinned iron plates held together with their separate
plane surfaces in contact with one another, as and for the purpose described.

page_text: 4. In a dynamo electric machine or motor having its inductor wire arranged as
described to pass transversely through the magnetic lines of force emanating from
the field of force pole piece, the combination with each said inductor wire of a
sheath of magnetic material entirely surrounding the same, as and for the purpose
described.
5. In a dynamo electric machine or motor, the combination with an armature
conductor upon the exterior of a magnetic body and between the same and a field
of force pole piece, of a surrounding sheath of magnetic material subdivided in
planes substantially parallel with the lines of force emanating from the field of
force pole piece.
6. In a dynamo electric machine or motor, the combination of an armature body
or carrier of magnetic material, an armature conductor applied to the same
between said body and the field of force pole piece, and an iron spiral surrounding
said conductor.