Improvements in and relating to Dynamo-electric Machines and Electric Motors.
Year: 1891

page_text: Date of Application, 17th June, 1891-Accepted, 16th Jan., 1892
Improvements in and relating to Dynamo-electric Machines and
Electric Motors.
I, CARL COERPER of Ehrenfeld-Cologne, in the Empire of Germany, Director
of the Helios Company, do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement :-
My invention relates to dynamo-electric machines and electric motors.
In the dynamo-electric machines and electric motors heretofore used, the armature
coils are generally fixed upon the iron core. This arrangement necessitates the
employment of a commutator and brushes. Now the commutator and brushes
may be dispensed with, if the armature coil is rendered stationary and only the
armature core is rotated.
To enable this improved arrangement to be more clearly understood, take for
instance a bipolar dynamo having a Siemens armature. By winding the armature
coils in this instance upon the iron core alternating currents are generated in the
revolution of the armature, which currents can be taken off at the coil ends by
means of simple sliding rings. The alternating currents can be caused to flow
in one direction by a commutating device. In case the armature coils are stationary
and the iron core is turned alone, intermittent currents are obtained from the
said coils.
I have found that entirely new results may be produced by allowing the armature
coils to remain stationary and rotating the armature core, which latter must have
a form and arrangement adapted for the purpose. The most advantageous results
have been achieved in machines having either drum, ring, pole, spherical or disc
armatures. But it is in the construction of these types of machines that considerable
difficulties are experienced. To overcome these difficulties I have devised a number
of arrangements which by way of example are represented in the accompanying
drawing as used for a machine having a drum armature.
Figure 1 represents the magnetic field of a machine provided with a drum
armature. In the pole pieces are formed on the side facing the armature, either
channels as shown at the north pole, or holes as shown at the south pole, in which
the conductors acting upon the armature are fixed. In case the coil on the drum
is to be closed a special ring, Figure 2, is secured upon the pole pieces. This ring
is likewise provided with channels or holes and thus enables the conductors to be
secured all round. A very good result has been obtained by connecting the pole
pieces by a bridge of iron, as represented in Figure 3. It is then possible to suitably
fix the conductors along the entire periphery of the circle.
Figures 4 and 5 represent another mode of construction. Here the windings
are placed on rings a Figure 4, which during the operation of the machine are held
upon a rigid support, so that when the finished coil is moved into the magnetic
field it will be firmly fixed. The rings may also in this case be provided with
channels (Figure 5 north pole) or holes (Figure 5 south pole), and a magnetic ridge
may extend from one pole piece to the other through these rings as indicated in
Figure 5.
Instead of providing the pole pieces themselves with slots or holes, separate rings
may be made which have inwardly or outwardly extending slots or holes. These
rings are pushed into the magnetic field so that they fit well therein and are held
as firmly as possible by the pole pieces. The armature core then rotates within
these fixed coils. If the said rings are made of magnetic material they not only
form a magnetic bridge between the armature cores' but also a bridge between

page_text: the two pole pieces of the magnetic field whereby the action of the machine is
improved.
In order to close the coil in the radial direction the several windings may either
be firmly, connected in a suitable manner or the radial connecting wires may be
mounted loosely on discs or rings and the stationary coils joined after the shaft
and armature core have been placed in their position.
The accompanying drawing represents only the more essential modes of carrying
my invention into practice in the case of a machine having a drum armature.
Numerous modifications are however possible in the arrangement of the several
"parts. In machines having either ring, spherical, pole or disc armatures the
arrangement undergoes appropriate modifications, as will be readily understood.
"
In all these cases an entirely new effect is realized by my invention. For instance
when, as indicated in Figure 3, a plain cylindrical armature adapted to turn upon
an axis is placed in the stationary coil, and a current is introduced into the coil at a
and b, the armature will move from left to right, but when a current is introduced
at c and d the armature will move from right to left. The position of the points a-b
and cd varies according to the construction of the coil; they can be easily found
by introducing the current tentatively at different points. It is immaterial whether
an alternating or a continuous current is introduced. The cause of this action is
evident. If the armature is made of a suitable shape so that in its rotation a
change in the magnetic circuit must take place a current is generated in the
stationary coil.
Of course the armature core may be stationary, the magnetic field together
with the armature coil being allowed to rotate, and the machine may also be made
multipolar.
In these machines having a stationary armature coil the working and regulation
takes place under peculiar conditions in case the armature coil is constructed in a
special manner. For example by joining in the arrangement shown in Figure 3 a
thick coil having few convolutions to the conductor at a and b, whilst a second thin
coil having many convolutions and forming a shunt, which is likewise stationary,
receives a current at c-d the armature will move from left to right, when the
resistance in the external circuit is small, that is to say when the strength of current
is great, whereas the armature moves from right to left when the resistance in the
external circuit is great. Therefore the motion of the dynamo may be automatically
reversed according to the changes in the resistances in the external circuit when
the said dynamo is used as a motor.
A perfect compound effect, that is to say, a constant velocity with a variable
load is obtained if the fixed armature coil consists of a main circuit coil and a shunt
circuit coil, and is electrically connected in a suitable manner with the coils of the
magnetic field. The main circuit coils and shunt circuit coils of the magnets and
of the armature may be connected in such a manner that any desired effect is
produced.
"
The machines can be made as easily for constant tension and constant strength
of current as for rising or falling tension curves and strength of current curves.
When fixing the armature coil upon a closed support, such as is for example
indicated in Figures 3, 4 and 5, I may construct this support in the form of a
bearing made of suitable material for enabling the armature core to rotate directly
in the said bearing. In case suitable kinds of iron are employed for this purpose
the magnetic resistance is reduced to a minimum, so that the most favourable degree
of efficiency can be realized in such machines.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
First. In electrical current receivers with a closed armature coil, the fixing of
the current-conducting armature coils (which are not to produce any effect either
upon the field magnets or upon any part of the same) to the pole pieces of the field

page_text: magnets, whilst the armature core itself (which is subjected to the action of the
current-conducting armature coils fixed to the pole-pieces of the field magnets, and
also acted upon by the field magnets themselves) is arranged to turn freely within
the fixed coils.
Second. In dynamo-electric machines and electric motors as hereinbefore described
the employment of pole pieces provided with channels or holes, for the purpose
of fixing the armature coils therein.
Third. In dynamo-electric machines and electric motors as hereinbefore described
the employment of a special armature which is provided with channels or holes for
the reception of armature coils and fixed upon the pole pieces.
Fourth. In dynamo-electric machines and electric motors as hereinbefore
described the winding of the coil upon a support so that when finished the
coil can be placed in the magnetic field and held by the pole pieces or secured
to them.
Fifth. In dynamo-electric machines and electric motors as herein before described
the connection of the pole pieces by a magnetic bridge which may be plain
perforated or toothed, and the employment of the said bridge for fixing the
armature coils.
Sixth. In dynamo-electric machines and electric motors characterized as herein-
before described the employment of a stationary armature coil made of several
parts which are put together and electrically connected with each other only in the
mounting of the machine.
Seventh. In dynamo-electric machines and electric motors as hereinbefore
described the arrangement of several stationary armature coils which can at will
be made as main circuit coils and shunt circuit coils and connected.
Eighth. In dynamo-electric machines and electric motors as hereinbefore described
the temporary connection or separation of two or more armature coils for the
purpose of diminishing or increasing the resistance of the armature coil.
Ninth. In dynamo-electric machines and electric motors as hereinbefore described
the construction of the magnetic field, which carries the stationary armature coils,
in the form of a bearing in which the armature is adapted to rotate.
Dated this 17th day of June 1891
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.