Improvements in Dynamo Electric Machines.
Year: 1892

page_text: Date of Application, 22nd Mar., 1892---Accepted, 19th Nov., 1892.
COMPLETE SPECIFICATION.
Improvements in Dynamo Electric Machines.
I, ANTOINE CHARLES REIGNIER, of 83 Rue Manin, Paris, in the Rupublic
of France, Engineer, 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 :—
The present invention has for its object an improved system of dynamo electric
machine which I have arranged with the view of an improved yield and of the
specific utilisation of the materials employed in its construction.
In certain existing machines of this type, there is always employed the magnetic
screen constructed, as is known, of a series of very thin soft iron discs insulated
from one another.
This precaution, which considerably attenuates the intensity of Foucault currents,
does not prevent this mass of iron from being the seat of a loss of energy in the
form of heat which arises from the successive magnetizations and demagnetizations
("hysteresis").
This amount of heat, in consequence of the caloric conductibility, reaches the
induction conductor.
As the density of current in this conductor is limited by the temperature pro-
duced by the heating, according to Joule's law, it will be understood that if the
conductor is already heated by the action of "hysteresis," it will bear only a small
increase of heat to raise its temperature to the practical limit of resistance of the
insulators. If therefore the iron core which constitutes the magnetic screen, is
suppressed, the induction conductor will be capable of delivering a greater amount
of electricity, the temperature limit of this conductor remaining the same.
In the same existing machines the winding is constituted by an assembly of
separate plates juxtaposed in the following order by simple pressure; a plate of
iron, a plate of copper, a plate of iron, a plate of copper, a plate of iron; a layer
of insulating material, and so on.
The contact of the plates, iron; copper, iron; obtained by the tightening of
wedges or cramps or by the trapezoidal form of the plates, is very defective,
because it augments considerably the interior resistance of the induction coil. On
the other hand, by their arrangeinent in accordance with the generators of the drum,
or of 'the ring in the prolongation of the radii, a line of force of the flux or flow of
induction, which emanates from the pole N (Figure 1), traverses the magnetic
screen E and then reaches the pole S, traverses necessarily several plates and
groups of plates; this line therefore encounters in its course, in the induction
conductor, a certain length of non-magnetic substance. There results from this, a
diminution in the useful magnetic induction.
If on the contrary all the lines of force were to traverse the iron of the induction
conductor according to the radii, or, more exactly, according to the heights of the
plates of iron; the inter-iron ("entrefer") would be reduced to its minimum; and
the useful magnetic induction would become maximum.
In known arrangements, of which Figure 1 represents diagrammatically the type,
there is only the helix which embraces a null flux or flow, which exists in the
above mentioned favorable condition, and, in proportion as the helix embraces a
greater flux or flow, the useful magnetic induction in this helix diminishes. When
the helix occupies the position, in which position it embraces the maximum
flux or flow, it is traversed through its own conductor by a certain flux or flow,
which is the more important in proportion as the plates are higher. This arrange-
ment will consequently produce an unequal density of current, which will con-
siderably limit the production of the machine to a less value than that resulting
from its own conductibility calculated according to Ohm's law.

page_text: Further, in consequence of the variable magnetic induction which the conductor
itself experiences, the distribution of the current is greatly modified in such manner
that the density is maxima on the sides and minima in the middle. Now, 'iron being
about seven times more resisting than copper, there will be from this fact a great
heating in the two iron plates placed on each side of the copper plate; then, on the
contrary, this copper plate will yield only a minimum quantity of electricity. This
production of heat, added to that which results from faulty contacts, tends con-
siderably to limit the yield of which the conductor would be capable by applying
to it Ohm's law and for heating it to a fixed temperature.
If therefore, in lieu of employing three plates, iron-copper-iron, there is
employed a bi-metallic metal (obtained by drawing, by the galvanoplastic process
or by other means) possessing a very intimate contact between these two constituent
metals, a magnetic metal and a good conducting metal, and that care be taken to
place the better conducting metal on the sides instead of placing it in the middle,
the inconveniences above referred to disappear; the iron plays its magnetic role
and is situated in the position where the density of current is minimum; the copper
placed at the points where the density of current is minimum, will be well utilised, in
such manner that an armature constituted by the series copper-iron-copper will
yield (with equal sections of the two constituent metals) much more than if it were
constituted by the series iron-copper-iron.
If, further, care is taken to arrange the bimetallic plates (such as have been
above defined) in a cylindrical field of force, that is to say, by employing flat pole
pieces and by causing these bimetallic plates to turn around an axis perpendicular
to the plane of the pole pieces and, that all the plates have their flat elements,
parallel to this axis, the lines of force will traverse only one helix at a time at any
given instant, so that, the inter-iron ("entrefer ") being reduced to its minimum, the
useful magnetic induction will be maximum.
Finally, by the realization of the arrangement forming the object of the present
invention, dispense with the magnetic screen and, consequently, the loss of
energy which results from this part; the iron contained in the middle of the
induction conductor acts the part of the magnetic screen, at the same time utilising
the current which is there produced.
The copper situated on each side of this iron collects the induction current almost
completely in such manner that this bimetallic conductor is capable of yielding a
very great quantity of electricity, and at the same time ensures a relatively con-
siderable magnetic induction without employing a magnetic screen. As an example
of the realization of the advantages presented by my invention I will now describe,
with reference to Figures 3 to 6B of the accompanying drawing, the application of
my special induction winding to a dynamo machine.
Figure 3 represents a longitudinal section of my improved dynamo machine.
Figure 4 is a sectional end view and Figure 5 is a plan of the same.
Figure 6 is an edge view of a detached helix and a portion of an adjacent
helix.
Figure 6 is a side elevation of a single helix, and
. Figure 6B is a plan of the same.
We will now consider the Gramme winding, and let, us suppose the lengths of
wire in line with the generators or radii of the circle, to be suppressed; there
will be obtained a Gramme ring without magnetic screen, and the surface of each
helix thereof will be null.
If now we bend each anterior radial side a bof the isolated helices shown at
Figures 2, so as to follow the line a c b, and thereby form with the first position a
curvilinear triangle, in such manner that all the sides of adjacent helices touch
each other without intervening space, and let the same operation be effected with
the posterior sides, but taking care to place the summit symmetrically with the
summit of the anterior side, and in the same relation to the primitive radial
position a b; there will thus be obtained the transformation of the Gramme
winding used with cylindrical pole pieces into a similar winding with flat pole

page_text: pieces. In effect the induction helix, instead of being a rectangle, will take the
profile of a curvilinear quadrilateral situated in a plane perpendicular to that of
the primitive helix of the Gramme winding. In other words each of my improved
bimetallic helices consists of a bi-metallic plate of the character hereinbefore
described slit longitudinally to within a short distance of one end so as to form two
stripsy connected together at one end by a short piece forming the base; one of
these strips is bent to the left and then to the right with its summit g³ over the
base, or in the same radial line therewith, or nearly so, thereby forming a curvi-
linear triangle on one side of an imaginary radial line; the other strip is similarly
treated, but is first bent to the right of said radial line, by which arrangement the
bi-metallic plate assumes the form of a curvilinear quadrilateral, as shown at
Figures 4 and 6. To obtain induction in these helices, it will suffice to place the
electro-magnets perpendicularly with the planes of these curvilinear quadrilaterals
and to cause these quadrilaterals to rotate around an axis perpendicular with their
plane., Figure 6, represents a portion of a second helix placed in close contact
with the first helix, except that insulating material is placed between them, and I
would here remark that, for the sake of clearness in the drawing, I have
represented the thickness of the bimetallic plates or helices g g as greatly in
excess of the thickness of such plates actually employed.
The attachments to the collector remain absolutely the same as in the first
Gramme ring considered. Such is the geometric arrangement of induction which
I adopt. It is now only necessary to substitute for the covered copper wire of
ordinary Gramme winding, my bimetallic conductor copper-iron-copper, such as
I have defined, to constitute completely my machine, such as is represented by
Figures 3, 4 and 5 of the drawing, which show respectively a vertical longitudinal
section, a vertical transverse section, and a plan seen from above.
In these figures a are the iron electrodes and b the magnetizing bobbins mounted
on the framing c whose sides are united by means of cross bars d. The armature g
is constituted, as above described, by coils made mechanically bimetallic fitting the
ones in the others, and connected so that the end of one is connected to the com-
mencement of the following, one of which is represented in detail and to a larger
scale by Figure 6.
The bobbins thus constructed constitute a cylindrical disc consolidated by the
insulated hoop f; this armature is mounted upon the motor shaft i by means of
binding plates ; motion is communicated to it by the pulley e. A Gramme
collector is applied between the framing c and the standard & supporting the free
end of the shaft i; it comprises the friction brushes 1, which are regulated by
means of the supports o; lastly the armature turns between the pole pieces n, and
the arrangement is mounted on a bed piece or frame m.
I have also represented at A (Figure 7) the ordinary cylindrical Gramme
winding; at B an intermediate transformer, and at C the winding such as I employ
by preference. Finally, in the above example I have considered the parts, iron
and copper, of each circuit, connected together electrically in quantity. But in
certain cases,
that of high voltages, for example, it will be advantageous to connect
them together in series.
A bi-metallic helix can be divided into three helices of equal superfices; the
electro motive force produced will therefore be, by connecting these three partial
helices in series, three times greater, all other things being equal. It is evident
on the other hand, that the intensity of the current with equal heating, will be
sensibly diminished in the same proportions. Several armatures can be arranged
on the same shaft and connected together in series.
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 an arrangement of dynamo electric machine, the constitution of the ring
by mens of bimetallic plates, that is to say, plates formed of two metals, the one

page_text: magnetic.and the other a good conductor, and in the following order; the con-
ducting metal, the magnetic metal, and the conducting metal, and being intimately
in contact.
2. The arrangement of dynamo constructed as herein described with reference
to Figures 3 to 5 of the accompanying drawings.
Dated this 22nd day of March 1892
A. C. REIGNIER,
By Harris & Mills,
23, Southampton Buildings, London, W.C., Agents.