IMPROVEMENTS IN DYNAMO- ELECTRIC MACHINES
Year: 1882

page_text: LETTERS PATENT to Marcel Deprez of Boulevard Saint Denis 1 at Paris,
Electrician Engineer for an Invention of "IMPROVEMENTS IN DYNAMO-
ELECTRIC MACHINES
"
PROVISIONAL SPECIFICATION left by the said Marcel Deprez at the Office
of the Commissioners of Patents on the 14th September 1882.
MARCEL DEPREZ of Boulevard Saint Denis 1 at Paris, Electrician Engineer,
"IMPROVEMENTS IN DYNAMO ELECTRIC MACHINES
"ን
A study of dynamo electric machines particularly with the object of adapting
them the better for transmission to a distance and for the distribution of forces
has led me to notice several objections and to construct an entirely new type of
machine.
In order that the points of difference from the old types may be understood
I will notice the objections successively and the processes or methods I adopt to
overcome them, these processes or methods constituting the improved machine
which forms the subject of this invention.
I. At present in order to mount the ring of an induction machine on its shaft
a wooden mandril in one piece is forced into the ring with great friction. The
lateral friction thus produced on the internal wires of the ring often causes their
denudation and renders the mounting difficult especially when the wires are thin.
To obviate this objection I construct a mandril in several pieces and with variable
tightening. This mandril is composed of 2 main parts; the first part is formed
of a number of wooden pieces which externally have the internal form of the ring
and externally terminate in two plane surfaces inclined in relation to the axis
of the machine. The second part is formed of a bronze collar or sleeve terminated
externally by plane surfaces which exactly fit against the internal faces of the
wooden pieces so that when the collar is displaced laterally in relation to the axis
of the machine the tightening wooden pieces receive a transverse displacement
in relation to the said axis; they are thus compelled to act forcibly against the
internal part of the ring. In order that they may not themselves be displaced
laterally a tightening washer is applied against the vertical surfaces. This washer
carries screws which screw into the collar and allow it to be drawn at will. Thus
the necessary locking can be obtained with them.

page_text: II a. In machines intended for the transmission of forces or energy to a
distance it is advantageous to employ high tensions. In this case it is useful
to insure insulation between the different spirals of wire. For this purpose I apply
to the windings of the inducers a process analogous to that which is employed for
the construction of Ruhmkorff coils. I make use of metal discs presenting the
diameter which the winding should have. I arrange them in couples at a little
distance from each other, and I wind the wire in the space between these discs,
keeping the whole immersed in melted resin or other like insulator. I thus make
a washer formed of wire spirals covered with the insulating material. The whole
inducing coil is formed by the juxtaposition of a sufficient number of these washers
the free ends of which are connected for quantity, for tension, or a mixed arrange-
ment as required.
b. By a special analogous arrangement I render possible a variable coupling
of the same kind for the induced body. This is effected, as is well known, by
distinct sections of wire, separated by partitions and whose ends terminate in the
successive plates of the collector. In machines of high tension particularly, these
sections as well as the corresponding plates of the collector are generally in large
number. By means of coupling screws and if required of covering tongues
(languettes) I connect two or several plates of the collector thus dividing the
sections of the induced body into a certain number of groups coupled in quantity
which is equivalent to increasing the thickness of the wire and allows of the
machine being adapted for different services.
"'
c. When high tensions are used, if the circuit is broken suddenly extra-currents
are developed which may cause inconveniences; to avoid this I have designed
a commutator of progressive resistance. Its principle consists in introducing
successively and rapidly into the circuit to be broken crossing resistances in such
manner as to arrive progressively at the resistance which constitutes the rupture.
This result can be obtained by means of two arrangements which I will proceed
to describe. One of them consists of a set of resistance coils arranged in series
and connected individually to the contacts or keys of a circular commutator. The
line is led to a contact and the continuation is connected to the centre of the
commutator. The movable rubber in passing successively over the contacts will
introduce the coils successively into the current so that the rupture shall take
place after the last contact only when, the resistance being already very great,
the disjunction can be without danger. The second arrangement comprises a piece
cut to a point and formed of a sufficiently resisting material such as charcoal for
example; the line. is brought to a metal block; its continuation is connected to
a metal piece placed parallel to the pointed piece but without communication with
it. A sliding metal piece communicates with the pointed piece and touches the
metal piece which is parallel therewith. By separating the sliding piece from the
block the resistance increases and the rupture takes place when the piece has
passed the point of the pointed piece. These arrangements are capable of
modification.
The above points relating to construction and detail being improved as set
forth, I will now. pass to the more essential and characteristic features of my
invention.
III. In dynamo electric machines as hitherto constructed one set of the inducers
are grouped together in such manner that they form on the armature which joins
them a consequent pole. In like manner the other set of inducers form a con-
sequent pole on the armature which joins them. The magnetism of these consequent
poles is much feebler than that of the ordinary poles for the same expenditure of
energy. Besides in all known machines of this kind the soft iron of the inducers
has a mass much too feeble and becomes saturated with currents of a small
intensity.
According to one arrangement the poles are obtained on the armatures by two
inducers connected together by a strong iron breech (culasse). Further, the mass
of soft iron is double that of the machines which have the same induced ring

page_text: The breech serves as a support to the shaft of the ring. The other support is
constructed of a non magnetic metal such as bronze or copper.
In a machine which realises in the best conditions my improvements in this
kind of machine, the breech is dispensed with, and the machine is provided with
two rings to utilize all the magnetism developed in the inducers; these rings turn
in two distinct magnetic fields formed by poles of opposite denomination and can
thus be coupled for tension and for quantity.
In another arrangement of this same machine the two rings are mounted on the
same axis and encompassed within the 4 poles of two electro magnets whose
breeches form part of the frame of the machine so as to reduce to a minimum the
weight of the masses which are useless for electric action. The poles between which the
one ring turns are naturally of opposite denominations as well as the other two poles
so that the combination of the two electro magnets and rings forms so to speak a
closed magnetic circuit. Further, the axes of the coils traversed by the inducing
current cut at a right angle the axes of the rings so that the latter could develop
an electro motive force even if the iron contained in the coils were removed, while
in the ordinary machines the inducing action of the wire of the inducers is
unutilized because the axes of these coils are parallel to the induced ring and the
inducing action is due only to the magnetic field resulting from the presence of the
iron of the inducers. In the present arrangement on the contrary the inducing
action exerted on the ring is due both to the very energetic magnetic field
resulting from the arrangements, adopted and to the electric field constituted by the
solenoids.
It is hardly necessary to say that the coils are placed at a distance as little as
possible from the rings on which they act.
It will be seen besides that from the fact that there are two inducing electro
magnets and two rings the machine is capable of a number of combinations which
cannot be obtained with any other; thus the brushes of the two rings can be
grouped for tension or for quantity according to requirement, the current from
only one or from both rings can be employed to excite the 4 coils the useful
current being engendered by the second ring and the machine thus rendered self
exciting.
These different forms by virtue of the principle of the machine favor, as is seen,
special combinations; I have said that the currents from the rings can be coupled
according to requirement, but a more useful and quite novel combination can be
obtained from them. In transmission or distribution by employing the two ring
machine as a receiver the following will be the operation:-I arrange on the
inducers two circuits the one of fine wire, the other of thick wire; one of the
induced rings will be likewise of fine wire and the other of thick wire. The
induced ring of fine wire is in communication with the line, and the fine wire
inducing circuit is placed in tension or in derivation thereon. The induced ring
of thick wire is in communication with the thick wire inducing circuit. At the
commencement of the transmission the line current at high tension traverses the
fine inducing circuit which for a reason about to be explained I call the "temporary
exciting circuit," as well as the corresponding ring; the machine is put in motion,
the thick wire ring therefore engenders a current which traverses the thick
wire inducing circuit and completes the exciting of the electro magnets. When
the machine has attained the required speed a suitable centrifugal interruptor
placed on the fine wire inducing circuit cuts this circuit if it is in derivation, or
suppresses it by establishing in its place that of the ring if it is in tension, and
the machine continues its work by taking its excitation from the thick wire ring.
This arrangement has two advantages: 1st it makes the construction of the machine
cheaper by suppressing a large part of the numerous fine wire spirals which would
be necessary if the excitation were due only to the line current; 2nd, it reduces
the expenditure of energy necessary in this line by considerably diminishing the
resistance of the circuit.
2
IV. To these various improvements I have added another: When a determined

page_text: amount of energy is expended for the magnetization of an inducer of determined
form the magnetic field produced is equally determined; the metal pieces of various
forms which can be applied to the poles change the arrangement of the lines of
force and the division of the magnetic energy produced; they cannot increase its
value. In general I estimate that the presence of these pieces leads rather to a
diminution in the inducing efficacity of the magnetic field by giving to the lines of
force imperfect directions and a diminution of tension. I therefore modify the
machines by dispensing with the pieces of this kind and reducing the magnetic
poles to the dimension of the core (noyau) directly magnetized or at least to
dimensions little more than those of this core. In these conditions each of the 1
spirals of a movable induced body is submitted to the inducing action during a
portion of the circumference which it describes; during all the rest of the revolution
it constitutes a non-useful resistance and there is an advantage in excluding it from
the circuit so as to leave therein only the active wires. I obtain this result in the
following manner. The induced body which I use is a bobbin or coil of the kind
of the ordinary dynamo electric machines provided with a collector in the usual
way. The inducing magnetic poles are of any suitable number. The brushes for
collecting the current instead of being diametrically opposite are arranged in
couples at the entrance and exit of the magnetic fields. In these conditions it will
be remarked that the induced body is arranged entirely like the ring of ordinary
machines the induced current engendered in the space where the brushes are
situated will have two ways to follow, the one through the external circuit by the
brushes, the other through the remainder of the ring. This second derivation is
injurious and should be suppressed. To effect this, I divide the ring into a certain
number of distinct sections, four if there are two magnetic poles. The division
will be made on the collector; for this purpose the winding being in sections in the
ordinary manner, the free ends of the sections which are at the ends of the
perpendicular diameters will not be connected to the same contact or key of the
collector as in the machines now in use. The induced ring will thus be divided
into 4 parts, 1, 2, 3, 4 quite distinct separated by breaks of continuity. Since then
the ring forms no longer a continuous circuit, the derived way open through the
induced ring no longer exists and all the current engendered will pass into the
useful circuit. But this arrangement leads to a result:-The apparatus will act as
has just been described so long as the continuous parts of the induced circuit are
comprised between the brushes but when a line of separation is in the magnetic
field no more current is engendered therein the two rubbers being then without
communication through the induced body. It is necessary that at this moment the
separation shall cease. For this purpose besides its ordinary collector the machine
carries an auxiliary apparatus which I call the communicator. It is composed of
two insulating discs each carrying four separate buckles or keys (languettes) which
for the sake of description I will call 1, 2, 3, 4, 11, 2, 31, 41. The end wires of the
sections 1, 2, 3, 4 are arranged as follows:-

page_text: the sections 1 and 2; the advance given will be ẞ. The action is therefore
easily understood:-When the separative line is at a distance / from the magnetic
field the sections 1 and 2 will be connected by the communicator; this state of
things will last during the passage of the field, and until the line describes an
angle beyond the field; then the connection is broken and the sections 2 and 3
will pass through the same phase. Thus arranged the machine realizes the required
conditions, the wires of the induced body submitted to the action of the inducer
are alone in the circuit, and the current can only pass in the useful circuit. The
magnetic field is therefore utilized under the best conditions and the resistance
reduced to the minimum. An identical reasoning will shew that three brushes are
necessary (two receiving the current and one forming the communicator) for each
magnetic pole. But another advantage can be obtained from this arrangement.
The electro motive force developed during the passage of the wires before a pole
depends, all things otherwise equal, upon the number of induced spirals submitted
to the action of this pole which are put in circuit; this number is determined by
the variable distance of the pairs of collecting brushes. If these pairs comprise the
whole extent of the magnetic field the electro motive force developed will reach its
maximum; if the brushes are made to touch it becomes null. This variable
separation of the pairs of brushes can be obtained for example by means of racks
worked by a pinion. The electro motive force can therefore be made to vary either
by exciting the inducers by an exterior current and causing the space between the
brushes to vary, or by exciting the electrodes (electros) by the current of the
machine in which case the magnetic field will also vary under the influence of
the same element, or by combining the two ways. The currents collected in the
passage through each of the magnetic fields of any number are intended to and can
be completed according to requirement for tension or for quantity or utilized
separately either as distinct useful currents, or some as exciting currents and others
as useful currents or otherwise.
By combining the various improvements above described I obtain a machine of
variable electro motive force. The external form of this machine can be varied
since it admits of any number of magnetic fields.
But the principle can be carried further and reduce to the last minimum the
resistance of the machine. For this purpose instead of sectioning the induced ring
into a certain number of parts electrically distinct, I form it of a series of bars
insulated by plates. Then during the passage of one of these bars through a
magnetic field there is developed a current of, a determined sense of which the two
ends of the bar form the poles. It therefore becomes necessary to place a collector
at each end, or rather to place a pair of brushes rubbing on the bars themselves at
the two ends of the bars; the machine then acts as a large collector. In order to
avoid sudden breaks, the brushes bear on a certain number of bars at once or rather
the rubber is composed of several connected brushes.' Naturally under these
conditions the magnetic fields are of large number. In order to increase the effect
I place on the axle of the machine a piece of soft iron loose on this axle and
presenting a number of projections or teeth equal to that of the magnetic fields;
these projections are attracted by the opposite poles which gives to this piece a
fixed position in the space during the rotation of the apparatus. Its utility is to
produce opposite each of the magnetic poles a pole of the opposite denomination
which concentrates the magnetic fields and gives tension to the lines of force.
In the various modifications which I have described the inducers, as in ordinary
machines, can be excited by the current of the machine itself, by an external
current or by various combinations of these ways.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Marcel Deprez in the Great Seal Patent Office on the 28th February
1883.
MARCEL DEPREZ of Boulevard Saint Denis 1 at Paris, Electrician Engineer
"IMPROVEMENTS IN DYNAMO ELECTRIC MACHINES
"
A study of dynamo electric machines particularly with the object of adapting
them the better for transmission to a distance and for the distribution of forces
has led me to notice several objections and to construct an entirely new type of
machine. In order that the points of difference from the old types may be under-
stood I will notice the objections successively and the processes or methods I adopt
to overcome them, these processes or methods constituting the improved machine
which forms the subject of this invention.
I. At present in order to mount the ring of an induction machine on its shaft
a wooden mandril in one piece is forced into the ring with great friction. The
lateral friction thus produced on the internal wires of the ring often causes their
denudation and renders the mounting difficult especially when the wires are thin.
To obviate this objection I construct a mandril in several pieces and with variable
tightening as represented in Figures 1, 2 and 3 of the annexed drawings. Figure 1
is a face view without the tightening washer and Figure 2 is a section; Figure 3 is
a face view of the tightening washer. This mandril is composed of two main
parts. The first part is formed of a number of wooden pieces A A A which
externally have the internal form of the ring and internally terminate in plane
surfaces inclined in relation to the axis of the machine. The second part is formed
of a bronze collar or sleeve B terminated externally by plane surfaces which
exactly fit against the internal faces of the wooden pieces A A A so that when the
.collar B is displaced laterally in relation to the axis of the machine the tightening
wooden pieces A A A receive a transverse displacement in relation to the said
axis; they are thus compelled to act forcibly against the internal part of the ring.
In order that they may not themselves be displaced laterally a tightening washer R
is applied against the vertical surfaces. This washer carries screws a α a which
.screw into the collar B at b b b and allow it to be drawn at will. Thus the
necessary locking can be obtained with them.
II. a. In machines intended for the transmission of forces or energy to a distance
it is advantageous to employ high tensions. In this case it is useful to insure
insulation between the different spirals of wire. For this purpose I apply to the
windings of the inducers a process analogous to that which is employed for the
construction of Ruhmkorff coils. I make use of metal discs presenting the diameter
which the winding should have, I arrange them in couples at a little distance from
each other, and I wind the wire in the space between these discs, keeping the whole
immersed in melted resin or other like insulator. I thus make a washer formed of
wire spirals covered with the insulating material. The whole inducing coil is formed
by the juxtaposition of a sufficient number of these washers the free ends of which
.are connected for quantity, for tension, or a mixed arrangement as required.
b. By a special analogous arrangement I render possible a variable coupling of
the same kind for the induced body. This is effected as is well known by distinct
sections of wire, separated by partitions and whose ends terminate in the successive
plates of the collector. In machines of high tension particularly these sections as
well as the corresponding plates of the collector are generally in large number.
By means of coupling screws and if required of covering tongues I connect two or
several plates of the collector thus dividing the sections of the induced body into a

page_text: certain number of groups coupled in quantity which is equivalent to increasing
the thickness of the wire and allows of the machine being adapted for different
services. In Figures 4, 5, 6 and 7 I have shown by way of example the two
arrangements which I can employ for effecting these groupings. In Figures 4 and 5
which represent a collector, in front and side view, I show at A metal screws
coupling the plates a a in pairs; at B tongues (see Figures 6 and 7) for effecting
the coupling in any required number; at C (Figures 4 and 5) is seen the screw-
tapping in the contiguous plates a a to receive a coupling screw when needed. I
can also adopt the arrangement shown in Figure 5bis.
- K
c. When high tensions are used, if the circuit is broken suddenly extra-currents
are developed which may cause. inconveniences; to avoid this I have designed a
commutator of progressive resistance. Its principle is to introduce successively and
rapidly into the circuit to be broken crossing resistances in such manner as to
arrive progressively at the resistance which constitutes the rupture. This result
can be obtained by means of two arrangements which I will proceed to describe.
One of them shown in Figure 8 consists of a set of resistance coils A B CD-.
arranged in series and connected individually to the contacts or keys a b c d - - - k
of a circular commutator. The line. Lis led to a contact ; and the continuation L¹
is connected to the centre o of the commutator. The movable rubber O F in
passing successively over the contacts a b c d --k will introduce the coils
A B C DK successively into the current so that the rupture shall take place
after the last contact k only when the resistance being already very great, the
disjunction can be without danger. The second arrangement shown in plan and
elevation in Figures 9 and 10 comprises a piece M N cut to a point and. formed
of a sufficiently resisting material such as charcoal for example; the line L is
brought to a metal block ; its continuation L' is connected to a metal piece min
placed parallel to the piece M N but without communication with it. A sliding
metal piece F communicates with the piece M N and touches the piece m n. By
separating the piece F from the block the resistance increases and the rupture
takes place when the piece having reached F' has passed the point N of the
piece MN. These arrangements are capable of modification.
"
The above points relating to construction and detail being improved as set
forth I will now pass to the more essential and characteristic features of my
invention.
III. In dynamo electric machines as hitherto constructed one set of the inducers a
and a (see Figure 11) are grouped together in such manner that they form on the
armature which joins them a consequent pole A. In like manner the other set of
inducers b b form a consequent pole B on the armature which joins them. The
magnetism of these consequent poles is much feebler than that of the ordinary
poles for the same expenditure of energy. Besides in all known machines of this
kind the soft iron of the inducers has a mass much too feeble and becomes saturated
with currents of a small intensity.
In the arrangement shown in Figure 12 the poles A and B are obtained on the
armatures by two inducers a and b connected together by a strong iron. breech or
piece c.
Further. the mass of soft iron is double that of the machines which have
the same induced ring. The breech c serves as a support to the shaft of the ring o.
The other support d is constructed of a non magnetic metal such as bronze or
copper.
In Figure 13 as well as in the side view Figure 14, longitudinal elevation
Figure 15, and plan Figure 16 I show a machine which realizes in the best
conditions my improvements in this kind of machine. The breech c of Figure 12
is dispensed with and the machine is provided with two rings o and o' to utilize
all the magnetism developed in the inducers; these rings o and o' turn in two
distinct magnetic fields formed by poles of opposite denomination and can thus be
coupled for tension and for quantity.
Figure 17. represents another arrangement of this same machine in which the
two rings dd are mounted on the same axis and encompassed, within the four

page_text: .
poles a ba¹ b¹ of two electro magnets a c b, b' c¹ a² whose breeches c and c¹ form
part of the frame of the machine so as to reduce to a minimum the weight of the
masses which are useless for electric action. The poles a and b' between which the
ring d turns are naturally of opposite denominations as well as the poles b and a¹
so that the combination of the two electro magnets and rings forms so to speak a
closed magnetic circuit. Further the axes of the coils f f¹g g¹ traversed by the
inducing. current cut at a right angle the axes of the rings & d¹ so that the latter
could develop an electro motive force even if the iron contained in the coils fgf'g'
were removed, while in the ordinary machines, the inducing action of the wire of the
inducers is unutilized because the axes of these coils are parallel to the induced
ring and the inducing action is due, only to the magnetic field resulting from the
presence of the iron of the inducers. In the present arrangement on the contrary
the inducing action exerted on the ring is due both to the very energetic magnetic
field resulting from the arrangements. adopted and to the electric field constituted
by the solenoids f g f¹ g'.
1
It is hardly necessary to say that the coils.fg f¹ glare placed at a distance as
little as possible from the rings on which they act...
It will be seen besides that from the fact that there are two inducing electro
magnets and two rings the machine is capable of a number of combinations which
cannot be obtained with any other; thus the brushes of the two rings can be
grouped for tension or for quantity according to requirement, the current from only
one of the two rings can be employed to excite the four coils f g f¹ g¹ the useful
current being engendered by the second ring and the machine thus rendered self
exciting.
These different forms by virtue of the principle of the machine favor, as is seen,
special combinations; I have said that the currents from the rings can be coupled
according to requirement but a more useful and quite novel combination can be
obtained from them. In transmission or distribution by employing the two ring
machine as a receiver the following will be the operation:-I arrange on the
inducers two circuits the one of fine wire a (see Figure 18) the other 6 of thick
wire; one of the induced rings o will be likewise of fine wire and the other o¹ of
thick wire. The induced ring o of fine wire is in communication with the line,
and the fine wire inducing circuit is placed in tension or in derivation thereon.
The induced ring of thick wire is in communication with the thick wire inducing
circuit. At the commencement of the transmission the line current at high tension
traverses the fine inducing circuit which for a reason about to be explained I call
the "temporary exciting circuit," as well as the corresponding ring; the machine is
put in motion, the thick wire ring therefore engenders a current which traverses
the thick wire inducing circuit and completes the exciting of the electro magnets.
When the machine has attained the required speed a suitable centrifugal inter-
ruptor I placed on the fine wire inducing circuit cuts this circuit if it is in
derivation or suppresses it by establishing if in its place that of the ring it is in
tension, and the machine continues its work by taking its excitation from the thick
wire ring. This arrangement has two advantages: 1, it makes the construction
of the machine cheaper by suppressing a large part of the numerous fine wire
spirals which would be necessary if the excitation were due only to the line
current; 2nd, it reduces the expenditure of energy necessary in this line by
considerably diminishing the resistance of the circuit.
IV. To these various improvements I have added another: When a determined
amount of energy is expended for the magnetization of an inducer of determined
form the magnetic field produced is equally determined; the metal pieces of various
forms which can be applied to the poles change the arrangement of the lines of
force and the division of the magnetic energy produced; they cannot increase its
value. In general I estimate that the presence of these pieces leads rather to a
diminution in the inducing efficacity of the magnetic field by giving to the lines of
force imperfect directions and a diminution of tension. I therefore modify the
machines by dispensing with the pieces of this kind and reducing the magnetic

page_text: poles to the dimension of the core (noyau) directly magnetised or at least to
dimensions a little more than those of this core. In these conditions each of the
spirals of a movable induced body is submitted to the inducing action during a
portion of the circumference which it describes; during all the rest of the revolution.
it constitutes a non-useful resistance and there is an advantage in excluding it from
the circuit so as to leave therein only the active wires. I obtain this result in the
following manner. The induced body which I use is a bobbin or coil of the kind
of the ordinary dynamo electric machines provided with a collector.in the usual
way. The inducing magnetic poles are of any suitable number. The brushes for
collecting the current instead of being diametrically opposite are arranged in pairs
at the entrance and exit of the magnetic fields. If we suppose there are two poles
these brushes will be at A B, A¹ B₁ Figures 19 and 21. In these conditions it will
be remarked that if the induced body is arranged entirely like the ring of ordinary
machines, the induced current engendered in the space A B will have two ways to
follow, the one through the external circuit by the brushes A B, the other through
the remainder of the ring. This second derivation is injurious and should be
suppressed. To effect this I divide the ring into a certain number of distinct
sections, four if there are two magnetic poles as shown in the figure. The division
will be made on the collector; for this purpose the winding being in sections in the
ordinary manner, the free ends of the sections which are at the ends of the
perpendicular diameters will not be connected to the same contact or key of the
collector as in the machines now in use. The induced ring will thus be divided
into 4 parts 1, 2, 3, 4 quite distinct, separated by breaks of continuity M N PQ.
Since then the ring forms no longer a continuous eircuit the derived way open
through the induced ring no longer exists and all the current engendered will pass
into the useful circuit. But this arrangement leads to a result:-The apparatus
will act as has just been described so long as the continuous parts of the induced
circuit are comprised between the brushes but when a line of separation M for
example is in the magnetic field no more current is engendered therein the two
rubbers A and B being then then without communication through the induced body.
It is necessary that at this moment the separation shall cease.
For this purpose
besides its ordinary collector the machine carries an auxiliary apparatus which I
call the communicator. It is composed of two insulating discs each carrying on its
edge (Figures 19 and 20) four separate buckles or metal pieces 1, 2, 3, 4, 1¹, 2¹, 3', 4¹.
The end wires of the sections 1. 2. 3. 4 are arranged as followe·

page_text: magnetic field A¹ B what the rubber c does for the field A B. Thus arranged
the machine realizes the required conditions, the wires of the induced body
submitted to the action of the inducer are alone in the circuit, and the current can
only pass in the useful circuit. The magnetic field is therefore utilized under the
best conditions and the resistance reduced to the minimum. Identical reasoning
will show that three brushes are necessary (two receiving the current and one
forming the communicator) for each magnetic pole. But another advantage can be
obtained from this arrangement. The electro motive force developed during the
passage of the wires before a pole depends, all things otherwise equal, upon the
number of induced spirals submitted to the action of this pole which are put in
circuit; this number is determined by the variable distance of the pairs of collecting
brushes such as A B on the one hand and A¹ B' on the other.
If these pairs
comprise the whole extent of the magnetic field the electro motive force developed
will reach its maximum; if the brushes are made to touch it becomes nil. This
variable separation of the pairs of brushes can be obtained for example by means of
racks worked by a pinion. The electro motive force can therefore be made to vary
either by exciting the inducers by an exterior current and causing the space A B
A B to vary, or by exciting the electro-magnets by the current of the machine in
which case the magnetic field will also vary under the influence of the same
element, or by combining the two ways. The currents collected in the passage
through each of the magnetic fields of any number A B A B¹ &c are intended to
and can be coupled according to requirement for tension or for quantity or utilized
separately either as distinct useful currents or some as exciting currents and others
as useful currents or otherwise.
t
By combining the various improvements above described I obtain a machine of
variable electro motive force. The external form of this machine can be varied
since it admits of any number of magnetic fields; supposing however there are only
two magnetic fields I have shown in Figures 21 and 22 and in Figures 23 and 24
two machines with one ring and two rings according to the arrangements above
explained fitted with communicators and with brushes having variable separation;
these brushes being mounted on a toothed are forming a rack and put in movement
by a pinion. I show at X Y X¹ Y¹ Figures 21 to 24 the form given to the cores of
the magnets which embrace the induced ring both at the side face and upper face.
But the principle can be carried further and reduce to the last minimum the
resistance of the machine. For this purpose instead of sectioning the induced ring
into a certain number of parts electrically distinct I form it of a series of bars b b
separated by plates a a as shown in Figures 25 and 26. Then during the passage
of one of these bars through a magnetic field d d there is developed a current of a
determined sense of which the two ends of the bar form the poles. It therefore
becomes necessary to place a collector at each end, or rather to place a pair of
brushes rubbing on the bars themselves at the two ends of the bars; the
machine then acts as a large collector. In order to avoid sudden breaks, the brushes
bear on a certain number of bars at once or rather the rubber is composed of several
connected brushes. Naturally under these conditions the magnetic fields are of
large number. In order to increase the effect I place on the axle c of the machine
a piece of soft iron g g' loose on this axle and presenting a number of projections
or teeth g¹ equal to that of the magnetic fields; these projections are attracted by
the opposite poles which gives to this piece a fixed position in the space during the
rotation of the apparatus. Its utility is to produce opposite each of the magnetic
poles a pole of the opposite denomination which concentrates the magnetic fields
and gives tension to the lines of force.
In the various modifications which I have described the inducers as in ordinary
machines can be excited by the current of the machine itself, by an external
current or by various combinations of these ways.
Having now described the nature of my said Invention and in what manner the
same is to be performed I declare that I claim as my "improvements in dynamo
electric mechines"

page_text: First-The improved mandril constructed as hereinbefore described with
reference.to Figures 1 and 2 for mounting the rings of induction machines.
Second: The construction of the inducers of the machines, of washers formed of
wire, wound separately and coupled as required, as hereinbefore described.
Third: The construction of the collectors with plates, the coupling or connecting
together of which can be varied whereby the machine can be adapted for different
uses as hereinbefore described with reference to Figures 4, 5, 6 and 7.
Fourth-The commutator of progressive resistance for breaking currents
without producing extra currents, as hereinbefore described with reference to
Figures 8, 9 and 10.
Fifth-The machines with two induced rings turning in distinct magnetic field
formed by two poles of opposite denomination as hereinbefore described with
reference to Figures 13, 14, 15 and 16.
Sixth-The special application or adaptation of these machines as receiving
apparatus in the transmission and distribution of energy, only one of the rings
being placed in connection with the line while the other furnishes the exciting
current as herein before described.
Seventh: The employment of magnetic fields of any desired number in the
same machine, reduced to the width of the magnetized cores or to widths slightly
exceeding it, these limited magnetic fields being combined with pairs of brushes
keyed so that at their maximum distance apart they embrace the width of a
magnetic field, as hereinbefore described with reference to Figures 19 to 24.
Eighth The dividing or sectioning of the induced ring into portions electrically
distinct and the employment of a special apparatus herein before called the
communicator for reestablishing communication between two consecutive sections
at the moment when their separating line is about to enter the magnetic field as
hereinbefore described with reference to Figures 19 to 24.
Ninth-The employment for each of the magnetic poles of a pair of brushes
having variable separation combined with a communicator such as has been
described so that a greater or less number of induced spirals can be comprised
between the brushes and so that the electro motive force can pass at all degrees
from zero to the maximum without changing the working conditions of the
apparatus, a machine being thus constituted of variable electro motive force as
hereinbefore described with reference to Figures 19 to 24.
Tenth Constructing machines in which the sections of the induced ring are
reduced to separate bars, submitted to the action of any desired number of inducing
magnetic fields and provided for each magnetic field with a pair of brushes rubbing
on their two ends as herein before described with reference to Figures 25 and 26.
Eleventh-The various novel arrangements of dynamo electric machines herein-
before described with reference to the annexed drawings.
In witness whereof I the said Marcel Deprez have hereunto set my hand
and seal this twenty sixth day of February One thousand eight hundred
Witness:
ALBERT CAHEN
Civil Engineer
of Boulevard Saint-Denis 1
.at Paris
MARCEL DEPREZ (L.S.)