An Electro-motor Worked by Alternating Currents.
Year: 1889

page_text: Date of Application, 3rd Dec., 1889
Complete Specification Left, 2nd Sept., 1890-Accepted, 29th Nov., 1890
PROVISIONAL SPECIFICATION.
An Electro-motor Worked by Alternating Currents.
I, MAURICE LEBLANC, of 23 Boulevard de Strasbourg, Paris, France, Engineer,
do hereby declare the nature of this invention to be as follows:-
This invention relates to the construction and arrangement of electro motors to be
worked by rapidly alternating currents according to certain principles which
briefly explained as follows:-
may be
It is easy to conceive a machine having its motive force constant in direction
although the current exciting it is periodically reversed. But if the coefficient of
self induction is high as it must be, the apparent resistance to the current is very
great, and thus a machine, which, if excited by a continuous current would develope
a great amount of work, develops comparatively little when it is excited by an
alternating current of like average tension.
In any dynamo the self induction of the field magnet is always very high, whilst
that of the armature is low, especially when it contains no iron. If therefore the
field magnets were excited by a continuous current, the alternating current having
only to pass through the armature, the apparent resistance of the system would be
comparatively low. This result might be attained by employing as motor an
ordinary alternating generator having its armature revolving synchronously with
that of the generator. This, however, involves great difficulties. The machine
would have to be started not only at first but every time that it might be stopped,"
and in order to avoid stoppages the force to be overcome must be much below the
maximum force developed by the machine, which would consequently be far from
efficient.
These difficulties might be overcome by a machine having its field magnets excited
by a continuous current, and its armature by an alternating current, the motive force
depending only on the intensities of the currents employed. When the field magnets
do not change their polarity while the armature current changes its direction, in order
to get constant direction of force, the speed of the armature relatively to that of the
poles must remain constant. If therefore the poles shift, the armature must move at
corresponding relative speed. There would be great objections to obtaining this
result by the revolution of the magnets, and it is quite possible to obtain it by the
motion of brushes.
Supposing for instance that there is a Gramme ring with its collector and brushes
excited by a continuous current which developes two opposite poles determined by the
contacts of the brushes, then on causing the brushes to revolve, the poles will revolve
along with them, and thus be capable of acting by induction on an arinature which is
excited by an alternating current and which will revolve at a relatively constant
speed in the same direction as the brushes, with a force independent of the speed.
Such a machine would be self starting and would work more quickly the less the
resistance to it.
In carrying these principles out in practice I employ a ring preferably of the
Pacinotti type with lateral radial teeth the core of the ring being formed by coiling
on itself an iron band which has its edge toothed, with insulating material hetween
the convolutions. The intervals between the teeth are coiled with insulated wire, the
If it is
coils being connected together and to a commutator in the usual way.
intended to have only two poles the contacts for the coils are diametrically opposite.
If there is a greater even number of poles, there must be a corresponding number
of brushes, or only a pair of brushes with a multipolar commutator.
A pair of rings may be placed side by side having their coils connected to the
commutator in such a manner, that the poles of the two rings always face each other

page_text: but are of opposite polarity. If six poles were produced in the ring, the armature
would have six coils for the alternating current. These coils may be of triangular or
sector form, each occupying a space between two of the six arms of the armature
frame. These coils are connected in series but are wound so that the current is
reversed in them alternately. The wire entering the first coil, and the wire leaving
the last are connected respectively to two insulated discs rubbed on by brushes
⚫ connected to the main conductors of the alternating current.
In order to keep the speed of the armature and of the shift of poles relatively
constant, the apices of the coils which are presented towards the axis of the armature
may be considered to form together a special armature acting on six small electro
magnets which are fixed on a disc and are excited by the continuous current supplied
by brushes bearing on insulated discs to which their coils are connected so as to give
them alternating polarity. The magnetism from these is collected in an iron disc
attached to the ends of their cores.
These electromagnets and the armature constitute an alternate current machine
with revolving fields, and as the mass is comparatively small, these fields can start
themselves or can easily be started by hand and their speed relatively to that of the
armature, whether it be at rest or in motion will be always the same and in the same
direction. The current after passing through the coils of the small magnets is again
delivered through insulated discs with a pair of revolving brushes to the coils of the
main field magnets. By shifting the position of these brushes on the axis, tho
armature which is influenced by both sets of magnets may be influenced by a variable
difference of phase between them. When the armature attains a speed corre-
sponding with the alternations of current, the poles and the subsidiary electro-
magnets and brushes remain at rest, which is the best working condition.
In what precedes it has been assumed that the field magnets are excited by a
continuous current. This might be obtained from a small dynamo, but this would
involve complication. Or the alternating current might be rendered continuous by
a commutator revolving at a precise speed which it is difficult to control and which
would involve considerable loss of energy. The simplest arrangement is to send a
continuous current from the generating station, but this is objectionable as
necessitating a separate conductor. The two currents the continuous and the
alternating may however be transmitted by one conductor from the generating station
and separated at the machine by branching the conductor into two, the one leading
direct to the field coils, the other to a condenser which is connected either directly or
through a transformer to the armature coils. The alternating current will have but
slight influence on the field magnets because of their high self induction, and the
continuous current cannot pass the condenser to the armature coils. The continuous
current transmitted, instead of having the energy which would be necessary for
working a continuous current motor, needs only to have a small fraction of that,
the main portion of the energy required being in the alternating current.
The machine above described of the disc form may be modified to be in the drum
form. In this construction the Pacinotti ring has its teeth not radial but parallel
to the axis, and is made up of a number of discs of sheet iron insulated from each
other and held together by insulated bolts passed through them.
The armature is made in the same way of discs bolted together, these discs being
notched so that six or other even nnmber of coils can be wound on the prominent
parts transversely to the axis.
The subsidiary electro magnets with their discs and brushes are mounted on a
separate axis in line with that of the machine, the magnets facing an iron disc fixed
on the axis of the machine. The operation is similar to that of the disc machine
first described.

page_text: An Electro-motor Worked by Alternating Currents.
I, MAURICE LEBLANC, of 23 Boulevard de Strasbourg, Paris, France, Engineer,
do hereby declare the nature of this invention and in what manuer the same is
to be performed to be particularly described and ascertained in and by the following
statement :-
This invention relates to the construction and arrangement of electro motors to be
worked by rapidly alternating currents according to certain principles which may be
briefly explained as follows:-
It is easy to conceive a machine having its motive force constant in direction
although the current exciting it is periodically reversed. But if the coefficient of
self induction is high as it must be, the apparent resistance to the current is very
great, and thus a machine, which, if excited by a continuous current would develope
a great amount of work, develops comparatively little when it is excited by an
alternating current of like average tension.
In any dynamo the self induction of the field magnet is always very high, whilst
that of the armature is low, especially when it contains no iron. If therefore the
field magnets were excited by a continuous current, the alternating current having
only to pass through the armature, the apparent resistance of the system would be
comparatively low. This result might be attained by employing as motor an ordinary
alternating generator having its armature revolving synchronously with that of the
generator. This, however, involves great difficulties. The machine would have to
be started not only at first but every time that it might be stopped, and in order to
avoid stoppages the force to be overcome must be much below the maximum force
developed by the machine, which would consequently be far from efficient.
These difficulties might be overcome by a machine having its field magnets excited
by a continuous current, and its armature by an alternating current, the motive force
depending only on the intensities of the currents employed. when the field magnets
do not change their polarity while the armature current changes its direction, in order
to get constant direction of force, the speed of the armature relatively to that of the
poles must remain constant. If therefore the poles shift, the armature must move at
corresponding relative speed. There would be great objections to obtaining this
result by the revolution of the magnets, and it is quite possible to obtain it by the
motion of brushes. Supposing for instance that there is a Gramme ring with its
collector and brushes excited by a continuous current which developes two opposite
poles determined by the contacts of the brushes, then on causing the brushes to
revolve, the poles will revolve along with them, and thus be capable of acting by
induction on an armature which is excited by an alternating current and which will
revolve at a relatively constant speed in the same direction as the brushes, with a
force independent of the speed. Such a machine would be self starting and would
work more quickly the less the resistance to it.
In carrying these principles out in practice I employ a ring preferably of the
Pacinotti type with lateral radial teeth.
Fig. 1 of the accompanying drawings represents part of such a ring. The metal
core is supposed to consist of a notched iron ribbon coiled on itself, with insulating
material such as paper or gutta percha between the convolutions to prevent production
of Foucault currents. On the rings are wound coils b which are held in the notches
of the rings; and which are connected in the usual way to one another and to the
segments of a commutator. If the inductors have only two poles the brushes should
touch the commutator at two diametrically opposite points. For several pairs of
poles there should be a corresponding number of brushes or any of the known
arrangements of a pair of brushes for a multipolar machine.
Two similar rings may be arranged as shewn in Fig. 2 with their coils connected
to one commutator so that the poles developed in the two rings always face each other
but are of opposite polarities. If, for instance there are to be six poles, each

page_text: armature ring may be constructed as shown in Fig. 1 consisting of a star wheel of
six arms L between which are accomodated the coils, overlapping the arms so as to
prevent displacement parallel to the axis, and held in position radially by wires or
bands wound round their periphery. All the coils are connected in series the odd coils
being wound in the one direction and the even coils in the opposite direction. The
entering wire of the first coil and the leaving wire of the last are joined to two
insulated metal discs D D' (Fig. 2) rubbed by stationary brushes FF conducting
the alternating current. In order to maintain constant relative speed of the poles
and the armature, the V shaped coils of the armature are extended towards the axis
somewhat more than would be necessary if they had only to embrace the lines of
force from the inductor; and the six points of the coils may be considered as con-
stituting a special armature which act upon an inductor consisting of six small
electromagnets E (Fig. 2) arranged uniformly around the axis as shewn in Fig. 1
and carried on an iron disc G (Fig. 2). The coils of these magnets are traversed by
the continuous current which is available, communicated by rubbers f f bearing on
two insulated metal discs d¹ which are fixed on the spindle x y, this current giving
the magnets E alternate polarity as indicated in Fig. 1. The spindle xy which
carries the disc G is in line with the axis of the armature but is free to turn inde-
pendently. The lines of force from the magnets E after passing through the
armature close in an iron ring i fixed on it. The magnets E and the armature
constitute an ordinary alternate current machine with moveable inductors, which
being of comparatively small mass can easily start, and their speed relatively to that
of the armature, whether it be at rest or in motion remains constant and equal to that
which corresponds to the production of a motive effort always in the same direction.
If the starting of the disc G should be difficult when the alternating current is sent
into the armature and the continuous current into the magnets E, the 'start can be
readily effected by hand applied to the wheel V. The continuous current, after
traversing the coils of the magnets E is collected by the brushes ßß bearing against
the collector C to which the coils of the inductor rings are connected, so that the
poles of the inductor turn with the brushes along with the electro magnets E with
constant speed relatively to that of the armature.
In what precedes it has been assumed that the field magnets are excited by a
continuous current. This might be obtained from a small dynamo, but this would
involve complication. Or the alternating current might be rendered continuous by
a commutator revolving at a precise speed which it is difficult to control and which
would involve considerable loss of energy. The simplest arrangement is to send a
continuous current from the generating station, but this is objectionable as necessitating
a separate conductor. The two currents the continuous and the alternating may
however be transmitted by one conductor from the generating station and separated
at the machine, by branching the conductor into two, the one leading direct to the
field coils, the other to a condenser which is connected either directly or through a
transformer to the armature coils. The alternating current will have but slight
influence on the field magnets because of their high self induction, and the continuous
current cannot pass the condenser to the armature coils. The continuous current
transmitted, instead of having the energy which would be necessary for working a
continuous current motor, needs only to have a small fraction of that, the main
portion of the energy required being in the alternating current.
Fig. 6 is a diagram showing how the alternating and the continuous currents may
be transmitted by the same conductors. Let A be the continuous current generator
and B the generator of alternating currents connected in series in one circuit to the
terminals m n from which there are two branches, the one including the inductor coils
of the motor, the other its armature coils, this latter being intercepted by a condenser.
The electromotive force of the B currents produce no sensible effect on the former
branch because of the high self induction coefficient of the inductors. The electro-
motive force of the A continuous current follows the Ohm law exactly, and cannot
enter the circuit of the armature from which it is cut off by the condenser, whilst
the passage of the alternating currents is facilitated by the condenser which neutralises

page_text: the effects of self induction. The alternative current in the second branch may be trans-
formed by known apparatus such as those described by Goulard and Gibbs, Zipernowsky,
Ferranti and others. Fig. 7 shows how the connections may be arranged, c being.
the condenser, pands the primary and secondary coils of a transformer and a the
armature. In order to avoid the objection of applying currents of high tension in
the premises of the consumer, there may be introduced in the circuit of the inductors
a coil having an iron core, of very small resistance but very high self induction, this
coil being placed in an inaccessible situation at the side of the transformer.
Instead of arranging the continuous current and alternate current generators in the
same circuit, they may be arranged in shunt, a condenser being introduced in that
part of the circuit which includes the alternating current machine, the passage of the
continuous current through this machine being thus avoided.
The machine above described of the disc form may be modified to be in the drum
form. In this construction the Pacinotti ring has its teeth not radial but parallel to
the axis, and is made up of a number of discs of sheet iron insulated from each other
and held together by insulated bolts passed through them.
In Fig. 3 I is the Pacinotti ring with teeth parellel to the axis; it is made of a
number of iron sheets separated by insulating material, and held together by bolts
insulated by ebonite sleeves b (Fig. 4). In Fig. 3 part of the ring is shewn in section
and part in elevation. The coils are connected to the segments of a commutator C
in the same manner as in multipolar continuous current machines having only one
pair of brushes. The brushes ẞ ẞ are caused to revolve by the disc G carrying the
electromagnets E. The continuous current is supplied by the rubber f on the
revolving disc d to the electro magnets E whence it passes by one of the brushes ẞ
to the coils on I, returning by the other brush and the disc d¹ and rubber f¹.
The armature of this machine is made like the ring I of iron sheets bolted together
and carried on discs P keyed on the shaft A B of the machine. Six coils e e
are traversed by the continuous current so that the cores of all the odd coils
present the one polarity and those of the even present the opposite polarity. The
entering wire of the first is connected to a disc D, and the leaving wire of the
last to a disc D¹; on these discs bear the brushes FF which conduct the alternating
currents for the armature. Obviously there may be any even number of coils e
corresponding with the number of poles developed in the ring. As the electro
maguets E cannot in this arrangement of machine act concurrently on the armature,
a disc G¹ fixed on the shaft A B facing the disc G carries a set of electro-magnets E¹
the coils of which are traversed by the same alternating currents as those of the
armature, so that the forces developed between them and the magnets E are the same
as they would be if developed between the coils of the armature and the magnets E.
The operation of this machine is similar to that of the machine previous described.
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:
1. In an alternating current electromotor the combination of an armature and a
coiled ring provided with collector and brushes revolving synchronously with the
generator of the alternating currents substantially as described.
2. The herein described method of transmitting by the same conductor the con-
tinuous currents for exciting theinductors of the machines and the alternating currents
for their armatures, and of separating these currents at the place of their application
into two branches, the one for the inductors including a coil of small resistance but
high self induction the other for the armatures including suitable condensers.
Dated this 2nd day of September.
ABEL & IMRAY,
Agents for the Applicant.