Improvements in Electric Motors.
Year: 1894

page_text: Date of Application, 26th Sept., 1894
Complete Specification Left, 22nd June, 1895-Accepted, 27th July, 1895
MISSION DE LA FORCE PAR L'ÉLECTRICITÉ, of 13 Rue Lafayette, Paris,
France.]
Improvements in Electric Motors.
I, JOHN IMRAY, of No. 28 Southampton Buildings, Chancery Lane, in the
County of London, Consulting Engineer and Chartered Patent Agent, do hereby
declare the nature of this invention to be as follows:-
This invention relates to the construction of an electric motor to be worked by
single phase alternating currents on the following principle.
An outer armature consisting of an even number of bobbins presenting their
poles, which alternate in polarity, inwards towards internal fields, as it revolves,
tends to produce two fluxes of constant intensity turning in opposite directions
around the axis with a certain velocity.
When one of these fluxes is suppressed the other acts in aid of the motor. This
suppression is effected by interposing between the armature and the internal fields
a hollow cylindrical screen consisting of thin sheet iron layers insulated from each
other, mounted so as to be free to revolve. When the armature revolves this
screen revolves with it in accord with the one flux, effecting suppression of the
opposite flux.
A motor arranged in this manner, having internal magnetic fields which may be
in the form of a Pacinotti ring with two interlacing windings, is provided with four
brushes bearing on rings on the axis connected to the coils of the fields, whilst
these brushes are connected to the conductors through resistances that can be
separately adjusted. For starting the motor the cylindrical screen first turned
by hand or by any suitable power in the desired direction, and the armature, being
then put in circuit, turns in the same direction, the screen continuing to revolve
with it.
Dated this 26th day of September 1894.
ABEL & IMRAY,
Agents for the Applicant.
I, JOHN IMRAT, of No. 28, Southampton Buildings, Chancery Lane, in the
County of London, Consulting Engineer and Chartered Patent Agent, 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:-
This invention relates to the construction of an electric motor to be worked by
single phase alternating currents on the following principle.
An outer armature consisting of an even number of bobbins presenting their
poles, which alternate in polarity, inwards towards internal fields, as it revolves,
[Price 8d.]

page_text: tends to produce two fluxes of constant intensity turning in opposite directions
around the axis with a certain velocity.
When one of these fluxes is suppressed the other acts in aid of the motor. This
suppression is effected by interposing between the armature and the internal fields
a hollow cylindrical screen consisting of thin sheet iron layers insulated from each
other, mounted so as to be free to revolve. When the armature revolves this
screen revolves with it in accord with the one flux, effecting suppression of the
opposite flux.
A motor arranged in this manner, having internal magnetic fields which may be
in the form of a Paccinotti ring with two interlacing windings, is provided with
four brushes bearing on rings on the axis connected to the coils of the fields, whilst
these brushes are connected to the conductors through resistances that can be
separately adjusted. For starting the motor the cylindrical screen is first turned
by hand or by any suitable power in the desired direction, and the armature, being
then put in circuit, turns in the same direction, the screen continuing to revolve
with it.
to-
I
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Referring to Fig. 1 of the accompanying drawing which shews an armature with
a single phase alternating current, the windings A A, ... A, of which are
identical and are so arranged as to present at each moment poles alternately of
opposite sign the armature being connected to a source of alternating currents;
both theory and practice shew that the magnetising force developed by this
armature may be considered as tending to generate two fluxes of constant intensity,
turning in contrary directions round the axis O of the armature with a speed equal
in which T represents the duration of the period of the current and 2º the
number of poles of the armature. I is an induced part of a motor with rotating
fleld (I call the armature of a motor with rotating field the whole of the circuits
that receive the currents furnishing the energy, and the induced part, the whole of
the circuits closed in themselves). If by a suitable arrangement the influence that
one of the two fluxes can exercise on the induced part be suppressed, there will
only be a single rotating field which can be utilised for the working of the motor.
This result is obtained by providing between the polar pieces and the induced
part a screen E that can turn round the axis O of the system; this screen bas the
form of a cylinder or fly wheel of the same width as the polar pieces and the
induced part, and is constructed of superposed rings of sheet iron, insulated from
each other. These rings form a hollow cylinder having at each end a bronze ring
which rings are connected together by copper bolts lying parallel to the axis of the
cylinder and passing through the sheet iron rings; the axis of this cylinder coincides
with the axis of the machine.
Assuming that this cylinder E be rotated at a speed approaching that of one of
the rotating fluxes, the question arises, what will be the influence of the fluxes
upon the cylinder which, by virtue of its construction constitutes an induced part,
the several circuits of which are closed in themselves.
The two fluxes will have the following speeds relative to the cylinder E. The
flux revolving in the same direction as the cylinder, has a relative speed equal to
the difference between its actual speed and that of the cylinder.
On the other hand, for the flux revolving in the contrary direction, the relative
speed will be equal to the sum of its speed and that of the cylinder. It results
from this that the latter flux cannot attain any considerable value without developing
in the cylinder a considerable electromotive force. This will produce currents that
will be all the more intense, the weaker the resistances of the circuits of the
cylinder are. The magnetising force of these currents will be in the contrary
direction to those which develop the flux under consideration. This flux will
therefore always be exceedingly small.
On the other hand, the flux that turns in the same direction as the cylinder can
attain a considerable value without producing by its variations a notable electro-
motive force in the circuits of the cylinder.

page_text: This latter flux will consequently act almost exclusively on the induced part I of
the motor.
The cylinder E therefore acts as a veritable screen for that flux which turns
in the contrary direction to its own motion. The motor and the cylinder always
rotate in the same direction. The motor may be made to revolve in the one
direction or the other, according to the direction of the first impulse given to the
cylinder.
The motor acting on the principle above described may be constructed as I will
describe by way of example with reference to Figs. 2 and 3 which shew respectively
an elevation and sectional plan of the same.
A B C D E F is a multipolar armature with single phase alternating current.
The windings, of which 6 are shewn (but which may be of any other equal number).
are all connected in series and the winding is effected in such manner, that at every
moment two successive polar extensions present poles of contrary sign. This
armature can react upon an ordinary induced part of a machine with revolving
field, a b c d e f I have assumed by way of example that this induced part is
formed as a Paccinotti ring provided with two crossed windings as shewn in the
drawing; the extremities of these windings terminate on four contact rings uv x y
Fig. 3, mounted on the shaft carrying the induced part.
Four brushes ff2f3f4 bear on these rings, and allow of the introduction of
resistances in each of the circuits of the induced part. The shaft carries a
pulley P.
In the free space between the polar extensions and the induced part is placed
the cylinder ab* c* dx ex fx constituting a screen. This cylinder is constructed,
as described, of rings of sheet iron placed side by side and insulated from each
other. These rings are traversed by copper bolts fixed to two outer rings of
bronze which confine the sheet iron rings and serve as conductors. The cylinder
has a disc at one end by which it is fixed to the end of a shaft U V carried by a
bearing S.
For motors of small power the parts are limited to those described, and the
action will be as follows. The cylinder is first started with a certain speed; this
may be effected by means of a crank handle temporarily fixed on the shaft U V.
The direction in which the cylinder is turned is that in which the motor is required
to turn. This having been done, the circuit of the armature is closed; the
cylinder will tend to assume a speed very near that of synchronism and it will
continue to revolve, in only allowing a single revolving field to pass through,
which will act upon the induced part of the motor. It will then be sufficient, for
starting the motor, even when loaded, to close the circuits of the induced part by
means of two rheostats r and r¹ (Fig. 4) connected to the brushes f¹ff³ ƒª.
By employing these rheostats the production of currents of detriment intensity is
prevented in the winding of the armature.
This special arrangement has already been described in the Specification to
Patent No. 584 of 1891.
The stopping and starting of the motor will be effected by means of these
rheostats; the cylinder is allowed to continue its rotary motion which will only
absorb a very insignificant amount of energy. By means of this continued motion
the motor can be started at any moment.
In motors of greater power, it will be advisable to start the cylinder by means of
a small special electric or other motor.
For starting the motor when using a small auxiliary electro-motor it will suffice
to start the cylinder in the desired direction; the circuit of the main armature of the
machine is then closed and the current for the auxiliary motor is stopped; the
rheostats are actuated for starting or stopping the motor as above described.
By this means the starting of the motor can be effected without sudden disturbance
of the conditions of the outer main circuit; the starting of the auxiliary motor
requires in effect only an insignificant amount of energy and the rheostats r and r
moderate the current required of the armature.

page_text: It is to be understood that I do not limit myself to the arrangements described
and that the method described can be applied to various forms of machines, the
mounting and grouping of the mechanical and electrical devices being capable of
being effected in various ways, provided there is a cylinder or fly wheel operating
in the manner described for the purposes set forth.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. In a single phase alternate current electric motors the method of suppressing
one of the two revolving fluxes by providing a revolving cylinder or fly wheel
between the armature and the induced part, which cylinder constitutes a screen
which practically only allows of the passage of a single flux revolving in the same
direction as the cylinder, whereby the machine is made to act effectually as a motor
and in particular the starting thereof, when loaded, is facilitated substantially as
described.
2. A single phase alternate current electric motor, having a revolving cylinder
or fly wheel between the armature and the induced part, said motor being constructed
and operating substantially as described with reference to the accompanying
drawing.
Dated this 22nd day of June 1895.
ABEL & IMRAY,