Improvements in Alternate Current Motors.
Year: 1890

page_text: Date of Application, 3rd Jan., 1890
Complete Specification Left, 3rd Oct., 1890-Accepted, 27th Dec., 1890
PROVISIONAL SPECIFICATION.
Improvements in Alternate Current Motors.
I, LLEWELYN BIRCHALL ATKINSON, of Woodfield Works, Harrow Road, in
the County of Middlesex, Civil Engineer, do hereby declare the nature of my
invention to be as follows:-
My invention relates to improvements in electrical motors for use with alternating
currents, whereby the motor is made self-starting and can be run at any speed
independently of the number of alternations per second of the supply current, and
consists in the construction and combination of parts in the motor, so that whatever
the speed of the motor the position of the active coils of the motor armature, with
respect to the pole pieces, will be, at any time, in the proper position for developing
motive power by rotation in a specific direction.
It is well known that the ordinary multipolar alternate current generator can be
run as a motor at a speed synchronous with the alternations of the supply current,
but if, from any cause, the speed of such a motor should drop, the motor eventually
stops.
To avoid this disadvantage I construct my improved alternate current motor by
winding the armature continuously, as in an ordinary Gramme or drum armature, and
connect the same in the usual manner to a collector of usual construction, having as
many divisions as practicable. Upon the collector are arranged either as many
pairs of brushes as there are pole-pieces, or only one pair of brushes, similar coils on
the armature being connected together according to any of the methods usual with
multipolar continuous current generators or motors.
The effect of this arrangement is to form as many sections on the ring as there
are poles in the machine, the current in each section being opposite in direction to
those adjacent to it, forming virtually a system similar to that of a synchronising
motor.
The said brushes, working on the collector, are mounted in a carrier, and revolved
by a small independent self-starting synchronising motor.
The results from this combination of devices are that if the main motor armature
be running below the proper speed for synchronization with the supply current, the
brushes being caused by the independent synchronising motor, to run at the proper
speed for synchronising with the supply current, so determine the distribution of
the current to the various parts of the coils on the armature, that the main divisions
receive a current giving an impulse between the armature and the pole pieces, so as
to produce rotation of the main armature in the proper direction,
The main motor may be in form say such as are used for alternating generators,
the armatures being wound continuously instead of in separate coils, wound in
relatively opposite directions as is usual.
The synchronising motor. aforesaid, used to drive the brushes may be either a
multipolar machine having as many coils, or pair of coils in the armature as in the
magnet and having both the field magnet and the armature laminated and with a
current rectifier to give the reversals in one part, necessary to produce motion, or it
may be of the form known as induction motors, in which certain coils in the
armature are either short circuited or are short circuited in definite positions.
In order to avoid the difficulty occurring from having coils in the armature short
circuited by the revolving brush (whilst the armature is running in the magnetic
field giving rise to overheating where such coils are of low resistance,) the armature
may be wound with two completely independent windings, each alternate coil being
part of the separate windings, and such separate windings are connected to alternate
sections of the commutator. By this means a coil is never short-circuited, although
-

page_text: the electrical continuity at the collector is maintained. In place of this device,
open coil armatures may be used with multiple 2 plate collectors in the usual
manner.
°
The magnetism of the pole of the principal motor is retained by the supply
current, rectified by the rectifier on the axle of the subsidiary brush motor running
synchronously.
Although on the motors as above described the pole pieces are fixed in space and
the relative positions of the effective part of the coil on the armature is adjusted in
certain cases, particularly in dealing with high tension currents the armature coils
may be fixed either in space or in their positions on the armature ring, whilst the
effective position of the magnetic poles may be varied in the same way as described
the current being if necessary supplied at lower potential than its normal amount
through a transformer.
By my invention therefore a motor is produced which has all the advantages of
the synchronous motor namely:
Large out-put of energy for a given weight of material, whilst the speed of the
motor may be varied and the load can be subjected to considerable fluctuation with-
out necessarily producing a lag between the current and the electromotive force,
with its attendant loss in efficiency and heating of the machine.
Dated this 2nd day of January 1800
FELL & WILDING,
1, Queen Victoria Street, Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Alternate Current Motors.
1, LLEWELYN BIRCHALL ATKINSON, of Woodfield Works, Harrow Road, in
the County of Middlesex, Civil Engineer, do hereby declare the nature of this
said 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 improvements in electrical motors for use with alternating
currents, whereby the motor is made self-starting and can be run at any speed
independently of the number of alternations per second of the supply current; and
consists in the construction and combination of parts in the motor, so that whatever
the speed of the motor, the position of the active coils of the motor armature and of
the polar points in the armature, with respect to the pole pieces, will be, at any
time, the proper position for developing motive power by rotation in a specific
direction.
It is well known that the ordinary multipolar alternate current generator can be
run as a motor at a speed synchronous with the alternations of the supply current ;
that is, so long as the moving polar points in the armature are always in the proper
position relatively to the external poles; but if, from any cause, the speed of such
a motor should drop, the motor eventually stops.
To avoid this disadvantage I construct my improved alternate current motor by
winding the armature continuously, as in an ordinary Gramme or drum armature,
and connect the same in the usual manner to a collector of usual construction,
having as many divisions as practicable. Upon the collector are arranged, either
as many pairs of brushes as there are pairs of poles, or only one pair of brushes,
similar coils on the armature being connected together according to any of the
methods usual with multipolar continuous current generators or motors.
The effect of this arrangement is to form as many sections or polar points on the
ring as there are poles in the machine, the current in each section being opposite
in direction to those adjacent to it, forming virtually a system similar to that of a
synchronizing motor.
The said brushes, working on the collector, are mounted in a carrier, and revolved
by a small independent self-starting synchronizing motor.

page_text: The results from this combination of devices are, that if the main motor armature
be running below the proper speed for synchronization with the supply current, the
brushes, being caused by the independent synchronizing motor to run at the proper
speed for synchronizing with the supply current, so determine the distribution of
the current to the various parts of the coils on the armature, that, whatever the
speed of rotation of the armature may be, the speed of rotation of the polar points
in the armature is the proper speed of synchronization.
The main motor may be, in form, any such as are used for alternating generators,
with either laminated or solid magnet cores and armatures, either with or without
iron, the armatures being wound continuously, instead of in separate coils, wound
alternately in opposite directions, as is usual.
The synchronizing motor aforesaid, used to drive the brushes, may be either a
multipolar machine having as many coils, or pairs of coils, in the armature as in the
magnet, and having both the field magnet and the armature laminated and with a
current rectifier to give the reversals in one part, necessary to produce motion; or
it may be of the form known as induction motors, in which certain coils in the
armature are either short circuited, or are short circuited in definite positions.
In order to avoid the difficulty occurring from having coils in the armature short
circuited by the revolving brush (whilst the armature is running in the magnetic
field, giving rise to overheating where such coils are of low resistance), the armature
may be wound with two completely independent windings, each alternate coil being
part of the separate windings, and such separate windings are connected to alternate
sections of the commutator. By this means a coil is never short circuited, although
the electrical continuity at the collector is maintained. In place of this device
open coil armatures may be used with multiple two-plate collectors in the usual
manner.
The magnetism of the poles of the principal motor is retained by the supply
current, rectified by the rectifier on the axle of the subsidiary brush driving motor,
running synchronously.
And in order that my invention may be the better understood, I now proceed to
describe the same in relation to the drawings hereunto annexed, reference being had
to the letters and figures marked thereon.
Figure 1 shows in diagram the main motor armature, its winding and connections
to the collector.
Figure 2 shows in diagram one form of synchronizing motor suitable for starting.
and driving the brushes of the main motor.
Figure 3 shews in diagram the method of connecting alternate sections on the
commutator to alternate windings in the motor-armature.
Figure 4 shews the general arrangement of one form of alternating motor con-
structed according to my invention.
Figure 5 shews in diagram the complete connections of a motor as shewn in
Figure 4.
In Figure 1 the main motor armature is shewn surrounded for example by a 4 pole
magnetic field N.S.N.S. The armature is wound continuously and connected to the
collector (a). On this collector are the four brushes b. b. the two opposite brushes
being connected to one another in parallel and the pairs being connected to the
source of supply, and being mounted in a carrier, are revolved by an independent
synchronous motor. For one particular part of the current variation, the distribution
of the current, and the polar points on the armature will be as shewn in the diagram
by the arrows and the letters ns, ns. The position of polar points shewn, is the
position which, in the case of a synchronizing motor with armature coils wound in
the usual manner, corresponds with or nearly with the maximum current in a half
period, and the brushes bb are rotated by the auxiliary synchronizing motor, at such
speed as to bring the brushes, and thus the polar points-to the position shewn, at
the time of maximum current, even though the armatures may be going at a slower
speed not synchronous.
One form of synchronizing motor suitable for starting and driving the brushes of

page_text: the main motor is shewn diagrammatically in Figure 2. In this synchronizing motor
the laminated magnetic field is built of thin stamped, or built plates of the form
shewn, the internal poles being surrounded by coils o. In the centre is the laminated
armature having on it four coils, corresponding to the four poles, each alternate coil
wound oppositely, the coils being connected in series, and the ends of the series being
brought to the collecting rings P. Q on which press brushes connected to the supply.
On the shaft is also a four part commutator having opposite section r. r, t. t,
connected, the section being connected to p and the section t connected to q. on
this commutator two brushes press, and these brushes are connected to the ends of
the magnetizing coil o and also to the ends of magnetizing coils of the main motor.
This commutator reverses the current in the magnet coil of the subsidiary motor in
such a manner as to revolve the armature in one direction, and when the armature is
running synchronously it also rectifies the current, so as to magnetise both motor
fields, with a unidirectional current.
In Figure 3 the method of connecting alternate sections on the commutator to
alternate windings in a motor each winding being separate and distinct, thus avoiding
short circuiting or discontinuity of circuit, the current passing either by one winding
or the other, depending on the position of the brush.
In Figure 4 which shows the general arrangement of one form of motor con-
structed according to the present invention, I arrange a four pole field of usual
form, surrounding a disc armature, the coils of which are connected to the com-
mutator as shewn. The armature of the subsidiary motor carrying the revolving
brush frame is free to run on the shaft of the motor which passes right through it
to the outer bearing. Surrounding the armature of the subsidiary motor is the
laminated field as described mounted on an extension of the same base.
In Figure 5 the complete connection of the motor is shewn diagrammatically.
The current is brought in to collecting rings, whence it passes to the subsidiary
armature coils and also to the rotating brushes bearing on the main armature
collector.
It passes
coils.
also through the rectifying commutator to the two sets of magnetizing
All these connections may be as shewn in parallel or in series, or the armature
may be in series and the fields in parallel, or other combinations may be used,
depending on special circumstances.
Although on the motors as above described the pole pieces are fixed in space and
the relative positions of the effective part of the coil on the armature is adjusted ;
in certain cases particularly in dealing with high tension currents, the armature coils
may be fixed either in space or in their positions on the armature ring, whilst the
effective position of the magnetic poles may be varied in the same way as described,
the current being if necessary supplied at lower potential than its normal amount
through a transformer.
By my invention therefore a motor is produced which has all the advantages of
the synchronous motor, namely:-large out put of energy for a given weight of
material, whilst the speed of the motor may be varied and the load can be subjected
to considerable fluctuation without necessarily producing a lag between the current
and the electromotive force, with its attendant loss in efficiency, and heating of the
machine.
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 :-
1st. In an alternating current motor the combination with a fixed magnetic field
of a continuously wound armature and commutator, having a rotating brush frame
and brushes, revolved by a subsidiary self starting synchronous motor, so as to cause
the polar points of the armature to revolve synchronously independently of the
speed of the motor.
2nd. The combination with a fixed armature of a continuously wound revolving

page_text: magnetic field having a commutator or distributor and coils forming consequent
poles, in connection with a rotating brush carrier and brushes, revolved by a
subsidiary self starting synchronous motor, so as to cause the resultant magnetic
poles to revolve synchronously independently of the speed of the motor.
3rd. In an alternating current motor, the brushes revolving with the commutator
in combination with a double wound armature having two circuits connected to
alternate commutator sections, substantially as described.
4th. The combination and arrangement of parts and connections of an alternating
current motor, substantially as described and illustrated in Figures 1. 2. 3. 4 and 5.
Dated this 3rd day of October 1890.
FELL & WILDING,
1, Queen Victoria Street, E.C., Agents for the Applicant.