Improvements in the Means of Obtaining Motive Power from Alternating Currents of Electricity.
Year: 1889

page_text: L
Improvements in the Means of Obtaining Motive Power from
Alternating Currents of Electricity.
LLEWELYN BIRCHALL ATKINSON, Woodfield Road, Harrow Road, London, W.,
Civil Engineer c/o W. T. Goolden & Co., do hereby declare the nature of this invention
to be as follows:-
It is known that in that class of motor in which the alternating current passes both
thro' the magnetizing circuit and the armature or working circuit, that the output for
a given weight or size of motor is usually small owing to the lag of the current behind
the E.M.F., due to the self induction of the circuit, and that the only way of reducing
this lag is to reduce the magnetic resistance of the motor. This resistance is largely
composed of the resistance of the air space between the armature core and magnet
faces. The object of the present invention is to reduce this space to a minimum by
leaving only the necessary mechanical clearance, which is effected by using the iron
of the core as the conductor. To do this the motor is constructed on the principle of
a non-polar or unipolar dynamo. Several forms may be constructed, the chief
object being to combine the following principles:-
Calling the direction of the magnetic induction, and the direction of motion of
the conductor y, and the direction of the current, the iron of the revolving part must
be divided electrically in planes parallel to z, the iron must also be divided in planes
parallel to the plane containing a.
Taking these general principles the motor is so constructed that the current is led
into the armature by sets of brushes on one end of the armature circuit, and passes
once through the magnetic field along the divided plates of iron of which the armature
is composed, and thence to another set of brushes.
The magnetization is produced by leading the same current either part of a turn,
or more than one turn according to circumstances, round the magnetic circuit, or in
some cases the construction of the armature is such that the current instead of
traversing at right angles to the direction of motion, takes a diagonal or spiral direction,
thus acting at once as magnetizing coil and armature coil.
The brushes are carried in rings all round the armature, and as the magnetic
induction must pass through at least one such ring, special construction must be
adopted to prevent a closed electric circuit being formed.
A property of "non-polar" or unipolar dynamos, and motors is that they are
adapted for use with large currents of low E.M.F., and as this is in opposition to the
essentials for the economical transmission of power, it is preferable to use a transformer
in conjunction with the motor, and the motor may itself form the transformer by
having the magnetic or electric circuits properly arranged, in which case the electric
circuit of the motor proper is closed upon itself, and the electric current is generated
by magnetic induction due to a primary electric current coupled to the mains.
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page_text: COMPLETE SPECIFICATION.
Improvements in the Means of Obtaining Motive Power from
Alternating Currents of Electricity.
I, LLEWELYN BIRCHALL ATKINSON, of Woodfield Road, Harrow Road, London, W.,
Civil 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:-
It is known that in that class of motor in which the alternating current passes both
through the magnetizing circuit and the armature or working circuit, that the output
for a given weight or size of motor is usually small, owing to the lag of the current
behind the E.M.F. due to the self induction of the circuit, and that the only way of
reducing this lag is to reduce the magnetic resistance of the motor. This resistance is
largely composed of the resistance of the air space between the armature core and
magnet faces.
The object of the present invention is to reduce this space to a
minimum, by leaving only the necessary mechanical clearance, which is effected by
using the iron of the core as the conductor instead of the usual copper winding between
the core and field pole pieces.
To do this the motor is constructed on the known principles of a non-polar or
"unipolar" dynamo.
Several forms may be constructed, the chief object being to combine the following
principle.
Calling the direction of the magnetic induction and the direction of motion of the
conductor Y, and the direction of the current z, the iron core of the revolving arma-
ture must be divided electrically into planes parallel to at right angles to the
direction of motion y, the iron of the field poles and yokes must also be divided in
planes parallel to the plane containing and the axis.
Taking these general principles the motor is so constructed that the current is led
into the armature by sets of brushes on each end of the armature core, and passes once
through the magnetic field along the divided plates of iron of which the armature is
composed and thence to another set of central brushes.
The magnetization of the divided conducting armature core is produced by leading
the main current either part of a turn, or more than one turn, according to circum-
stances, round the axis of the said rotating armature core or in some cases the
construction of the armature is such, that the current instead of traversing at right
angles to the direction of motion, takes a diagonal or spiral direction to that motion
or axis of rotation acting at once as a magnetizing coil and armature coil. The brushes
are carried in rings arranged round the armature, and as the magnetic induction must
pass through at least one such ring, special construction must be adopted to prevent
a close electric circuit, being formed, as hereinafter described.
Figures 1 and 2 show in sectional diagrammatic plans one form of motor, constructed
in accordance with these principles.
Figures 3 and 4 are longitudinal and transverse sections of the same.
Figure 5 is a sectional plan of a motor in which the motor magnetic circuit is also
the magnetic circuit of the potential lowering transformer.
Figure 1 shews diagrammatically the magnetic flow or induction through the
armature A air space B and external magnetic circuit c.
Figure shews in diagram the direction of the electric flow or current, the motor
being supplied through an independent transformer indicated diagrammatically at Q.
The current enters by the brushes or sliding contacts E at each end of the armature,
passes to the centre and thence out by the brushes F at the centre.
Figures 3 and 4 shew the mechanical and magnetic construction in the case, where,
by the spiral, or slightly bent arrangement of the conducting surface of the armature
core as shown at R the armature current also acts as a magnetizing current.
The armature core A is made of soft iron and is radially divided or laminated in
a direction parallel to the axis, the laminae having a spiral direction towards the

page_text: centre. The collecting brushes G press on collecting rings at each end, electrically.
connected to all the sections of the armature core. Round this core A are arranged
two hollow cylinders H of laminated plates separated by insulating material, each plate
also being cut through radially to break the electric continuity these two cylinders
have grooves in them into which are placed bundles of plates K completing the
laminated magnetic circuit. Through a ring L either internal or external to these
plates pass the brushes M. If the ring is internal as shown in the figures it must be
divided to prevent a complete conducting circuit being formed. If it is external, as
the induction twice threads through it, this is less necessary.
In figure 3 instead of the spiral arrangement of armature conductor, a separate
magnetizing coil may be substituted being wound in the spaces S. S.
"
A property of "non-polar or unipolar dynamos and motors is that they are
adapted for use with large currents of low E.M.F. and as this is in opposition to the
essentials for the economical transmission of power, it is preferable to use a trans-
former in conjunction with the motor and the motor may itself form the transformer
having the magnetic or electric circuits properly arranged in which case the electric
circuit of the motor proper is closed upon itself including a low tension induction or
transformer coil, and the electric current is generated by magnetic induction due to a
primary electric current coupled to the mains.
This arrangement is illustrated in figure 5 where two coils N are shewn connected
to the high tension supply. A single turn or two or three turns of the thick
conductor are fastened at one end to the centre brush and the other end passes to
the end collecting rings. The required E.M.F. is set up in the few turns of thick wire
to produce the armature current.
It will be understood instead of a parallel axial armature a disc armature with
suitably modified external magnetic circuit may be used.
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.
1st. In a unipolar motor the construction of the armature can with magnetic
laminated strips or plates of iron so that the core may both act as a conductor and
as a magnetic core to reduce the air space to a minimum between itself and the field
magnet faces.
2nd. In a unipolar motor the construction of the cores of the outer magnetic field
with discoidal bundles of laminated and insulated plates connected parallel to the axis of
the rotation by bundles of plates laminated and insulated at right angles to the former
substantially as described."
3rd. The combination with a unipolar motor with laminated plates as described of
a transformer for use with alternating currents of high potential.
4th. The combination in a
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unipolar "motor with laminated plates as described, of
a high tension supply circuit with a low tension transformer circuit, adapted to the
motor itself for use with alternating currents of high potential.
5th. The construction and combinations of parts forming a unipolar motor for use
with alternate currents, substantially as described and illustrated in figures 1, 2, 3, 4
and 5 herewith.
FELL & WILDING,
1, Queen Victoria Street, E.C., Agents for the Applicant.