Improvements in Self-exciting Alternate Current Dynamos and Self-starting Synchronizing Motors.
Year: 1889

page_text: Date of Application, 25th Apr., 1889
Complete Specification Left, 27th Jan., 1890 -Accepted, 25th Apr., 1890
PROVISIONAL SPECIFICATION,
Improvements in Self-exciting Alternate Current Dynamos and
Self-starting Synchronizing Motors.
LLEWELYN BIRCHALL ATKINSON, c/o W. T. Goolden & Co. Woodfield Road
Harrow Road, London, W. Civil Engineer, do hereby declare the nature of this
invention to be as follows:-
The dynamo is of the type having only two fields, each sub-divided so that any
conductor moving in the field has an E.M.F. rising from zero to its maximum value
and returning to zero but not reversing. The magnetization of the field is produced
by a single coil, preferably wound on the armature, which also carries the armature
coils proper. The general construction is as follows:-
Two bearings support a shaft. This shaft carries a soft iron core which in a
particular size is say 6 inches in diameter and about 2' 6" long. At each end of this
core for about a length of 12 inches are threaded iron discs, properly secured,
producing a laminated armature surface, the radial depth of these plates being about
4 inches. On these cores flat coils of wire suitably connected are laid longitudinally.
Surrounding these cores are circular poles having internal projections, there being
half as many projections as coils on each surface. The two polar rings are connected
together magnetically, so that the magnetic circuit is from one pole, across the air
space, through the second set of laminated plates, across the second air space to the
second polar ring and then completed through the connecting yoke. In the metal
forming the central core the induction is fairly uniform, and on revolving there is an
almost uniform and unreversing E.M.F. from center to circumference, or conversely,
due to the "unipolar" or non-polar" induction. By applying brushes to these
points unidirectional current can be collected which is passed throughthemagnetizing
coil wound on the space between the laminated discs on the central core.
The same construction gives a self-starting synchronizing motor. To start the
motor the coils on the surface of the armature are disconnected from the supply,
which is connected to the exciting coil, and through the core to the brushes only.
On passing a current through these which form a non-polar" or
66
"
unipolar
motor, the motor starts, and is run light until it attains a proper speed when the
supplycircuit is switched on to the armature coils,and the machine is excited byshort
circuitingthe exciting coil through the brushes andunipolar inductionsystem,it then
forming a synchronizing motor.
COMPLETE SPECIFICATION.
Improvements in Self-exciting Alternate Current Dynamos and
Self-starting Synchronizing Motors.
I, LLEWELYN BIRCHALL ATKINSON c/o W. T. Goolden & Co. 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:-
The dyname is of the type having only two fields, each subdivided so that any
single conductor moving in the field has an E.M.F. rising from zero to its maximum
value, and returning to zero but not reversing, the reversal of current being
produced by coiling the said conductor so that the opposite sides of the coil produce
in the coil an E.M.F. first in one and then in the other directions in passing under
each pole piece.

page_text: The magnetization of the field magnet and armature core is produced by a single
coil surrounding the armature core and preferably wound on the armaturewhich also
carries on the two peripheral surfaces at each end of the armature coils proper.
In order that my invention may be the better understood I now proceed to describe
the same in relation to the Drawings hereunto annexed. Like letters refer to like
parts in the various figures.
Figures 1. and 2. show in transverse and longitudinal section respectively my
improved dynamo or motor.
Two bearings 0.0. respectively support a shaft M. This shaft carries a central
core A. of soft iron, which is slit or laminated radially, parallel to the axis of the
shaft, so that it may act both as a core to develop the main magnetic fields and
simultaneously as a bundle of conductors revolving in that field.
In a particular size of machine the external diameter of this core is about 6 inches
for about 26" in length.
B. B. are a series of iron discs threaded upon this core for a distance of about
12 inches at either end magnetically secured to the central core A. and form a
laminated armature core or surface. The radial depth of this core is about 4 inches
to correspond with the dimensions before mentioned.
On the periphery of these dises B. are placed flat trapeyoidal coils of insulated
wire K, laid longitudinally, there being twice as many coils as there are internal pole
pieces L. on the external magnetic pole C. C.
The said longitudinal coils K K on the periphery of the armature discs are
connected in series from one to another with alternately opposite directions of
winding throughout the periphery of each drum the terminals being one of each
drum connected to the insulated collecting rings G. G. respectively the remaining
terminal series being connected together. These connections are carried through a
suitable hole or groove in the centre core A.
Surrounding these armature coils Kare circular polesC.C.magnetically connecting
the projecting pole pieces L. to one another circumferentially, and longitudinally
between the said sets of poles at each end, so that when the centre core A, is
magnetically excited, the magnetic circuit is closed from each pole piece, across the
air space(between each pole piece, and through the armature longitudinal coils) tothe
laminated plates B. at one end; through the centre core A. through the second set of
laminated plates at the opposite end of the core A. across the second air to the
space
second polar ring at the opposite end of the machine, and then completed through the
connecting yoke C. as shown diagrammatically by closed rings in Figure 2.
These indicate the main magnetic field entirelynorth at one end and entirely south
at the other, through which the longitudinal armature coils K.are revolved, in which
latter as they alternately pass and leave the projecting pole pieces, a current is
induced, rising alternately from zero to maximum,and falling back to zero again and
then reversing in the coils.
The excitation of the central core A. to develop the magnetic field is effected by
a coil of wire D. wound on the central part of the core A, between the armature
dises B. B. and connected to the core A, so as to rotate with it.
The inner end of this coil is attached electrically to the lamination bars of the
central core A which though radially slit, is electrically continuous through the
central portion of the core whilst the outer end is attached to the metal band E.
enveloping the coil andwhich forms a collecting ring towhich electrical communica-
tion may be made by brushes P. P. If a current then be set up in this exciting
coil D. it will magnetize the central core A. and induce the whole magnetic field as
above described.
The continuous current is set up in this exciting coil D. as follows:--
In Figure 1. the magnetic circuit passing from the pole pieces L. on the external
pole to the central core A. is indicated by straight lines and arrows, whence it will
be seen the magnetic force passes only through every alternate longitudinal coil K.
upon the armature simultaneouslythe coils intermediately betweenthe poles being for
the timewithout the influence of the magnetic fields concentrated at the polepiecesL

page_text: It will be seen however that by the time the magnetic circuit from the isolated
poles has reached the central core A, the magnetic saturation of this core at the
surface will be almost uniform and forms what is technically known as "a unipolar
induction system," since the polar induction is singleonlyand of a uniformeharacter.
The core A, therefore from its longitudinal laminated character when revolvinginthe
said unipolar, field, will generate in its longitudinal laminated conducting bars a
unidirectional and fairly constant current from the centre to either end of the
laminated core.
One end of this unidirectional and constant current is collected at theend of the
core A by the uninsulated ring H, on which presses a brush, or brushes F. the
number being made sufficient to carry the required current, in most cases rather
large.
If now the brush F, be electrically connected to the brush or brushes P, pressing
upon the collecting ring E, of the central exciting coil D, the other end of which
latter is electrically connected to the core A, a uniform and continuous current will
be set up in the exciting coil D which thus serves to act as a self exciter of the field
magnetism of the whole machine as aforesaid.
For the machine to commence work as a generator, a slight residual magnetism in
the external poles of the field magnet must be presupposed as is usual, the generation
of the exciting current thereafter being self accumulating.
By placing a separate source of current in the connecting circuit between the
brushes F and P, the machine may be independently excited.
A synchronizing motor is of the same construction.
To start the motor the coils on the surface of the armature K are disconnected
through the collector and brushes G, from the supply, which is then connected to the
exciting coil D by the brushes P. and through the core to the brushes F, only.
On passing a current through this circuit it forms a" unipolar motor, the laminated
core A, acting both as part of the magnetic circuit with the outer pole C, and also, as
armature conductor inducing revolution in that magnetic field.
The motor therefore starts, and is run light until it attains a proper speed to
synchronise with the alterations of the supply current, when the supply circuit is
switched to the armature coils by the rings and brushes G. G and the machine is
excited by short circuiting the exciting coil and iron core through the brushes F
and P, as before described the machine thus forms a synchronizing self exciting
motor. When used as a motor from an alternating current the external magnetic
field is preferably laminated by building the external magnet and poles of bundles
of plates, the laminae running parallel to the axis, and lying in radial planes as
more particularly described in my sister application bearing number 6884, of even
date.
The whole machine may be inverted, that is to say, the outside frame may be
laminated and have the coils fixed on its interior surface with, or without projecting
pole-pieces and the inside core may have rotating projections, or pole pieces, theaction
being similar.
In this case no brushes are required to take off the alternating current as the
generating coils are fixed, but the machine must be separately excited.
Other mechanical arrangements embodying the same electrical principles may
be made.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner is to be performed I declare that what I claim is
1. In an alternator an arrangement of magnetic field not uniform at the circum-
ference of the armature where alternate currents are desired to be generated, but
becoming uniform by convergence at the centre enabling a direct current to be
collected therefrom by a conductor, for purposes of self excitation substantially as
described.
2. An alternating generator or motor having one magnetizing coil preferably
revolving with the armature, a laminated armature surface sufficiently deep to give

page_text: a practically uniform magneticflux through the central longitudinallylaminatedcore,
an external magnetic frame with polar projections, giving a variable magnetic flux
through different parts of the armature surface, coils, carried on the same armature
surface, and with brushes for completing the electric circuit through the coil,and core
substantially as described.
3. An electric motor for alternating currents started by passing an alternating
current through the direct current exciting system (as defined and claimed in
claim 1) eventually driven by the alternating current in the main armature coils as a
direct reversal of the above claimed generator at a speed synchronous with the
alternation of the supply circuit substantially as described.
Dated the 27th day of January 1890.
FELL & WILDING,
1, Queen Victoria Street, E.C., Agents for the Applicant.