Improvements in Magnetic Circuit Arrangements for Dynamo Electric Machines and other purposes.
Year: 1897

page_text: Improvements in Magnetic Circuit Arrangements for Dynamo
Electric Machines and other purposes.
I, REGINALD WOOD, of 35, Nightingale Road, Harlesden, London, N.W.,
Electrical Engineer, do hereby declare the nature of this invention to be as
follows:-
The invention refers to means for decreasing the reluctance of an air gap in
a magnetic circuit, and for varying the magnitude and direction of the magnetic
pull across the gap.
For this purpose, considering a slot or tunnel wound armature, continuous
or alternating current or induction motor as illustrations, I use an armature
of diameter somewhat greater than the distance between the outer edges of the
slots and instead of turning it smooth cylindrical, turn it with ridges and de-
pressions alternately and turn the face of the magnet poles so that the ridges
of the former run in the grooves of the latter and the ridges of the latter lie
in the grooves of the former. V-grooves are suitable the angle of the V
determining the multiplication of gap area and with a given total flux the
magnitude of the pull and of its radial component. The armature may be de-.
centralised radially or longitudinally to get particular pulls for special purposes.
The discs may be plate-like fitting one inside the other if longitudinal pull
is desired, each ridge on the armature being formed by the lips of the series of
discs fitting one inside the other.
The armature ridges may be slit longitudinally to prevent or minimise leakage
and self-induction.
The principle is applicable to the cylindrical face as above and also to the
circular faces in a flat ring type.
In all cases proper lamination prevents eddies.
I use the same principle in order to enable me to run at a high speed an iron
disc or an aluminium or other disc plated with iron, or carrying iron, on the
inner surface of the ridges which in this case would be about parallel to the axis,
the ridges being concentric and on both faces of the disc. As it is apparantly im-
practicable to laminate the disc the magnet faces would be annular and grooved
concentrically so that the ridges of the disc ran in the grooves of the magnet.
Here the object is not to decrease the reluctance of an air gap, but to make the
radial component of the magnetic pull large, in order to counteract centrifugal
force.
It is apparent that an acceleration parallel to the axis may be given to any
diameter of the disc by properly shaping the magnet ridges and disposing the
iron of the disc, & that gravity may be counteracted.
The disc may be used as an armature and may carry vanes for a turbine.
In a bipolar double horse-shoe dynamo using this device the reluctance in
the armature cross induction circuit is very great and the cross turns require

page_text: little or no neutralisation, with appropriate commutation. The armature sur-
face for giving off heat is also largely increased.
In many machines with this device advantage would be taken of the longi-
tudinal pull to run the armature vertically suspended magnetically by the
poles, specially with transformers.
Datal thia 11th dox of Cataka, 1807
REGINALD WOOD,
Applicant.
_ Improvements in Magnetic Circuit Arrangements for Dynamo
Electric Machines and other purposes.
I, REGINALD Woon, 35, Nightingale Road, Harlesden, London, Electrical
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 invention refers to means for decreasing the reluctance of an air gap in
a magnetic circuit, and for varying the magnitude and direction of the magnetic
pull across the gap.
For this purpose, considering a slot or tunnel wound armature, continuous
or alternating current or induction motor as illustrations, I use an armature
of diameter somewhat greater than the distance between the outer edges of the
slots and instead of turning it smooth cylindrical, turn it with ridges and de-
pressions alternately and turn the faces of the magnet poles, so that the ridges
of the armature run in the grooves of the poles, and the ridges of the poles lic
in the grooves of the armature.
V-grooves are suitable, the angle of the V roughly determining the multiplica-
tion of gap area and, with a given total flux, the magnitude of the pull and
of its radial component. The armature may be decentralised radially or axially
in order to get particular pulls for special purposes. The V's may be curved.
The grooves may be any shape in axial section.
The armature ridges may be slit longitudinally to prevent or minimise leakage
& self induction.
The principle is also applicable to the grooving of the annular faces of a flat
ring armature.
In all cases proper lamination prevents eddy currents.
In applying this principle to enable me to revolve a wheel at a high peripheral
speed, I make the wheel thus:-I take a steel or iron disc and turn it similarly
on both sides with concentric grooves these being nearer together usually to-
wards the periphery. I then take two similar annular pieces of iron or steel
for magnets. On the opposing faces of these annular pieces of iron or steel I
turn concentric ridges to correspond with the disc. I also turn in about the
middle of those faces grooves large enough to contain the exciting coils. But
I so arrange the size and shape of the exciting coils that only a very little of
the faces of the annular pieces of iron or steel is cut away in order that there
may be little or no discontinuity radially in the annular magnet faces. The
magnets may be built up in order to get the coils in more easily. I then place
one of these magnets on each side of the disc so that the ridges of the magnets
lie in the grooves of the disc, and the ridges of the disc run in the grooves of

page_text: the magnets, the disc being provided with shaft and bearings so as to be able to
revolve on the application of a turning moment. The magnets & bearings are
fixed to a frame which is non-magnetic where necessary.
The turning is done so that the outsides of the magnet ridges are nearer to
the insides of the disc, ridges than the insides of the magnet ridges are to the
outsides of the disc ridges, and the insides of the disc ridges and the outsides
of the magnet ridges are generated by the revolution about the axis of lines
which are preferably parallel to the axis.
Supposing the axis vertical and a right-hand section of the arrangement in
view, the path of a line of force would be say up the inside cylinder of the upper
magnet out radially through the yoke, down the outer cylinder of the upper
magnet to a ridge, from the outside of the ridge, across the air gap to the inside
of the disc ridge, through the disc, from the inside of the lower disc ridge across
the air gap to the outside of a magnet ridge on the lower magnet, down the
outer cylinder of the lower magnet, in radially through the yoke, up the inside
cylinder of the lower magnet to a ridge, similarly up through the disc back to
the inside cylinder of the upper magnet.
The bearings are arranged so that the disc can be decentralised radially or
axially.
The frame is mounted so that the axis can be placed in any position.
The magnets are cut through diametrally in at least two diameters so that the
sectors cut out can be moved radially or axially, & may also be cut through in
any way.
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Usually and preferably the perpendicular distance, that is parallel to the
axis, between the magnets through the disc is the same at all points, so that
each portion of the disc moves in a magnetic field of the same strength and
direction and eddy currents & hysteresis are avoided.
The elementary idea underlying this is that
an iron hoop can
revolved in space at any speed if it can be kept with its centre
stationary and magnets be used to overcome centrifugal force. To keep
the centre stationary and transmit power to a shaft the hoop becomes a series
of hoops on both sides of a disc
For the iron or steel disc I sometimes & preferably use an aluminium or other
disc and I plate or fix iron or steel on the insides of its ridges, and sometimes
on the top of its ridges & bottoms of its grooves.
When the magnet sectors are not displaced & the disc is radially & axially
central and the magnet or electromagnet is excited, each ridge of the disc will
be pulled radially inwards and part of this inward radial pull will be trans-
mitted to the solid part of the disc between the ridges on the two faces, when
the disc is revolved.
Then with proper construction and regulation of the exciting current the
inward radial pull of the magnet ridges on the disc ridges can counteract
the centrifugal force of the disc with its ridges at all speeds within the limits
imposed by the construction.
Gravity can be counteracted with vertical axis by axial upward displacement
of the disc, & with horizontal axis by radial upward displacement of the disc.
For the sake of clearness we will assume that gravity is not counteracted mag-
netically, and that centrifugal force, only, is, by providing as above described
a magnetic centripetal force on each particle, practically, of the disc.
If now in addition to revolving the disc the whole machine is moved bodily
in any manner the force which must be applied to each particle of the disc may
be no longer centripetal & no longer. the same at all points in its revolution.
But whatever this bodily movement and however it changes the forces can be
accurately predetermined and magnetically applied by means of the adjust-
ments provided, without causing hysteresis or eddy currents. More elaborate
means for adjustment may be added.
The disc may be used as an armature and vanes fixed upon it for a turbine,

page_text: and the magnets may be cut through in any manner so that parts of them
are adjustable as to position.
The Figures I. & II, accompanying this specification shew the carcase of a
double horse-shoe drum dynamo with V-grooves.
Fig. I, is a plan.
Fig. II. is a part section of Fig. I, through A B.
Referring to Figs. I. & II.
CC are the horse-shoe magnets.
Dis the armature core the laminations of which are not shewn.
E are the ridges on the armature.
F are the ridges on the magnet poles.
Gare the grooves on the armature.
H are the grooves on the poles.
I is the armature shaft, the bearings or supports for which are not shewn.
K is a slot for the armature conductor, one slot only being shewn.
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:
In a magnetic circuit, one part of which is moveable with respect to the other
part, a grooved or interleaved gap between the two parts substantially as described
for the purposes of determining the magnetic reluctance and the magnitude &
direction of the pull across the gap considered as a whole or in parts.
Dated this 9th day of August 1898.