Improvements in Alternating Electric Current Generators.
Year: 1897

page_text: Date of Application, 14th Sept., 1897-Accepted, 30th Oct., 1897
COMPLETE SPECIFICATION.
[Communicated from abroad by HENRY FAIRBANKS, of St. Johnsbury, Vermont,
United States of America.]
Improvements in Alternating Electric Current Generators.
I, WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake & Co., Patent
Agents, 45 Southampton Buildings, in the County of Middlesex, 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 class of dynamos known as inductor alternators,
in which there is no moving copper, the generating coils being wound upon
stationary iron cores through which the magnetic flux is directed by inductor
masses of iron moved across the ends of these cores. It has been usual to arrange
that these cores should be entirely unmagnetized, except as they receive
magnetism through the inductors, which moving past their ends, and bridging
across, connect them alternately with opposite poles of a strong magnetic field
producing in them rapid reversals of polarity, whereby an alternating current is
generated in the coils wound upon them. I have found that instead of reversals
of polarity it is equally effective to provide for rapid periodic variations of the
intensity of the magnetism in these cores, wound with the generating coils. To
effect this I form these cores as extensions of the poles of the field magnet, dividing
each pole at its end into branches, or pole divisions, and winding the generating
coils upon these divisions. For I have observed that when the presenting
surface of an armature is smaller than the end of the pole of the magnet to which
it is applied, the magnetic flux is directed through that part of the pole which the
armature meets, and that if the pole is divided at the end, and the armature applies
only to one pole-division, the magnetism is directed through that division.
In my improved generators the field is continuously magnetized, each pole
being divided into two or more pole divisions, having their ends shaped to the
path of the armature teeth or inductor masses, these divisions being wound
alternately right hand and left hand with the generating coils. The pole-
divisions and the teeth of the armature of inductors are spaced so with reference
to each other, that in one position all the right hand wound divisions are armed
and in the next position all these left hand wound' (with the coils connected into
a single circuit) and the effect of the sharp variation of magnetic flux appears in
the alternatino electric current induced in that circuit, when the armature moves.
My principle of construction is applicable to many forms of machines, and may be
adapted to those delivering polyphase currents.
Figure 1 illustrates the simplest application of this principle, a machine having
each of the two poles of its field divided into two projections shaped to the
cylindrical path of the armature teeth, and wound right and left with the
generating coils of a single circuit, the presenting ends of these pole-divisions
and the ends of the armature teeth being of substantially the same angular
breadth, namely sixty degrees.
Figure 2 exhibits a practical four pole machine, each pole having two pole--

page_text: divisions facing the six teeth of the armature, and having an angular breadth of
one twelfth of a circumference.
Figure 3 gives the outlines of a machine with two poles much divided to
receive the windings, and wound with two generating wires overlapping; so as
to give a two-phase current, as plotted in Figure 4.
Figure 5 outlines a six-pole machine, having poles arranged in pairs, and each
pole divided to present two pole-divisions, the pole-divisions of each pair or group
corresponding in angular breadth and spacing to the teeth of the ten-tooth
armature, but the distance between the groups not corresponding, and so in this
case giving three-phase currents, as plotted in Figure 6.
Figure 7 shows in outlines a machine having its armature wound to generate
the current required to magnetize the field, and its two poles divided each into
four-pole divisions spaced for a six-tooth armature.
Figure 8 and Figure 9 give two views, partly in section, and with parts broken.
away, of a machine in which the resultant poles of the field are two short
cylinders standing out toward each other, their presenting ends cut into pole
divisions which are wound right and left with generating coils, and instead of a
single armature, inductor masses bridge across, in one position between all the
right hand wound, and in the next position, between all the left hand wound pole-
divisions.
All these machines except that illustrated in Figure 7 require separate exciters
for the field current, but most of them could be made to generate this current by
proper armature windings. In all of them except the last the armature is made
up of stampings of soft iron or mild steel, slightly insulated from each other to
prevent eddy currents, and threaded on the shaft and strongly clamped together.
The laminated mass is then turned, to form the cylindrical surface, and grooved
parallel to the axle to form the teeth, or projections, the grooves being of the
same angular width as the presenting faces or ends of the teeth. The poles of the
field are built up in the same way with similarly insulated laminæ, and stand out
from the cast iron ring or frame; the inside next the armature being bored out, and
the presenting ends being grooved or channelled parallel to the axis of the
armature, to form the pole-divisions, and to receive the generating coils.
In the machine shewn in Figure 1 the field current from the exciter enters at
magnetizes the two poles, and leaves at b. Inspection of the drawing will show
that when the armature is in the position shown, the magnetic flux will be from
the half-pole o through the armature teeth 3 and 2 to the half-pole r, but when.
the armature has advanced one sixth of a revolution it will connect the half-
poles m and t, and there will be a magnetic drop in the half-poles o and r and a
corresponding rise in m and t resulting in an electric reversal in the generator
coils in the first two, and an opposite reversal in the coils of the last two. The
two generating coils upon the two divisions of the north pole are wound in
contrary directions, and also the two upon the two divisions of the south pole and
these are joined so that the coil for the moment acting in one direction upon the
north pole co-operates with a coil upon a division of the south pole, and when the
armature passes along and bridges across between two other divisions, all con-
tribute to a sharp electric reversal, and from its continued motion a strong
alternating current is delivered through the terminals c and d. This machine
with three-toothed armature is hardly practical, for the reason that the attraction
is necessarily unbalanced, the armature in the position figured being drawn
strongly down, and in the next position as strongly up, but it is shown as the
simplest application of the invention, and the one most easily described. The
machine illustrated in Figure 2 with a six-tooth armature is a good practical
machine, avoiding the difficulty just referred to, since with six teeth two are
always opposite to each other and the attraction is balanced. Referring to this
Figure 2, and observing the poles N.S. magnetized by the exciting current a b,
it is apparent that in the position figured the magnetic flux is through the half-
poles tm t¹ m, and in the next position will be through the half poles o, r, o, r²,

page_text: the movement causing sharp electrical alternations in the right and left hand
wound generator coils.
In the machine shown in Figure 3 the field has two poles excited by the
current a, b and divided into narrow subdivisions by slots, enlarged at the bottom,
through which the wires of the generating coils are wound, these coils united into
two circuits, the coils of one circuit overlapping the coils of the other circuit by
half their breadth, the two sub-divisions encircled by any one coil having together
the same angular breadth as the presenting end of one tooth of the armature, and
all the sub-divisions spaced so that all those encircled by the right hand
wound coils of one circuit shall in one position of the armature, be covered by
these presenting ends of these teeth, and when the armature has moved half the
angular breadth of one tooth, then all the sub-divisions encircled by the right
hand wound coils of the other circuit shall in like manner be covered by armature
teeth presented fairly to them. The coils of each circuit are alternately right
and left hand wound. It is plain that in this machine the two sub-divisions
encircled by a single coil form practically, with reference to that coil, a single
pole-division. Each pole of the field figured in Figure 3 has upon its twelve
sub-divisions six coils of one series and six of the other so that with reference to
the coils of either series, it has practically only six pole-divisions, the dividing
again not changing the effect of the projecting iron upon the encircling coil, but
only giving opportunity to introduce overlapping this, a coil of the other series.
This being understood it is clear that this machine has all the features of those
previously figured, only that those features as they appear in reference to the
pole-divisions encircled by the coils of one circuit, are all duplicated, and appear
again in the divisions encircled by the coils of another, so that this machine is
merely a practical combination of two machines of the simpler type, arranged to
bring the resulting electrical impulses in different phase, and we have a two-
phase machine, generating an alternating current in the coils between the
terminals c, d, and another similar current in those joining e, f, these two series
or alternations being half a wave length apart, as plotted in Figure 4. For
generating two-phase currents, by using overlapping windings, the number of
sub-divisions of the field poles is two against each armature tooth, and two
against each groove of the same, four times as many sub-divisions as there are
teeth in a given part of the curve.
The machine illustrated in Figure 3 has three groups of poles, one north and
one south in each group, and each pole divided for the right and left hand wound
generator coils the divisions of the poles in each groove being spaced to correspond
to the teeth of the armature, but the spacing between the adjacent half-poles of
different groups being one third wider than the breadth of said teeth, whereby
the currents generated in the three groups differ in phase by one third, as plotted.
in Figure 6.
It is apparent that the same result would be obtained by spacing the adjacent
half-poles of different groups one third closer than to correspond with the armature
teeth, or by separating them to one and two thirds the width of the said teeth;
also that more than two poles might be arranged in each group; also that four
groups might give four-phase currents, and this method of securing variations
in phase is capable of wide application, and is not limited to any one number of
phases, or to any one form of field.
Figure outlines a machine which is self-contained, the exciting current for
the field being secured by a few turns of ordinary drum winding upon the
armature, and the addition of a commutator. The current required for this is
very small and of low voltage in proportion to the output of the machine, and the
objections to a commutator and brushes are correspondingly small. A similar
winding with commutator is evidently applicable to most of the other machines
described, one being indicated in Figure 3. This machine of Figure 7 has the
same general form as the one first figured, but each pole has four divisions and
its arimature six teeth, securing balanced attraction, so that the flow of magnetic

page_text: force, in the position shown, is across from m¹ to rand m to r¹ and one twelfth of
a revolution later, from o¹ to t, and from o to t' generating an alternating current
of six cycles per revolution.
Figures 8 and 9 illustrate a machine which acts upon the same principle as the
others; the poles being similarly divided, at the presenting ends, and the divisions
being alternately right and left hand wound, while an armature bridge connects
first the right hand wound and in the next position the left hand wound pole-
divisions. These pole divisions instead of standing in toward the cylindrical
path traced by the teeth of the armature stand out from each resultant pole
toward the other like teeth of a crown wheel. The ends of these teeth are cut off
by two planes parallel to each other, and the armature moves between these
parallel ends. This armature might be. an iron disc with teeth like crown wheel
teeth standing out on the sides near the circumference passing the parallel ends
of the pole-divisions. But the rotating disc can be made lighter if some. non-
magnetic metal is used, and made to carry small inductor masses of iron which
bridge across between these said ends, which with this construction can be brought
near each other. Preferably these inductor masses are short coils of iron ribbon,
or mild steel jj; set in a light brass disc k, arranged to revolve on its axis shaft T.
The field magnet may be made in any form which shall bring the poles to face
each other. A simple horse-shoe magnet is shown, excited by the coils to which
the terminals a and lead, directing the magnetic flux through two discs and
to two short cylinders P P facing each other which are the resultant poles. These
short cylinders are preferably coils of narrow ribbon of mild steel or soft iron
rolled into the form of hoops and attached to the sides of the discs x and y, and
where they face each other are cut across by radial slots, forming
the projecting pole-divisions, r t r t &c., and m, o, m¹, o¹, &c., into
wound
which slots are placed the alternately right and left hand
generator coils, of which the terminals appear at e, f, and c, d. In case
the pole-divisions m³, o stand in the circle opposite the corresponding divisions t¹ ri
of the other pole, so that the inductor masses would present fairly to them both
at once, the terminals c and f may be joined and the whole single phase current
taken off by the terminals e and d. If two-phase currents are desired the pole-
projections or &c., on the opposite poles are staggered, so that om o¹ m¹ &c.,
are reached later in the rotation of the carrier than 1 and its series, and the
currents generated on the two poles differ by half a phase in the alternations, and
are taken off at the terminals e, f and c, d, separately. The drawing shews this
two-phase arrangement.
æ
Instead of the pole-divisions thus standing out like the teeth of a crown wheel
they might be arranged like teeth of a bevel gear, the armature being constructed
to face them properly, at any angle between the forms illustrated in the earlier
figures, where these divisions stand in toward the axis of the armature, and this
one where they are formed upon the side, and I do not confine myself to all the
details of construction here described. As illustrating the variety of applications
of which my invention is capable I have purposely shown it as it appears in
various forms of machines, and as adapted to one or polyphase alternators, and
these are not all, since in any form of machine the poles of the field magnets may
be divided, those of each circuit wound alternately right and left, and alternating
currents generated by the movement of armature inductors that carry no winding.
It is not even essential that the armature revolve, as a vibratory movement
presenting the magnetic bridge alternately to the right hand wound and left
hand wound pole-divisions would generate the current equally well.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, as communicated to
me by my foreign correspondent, I declare that what I claim is:
1. An alternating current generator, consisting of a continuously magnetized
field, at which each pole is divided at the end into two or more pole-divisions

page_text: which serve as cores for alternating right and left hand wound generator coils,
connected into a circuit in combination with an armature arranged to carry
inductor teeth or masses past the ends of these cores in a way as it moves to
furnish a magnetic bridge across first from the right hand wound, and then from
the left hand wound pole-divisions, whereby the magnetic flux is directed
alternately through the cores of the right hand wound and the cores of the left
hand wound coils, and the rise and fall of magnetic intensity in these cores,
without reversal of polarity, induces sharp electrical alternations in the said
circuit, as herein set forth.
2. In an alternating current generator, a continuously magnetized field magnet,
each pole presenting to the armature two or more divisions upon which pole-
divisions are alternately right and left hand wound current generating coils, and
in combination with these, a revolving armature having projecting inductor
teeth or inductor masses of which the angular breadth (measured from the axis
of rotation) and also the spacing are substantially the same as the angular breadth
of the presenting ends of the said pole-divisions, the spacing of these divisions
being such with reference to that of the armature inductor teeth or masses that
those teeth or masses furnish, at one point of the rotation paths completing the
magnetic circuit across through all the right hand wound north pole-divisions.
to all the left hand wound south pole-divisions, and, an instant later, paths from
all the left hand wound north pole-divisions to all the right hand south pole-
divisions, producing thereby a violent ebb and flow of magnetic force in all these
divisions whereby an alternating electric current is generated in the circuit into
which the said coils are united, as herein specified.
3. In an alternating current generator, a continuously magnetized field, each
pole being divided to present two or more divisions to the armature inductor and
shaped to the path of its movement, an armature with the presenting ends of
inductor teeth or masses having nearly the same form and angular breadth as
the said divisions of the field poles, and arranged to move close to them, these
inductor teeth or masses separated by air spaces of substantially the same angular
breadth as themselves, and, in combination with these elements, circuit generat-
ing coils right and left hand wound upon these divisions of the field poles, the
arrangement, and spacing of the whole being such that, for the generating coils
of each circuit, all the right hand wound north pole-divisions and all the left
hand wound south pole divisions shall in one position of the armature, have its teeth
or inductors presented fairly to them, and when the armature has moved, the
breadth of one tooth or inductor mass, all the left hand wound north pole-divisions
and all the right hand wound south pole-divisions shall have its inductors presented
to them, whereby the magnetic flux is directed alternately through the two
opposite wound sets of pole-divisions or cores and an alternating current is
induced in the generating coils by the variation of flux without reversing the
polarity of these cores, as herein described.
4. In an alternating current generator, an armature having inductor teeth or
masses separated by spaces of the same breadth as the presenting ends of these
inductors, in combination with a continuously magnetized field, of which each pole
presents to the armature inductors pole-divisions of substantially the same angular
breadth as the ends of the said inductors, these projecting pole-divisions being
alternately right and left hand wound with generator coils which are connected
into two or more circuits, the angular spacing of the pole-divisions being such
that at a given instant when the pole-divisions of one circuit are fairly presented
to the inductor ends of the armature, those of another circuit are only partially
covered, being fairly presented an instant later, when the armature has moved a
few degrees further, whereby the wave of magnetic flux is also later, and the
currents generated in these circuits are in different phase substantially as herein
set forth.
5. In an alternating current generator, an armature carrying inductor teeth or
masses separated by spaces of substantially the same breadth as the presenting

page_text: ends of these inductors, in combination with a continuously magnetized field, of
which each pole presents to the armature inductors several projecting sub-
divisions, upon which sub-divisions are overlapping coils of two or more current
generating circuits, the coils of each circuit being alternately right and left hand
wound, and the sub-divisions encircled by each coil having together substantially
the same angular breadth as the end of one armature inductor tooth or mass, and
the spacing of all the sub-divisions being such that, at a given instant, all those
right hand wound in one circuit shall be fairly presented to the armature
inductors and when the armature has moved part of the breadth of the presenting
end of an inductor tooth or mass, all those right hand wound by the overlapping
coils of another circuit shall in like manner be fairly presented, whereby the
magnetic flux in the latter being delayed, the currents generated in these two
circuits are in different phase, as herein fully set forth.
6. In an alternating current generator, an armature having inductor teeth,
separated by spaces equal to the breadth of these teeth, in combination with a
continuously magnetized field, upon the divisions of the presenting poles of which
are right and left hand wound circuit generating coils, and in combination with
these a winding upon the armature, and a commutator arranged to generate and
convey the current necessary to magnetize the field magnet as herein set forth.
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HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicants.