Year: 1885

page_text: I, SILVANUS PHILLIPS THOMPSON of 20 Arundel Gardens, Notting Hill, London,
Doctor of Science, do hereby declare the nature of this Invention to be as
follows:-
My Invention relates to dynamo electric machines designed to generate a current
of constant or approximately constant strength, or to be run as motors with a
current of constant or approximately constant strength, and my said Invention
relates more particularly to those forms of machine in which the armature consists
of an iron ring either solid or laminated having coils of wire wound in radial
or peripheral hollows or pockets, between teeth or projections at the flanks or
circumference of the said ring, and my said Improvements have for their object
the construction of machines, which while preserving the aforesaid general type are
both electrically and mechanically stronger and more efficient than any machines
of such type hitherto constructed, and are also better able to give out (or work at
as the case may be) a constant or approximately constant current under all usual
varying conditions of the external circuit.
In lieu of the cast-iron cores and pole pieces hitherto employed in machines of
this type, I use bars of Swedish or other soft iron, preferably rectangular, in cross
section. These bars, (of which there may be two or more,) are arranged in groups
on either side of the armature and lie in planes which are at right angles to the
axis of rotation of the armature. When groups of bars are employed, they
may be suitably bolted together, with or without the interposition of layers of
varnished paper or other insulating material between them. The two bars or
groups of bars are arranged either in one straight line, end-on, toward one another,
with the armature between their nearer ends or else in two parallel lines with the
armature between them. When the said bars or groups of bars are arranged,
end-on toward one another, the ends are provided with a concavity or pocket to
receive the armature and provide the requisite polar surface. When the said bars
or groups of bars are placed parallel beside one another, the requisite polar surface
is preferably obtained in the following manner. A pocket or cavity is made or
provided at the middle or other suitable part of each of the two bars or groups of
bars, the object of the said cavities or pockets being to receive the two edges of the
said ring armature. When single bars are employed, this cavity is preferably cut
TD 077

page_text: at the middle of one face of each bar, the cavity consisting of a longitudinal groove
or trough, with parallel sides, a little wider than the ring is from face to face the
bottom of each said cavity groove or pocket being curved to receive the ring that
is to say being deep in the middle and shallowing towards its two ends. Each
cavity fits (with due space for clearance) over a certain segmental portion of the
ring and it is convenient that the segments so covered should be diametrically
opposite and should each subtend between 25 degrees and 155 degrees of the
circumference of the ring The rings may be either discoidally flattened and
provided with radial grooves or pockets or they may be cylindrically elongated and
provided with peripheral grooves or pockets or they may be of any intermediate
mixed form of ring When a cylindrically elongated or prolate ring having
peripheral grooves or pockets is employed each said cavity or curved pocket may
be made without any enclosing sides it being in that case a mere cylindriform
hollow surface in the side or end of the bar or group of bars. When an oblate or
discoidally flattened ring is employed the side by side arrangement of the bars or
groups of bars is preferable to the end to end arrangement-When groups of two
or more bars are employed the cavities or pockets which receive the ring may be
made by cutting away a proper segmental portion of one or more of the inner bars
of the group and laying on either side of the bars that have been so cut one or
more bars that are not cut the latter forming the sides or flanges of the said
cavities The coils are wound either on the said bars or groups of bars or on
suitable cores connected with them-When wound upon the bars or groups of bars
they are wound on the parts which lie beyond the said pockets or cavities and
may be wound either on the iron direct suitable insulation being interposed or else
are wound upon suitable frames or formers which are placed over or receive the
said bars or groups of bars In certain forms of machine constructed according to
this my Invention one or more of the outer bars of the group is replaced by a bar
or flange which is itself a portion of the framing or foundation of the machine and
may be either of wrought or cast iron but the inner bars are always of wrought
iron The ends of the said iron bars or groups of bars are bolted or otherwise.
rigidly secured to end pieces or connecting pieces or frames of iron which unite
them both magnetically and mechanically together and with them constitute a
portion of the framing of the machine And in certain forms of machine the colis
are wound upon the said end pieces or connecting pieces instead of being wound
over the aforesaid bars or groups of bars themselves.
When such machines are designed for the purpose of giving a constant or
approximately constant current at a uniform speed without any other governor
than that of the steam engine or prime mover the machine must be wound with
series or main circuit coils to provide a steady excitation and also with shunt
coils to provide a variable excitation proportional or nearly proportional to the
resistance of the external circuit and I find it best to place the shunt coils nearest
the pockets or hollows hereinbefore mentioned and to place the series coils behind
them the forward position of the shunt coil enabling its varying currents to vary
the magnetism of the polar parts more rapidly than would be the case if the
positions of the coils were reversed.
In my improved machine the armature may be of any form that comes within
the type described that is to say I may employ such an armature as is used to the
well known Brush Machine or I may use other forms built or wound in other
ways. When I use an armature wound in separate sections I prefer that the
number of the sections should be three or some multiple of three, and that they
should be connected together in the following way. Three coils lying equidistant
at positions 120° apart around the ring are connected together in a closed circuit as
in the case of the more numerous coils of an ordinary Gramme Ring, and the
junctions of the three coils are connected to a three-part collector or commutator in
the usual way. If the armature coil has only three sections there will be one such
commutator or collector. If the armature consist of six sections (which I will
call A, B, C, D, E, F respectively) there will be two independent circuits in the

page_text: ring, 4, C and E being connected together into one closed circuit and B, D and F
being connected together into another closed circuit each circuit being united to a
separate collector or commutator. The second commutator or collector may have
a second independent pair of brushes joined either in series or in parallel arc with
those of the first commutator or collector.
Or a single pair of double broad brushes serves for both commutators or
collectors they being disposed upon the axle one behind the other at suitable
relative positions. When there are nine sections (A B C D E F G H and I) in
the armature these will be connected in three closed circuits, (videlicit A D G in
one circuit, B E H in another circuit and C. F. I. in a third circuit) to three com-
mutators or collectors, with 3 pairs of brushes or one trebly broad pair When
there are twelve sections there will be four closed circuits and so forth. A simple
modification of this method of grouping and connecting the armature coils, is to
take in each group (instead of three equidistant coils) three equidistant pairs of
coils whereof each pair consists of two that are situate at opposite ends of a
diameter, and these two in each pair may be connected to one another either in
parallel arc or in series, but always so as to be joined in a closed circuit with each
of the other pairs of the group.
When the commutators or collectors are constructed like ordinary Gramme
collectors of parallel bars of metal the requisite insulation is preferably attained by
leaving air gaps. But in some cases it is more convenient to use radial pieces of
metal fixed to the surface of a disc and in such cases it is expedient that the
brushes should be backed with an asbestos strip to mitigate the oxidising effect
of sparks.
The improved machine may be governed in any of the ordinary known electrical
or mechanical ways to generate a constant or approximately constant current
It may be also used as a motor, a constant or approximately constant current being
supplied to it either by a generating machine of a similar type or by any other
suitable means.

page_text: COMPLETE SPECIFICATION.
Improvements in Constant-current Dynamo Electric Machines.
I, SILVANUS PHILLIPS THOMPSON of 20 Arundel Gardens, Notting Hill London,
Doctor of Science 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:―
My Invention relates to Dynamo Electric machines designed to generate a
current of constant or approximately constant strength or to be run as motors
with a current of constant, or approximately constant strength and my said
invention relates more particularly to those forms of machine in which the
armature consists of an iron ring either solid or laminated having coils of wire
wound in radial or peripheral hollows or pockets between teeth or projections at
the flanks or circumference of the said ring and my said improvements have for
their object the construction of machines which while preserving the aforesaid
general type are both electrically and mechanically stronger and more efficient
than any machines of such type hitherto constructed and are also better able to
give out or work at (as the case may be) a constant or approximately constant
current under all usual varying conditions of the external circuit.
In lieu of the cast iron cores and pole pieces hitherto employed in machines of
this type I use bars of Swedish or other soft iron preferably rectangular in cross
section. These bars are arranged on either side of the armature and lie in planes
which are at right angles to the axis of rotation of the armature. When groups of
bars are employed they may be suitably bolted together with or without the
interposition of layers of varnished paper or other insulating material between
them The two bars or groups of bars are arranged either in one straight line end-
on toward one another with the armature between their nearer ends or else in two
parallel lines with the armature between them.
Figure 1 illustrates diagrammatically in front elevation an arrangement on the
first plan whilst Figure 3 is an elevation of an arrangement on the second plan
The bars referred to are marked y and are shewn as single bars one on each side
of the armature. The armature is merely indicated by a circle at x as it may be
the ordinary Brush ring as at present made. The armature shaft bearings are not
shewn as they may be of the ordinary kind supported in any suitable way as is
well understood. When the said bars or groups of bars are arranged end on
toward one another the ends are provided with a concavity or pocket to receive the
armature and provide the requisite polar surface One of these bars is shewn in
Figure 2 where the pocket is marked a-The other bar is made in the same way
When the said bars or groups of bars are placed parallel beside one another the
requisite polar surface is preferably obtained in the following manner-A pocket or
cavity is made or provided at the middle or other suitable part of each of the two
bars or groups of bars as shewn at a with regard to one of the bars in Figure 3a
the object of the said cavities or pockets is to receive the two edges of the said ring

page_text: armature-When single bars are employed this cavity is preferably cut at the
middle of one face of each bar as shewn in the said Figures 2 and 3—the cavity
consisting of a groove or trough forming part of a circle with parallel sides a little
wider than the armature ring is from face to face, the bottom of each said cavity
groove or pocket being curved to receive the ring, that is to say being deep in the
middle and shallowing towards its two ends-Each cavity fits (with due space for
clearance) over a certain segmental portion of the ring and it is convenient that
the segments so covered should be diametrically opposite and should each subtend
between 25° and 155° of the circumference of the ring-The rings may be either
discoidally flattened and provided with radial grooves or pockets, or they may be
cylindrically elongated and provided with peripheral grooves or pockets; or they
may be of any intermediate mixed form of ring. When a cylindrically elongated
or prolate ring, having peripheral grooves or pockets is employed each said cavity
or curved pocket may be made without any enclosing sides; it being in that case
a mere cylindriform hollow surface in the side or end of the bar or group of bars-
When an oblate or discoidally flattened ring is employed the side by side arrange-
ment of the bars or groups of bars is preferable to the end to end arrangement―
When groups of two or more bars are employed the cavities or pockets which
receive the ring may be made by cutting away a proper segmental portion of one
or more of the inner bars of the group and laying on either side of the bars that
have been so cut one or more bars that are not cut the latter forming the sides or
flanges of the said cavities-The coils are wound either on the said bars or groups
of bars or on suitable formers, moulds or cores connected with them. When wound
upon the bars or groups of bars they are wound on the parts which lie beyond the
said pockets or cavities, and may be wound either on the iron direct, suitable
insulation being interposed or else are wound upon suitable frames or formers
which are placed over or receive the said bars or groups of bars. In certain forms
of machine constructed according to my invention, one or more of the outer bars of
the group is replaced by a bar or flange which is itself a portion of the framing or
foundation of the machine, and may be either of wrought or cast iron; but the
inner bars are always of wrought iron. The ends of the said iron bars or groups of
bars are bolted or otherwise rigidly secured to end pieces or connecting pieces or
frames of iron which unite them both magnetically and mechanically together, and
with them constitute a portion of the framing of the machine. And in certain
forms of machine the coils are wound upon the said end pieces or connecting pieces
instead of being wound over the aforesaid bars or groups of bars themselves. In
Figures 1, 2 and 3 the coils are shewn as wound over the bars but in Figures 4
and 5 I have shewn in elevations at right angles to each other a machine with the
coils wound upon the end or connecting pieces-This machine has three bars above
and below the armature arranged as shewn in Figure 5.
When such machines are designed for the purpose of giving a constant or
approximately constant current at a uniform speed, without any other governor
than that of the steam engine or prime mover, the machine must be wound with
series or main circuit coils to provide a steady excitation, and also with shunt coils
to provide a variable excitation proportional or nearly proportional to the resistance
of the external circuit, and I find it best to place the shunt coils nearest the pockets
or hollows herein before mentioned, and to place the series coils behind them, the
forward position of the shunt coil enabling its varying currents to vary the
magnetism of the polar parts more rapidly than would be the case if the positions
of the coils were reversed. This arrangement is illustrated by Figure 6 where the
series coils are marked b² and the shunt coils 6³.
In my improved machine the armature may be of any form that comes within
the type described; that is to say I may employ such an armature as is used in
the well known Brush machine, or I may use other forms built or wound in other
ways. When I use an armature wound in separate sections I prefer that the
number of the sections should be three or some multiple of three and that they

page_text: should be connected together in the following way Three coils lying equidistant
at positions 120° apart around the ring are connected together in a closed circuit as
in the case of the more numerous coils of an ordinary Gramme Ring and the
junctions of the three coils are connected to a three part collector or commutator in
the usual way
If the armature coil has only three sections there will be one such
commutator or collector If as shewn by the diagram Figure 7 the armature
consist of six sections (which I call A B C D E F respectively there will be two
independent circuits in the ring A C and E being connected together into one
closed circuit and B. D and F being connected together into another closed circuit
each circuit being united to a separate collector or commutator I have shown the
connections A E C the connections of F. B. D-being similar thereto The second
commutator or collector may have a second independent pair of brushes joined
either in series or in parallel arc with those of the first cominutator or collector
Or a single pair of doubly broad brushes serves for both commutators or collectors
they being disposed upon the axle one behind the other at suitable relative
positions When there are nine sections (A B C D E F G H and I) in the
armature these will be connected in three closed circuits (viz A D G in one
circuit BEH in another circuit and C F I in a third circuit) to three commutators
or collectors with three pairs of brushes or one trebly broad pair When there are
twelve sections there will be four closed circuits and so forth A simple modifica-
tion of this method of grouping and connecting the armature coils is to take in
each group (instead of three equi-distant coils,) three equi-distant pairs of coils
whereof each pair consists of two that are situate at opposite ends of a diameter
and these two in each pair may be connected to one another either in parallel arc
or in series and then joined to the two corresponding bars of the commutator or
collector but always so as to be joined in a closed circuit with the two other pairs
of the group.
When the commutators or collectors are constructed like ordinary gramme
collectors of parallel bars of metal, the requisite insulation is preferably attained
by leaving air gaps. But in some cases it is more convenient to use radial pieces
of metal fixed to the surface of a disc and in such cases it is expedient that the
brushes should be backed with an asbestos strip to mitigate the oxidising effects
of sparks.
The improved machine may be governed in any of the ordinary known Electrical
or mechanical ways to generate a constant or approximately constant current. It
may be also used as a motor, a constant or approximately constant current being
supplied to it either by a generating machine of a similar type or by any other
suitable means.
It is to be understood that there may be one or any number of bars on each side
of the armature, either side by side or superposed upon each other or both, for
example, Figure 8 shews a number of bars arranged in groups of three, side by
side, but in considerable number in the other direction, that is to say, the groups
of three bars are superposed to form the requisite depth of bar, although of
course the bars may be of the requisite depth so that there is only one series of
three bars.
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:
First. In a Dynamo Electric machine, in which the armature consists of coils of
conductors wound in radial or peripheral hollows or pockets between teeth or
projections at the flanks or circumference, the improved field magnet, substantially
as described with reference to the accompanying Drawings.
Second. The construction of the cores of field magnets for Dynamo Electric
machines, of bars with cavities or pockets in their ends or sides, within which,
armature of the class named, rotates, substantially as described and illustrated by

page_text: the several examples shewn, whether the cavities or pockets be cut out of or
formed in a single bar or be made by building up a number of bars, substantially
as described.
Third. In a Dynamo Electric machine for supplying a constant or approximately
constant current, the winding of the field magnets by placing the shunt coils
nearest to the polar portions, and the series coils behind them as explained with
regard to Figure 6.
Fourth. The construction of the armature of a Dynamo-Electric machine, in
groups of three coils, each group forming in itself a separate closed circuit, sub-
stantially as described with reference to the diagram, Figure 7.