Improvements in Dynamo-electric Machines, in Part Applicable to Electro Motors.
Year: 1889

page_text: Date of Application, 9th July, 1889
Complete Specification Loft, 1st Apr., 1890-Accented, 3rd May, 1890
PROVISIONAL SPECIFICATION.
Improvements in Dynamo-electric Machines, in Part Applicable to
Electro Motors.
I, JAMES JOHN WOOD, of No. 126 Cambridge Place, Brooklyn, in the State of
New York, United States of America, Electrical Engineer, do hereby declare the
nature of this invention to be as follows:-
This invention relates to the construction of dynamo-electric machines, and
especially to such machines as are designed for generating a current of uniform
volume and of high electro-motive force. Machines of this class are used chiefly for
feeding electric arc lamps connected serially in the circuit, although useful also for
some other purposes.
This now dynamo is of the Gramme-ring type and generates a continuous current
of uniform direction. It is self-regulating so that it maintains the current at a
uniform volume (i.e. a certain number of amperes), notwithstanding any variations.
in the resistance of the external circuit.
The invention consists, firstly, in an improved method of winding the armature
whereby the short-circuiting of the armature-coils within themselves is prevented;
and secondly, in improved means for effecting the automatic regulation of the
current generated, in order to maintain it at a uniform volume.
The accompanying drawings show one suitable construction of dynamo embodying
this invention.
Fig. 1 is a side elevation of the machine, partly in vertical section.
Fig. 2 is a front elevation, partly in vertical section cut on the line 2-2 in Fig. 1.
Fig. 3 is a sectional view looking in the same direction as Fig. 2, the right half
being in mid-section on the line 3-3 in Fig. 1, and the left balf in section through
the commutator and the field-magnet coils.
Fig. 4 is a diametrical section of the armature and commutator on a larger scale.
Fig. 5 is a fragmentary mid-section of the armature on a still larger scale, (the
section being in the same plane as the right-hand half of Fig. 3), partly dissected to
show the winding of the armature coils.
Fig. 6 is a view (on a scale intermediate of Figs. 4 and 5) of one of the insulating
plates or sheets placed between the two halves of each of the armature coils.
Fig. 7 is a diagram showing the preferred circuit connections, the armature,
commutator and regulator being shown removed from the field-magnet for the sake
of clearness.
Figs. 8, 9 and 10 are similar diagrams, showing modifications of the regulator.
Fig. 11 illustrates another modification, and Fig. 12 is a horizontal section of
part of Fig. 11.
In the drawings, F designates the field-magnet, A the armature, C the commutator,
and B B the main commutator brushes.
The field-magnet is in general of horse-shee shape, having curved pole-pieces
partially embracing the armature on opposite sides, its neutral portion being made
integrally with the base D, and its polar cores bolted thereto and projecting vertically.
These cores are wound each with a main exciting coil E and a supplemental or
regulating coil E', of insulated wire.
The armature is fixed on a shaft G which turns in bearings formed on frames H Hi
bolted to the base. The arn.ature is constructed with an annular core J of soft iron
wire, carried on the radial arms of a spider K. Between the spider arms this core is
covered by a sheath b of insulating material,. around which are wound the armature
coils a a of insulated wire, separated by plates or sheets c c of insulating material,

page_text: There are 120 armature coils in the machine shown, although more or less may be
used.
The commutator C consists of 120 metal segments e e separated by plates of mica,
and clamped at their ends between two disks d and d¹, rings of insulating material
being interposed, as shown in Fig. 4.. Each segment has a radial strip of metal e¹
soldered to it, and on the outer end of this strip is fixed a screw clamp. Each
armature coil a has its opposite ends fastened to two successive clamps, and each
clamp thus connects with the wires of two adjoining coils. Thus all the armature
coils are connected to each other in series, and the commutator segments are joined
between each two coils, as is usual.
Fig. 5 shows in detail the method of winding the armature coils a a. These coils,
being of uniform resistance, are wound of wire of uniform size and cut in uniform
lengths. The coils on the right of the spider arm are shown as wound by the old
method, in use prior to the present invention. The middle portion f of each wire is
first wound around the core, as shown in the right-hand coil which is partly wound.
Its two end portions are then wound around in opposite directions until all the wire
is wound on. In thus winding the coil one of the end portions or halves of the
length of wire is wound in the right-hand half (shown at g) of the segmental space
between the two plates c c, and the other portion or half is wound in the left hand
half of the space (shown at g¹).
י
This method of confining each half of the wire to one half of the space is the best
way of winding heretofore known. It is subject, however, to the disadvantage that
the coils are liable to burn out by the current jumping across between the
adjoining outer convolutions i and i, forming an arc, and short-circuiting the
coil within itself, thereby heating the wire and burning off its insulation. It is
well known to electricians that when a wire or coil is passing through a magnetic
field the difference of electric potential generated in it is directly proportional to its
length. The difference of potential between any two convolutions, or between any
two superposed layers in the coils a a is very slight, so that the tendency to short-
circuit between these convolutions is insignificant, and is amply resisted by the
insulating coating of the wire. But between the convolutions of the respective
half-coils g and g there exists a much greater difference of potential, which increases
with each layer to an extent proportional to the entire length of wire used in winding
that layer, and which at the outermost convolutions i i¹ becomes very considerable and
exerts a strong tendency to short-circuit or are between them. To overcome this
tendency an excessively thick insulation must be used, which reduces the length of
wire that can be wound in a given space.
According to the present invention the, coil is wound as shown at the left of the
spider-arm in Fig. 5. After winding one middle convolution of the length of
wire, as heretofore, I apply an insulating plate or sheet h, shown separately in Fig. 6,
placing it in the middle of the space to be occupied by the coil. The opposite end
portions or halves of the length of wire are then wound in the spaces on opposite.
sides of this sheet h. Thus the two half-coils g and glare separated by the inter-
vening sheet which is of sufficient thickness to resist the tendency to short-circuit
across between the convolutions i and i'.
The following advantages result from this novel method of winding: The insulating
coating of the wire need be no thicker than sufficient to resist the difference of
potentials between adjoining layers of convolutions, thereby enabling a greater length
of wire to be wound in the same space and consequently increasing the efficiency of
the machine. A cheaper quality of insulation can also be used, with less danger of
burning out than has heretofore existed with the most expensive insulating coverings.
In case of any defect in the insulating covering the formation of a short-circuit is
less likely to occur than with the old winding.
The adoption of this invention has enabled. me to make a dynamo developing an
electro-motive force of 4,600 volts, whereas the same armature wound in the old way
could not safely be run higher than 2,700 volts. Or in other words an armature

page_text: with the old winding feeding 54 arc lamps can be made with the new winding to
feed 82 lamps.
The insulating sheet h is preferably made of tough flexible material. It need not
extend entirely to the inner side of the coil, but instead several layers may be wound
on before the sheet is applied, as shown in the coil a¹ in Fig. 5. It is at the
extreme outer convolutions that the burning out of the coils occurs or commences,
and it is important only to separate these outer convolutions by the sheet h.
I will now describe the means for regulating the current.
The field-magnet is excited by the coils E E, which are connected in the main
circuit with the commutator brushes B B¹, as is usual in self-excited series dynamos.
As shown in Figs. 7, 8 or 10, the brushes B B' touch the commutator on the
66 maximum line " xx, or line of maximum difference of potentials, and consequently
take off the entire current from the armature. The main circuit includes arc lamps,
indicated at L L, or electro motors, and also if desired, some incandescent lamps
indicated (in Fig. 7 at 1 1.
The supplemental or regulating coils E' E¹ are connected in a shunt-circuit j
which in Fig. 8 terminates at one end in a supplemental brush N, and at the other
end in one of the main brushes B (or B' if preferred). These shunt-terminal brushes N
and B are movable to different relative positions around the commutator, preferably
by shifting the brush N, which for that purpose is carried by a movable yoke k,
connected by any suitable mechanism (as the rod m and lever n in Fig. 8) with the
movable member or core of the regulating magnet M, which is preferably of the
solenoid type, as shown. The coil of this magnet is in the main circuit, so that as
the current increases or decreases, its varying attraction moves the core up
or down, and hence the brush N is moved correspondingly around the com-
mutator.
It is well known that the current taken off by commutator brushes against a fixed
resistance depends upon the difference of potentials at the two brushes, and that their
potentials depend upon the position at which the brushes touch the commutator. If
there is a considerable difference of potentials they will take off a considerable current
and if they are (or one of them is) moved to such position that there is little or no
difference of potentials they take off little or no current. Hence by relatively adjust-
ing the shunt-terminal brushes N B to different positions upon the commutator the
current that is caused to flow through the shunt circuit j and coils E' E' may be varied
to any extent. The coils E' are so connected that the current in them flows in the
opposite direction to that in the main coils E E so that this inverse current acts to
neutralize more or less the magnetizing effect of the main coils. Thus as the current
in the coils E is increased by the movement of the brushes N B to positions further
apart, so that there is a greater difference of potential between them, the magnetization
of the field-magnet is correspondingly reduced.
The operation is as follows:-In the ordinary running of the dynamo with all the
arc lamps L L in circuit the brush N stands close to the brush B, so that only a small
current is flowing through the coils E. If now one or more lamps are cut out of
circuit, thereby reducing the resistance of the line, the consequent increase of current
excites the magnet M, which acts to move the brush N away from the brush B,
thereby increasing the current through the coils E' so that these coils act to reduce
the magnetization of the field-magnet and consequently to decrease its inductive effect
on the armature, so that the electro-motive force generated therein is reduced. This
action continues until the electro-motive force has been readjusted to the new
condition of resistance on the line, whereupon the current falls to approximately
the normal volume, thereby re-establishing an equilibrium. Upon an increase of the
resistance on the line the weakening of the magnet M effects a movement of the
brush N toward the brush B, thereby decreasing the inverse current in the coils E¹
and consequently increasing the magnetization of the field-magnet and hence, also,
the electro-motive force of the armature, until the current is restored to the normal.
If the speed of rotation of the armature should be reduced, thereby reducing the
electro-motive force, the current would be reduced and the weakening of the

page_text: magnet M would cause a decrease in the inverse current in the coils E¹ in the same.
manner as though the resistance on the line were increased. Thus when the machine
is either over-loaded or is under-speeded the brush N will be moved quite into contact
with the brush B, so that their potentials become alike and no current flows through
the coils E'.
By this means the dynamo is made self-regulating in a very simple and effective.
manner. The coils E' may be wound in any desired position on the field-magnet and
may be of any suitable resistance.
Instead of using one supplemental brush N and connecting the other terminal of
the shunt to one of the main brushes B or B', two distinct supplemental brushes may
be used, arranged on any suitable part of the commutator, and one or both of them.
may be moved around the cominutator to vary their relative potentials. Or, as,
shown in Fig. 9, the one supplemental brush N may be stationary and the main
brush B constituting the opposite terminal of the shunt ; (or both brushes B and B',"
as shown) may be mounted on a yoke k and movable to or from the maximum line.
Thus when the current is excessive the movement of the brush B away from the
maximum causes it to take off less current to the line, and at the same time by.
decreasing its potential relatively to the brush N increases the inverse current in the
coil E. The respective terminal brushes of the shunt j may be moved relatively in
many other different ways in order to vary their relative potentials.
Fig. 7 shows the perferred construction of the regulator. The core of the magnet M
connects with the yoke k through the medium of an elbow-lever n formed with a.
toothed sector meshing with a similar sector on the yoke k. The magnet core is
connected to a dashpot P to resist any sudden movements. The main circuit includes
the coil of a relay-magnet or solenoid R, the core of which when down touches a
contact-piece p and thereby closes a branch circuit 9 which short circuits the
magnet M. A resistance coil r is connected on opposite sides of the relay contacts to
prevent sparking. The relay R having but little to do is very sensitive, so that a
very slight increase of current causes it to lift its core, thereby breaking the
shunt q and causing almost the entire current to flow through magnet M, thereby
disproportionately increasing the excitation of this magnet and causing it to act
forcibly to move the brush N away from brush B so as to increase the inverse or
demagnetizing current in the coils E'. When the generated current has thus
been reduced to the normal the relay R releases its core, which again closes the
shunt g and short circuits the magnet M, thereby disproportionately reducing its
excitation and causing the brush N to again approach the brush B, whereupon the
increased current again excites the relay R, and so on. Thus the regulator effects a
minute intermittent rise and fall of the current, the relay R rendering it very sensitive
to current fluctuations.
Fig. 10 shows the application of this system to a separately-excited dynamo. Tis
the main dynamo with its field-magnet excited by a coil Q which is in the main
circuit of the separate exciter dynamo X. This dynamo X is provided with the
inverse shunt coil E' and supplemental brush N, as already described, the only
difference being that the coil of the regulator magnet M is in the main circuit tt of
the dynamo T. A decrease of resistance in this circuit t augments the current
therein and excites the magnet M which increases the demagnetizing current in the
coi! E and consequently reduces the current generated by the dynamo X, so that a
less current flows through the coil Q and the excitation of the field-magnet is reduced
until the current in the circuit t falls to the normal.
The supplemental brush N may be shifted by other means than the direct action of a
megnet or solenoid. In Fig. 11 the yoke k is shown as connected by a train of
gears ss to a friction-wheel S having two flanges u¹ between which revolves a
friction-roller U, as shown in Fig. 12. This roller may be fixed on the armature shaft
or driven therefrom. The wheel S is moved by a lever V which is acted on by the
armature of the regulating magnet M and by a retracting spring S¹. Normally the
roller U revolves between its flanges u u¹ without touching either. If the current
increases, the magnet M pulls the lever V upwardly, which brings the flange u against

page_text: the roller U, thereby propelling brush N away from brush B and increasing the
inverse current in the coil E'. If the current becomes less than the normal the
spring S¹ pulls down the lever V and brings flange u' against roller U which revolves
wheels in the opposite direction and moves brush N toward brush. B, thereby
decreasing the current in the shunt.
The part of this invention relating to the winding of the armature is applicable to
electro-motors as well as to dynamos.
1000
COMPLETE SPECIFICATION.
Improvements in Dynamo-electric Machines, in Part Applicable to
. Electro Motors.
I, JAMES JOHN WOOD of No. 126 Cambridge Place, Brooklyn, in the State of New
York, United States of America, 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:-
!
This invention relates to the construction of dynamo electric machines, and especially
to such machines as, are designed for generating a current of. uniform volume and
of high electro-motive force. Machines of this class are used chiefly for feeding
electric arc lamps connected serially in the circuit, although useful also for some
other purposes.
This new dynamo is of the Gramme ring type, and generates a continuous current
of uniform direction. It is self-regulating, so that it maintains the current at a
uniform volume (i.e., a certain number of amperes) notwithstanding any variations in
the resistance of the external circuit.
The invention consists, firstly, in an improved method of winding the armature
whereby the short-circuiting of the armature-coils within themselves is prevented; and
secondly, in improved means for effecting the automatic regulation of the current
generated, in order to maintain it at a uniform volume.
The drawings filed with my Provisional Specification show one suitable construction
of dynamo embodying this invention.
Fig. 1 is a side elevation of the machine, partly in vertical section.
Fig. 2 is a front elevation, partly in vertical section cut on the line 2-2 in Fig. 1.
Fig. 3 is a sectional view looking in the same direction as Fig. 2, the right-half
being in mid-section on the line 3-3 in Fig. 1, and the left half in section through
the commutator and the field-magnet coils.
Fig. 4 is a diametrical section of the armature and commutator on a larger scale.
Fig. 5 is a fragmentary mid-section of the arinature on a still larger scale (the
section being in the same plane as the right-hand balf of Fig. 3), partly dissected to
show the winding of the arinature coils.
Fig. 6 is a view (on a scale intermediate of Figs. 4 and 5) of one of the
insulating plates or sheets placed between the two halves of each of the armature
coils.
1
Fig. 7 is a diagram showing the preferred circuit connections, the armature,
commutator and regulator being shown removed from the field-magnet for the sake
of clearness.
Figs. 8, 9 and 10 are similar diagrams, showing nodifications of the regulator."
Fig. 11 illustrates another modification, and Fig. 12 is a horizontal section of part

page_text: ..In the drawings. F designates the field-magnet, A the armature, C the commutator,
and B B' the main commutator brushes.
The field-magnet is in general of horse-shoe shape, having curved pole-pieces
partially embracing the armatures on opposite sides, its neutral portion being made
integrally with the base D, and its polar cores bolted thereto and projecting vertically:
These cores are wound each with a main exciting coil E and a supplemental or
regulating coil E', of insulated wire.
The armature is fixed on a shaft G which turns in bearings formed on frames H H¹
bolted to the base. The armature is constructed with an annular core J of soft iron
wire carried on the radial arms of a spider K. Between the spider arms this core
is covered by a sheath b of insulating material, around which are wound the armature
coils a a of insulated wire, separated by plates or sheets cc of insulating material.
There are 120 armature coils in the machine shown, although more or less may
.be used.
The commutator C consists of 120 metal segments e e separated by plates of mica,
and clamped at their ends between two disks d and d', rings of insulating material
being interposed, as shown in Fig. 4.
Each segment has a radial strip of metal ¹ soldered to it, and on the outer end of
this strip is fixed a screw-clamp. Each armature coil a has its opposite ends fastened
to two successive clamps, and each clamp thus connects with the wires of two adjoining
coils. Thus all the armature coils are connected to each other in series, and the
-commutator segments are joined between each two coils, as is usual..
Fig. 5 shows in detail the method of winding the armature coils a a. These coils,
being of uniform resistance, are wound of wire of uniform size and cut in uniform
lengths. The coils on the right of the spider arın are shown as wound by the old
method, in use prior to the present invention. The middle portion, r, of each wire is
first wound around the core, as shown in the right-hand coil which is partly wound.
Its two end portions are then wound around in opposite directions until all the
wire is wound on. In thus winding the coil one of the end portions or halves of
the length of wire is wound in the right-hand half (shown at 9) of the segmental
space between the two plates c, and the other portion or half is wound in the
left-hand half of the space (shown at g').
This method of confining each half of the wire to one-half of the space is the
best way of winding heretofore known. It is subject, however, to the disadvantage
that the coils are liable to burn out by the current jumping across between the
adjoining outer convolutions and i, forming an arc, and short-circuiting the coil
within itself, thereby heating the wire and burning off its insulation. It is well
known to electricians that when a wire or coil is passing through a magnetic field the
difference of electric potential generated in it is directly proportional to its length.
The difference of potential between any two convolutions, or between any two super-
posed layers in the coils a a is very slight, so that the tendency to short circuit
between these convolutions is insignificant, and is amply resisted by the insulating
coating of the wire. But between the convolutions of the respective half coils g and gi
there exists a much greater difference of potential, which increases with each layer to
an extent proportional to the entire length of wire used in winding that layer, and
which at the outermost convolutions becomes very considerable and exerts a strong
tendency to short-circuit or are between them. To overcome this tendency an
excessively thick insulation must be used, which reduces the length of wire that can
be wound in a given space.
According to the present invention the coil is wound as shown at the left of the
spider-arm in Fig. 5. After winding one middle convolution fof the length of the wire,
as heretofore, I apply an insulating plate or sheet h, shown separately in Fig. 6, placing
it in the middle of the space to be occupied by the coil. The opposite end portions
or halves of the length of wire are then wound in the spaces on opposite sides of
this sheet h. Thus the two half coils 9 and 9' are separated by the intervening
sheet which is of sufficient thickness to resist the tendency to..short-circuit across
between the convolutions i and i.

page_text: The following advantages result from this novel method of winding :-The insu
lating coating of the wire need be no thicker than sufficient to resist the difference
of potentials between adjoining layers of convolutions, thereby enabling a greater
length of wire to be wound in the same space, and consequently increasing the
efficiency of the machine. A cheaper quality of insulation can also be used, with
less danger of burning out than has heretofore existed with the most expensive
insulating coverings. In case of any defect in the insulating covering the formation
of a short-circuit is less likely to occur than with the old winding.
The adoption of this invention has enabled me to make a dynamo developing
an electro-motive force of 4,600 volts, whereas the same armature wound in the old
way could not safely be run higher than 2,700 volts. Or, in other words, an armature
with the old winding feeding 54 arc lamps can be made with the new winding to
feed 82 lamps..
The insulating sheet is preferably made of tough flexible material. It need
not extend entirely to the inner side of the coil, but instead several layers may be
wound on before the sheet is applied, as shown in the coil a¹ in Fig. 5. It is at
the extreme outer convolutions that the burning out of the coils occurs or com-
mences, and it is important only to separate these outer convolutions by the sheet h.
I will now describe the means for regulating the current.
The field-magnet is excited by the coils E E, which are connected in the main
circuit with the commutator brushes B B', as is usual in self-excited series dynamos.
As shown in Figs. 7, 8 or 10, the brushes B B' touch the commutator, on the
"maximum line xx, or line of maximum difference of potentials, and consequently
take off the entire current from the armature. The main circuit includes arc
lamps, indicated at L L, or electro-motors, and also if desired, some incandescent
lamps indicated (in Fig. 7) at 1 l.
The supplementalnor regulating coils E' Eare connected in a shunt-circuit j
which in Fig. 8 terminates at one end in a supplemental brush N, and at the other
end in one of the main brushes B (or B' if preferred). These shunt-terminal
brushes N and B are movable to different relative positions around the commutator,
preferably by shifting the brush N, which for that purpose is carried by a movable
yoke k, connected by any suitable mechanism (as the rod m and lever n in Fig. 8)
with the movable member or core of the regulating magnet M, which is preferably
of the solenoid type, as shown. The coil of this magnet is in the main circuit, so.
that as the current increases or decreases its varying attraction moves the core
up or down, and hence the brush N is moved correspondingly around the
commutator.
It is well known that the current taken off by commutator brushes against a fixed
resistance depends upon the difference of potentials at the two brushes, and that.
their potentials depend upon the position at which the brushes touch the commutator..
If there is a considerable difference of potentials they will take off a considerable
current and if they are (or one of them is) moved to such position that there is
little or no difference of potentials they take off little or no current. Hence by
relatively adjusting the shunt-terminal brushes N B to different positions upon the
commutator the current that is caused to flow through the shunt circuit j and
coils E E may be varied to any extent. The coils E are so connected that the
current in them flows in the opposite direction to that in the main coils E E, so that
this inverse current acts to neutralize more or less the magnetizing effect of the
main coils. Thus as the current in the coils E is increased by the movement of the
brushes N B to positions further apart, so that there is a greater difference
of potential between them, the magnetization of the field-magnet is correspondingly
reduced.
The operation is as follows:-In the ordinary running of the dynamo with all the
arc lamps L L in circuit, the brush N stands close to the brush B, so that only a
small current is flowing through the coils E'. If now one or more lamps are cut
out of circuit, thereby reducing the resistance of the line, the consequent increase of
current excites the magnet M, which acts to move the brush N away from the

page_text: brush B, thereby increasing the current through the coils E' so that these coils act
to reduce the magnetization of the field-magnet, and consequently to decrease its
inductive effect on the armature, so that the electro-motive force generated therein is
reduced. This action continues until the electro-motive force has been readjusted
to the new condition of resistance on the line, whereupon the current falls to
approximately the normal volume, thereby re-establishing an equilibrium. Upon an
increase of the resistance on the line the weakening of the magnet M effects a move-
ment of the brush N toward the brush B thereby decreasing the inverse current in
the coils E', and consequently increasing the magnetization of the field-magnet, and
hence, also the electro-motive force of the armature, until the current is restored to
the normal.
If the speed of rotation of the armature should be reduced, thereby reducing the
electro-motive force, the current would be reduced and the weakening of the magnet M
would cause a decrease in the inverse current in the coils E' in the same manner as
though the resistance on the line were increased. Thus when the machine is either
overloaded or is underspeeded the brush N will be moved quite into contact with the
brush B, so that their p tentials become alike and no current flows through the
coils E.
By this means the dynamo is made self-regulating in very simple and effective
manner. The coils E' may be wound in any desired position on the field-magnet and
may be of any suitable resistance.
.
Instead of using one supplemental brush N and connecting the other terminal of
the shunt to one of the main brushes B or B', two distinct supplemental brushes
may be used, arranged on any suitable part of the commutator, and one or both of
them may be moved around the commutator to vary their relative potentials. Or, as
shown in Fig. 9, the one supplemental brush N may be stationary and the main
brush B constituting the opposite terminal of the shunt (or both brushes B and B',
as shown) may be mounted on a yoke k and movable to or from the maximum line.
Thus when the current is excessive the movement of the brush B away from the
maximum causes it to take off less current to the line, and at the same time by
decreasing its potential relatively to the brush N increases the inverse current in the
coil E. The respective terminal brushes of the shunt j may be moved relatively in
many other different ways in order to vary their relative potentials.
Fig. 7 shows the referred construction of the regulator. The core of the
magnet M connects with the yoke k through the medium of an elbow-lever n formed
with a toothed sector meshing with a similar sector on the yoke k. The magnet core
is connected to a dash-pot P to resist any sudden movements. The main circuit
includes the coil of a relay-magnet or solenoid R, the core of which when down
touches a contact-piece p and thereby closes a branch circuit q which short-circuits
the magnet M. A resistance coil is connected on opposite sides of the relay contacts
to prevent sparking. The relay R having but little to do, is very sensitive, so that
a very slight increase of current causes it to lift its core, thereby breaking the shunt q
and causing almost the entire current to flow through magnet M, thereby dispropor-
tionately increasing the excitation of this magnet and causing it to act forcibly to
move the brush N away from brush B, so as to increase the inverse or demagnetizing
current in the coils E'. When the generated current has thus been reduced to the
norinal the relay E releases its core, which again closes the shunt 9 and short
circuits the magnet M, thereby disproportionately reducing its excitation and causing
the brush N to again approach the brush B, whereupon the increased current again
excites the relay R, and so on. Thus the regulator effects a minute intermittent
rise and fall of the current, the relay R rendering it very sensitive to current
fluctuations.
Fig. 10 shows the application of this system to a separately-excited dynamo. T is
the main dynamo with its field-magnet excited by a coil Q which is in the main
circuit of the separate exciter dynamo X. This dynamo X is provided with the
inverse shunt-coil E¹ and supplemental brush N, as already described, the only
difference being that the coil of the regulator inagnet M is in the main circuit t t of the

page_text: dynamo T. A decrease of resistance in this circuit t augments the current therein
and excites the magnet M which increases the demagnetizing current in the coil E'
and consequently reduces the current generated by the dynamo X, so that a less
current flows through the coil Q and the excitation of the field-magnet is reduced until
the current in the circuit t falls to the normal.
•
The supplemental brush N (or brushes N N¹) may be shifted by other means than
the direct action of a magnet or solenoid. In Fig. 11 the yoke k is shown as
connected by a train of gears ss to a friction-wheel S having two flanges u between
which revolves a friction-roller U, as shown in Fig. 12. This roller may be fixed on
the armature shaft or driven therefrom. The wheel S is moved by a lever V which
is acted on by the armature of the regulating magnet M and by a retracting spring St.
Normally the roller U revolves between its flanges u u' without touching either. If
the current increases, the magnet M pulls the lever V upwardly, which brings the
flange u against the roller U, thereby propelling brush N away from brush B and
increasing the inverse current in the coil E. If the current becomes less than the
normal the spring S¹ pulls down the lever V and brings the flange u against roller U
which revolves wheels ss in the opposite direction, and moves brush N toward
brush B, thereby decreasing the current in the shunt.
The part of this invention relating to the winding of the armature is applicable to
electro-motors as well as to dynamos.
Having now fully described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
1. The improved means of winding the armature coils hereinbefore described,
these coils consisting each substantially of a single length of wire with its middle
portion wound around the core at the inner part of the coil, and its terminal portions
at the outer part, and with the outer convolutions of the opposite end portions of the
length of wire wound as separate half coils on opposite sides of an insulating sheet /
interposed between such half coils.
2. The improved means for regulating the current hereinbefore described, the
same consisting in providing the field-magnet, in addition to the main exciting coil,
with a regulating coil in a shunt circuit wherein normally a continuous current is
flowing, this coil being connected inversely so that the current in it tends to demag-
netize the field-magnet, and with automatic means for varying the electro-motive force
of the current in the shunt circuit inversely to, and in proportion to, the variations of
resistance in the external, circuit, whereby the magnetization of the field-magnet is
varied to such extent as to compensate for variations of external resistance, and the
current is maintained uniform.
3. The means for varying the inverse current in the regulating shunt-coil, con-
sisting in connecting the terminals of the shunt circuit to two commutator brushes,
one or both of which are adjustable around the commutator in order to vary their
relative potentials, and consequently to vary the electro-motive force of the current in
the shunt, and a regulating-magnet connected to the movable brush or brushes in such
manner as to effect a relative movement thereof corresponding to an increase or
decrease of the current in the external circuit, substantially as described.
Dated the 31st day of March 1890
J. C. MEWBURN,
55 & 56, Chancery Lane, London, Patent Agent.