IMPROVEMENTS IN DYNAMO ELECTRIC A communication from MACHINES, AND IN APPARATUS USED THEREWITH
Year: 1880

page_text: LETTERS PATENT to Herbert John Haddan, of the Firm of Herbert and
Company, Solicitors of Patents, of 67, Strand, in the City of Westminster,
Civil Engineer, for an Invention of "IMPROVEMENTS IN DYNAMO ELECTRIC
A communication from
MACHINES, AND IN APPARATUS USED THEREWITH,”
abroad by Charles F. Brush, of Clevoland, Ohio, United States of America.
"
PROVISIONAL SPECIFICATION left by the said Herbert John Haddan at
the Office of the Commissioners of Patents on the 26th February 1880.
HERBERT JOHN HADDAN, of the Firm of Herbert and Company, Solicitors of
"IMPROVE-
Patents, of 67, Strand, in the City of Westminster, Civil Engineer.
MENTS IN DYNAMO ELECTRIC MACHINES, AND IN APPARATUS USED THEREWITH.'
A communication from abroad by Charles F. Brush, of Cleveland, Ohio, United
States of America.
The Invention relates to dynamo electric machines, and has for its object the
adaptation of such machines to variable external conditions without variation of
the speed at which their armatures are rotated, but by variation of the intensity
of the magnetic field, and this by means not directly depending on the volume
of current circulating in the external circuit. The magnetic field of the machine
is weakened either by shunting away from the coils of the field magnets a portion
of the current which excites them, or by cutting out or short circuiting some
portion of one or more of the coils, so that the current shall make a less number
of convolutions about the cores of the magnets.
The resistance of the shunt circuits may either be varied by hand or auto-
matically, and one or more (but preferably all) of the magnet helices of a machine
may be included in that part of the circuit of the machine affected by the shunt;
one end of the conductor formed by these helices being attached to the corre-
sponding (first) commutator brush, while the other end is attached to the binding
post forming one terminal of the machine, and the other (second) terminal is
connected with the corresponding (last) commutator brush.
Between the second terminal and the first commutator brush a variable shunt
conductor is inserted consisting chiefly of several consecutive coils, the first of
which is attached with one end to the first terminal, and with the other to a
button or stud connected with one end of the second coil, the other end of which is
attached to a second button connected with one end of the third coil, and so on.

page_text: The other end of the shunt conductor is formed by a wire attached with one end
to the first commutator brush, and with the other to the fulcrum of a lever, so
placed that the end of the lever can be brought into contact with any of the said
buttons or studs connecting two consecutive coils, the buttons being for this
arranged in an are having the fulcrum of the lever for its centro.
purpose
By bringing the lever in contact with the first button the shunt circuit passes
only through the first coil, and from there through the lever to the commutator.
This position corresponds to the maximum strength of the shunt circuit, and
consequently the minimum strength of the magnet circuit. When the lever is in
contact with the last button of the series the resistance of the shunt circuit is at
its maximum, and consequently also the strength of the magnet circuit.
It is preferred to arrange the resistance coils on metal cores in a metal case
provided with suitable openings for the circulation of air.
For altering the resistance of the shunt circuit automatically, the lever above
mentioned is connected with a spring which draws the lever so as to interrupt the
shunt circuit when not counteracted by an armature forming a prolongation of the
lever, and attracted by an electro-magnet excited by the working current from
the machine.
The stronger this current is the smaller is the number of coils inserted in the
shunt circuit, and the weaker becomes the magnet circuit.
The variable shunt conductor may be formed by a pile of carbon discs, the
resistance of which is varied by altering the pressure brought to bear upon the pile
through the agency of an electro-magnet excited by the working current from the
dynamo machine. This may be effected by attaching the anchor of the said electro-
magnet to a lever which presses against the end of the carbon pilo; the armature
or anchor may also be replaced by a moveable core.
Instead of magnetism various other means may be employed for altering the
resistance of the shunt circuit, such as the expansion of metal produced by the
varying temperature caused by currents passing through them.
For eliminating a number of coils from the magnet circuit, and thus diminishing
the magnetization of the cores, metallic plugs may be inserted between the different
layers of the wire forming the magnet coil. Instead of inserting metallic plugs a
switch arm may be connected with the outer convolution of wire, and adapted to
make contact with various other convolutions, thus short circulating all convolutions
which lie between. The switch arm may form the torininal of the helix conductor,
and the plugs or switch arms may be worked automatically by means analogous to
those described above.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Herbert John Haddan in the Great Seal Patent Office on the
26th August 1880.
HERBERT JOHN HADDAN, of the Firm of Herbert and Company, Solicitors of
Patents, of 67, Strand, in the City of Westminster, Civil Engineer.
"IMPROVE-
MENTS IN DYNAMO ELECTRIC MACHINES, AND IN APPARATUS USED THEREWITH."
A communication from abroad by Charles F. Brush, of Cleveland, Ohio, United
States of America.
The Invention relates to dynamo-electric machines, and has for its object the
adaptation of such machines to variable external conditions without variation of
the speed at which their armatures are rotated, but by variation of the intensity
of the magnetic field, and this by means not directly depending on the volume of
current circulating in the external circuit. Whon dynamo-electric machines of
usual construction are driven at a normal speed, the external or working resistance
must be of certain amount in order to secure a normal volume of current in
circulation. Any addition to the work to be performed, or increase of external
resistance, is attended by a diminution of the current strength; while any decrease
in the resistance of the external circuit is productive of an increased volume of
current. In other words, the current produced by these varies inversely as tho
work they are called upon to perform. It is generally desirable, and often
necessary, that the volume of current maintained in circulation by a machine
should remain nearly constant, while the external of working resistance is varied
within reasonable limits to conform to variable requirements. This end has here-
tofore been attained by varying the speed at which the armature of the machine is
rotated. This method is generally impracticable, especially when many variations
of external conditions are encountered. This object is effected by varying the
intensity of the magnetic field in which the armature rotates. Suppose a machine
driven at its normal speed maintains its normal current through a certain external
resistance; now if this resistance is diminished, and at the same time the intensity
of the magnetic field of the machine is also diminished a certain amount, then the
current in circulation will remain the same as before, because its electro motivo
force has been lowered. The magnetic field of the machine is weakened either by
shunting away from the coils of the field magnets a portion of the current which
excites them, or by cutting out or short circuiting some portion of one or more of
the coils, so that the current shall make a less number of convolutions about the
cores of the magnets. By varying the resistance of the shunt, which diverts a
portion of the current from the magnet coils, or by varying the number of con-
volutions of the coils cut out or short circuited, any number of variations in the
intensity of the magnetic field of the machine may be produced. In the Drawings,
Sheet 1a, Fig. 1 represents a portion of a dynamo electric machine provided with a
shunt of manually adjustable resistance round the field magnet circuit; Fig. 2
represents a modified embodiment of the Invention, wherein its operations aro
performed in an automatic manner; Figs. 3, 4, and 5 show other similar modi-
fications; Fig. 6 represents a field magnet coil adapted to have various portions of
itself short circuited; Fig. 7 shows a modification of the same; Fig. 8 represents_a
a magnet helix adapted to have various portions of itself cut out of circuit. In
Fig. 1, A, A, represents the two helices of one of the magnets of a dynamo electric
machine. They are joined together in single circuit, and one end of the conductor
so formed is attached to the commutator brush B, while the other end is attached
to the binding post P, forming the terminal of the machine. The other binding
post or terminal N is connected with the remaining commutator brush C. a, b, c,
d, e, are resistance coils connected with each other in series by means of the studs
or buttons a, b, c, &c., the coil a being also connected with one end of the field
magnet conductor at P; D is a switch arm pivoted at g, and adapted to connect g
with a¹, b', c', &c., at pleasure. The study is connected with the commutator

page_text: brush B, and these with the other end of the magnet circuit. Now when the
terminals P, N, are connected by means of the external or working circuit (not
shown), all of this current developed by the machine in operation will circulate in
the helices A, A, as long as the switch arm B is not in contact with any of the
buttons a, b, c, &c. But when the arm D is moved into contact with the button
a, then a portion of the current developed by the machine will be diverted from
the helices A, A, and will flow through the shunt circuit P, a, a', D, g,.B; the
amount so shunted being determined by the resistance of the shunt circuit as
compared with that of the magnet circuit. The machine will now be in a condition
to develop its normal current through a small external resistance only, because its
field magnets are greatly weakened through the decrease of the current exciting
them. The coil a is made of such resistance that when it only is included in the
shunt circuit the machine shall be adapted to operate normally, the smallest
external resistance met with in practice. When the armn D is moved to the button
b¹, the resistance b is added to the shunt circuit, whereby less current is diverted
from the magnet circuit, the intensity of the magnetic field is increased, and the
machine is adapted to operate an increased external resistance. By moving the
arm D to c', &c., and thus adding the resistance c, &c., to the shunt circuit,
the machine will in like manner become adapted to operate inore and more external
resistance, until finally, when the arm D is moved off from the last button e (the
resistance of the shunt circuit being now infinitely great), the machine will have
attained its full power. In order to adapt the machine to regularly increasing
external resistance, the resistances b, c, d, e, are made successively greater, because
each one, in order to increase the total resistance of the shunt in a given proportion,
must obviously be larger than the one preceding it; thus the last resistance after e
(circuit open) is infinitely greater. Obviously one or more (preferably all) of the
magnet helices of a machine inay be included in that part of the circuit of the
machine affected by the shunt. In practice it is convenient to arrange the
resistances a, b, c, &c., on metal cores in a metal case, and connect the piece, of
apparatus with the dynamo-machine by means of suitable wires. The metal of the
cores encased absorbs the heat developed in the resistance coils, and dissipated by
radiation and convexion. The metal case surrounding and protecting the resistance
coils is also provided with suitable openings above and below, to allow a circulation
of air about the coils, which arrangement materially aids in keeping them cool.
The Invention is well adapted for use with dynamo electric machines operating
several electric lights in single circuit, since by means of this device such machines
may operate normally any number of lights from one (the other lights being short
circuited) up to their full capacity without change of speed, and with an absorption
of driving power varying (though not proportionally) with the number of lights
used; Fig. 2 of the Drawings illustrates a method of operating the switch arm D
automatically, according to the varying requirements of the working circuit of the
machine. The arm D is held in the position shown in the Figure by means of the
spring H, so that the shunt resistances are open-circuited when the machine is
operating its highest external resistance. An armature is attached to a short
prolongation of the arm D in front of an electro magnet E, which is excited by
the working current from the machine, as shown. The tension of the spring H
is so adjusted that it shall be just sufficient to hold the arm D in the position
shown, when the current exciting the opposing magnet E is of normal amount.
Now if the external or working resistance of the machine is diminished, the first
effect will be an augmentation of the volume of current in circulation; but this
will at once increase the attraction of the magnet E for its armature, and the
arm D will be thrown successively into contact with the buttons e, d¹, &c., until
the shunt resistance is sufficiently reduced to effect the reduction of the general
current nearly to its normal condition, in the manner already specified. Con-
versely an increase of resistance in the working circuit will first diminish the
current in circulation; the magnet E will become weakened, and the opposing
spring H will throw its arm D in the other direction, until the increasing resistance