Improvements in or appertaining to Self-exciting Electric Generators.
Year: 1890

page_text: Date of Application, 1st July, 1890
Complete Specification Left, 1st Apr., 1891-Accepted. 23rd May, 1891
Improvements in or appertaining to Self-exciting Electric
Generators.
A communication from abroad by WILLIAM STANLEY Junior of Great Barrington,
State of Massachusetts, Electrician, and OLIVER B. SHALLENBERGER of
Rochester, State of New York, Electrician, both in the United States of
America.
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E., of the Agency for
Foreign Patent Solicitors, 6, Lord Street, Liverpool, and 6, Bank Street,
Manchester, both in the County of Lancaster, and 323, High Holborn, in the
County of Middlesex, Civil Engineer, do hereby declare the nature of this invention
to be as follows:-
This invention relates to that class of electric generators in which the current
required for exciting the field magnets is derived from the armature of the machine
itself, instead of from an external source; the said invention being applicable to
both alternating and continuous current generators.
The object of the invention is to so construct and arrange a generator that the
excitation of the field magnets shall be varied automatically, in proportion to
variations in the load or in the amount of work being done in the work circuit, in
order to maintain as may be desired a constant or variable difference in potential
between the terminals of the work circuit in accordance with the variations in
resistance of said work circuit.
Such variations in the excitation of the field magnets are accomplished by
increasing or decreasing, as the case may be, the number of effective lines of
magnetic force threading certain of the armature coils.
The invention may be carried into effect in various ways. In one form of the
invention, the armature of the dynamo electric machine is wound with two
independent coils, or sets of coils, one of which supplies current to the work circuit,
while the other has its terminals connected to the field magnet coils for the purpose
of exciting the same.
This second coil is placed at an angle to the first and is affected by a third coil
lying adjacent to it or in such a manner that any variation in the amount of
current flowing through the third coil will cause a corresponding variation in the
number of effective lines of force threading the second coil, and thus vary the field
strength. This third coil is connected in series with the first coil.
In another form of this invention the two first named coils are wound on two
armatures on the same shaft and in the same magnetic field, the one supplying
the field magnets being affected in a similar manner by a third coil, as described
above.
In this invention, the form of armature and dynamo may be varied according
to any of the well known types as may clearly be understood by one skilled in
the art.
Dated this 20th des of Lune 1890.

page_text: COME JELE DE DUIN ICATION.
Improvements in or appertaining to Self-exciting Electric
Generators.
A communication from abroad by WILLIAM STANLEY Junior, of Great Barrington,
Berkshire, in the State of Massachusetts, Electrician, and OLIVER B.
SHALLENBERGER, of Rochester, County of Beaver, in the State of Penn -
sylvania, both in the United States of America.
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E., of the Agency for
Foreign Patent Solicitors, 6, Lord Street, Liverpool, and 6, Bank Street,
Manchester, both in the County of Lancaster, and 323, High Holborn, in the
County of Middlesex, Civil 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 that class of electric generators in which the current
required for exciting the field magnets is derived from the armature of the machine
itself, instead of from an external source; the said invention being applicable to
both alternating and continuous generators, but specially the former.
The object of the invention is to so construct and arrange a generator that the
excitation of the field magnets shall be varied automatically, in proportion to
variations in the load or in the amount of work being done in the work circuit,
in order to maintain a constant or required difference in potential between the
terminals of the work circuit, notwithstanding variations in the quantity of current
flowing therethrough.
Such variations in the excitation of the field magnets are accomplished by
increasing or decreasing, as the case may be, the number of effective lines of
magnetic force threading certain of the armature coils.
To this end, the armature of the machine is wound with two independent coils, or
sets of coils, one connected with the work-circuit and the other with the field
magnet coil (or coils). The field magnet armature coil (or coils) is threaded by a
portion only of the lines of force of the magnetic field. A supplemental coil
connected with the work circuit armature coil is so arranged with respect to the
field magnet armature coil that variations of current in the work circuit, resulting
in corresponding variations in the said supplemental coil, increase or decrease the
number of effective lines of force threading the field magnet armature coil, and the
latter so re-acts upon the field magnets that their excitation is varied in a similar
ratio, and the difference in potential between the terminals of the work circuit is
kept approximately as desired.
The invention may be carried into effect in various ways, two only of which may
be described by way of illustration.
In the drawings:-
-:
Figure shows, in a diagrammatic manner, a form of the invention in which the
various armature coils are wound upon one armature core.
Figure 2 shows, partly in diagram, a form of the invention in which the coils are
wound upon separate armature cores rotating in unison about the same axis.
Figures 3 and 4 show two slightly different ways of forming one of the armatures
shown in Figure 2.
Referring first to Figure 1 :-
N. S. represent the field magnets of a dynamo having field magnet coils m m.
C is the armature core upon which are wound two independent armature coils A B,
or two sets of coils. The coils A B are usually placed, by preference, approximately
at right angles to each other, so that, while one is in its position of zero electro
motive force, the other is at or near the position of maximum induced electro motive
force. One of the coils, A, is connected with the mains L1 L2 of the work
circuit W by means of collector rings ce¹ (or a commutator), while the terminals

page_text: of the other coil B are connected with the field magnet coils m m by means of
a rectifying commutator D and brushes d¹ d², for the purpose of exciting the said
magnets.
The armature is so constructed that the field magnet armature coil (or coils) B
is threaded only by a portion of the lines of force in the magnetic field. To this
end, the said coil B may be wound in recesses b b formed in the core C (at or near
the periphery thereof) into which the wires are introduced through openings o0
After the wires are introduced into the recesses b b, the openings oo are closed by
plugs or strips of iron i secured in the openings. Or the recesses b b may be bored
longitudinally through the core C and the wires of the coils threaded back and
forth therethrough. Thus a closed magnetic circuit is formed giving passage to a
portion only of the lines of the magnetic field of force; but this is not essential
to the working of the apparatus as the wires can lie near the periphery of the
armature.
Applied to the coil B-preferably by being wound round the same with its turns
parallel to those of the coil-is a supplemental coil E consisting of comparatively
few turns of wire and connected in series with the coil A. Both the armature
coil B together with the supplemental coil E are preferably wound in the recess b
so as to lie within the exterior circumference of the armature core C.
It is evident that current from the coil A will flow through the supplemental
coil E at the moment when the coil B is in its position of minimum electro-motive
force, and an increase of the flow of current through the coil E will develop lines
of force in a direction operating to strengthen or weaken the polarity of the
armature core and to increase or decrease the number of the lines of force threading
the coil B, according to the direction in which the current is flowing in the
coil E.
In the first case, when the translating devices are connected in parallel in the
work circuit W, an increase in the number of said devices tends to cause a decrease
in the difference of potential between the terminals of the work circuit coil A, and,
in order to maintain the difference of potential constant, an increase in the
excitation of the field magnets is necessary. This increase is, however, accom-
panied by an increased flow of current in the work circuit, and, consequently,
through the supplemental coil E, and the number of lines of force of the magnetic
field of the machine threading the coil B is augmented by the additional lines of
force developed by the increased flow of current through the coil E. Hence, there
will be an increase in the potential developed in the coil B with a corresponding
increase in the excitation of the field magnets and the difference of potential
between the terminals of the work circuit will be maintained approximately
constant. Conversely, the tendency to a rise in the difference of potential between
the terminals of the work circuit, consequent upon a decrease in load, will be
checked, since the number of lines of force threading the coil B will decrease with
the decrease in the quantity of current flowing through the coil E.
If it is desired to produce the opposite effects, that is, to cause a decrease in the
field strength upon an increase in the flow of current in the work circuit, as, for
example, when it is desired to maintain a constant current upon the work circuit,
the connections of the wire E should be reversed so that the lines of the magnetic
field, set up by the current flowing through it, will so act as to decrease the number
of lines of force threading the coil B, upon an increase in the flow of current in
the wire E, this resulting in a decreased excitation of the field magnets.
It is evident that the position of the coil E will be reversed with each reversal
in the direction of the current flowing through it, and thus the lines of force
developed by the current in the coil E will maintain a constant direction as related
to the direction of the lines of force of the magnetic field of the machine, and will
always operate to assist the magnetisation, of the armature core.
For convenience of illustration, the machine has been shown as constructed with.
only two armature. coils, the one supplying current to the work circuit, and the

page_text: other, to the field magnet coils. In practice, however, it may be desirable, for
reasons well understood by those skilled in the art, that there should be two or
inore armature coils in each set, the regulating coils being arranged with reference
to the field supplying and work supplying coils in the manner already shown.
Referring now to Figures 2 to 4:
The armature is formed with two separate cores rotating about the same axis,
the two cores being provided respectively with two independent coils or sets of
coils A B as before described. The two coils A B (or sets of coils) are mounted
side by side, and revolve in usion in a field of force established by a cominon field
magnet or magnets N. S., so that only a portion of the lines of force established by
the said magnet threads the field magnet armature coil (or coils) B.
The coil (or coils) B is connected, as before, with the field magnet coils m hy
means of a commutator D and brushes d¹ d², and the coil (or coils) A is connected
with the mains I L² of the work circuit by means of collecting rings cc¹
and brushes ³, or by commutators and brushes, if a continuous current is
required.
The supplemental coil E-which, as before, is connected in series with the work
circuit coil A is so arranged with respect to the field magnet armature coil (or
coils) B that it tends to polarise the core of the latter in a certain definite direction
with reference to the work circuit coil A, so that the two coils (or sets of coils) A B
have their polar planes normally intersecting each other at an angle as in the case
of the arrangement described with reference to Figure 1. This polarity of the
coil B may be conveniently effected by winding the supplemental coil E round the
diametrically placed arm 6 of its core, as seen in Figures 2 and 3.
As before stated, an increase in the flow of current through the supplemental
coil E will develop lines of force in a direction operating-according to the
direction in which the current is flowing in the coil E-either to strengthen or
to weaken the polarity of the armature core b¹, and to increase or decrease the
number of the lines of force threading the coil B.
The mode of operation of this latter form of the invention is thus precisely
similar to that described with reference to the arrangement shown in Figure 1, and
it is therefore unnecessary to repeat the description here.
By properly proportioning the amount of winding of the supplemental coil and
its position, the variation in difference of potential obtained as before described
may be made to assume any required amount within certain limits, so that a rising
potential, a falling potential, or a constant difference of potential may be obtained
at the terminals, as desired.
Although this invention is applicable to those dynamos which supply other than
alternating currents to the work circuit, yet its special advantage lies in the fact
that, by means of it, a constant difference of potential or constant current value
may be automatically maintained between the terminals of an alternating current
dynamo through great variations in the amount of the load upon the work circuit.
There has been no attempt to describe herein all possible modifications of the
invention, but only the two best representative forms at present known to my
correspondents, showing the invention applied to a gramme and a drum armature,
this method of regulating being applicable to almost all kinds of dynamos.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me by
my foreign correspondents, I declare that what I claim is :-
In a self-exciting dynamo :-
1. Two armature coils and a supplemental coil, which latter is connected in series
with one of the above armature coils and the work circuit, and which regulates the
output of the other armature coil, which is connected to the field circuit, substantially
as described.
2. Causing the lines of force threading the armature coil supplying the field

page_text: circuit to be varied by a coil connected to the work circuit and to the main armature
coil.
3. The arrangement and combination of the armature coils in a self-acting
electric generator substantially as and for the purposes herein set forth and
illustrated.
WM. P. THOMPSON & Co.,
Agents for the Applicant.