Year: 1887

page_text: Date of Application, 12th July, 1887.
Specification Accepted, 16th Aug., 1887.
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 :-
The object of the invention is to so wind the coils of the armatures of Electric
Generators as to obtain therefrom the highest efficency; to avoid the necessity of
placing conductors carrying currents having great difference of potential in proximity
to each other; and to insure that the maximum inductive effect shall be realized from
the coils during their passage across the lines of force emanating from the poles of
the field-magnets.
In the accompanying drawing, Figure 1 is a diagram illustrating the plan of
winding the wire, and Figure 2 shows the construction of the armature with reference
to the pole-pieces of the field-magnets.
Referring to the Figures, a¹, a², a³ etcetera represent the coils of an armature, of
any desired construction, preferably, however, the armature is constructed in a
cylindrical form, the wire being wound in flat elongated coils, encircling non-magnetic
projections, which latter are formed on the face of the armature.
It has heretofore been usual to wind each separate coil of an armature in the same
manner, and to connect the outer terminal of one coil with the outer end of the suc-
ceeding coil, and the inner end of that coil with the inner end of the next coil and so
on throughout the series. From this arrangement it necessarily results that the
adjacent conductors of neighbouring coils are traversed by currents having a difference
of potential corresponding to the sum of the electro-motive forces due to both
coils and thus there is danger, in machines designed to produce currents of high
potential, that there will be a short circuit or, as it is termed, an arc, formed across
from one coil to another, destroying the insulation of the conductor, and sometimes
the conductor itself.

page_text: According to this invention, the inner end of each coil is connected with the outer
end of the succeeding coil throughout the series, while the coils themselves are wound
in opposite directions in order that the alternating coils may be of opposite polarity.
Thus for example the coil a¹ is wound in a left-hand direction, commencing at the
outer end, while the succeeding coil a² is wound toward the right-hand or in the
reverse direction; the coil a³ is again wound toward the left hand; the inner end 4 of
the coil a is connected with the outer end 5 of the coil a³, and the inner end 6 of
this coil is connected with the outer end 7 of the coil a³, and so on around the
circumference of the armature to the coil a³.
Starting again at the point o, the connections of the conductor are continued from
the inner terminal of the coil a¹ to the outer terminal of the coil a", and so on round
to the coil aº. The inner terminal of this coil is united with the inner terminal of the
coil as to form a terminal conductor 20. These terminal conductors o and 20 lead to
the respective collector plates on the axis of the armature.
The second feature of the invention is designed to avoid the danger of a discharge
occurring between the terminals of the armature wire. It has been usual to wind
the wire of the coils from some one point in the armature around the bobbins in
succession, until the same point is reached, and then to lead the two wires from the
armature to the collector, necessarily in close proximity to each other. It will be seen
that in this arrangement, the coil containing the highest potential is immediately
adjacent to that containing the lowest potential. Instead of such winding it has been
found advisable to place the points of highest potential in the conductor upon
diametrically opposite sides of the armature, and thus as far apart as possible. This
renders it necessary that the connections of the two halves of the armature-coils
should be opposite with reference to each other. Thus in the diagram, Figure 1,
starting from the point o, the current generated in the series of coils a¹ to a³ inclusive,
upon one half the armature, is delivered at the point 20 diametrically opposite the
point o. In like manner the current generated in the other half of the armature
coils, a to a inclusive, is delivered at the point 20 and is of the same polarity as
that derived from the coils a¹ to a inclusive, while at the same time the points o
and 20 of highest difference of potential, are as far as possible removed from each
other.
It is to be observed that the inner terminal of the coil a³ is connected with the
inner terminal of the coil a instead of with its outer terminal, and the connections
are continued to the coil a¹ from the outer to the inner terminal. Such a method of
winding is obviously necessary to deliver like currents at the points o and 20 from the
two halves of the armature. While it is for the reason stated, usually desirable to
connect the coils upon the two halves of the armature in an opposite sense, yet it is
not absolutely, in all cases, as the connection may be continued from the coil a to the
coil a¹ in the same manner as from the coil a¹ to the coil aⓇ.
In the construction of the armature, it has been common to make divisions between
the coils of wire of the same breadth as the faces of the armature-cores, and these
have also been approximately equal to the breadth of the faces of the cores or poles
of the field-magnets.
In practice it has been found that certain advantages are secured by making
divisions of wire wider than the faces of the field-magnet-cores. This is due to the
self-induction or retardation of the current in the coils of the armature. It will be
evident that were there no such retardation, the current, commencing to flow at the
instant the coil comes opposite the nearest edge of the core, would rise to its maximum
at the moment the entire face of the core was confronted by the wire, and from this
point would gradually fall off; in other words, the phases of the current would be
co-incident with the phases of the electro motive force. Owing, however, to the
inductive retardation, the current cannot reach its possible maximum at the moment
the wire comes into the position of theoretical maximum, but would be still further
augmented, after passing this point, were it not that in machines having coils equal
in breadth to the pole-pieces, the electro motive force begins to fall before the current
has risen to a corresponding value, as the wire recedes from the further edge, and

page_text: passes out of the field. By constructing the coil of a breadth in excess of that of
the pole, this latter effect is not produced, because the actual number of convolutions
cutting the lines of force does not change immediately and hence the current is
allowed time to rise to its maximum value, before the last edge of the coil has passed
across the face of the poles.
Having now particularly described and ascertained the nature of the 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. In an electric generator, the combination with the field-magnets of an armature
having its alternate coils wound in opposite directions, and the outer end of each coil
connected with the inner end of the succeeding coil.
2. In an electric generator, an armature having its alternate coils wound in
reverse directions and the inner ends of each coil connected with the outer end
of the succeeding coil throughout the entire series of armature coils or any portion
of such series.
3. In an electric generator, a series of armature coils, the alternate coils being
wound in reverse directions, and the inner end of each coil connected with the
outer end of the succeeding coil, conductors leading from points directly opposite
each other in the length of the continuous conductor forming the said series of
armature coils, and collecting plates with which said conductors are electrically
connected.
4. In an electric generator, an armature wound with two series of coils, arranged
in multiple arc, the terminals delivering like currents from each series being
united at points approximately diametrically opposite each other upon the armature,
substantially as described.
5. In an electric generator, the combination with a multiple field-magnet and
its polar projections, of an armature revolving within said field-magnet, having its
conductor formed with coils upon its periphery, of greater breadth than said polar
projections, substantially as described.
Dated th: 1
1
C
T 1
1007
WM. P. THOMPSON & Co.,
Agents for the Applicant.