Improvements in the Construction of Armatures for certain kinds of Electrical Machines.
Year: 1891

page_text: Date of Application, 27th July, 1891'
Complete Specification Left, 26th Mar., 1892-Accepted, 7th May, 1892
PROVISIONAL SPECIFICATION.
Improvements in the Construction of Armatures for certain kinds
of Electrical Machines.
A communication from abroad by W. LAHMEYER & Co., of Frankfort-on-the-
Maine, in the Empire of Germany.
1, 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 inven-
tion to be as follows, reference being had to the accompanying sheet of drawings
and to the figures and letters of reference marked thereon:-
Considerable advantages accrue in transformer-dynamos as regards the degree of
power, cost of production, freedom from emission of sparks, yield of current and
all practical considerations, if both the high as well as the low tension coils are
placed on a common armature.
The sole objection which has hitherto been raised to this, was, the possibility that
the high tension might, through defective insulation, be conveyed to the low
tension coil, and thereby also to the low tension wires running to the houses.
This danger may with certainty be avoided in motor-dynamos, that is to say,
electrical double machines in which a high tension motor and a low tension dynamo
are made with a common axle.
For transmitting the high tension to the low tension coil, the current must first
traverse the iron frame lying between the two, that is, the armature frame and the
axis. Now if this frame be placed in communication with the earth, such
transmission is rendered quite impossible, as a closer consideration shows.
This invention relates to a method of constructing the armature of a transformer
in such a way that between the high and low tension coil metal is employed which
may be connected with the earth, and which does not serve as a current conductor.
By such a mode of construction, the same safety is evidently obtained for the
transformers, as in the case of motor dynamos.
Figure shows a sector of a ring armature constructed according to this
invention.
As shown in the figures, the high tension coil is wound on the outer side of
the ring and the low tension coil n in special grooves. The same process could
also be carried out on the inner side of the ring, but as on the inner side there
are large interstices opposite the teeth, which may be filled up with wood or
other insulating material, this arrangement of grooves is not necessary. Any
communication between the coils through the thick insulation of the inner sides,
or on the outer surfaces is naturally as good as impossible: Any direct com-
munication on the outer side is impossible, as between the high tension coil and
the low tension coil there always intervenes a tooth of the iron body of the
armature. This iron part, that is the whole frame of the machine, is however
brought into connection with the earth.
In drum armatures this mode of construction is not possible without further
modification, as the wires must be passed over one another on the surfaces.
In applying this improved method, which, owing to its simplicity and plainness-
is of extraordinary importance, to drum armatures so as to obtain the same effect;
there is introduced between the high tension and low tension coils a strip of metal.
coated on both sides with insulating material, so that such metal no longer acts

page_text: as a current conductor, but is connected with the armature frame, which is again
connected with the earth in a suitable manner.
The connection of this metallic strip with the armature frame may also be
omitted, and the connection between the earth and the mass of metal lying
between the coils may be also entirely omitted, without perceptibly diminishing
the degree of safety. The metallic mass between the coils will still form in such
case an absolute protection for the low tension coil against the action of the high
tension even where an earth circuit is not also employed.
The
..Figure. 2 shows a cross section of part of a sector of a drum armature with an
arrangement of the foregoing kind. In a groove coated with insulating material i
the low tension coil is wound at the bottom. When this winding is quite completed,
the following steps are taken. Waterproof canvas or other insulating material is
wrapped over both the front faces until nothing more can be seen of the wires.
fibrous strips are laid in the groove over the wires for the purpose of insulating
them. A double layer of soft copper netting of millimetre strength is then
pressed down on the waterproof cloth, which forms the protecting metal layer
over the front surfaces. Another layer of waterproof cloth is then placed over
one of the two metallic envelopes on the outer surfaces whilst the other metallic
envelope still remains bare. The metal strips m are successively placed over the
fibrous strips i in the grooves, and are made so long that they project beyond
the same on both sides and are pressed down on the outer surface rings. On
the one ring they remain therefore in connection with the metallic case, on the
other they are separated therefrom by insulating waterproof cloth. This last
separation is necessary in order that no Foucault currents may exist in these
metallic cases when both surface cases are brought in contact with the armature
frame. Then insulating material is again laid over the whole metal case, wherever
the latter is not already coated with insulating material; waterproof cloth is placed
over the outer surfaces and strips of fibre in the grooves. The armature is now
ready for the reception of the high tension coil. The same is simply wound in the
grooves and it is evident that a connection between the two coils cannot possibly
take place at any point without the current previously passing through metal from
whence it may be conducted to the ground in any suitable manner.
For drum or ring armatures which are not provided with grooves, the above
described principle can be easily applied in the following manner; namely, by
winding one coil evenly on the armature, and then placing thereon the metal cases
coated with insulating material on both sides, and disconnected in suitable manner
for preventing Foucault currents, and finally by winding the second armature coil
over the case. The metallic case can then be again brought into connection in
suitable places with the armature frame.
Figure 3 shows a sector portion of a ring armature in cross section in which
the new principle is employed, in such a way that all the bobbins of the one
coil in the drawing the high tension coil -are enclosed by the metallic case
which is insulated on both sides, in such a way, that the case has the form of an
open channel. The arrangements correspond to those in the previously described
figures, so that a further description is unnecessary.
The same arrangement may also be employed in the case of drum armatures, by
separating the metal channels over the front surfaces and the coils by means of
copper net coated with insulating material which is conductingly connected with
the channels, or with the armature frame. An interruption of the metallic layer
must naturally take place in all cases across the direction of the single wires
as described in Figure 1, in order to exclude any Foucault currents which may
be present.
Figure 4 shows the same principle employed in the construction of a drum
armature in which the one armature coil in the drawing, the, low tension coil, is
wound in grooves, whilst the other armature coil, in the drawing, the. high. tension.
coil, is wound on the surface of the armature. The metal strips m coated on: both
sides, with insulating material, form at the same time cover plates for the grooves.
"

page_text: This construction is of peculiar practical importance as it combines positive security
against the breaking out of the high tension, with the highest degree of power in
the transformer.
All the arrangements herein before described have naturally quite the same
importance as with transformer dynamos, in the case of double tension-dynamos,
that is to say, in machines for the production of current, which are driven by
mechanical force, and the armatures of which have also two coils, one of which
yields the current of high tension, and the other the current of low tension. In
this case it is of equal importance as with the transformer dynamos, to prevent the
higher tension from being transferred to the low tension coil.
D
1001
WM. P. THOMPSON & Co.,
Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in the Construction of Armatures for certain kinds
of Electrical Machines.
A communication by W. LAHMEYER & Co., of Frankfort-on-the-Maine, in the
Empire of Germany.
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:-
Considerable advantages accrue in transformer-dynamos as regards the degree of
power, cost of production, freedom from emission of sparks, yield of current and all
practical considerations, if both the high as well as the low tension coils are placed
on a common armature.
The sole objection which has hitherto been raised to this, was, the possibility
that the high tension might, through defective insulation, be conveyed to the low
tension coil, and thereby also to the low tension wires running to the houses.
This danger may with certainty be avoided in motor dynamos, that is to say,
electrical double machines in which a high tension motor and a low tension dynamo
are made with a common axle.
For transmitting the high tension to the low tension coil, the current must first
traverse the iron frame lying between the two, that is, the armature frame and the
axis. Now if this frame be placed in communication with the earth, such trans-
mission is rendered quite impossible, as a closer consideration shows.
This invention relates to a method of constructing the armature of a transformer in
such a way that between the high and the low tension coil metal is employed which
may be connected with the earth, and which does not serve as a current conductor.
By such a mode of construction, the same safety is evidently obtained for the
transformers, as in the case of motor dynamos.
Figure 1 shows a sector of a ring armature constructed according to this
invention.
As shown in the figures, the high tension coil his wound on the outer side of the
ring and the low tension coil n in special grooves. The same method could also be
adopted in the case of the inner side of the ring, but as on the inner side there are
large interstices opposite the teeth, which may be filled up with wood or other
insulating material, this arrangement of grooves is not necessary. Any communi-
cation between the coils through the thick insulation of the inner sides, or on the
outer surfaces is naturally as good as impossible. Any direct communication on the
outer side is impossible, as between the high tension coil and the low tension coil

page_text: there always intervenes a tooth of the iron body of the armature. This iron part,
that is the whole frame of the machine, is however brought into connection with
the earth.
In the case of drum armatures this mode of construction cannot be adopted
without further modification, as the wires must be passed over one another on the
surfaces.
In applying this improved method, which, owing to its simplicity and plainness,
is of extraordinary importance, to drum armatures so as to obtain the same effect,
there is introduced between the high tension and low tension coils a strip of metal
coated on both sides with insulating material, so that such metal no longer acts as
a current conductor, hut is connected with the armature frame, which is again
connected with the earth in a suitable manner.
The connection of this metallic strip with the armature frame may also be
omitted, and the connection between the earth and the mass of metal lying between
the coils may be also entirely omitted, without perceptibly diminishing the degree of
safety. The metallic mass between the coils will still form in such case an absolute
protection for the low tension coil against the action of the high tension even where
an earth circuit is not also employed.
Figure 2 shows a cross section of part of a sector of a drum armature with an
arrangement of the foregoing kind. In a groove coated with insulating material i,
the low tension coil n is wound at the bottom. When this winding is quite com-
pleted, the following procedure is adopted. Waterproof canvas or other insulating
material is wrapped over both the front faces until nothing more can be seen of the
wires. The fibrous strips i' are laid in the groove over the wires for the purpose
of insulating them. A double layer of soft copper netting of millimetre strength
is then pressed down on the waterproof cloth, which forms the protecting metal
layer over the front-surfaces. Another layer of waterproof cloth is then placed
over one of the two metallic envelopes on the outer surfaces, whilst the other
metallic envelope still remains bare. The metal strips m are successively placed
over the fibrous strips in the grooves, and are made so long that they project
beyond the same on both sides and are pressed down on the outer surface rings.
On the one ring they remain therefore in connection with the metallic case, on the
other they are separated therefrom by insulating waterproof cloth. This last
separation is necessary in order that no Foucault currents may exist in these
metallic cases when both surface cases are brought in contact with the armature
frame. Then insulating material is again laid over the whole metal case, wherever
the latter is not already coated with insulating material; waterproof cloth is placed
over the outer surfaces and strips of fibre in the grooves. The armature is now
ready for the reception of the high tension coil. The same is simply wound in the
grooves and it is evident that a connection between the two coils cannot possibly
take place at any point without the current previously passing through metal from
whence it may be conducted to the ground in any suitable manner.
For drum or ring armatures which are not provided with grooves, the above
described principle can be easily applied in the following manner; namely, by
winding one.coil evenly on the armature, and then placing thereon the metal cases
coated with insulating material on both sides, and disconnected in suitable manner
for preventing Foucault currents, and finally by winding the second armature.coil
over the case. The metallic case can then be again brought into .connection in
suitable places with the armature frame.
Figure 3.shows a sector portion of a ring armature in cross.section in which the
new principle is employed, in such a way that all the bobbins of the one scoil-in
the drawing the high tension coil -are enclosed by the metallic case which is
insulated on both sides, in such a way, that the case has the form of an open
channel. The arrangements correspond to those in the previously described
figures, so that a further description is unnecessary.
The same arrangement may also be employed in the case of drum armatures, by
separating the metal channels. over the front surfaces and the coils by means of

page_text: copper netting coated with insulating material which is conductingly connected with
the channels, or with the armature frame. An interruption of the metallic layer
must naturally take place in all cases across the direction of the single wires as
described in Figure 1, in order to exclude any Foucault currents which may be
present.
Figure 4 shows the same principle employed in the construction of a drum
armature in which the one armature coil, in the drawing, the low tension coil n, is
wound in grooves, whilst the other armature coil h, in the drawing, the high tension
coil, is wound on the surface of the armature. The metal strips m, coated on both
sides with insulating material, form at the same time cover plates for the grooves.
This construction is of peculiar practical importance as it combines positive security
against the breaking out of the high tension, with the highest degree of power in
the transformer.
All the arrangements herein before described are naturally quite as important as
they are with transformer dynamos, in the case of double tension dynamos, that is
to say, in machines for the production of a current, which are driven by mechanical
force, and the armatures of which have also two coils, one of which yields the
current of high tension, and the other the current of low tension. In this latter
case, it is of equal importance as in the case of the transformer dynamos, to prevent
the higher tension from being transferred to the low tension coil.
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 correspondent, I declare that what I claim is :-
1. The improvements in the construction of armatures of the hereinbefore
specified kinds of electrical machines, for the purpose of isolating the high tension
coils from the low tension ones, which consist in arranging or disposing portions of
the metallic armature-frame, which can be put in connection with the earth, between
the coils of different tension.
2. The improvements in the construction of armatures of the hereinbefore
specified kinds of electrical machines, for the purpose of isolating the high tension
coils from the low tension ones, which consist in arranging or disposing a metallic
layer between the coils of different tension, which layer can be on both sides
surrounded with insulating material and, for preventing Foucault currents, be
broken one or more times, and further in arranging a conductive connection between
this metallic layer, or parts of it, and the armature-frame, and by means of this
latter with the earth.
Dated this 25th day of March 1802
WM. P. THOMPSON & Co.,
Agents for the Applicant.