Improvements in Armatures for Electrical Machinery.
Year: 1891

page_text: Date of Application, 13th Mar., 1891
Complete Specification Left. 7th Nov., 1891-Accepted. 19th Dec., 1891
PROVISIONAL SPECIFICATION.
Improvements in Armatures for Electrical Machinery.
I GEORGE FREDERICK REDFERN of the firm of G. F. Redfern & Co., The
General Patent Office, No. 4 South Street, Finsbury, in the County of Middlesex,
Patent Agents do hereby declare the nature of this invention (communicated to me
by Messrs. Wirth & Co. of Frankfort-on-the-Main, in the Empire of Germany
Patent Agents, acting as Agents for Messieurs W. Lahmeyer & Co. of Frankfort-
on-the-Main aforesaid, Stock Brokers) to be as follows:-
This invention relates to armatures for electrical machinery if the armature of
a dynaino-electric machine be constructed with grooves, and the wires be wound in
these, two advantages in particular will result :-
1. The iron of the armature can be brought close to the iron of the magnet,
and so a stronger magnetism is obtained.
2. Great space is gained for the coils of the armature, which may thus consist of
many turns.
Both these advantages.naturally bring about an increase in the effective energy
of the machine. The arrangement has however an important disadvantage.
As the iron teeth and the recesses between them pass alternately in front of
every point of the polar surface, there is brought about a so-called fluctuation of
the magnetism which gives rise to "Foucault's currents" in the framing of the
magnet.
The waste of energy thereby caused is generally noticeable, and evidences itself
clearly by the strong heating of the frame of the magnet.
In accordance with nature, and as has repeatedly been found in practice, the
fluctuation of the magnetism and the waste of energy which arises from it, may be
diminished in the most simple way, wiz., by increasing the distance of the iron of
the pole from the iron of the armature.
This consideration has led to the construction of an armature, which may be
designated as a grooved armature with its coils and a smooth armature with its
coils, in combination.
In carrying out the invention the grooves or recesses of the armature are lined
with fibre, in such a way that every alternate, lining of the wall of a groove projects
out of it. The grooves are now first wound full, and the surface of the armature
covered with insulating fibre.
The projecting strips of fibre now form divisions, and in these armature coils
are again wound. The advantages which this process offers are not far to seek.
The space for the coils of the armature is rendered extraordinarily great, and at
the same time a lesser separation between the iron of the pole and the iron of the
armature is possible, since only a portion of the coils of the armature lies on the
surface, whilst the other portion is bedded in the mass of iron forming the armature.
If this portion were to be also wound upon the surface of the armature, the
separation between, the iron of the pole and armature would need to be almost
twice as great. The amount of separation, however, which is given in this novel
method of construction corresponds exactly to the dimensions of the grooves and
iron teeth of the armature, in order to reduce the fluctuation of the magnetism to
an imperceptible amount.
The space which is appropriated to the second division of the coils of the
armature has in, this case, as in the other, its importance with reference to the
amount of energy. The above described combination of an armature having its
coils in grooves with an armature with smooth coils or coils wound level thus

page_text: yields the greatest effective energy of which a dynamo-electric machine is
capable.
The effective energy is considerably greater than if either an armature with
coils wound level, or an armature with coils wound in grooves, were employed
alone.
As a rule the dimensions will be so regulated in this method of construction
that the depth of the grooves will be equal to their breadth plus the breadth of
the teeth and the height of the coils of the armature equal to the breadth of the
grooves. The divisions of the coils within the iron of the armature and those on
its surface are then always in accordance with each other.
When the improved arrangement is employed in alternating current dynamos,
one coil (the low tension coil for example) is wound only in the grooves, whilst the
other coil (the high tension coil) is wound only in the superficial divisions.
Strips of metal are laid between the two coils, and insulated by packing on both
sides the said strips serving to keep the low tension coils securely separated from
those of high tension.
If these strips of metal be made of iron, they also serve to diminish the
fluctuations of the magnetism.
The improved arrangements hereinbefore described can obviously be applied to
ring armatures as well as to drum armatures.
Dated the 13th day of March 1891.
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Armatures for Electrical Machinery.
I, GEORGE FREDERICK REDFERN, of the firm of G. F. Redfern & Co., The
General Patent Office, No. 4, South Street, Finsbury, in the County of Middlesex,
Patent Agents, do hereby declare the nature of this invention (communicated to
me by Messrs. Wirth & Co., of Frankfort-on-the-Main, in the Empire of
Germany, Patent Agents, acting as Agents for Messieurs W. Lahmeyer & Co., of
Frankfort-on-the-Main, aforesaid, Stock Brokers) 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 armatures for electrical machinery. If the armature of
a dynamo-electric machine be constructed with grooves, and the wires be wound in
these, two advantages in particular will result.
1. The iron of the armature can be brought close to the iron of the magnet,
and so a stronger magnetism is obtained.
2. Great space is gained for the coils of the armature, which may thus consist
of many turns.
Both these advantages naturally bring about an increase in the effective energy
of the machine. The arrangement has however an important disadvantage.
As the iron teeth and the recesses between them pass alternately in front of
every point of the polar surface, there is brought about a so-called Huctuation of
the magnetism which gives rise to "Foucaults currents in the framing of the
magnet.
"
The waste of energy thereby caused is generally noticeable, and evidences itself
clearly by the strong heating of the frame of the magnet.
In accordance with nature, and as has repeatedly been found in practice, the
fluctuation of the magnetism and the waste of energy which arises from it, may
be diminished in the most simple way, viz., by increasing the distance of the iron
of the pole from the iron of the armature.
This consideration has led to the construction of an armature, which may be

page_text: designated as a grooved armature with its coils and a smooth armature with its
coils, in combination.
In the accompanying drawing,
Figure 1 is a cross section of a portion of a drum-armature for electrical
machinery constructed according to this invention, and
Figure 2 is a similar view of an armature suitable for employment in alternating
current dynamo-electric machines.
In carrying out the invention, which I will first describe by reference to Figure 1,
the grooves or recesses of the armature are lined with fibre i, in such a way that
every alternate lining of the wall of a groove projects out of it. The grooves are
now first wound full, and the surface of the armature covered with insulating
fibre i¹.
The projecting strips of fibre now form divisions, and in these armature coils
are again wound. The advantages which this process offers are not far to seek.
The space for the coils of the armature is rendered extraordinarily great, and at
the same time a lesser separation between the iron of the pole and the iron of the
armature is possible, since only a portion of the coils of the armature lies on the
surface, whilst the other portion is bedded in the mass of iron forming the armature.
If this portion were to be also wound upon the surface of the armature, the
separation be ween the iron of the pole and armature would need to be almost
twice as great. The amount of separation, however, which is given in this novel
method of construction corresponds exactly to the dimensions of the grooves and
iron teeth of the armature, in order to reduce the fluctuation of the magnetism to
an imperceptible amount.
The space which is appropriated to the second division of the coils of the
armature has in this case, as in the other, its importance with reference to the
amount of energy. The above described combination of an armature having its
coils in grooves with an armature with smooth coils or coils wound level thus
yields the greatest effective energy of which a dynamo-electric machine is
capable.
The effective energy is considerably greater than if either an armature with
coils wound level, or an armature with coils wound in grooves, were employed
alone.
The above described arrangement is also applicable to ring armatures as will be
well understood without further description.
As a rule the dimensions will be so regulated in this method of construction that
the depth of the grooves will be equal to their breadth plus the breadth of the
teeth and the height of the coils of the armature equal to the breadth of the
grooves. The divisions of the coils within the iron of the armature and those on
its surface are then always in accordance with each other.
When the improved arrangement is employed in alternating current dynamos,
as shewn in Figure 2, one coil (the low tension coil n for example is shewn in the
drawing) is wound only in the grooves whilst the other coil (the high tension
coil ) is wound only in the superficial divisions.
The drawing also shews the strips of metal m laid between the two coils, and
insulated by packing on both sides the said strips serving to keep the low tension
coils securely separated from those of high tension.
If these strips of metal be made of iron, they also serve to diminish the
fluctuations of the magnetism.
This arrangement can obviously be applied to ring armatures as well as to drum
armatures.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
:-
1. An arrangement of armature for dynamo-electric or magneto-electric
machines in which a portion of the coils is wound in grooves in the iron of the

page_text: armature, while another portion is wound upon the surface of the armature
substantially as hereinbefore described.
2. Constructing an armature of the kind described in Claim 1, in such a manner
that the insulating coatings of the sides of the grooves stand out between the
wires wound on the surface of the armature, to retain the latter in their places
substantially as herein before described.
3. The improved armatures for electrical machinery, hereinbefore described and
illustrated in the accompanying drawing.
Dated the 7th day of November 1891
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.