Improvements in the Manufacture of Secondary Coils for Transformers.
Year: 1894

page_text: Date of Application, 17th Mar., 1894
Complete Specification Left, 15th Dec., 1994-Accepted, 26th Jan., 1895
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Secondary Coils for
Transformers.
We, AUGUST SCHNELLER, of Aarlanderveen-Alfen, near Leyden, Engineer,
and WILLIAM JOHN WISSE, of Haarlem, in the Kingdom of Holland, Engineer,
lo hereby declare the nature of this invention to be as follows:-
1
This invention has reference to improvements in the manufacture of secondary
coils for transformers designed to transform electric currents of low tension into
electric currents of high tension say for example 30,000 volts and upwards, for
which purpose it is requisite that the insulation at all parts of the coil should be
compact or dense, that is to say without interstices, and perfectly dry.
In the accompanying drawings
Fig. 1 illustrates a sector-like piece supposed to be cut out of the transformer-
ring or coil and
Fig. 2 represents to a larger scale a part cross-section of the same.
The secondary coil is constructed as follows:-
Copper-wire a covered say with four thicknesses of insulating material b, it may
be with layers of silk or tape wound upon the wire in the ordinary manner, is
wound helically in such a manner as to produce a ring or coil (hereinafter called
a coil) preferably of rectangular form in cross-section.
Between the several adjacent layers of wire a thin layers c of material such as
paper, shewn only in Fig. 1, are inserted during the winding, and at greater
distances apart there are inserted thicker layers c¹ of paper so that the layers of
wire are completely separated one from the other. The several layers of wire and
insulating material c c composing the coil are tied or fastened securely together by
binding-cords d passed several times transversely through the coil as shown in
Fig. 1.
The coil thus formed is then boiled in wax for, say, 12 hours, after which it is
dried by pressure. The coil is then put into position for use as a secondary coil
in a transformer and an electric current passed through the transformer, so that
the said coil forming the secondary coil, effects the conversion of the current into
a current of high tension. By this means the ring becomes heated and the wax
therein remelted; the coil being left in operation until the last trace of moisture
has been removed. During this operation a further quantity of wax is added
from time to time to the coil, it may be by means of a brush.
:
When, finally, the coil is no longer warm, it is preferably given a coat of paint
and then a coat or layer of protecting material such as shellac varnish.
As will be obvious, the main object of the invention is to remove every tracé
of moisture from the coils and to avoid the presence of any spaces or cavities
however small in the insulating material. Only in this manner can short-circuiting
and heating be avoided.
1
By the preliminary working of the transformer, moisture always present in the
coil after the same has been boiled and compressed is effectually removed, and the
interstices in the coil filled up with certainty since, as is evident where there are
spaces and moisture short-circuiting and heating of the coil very readily take place;
so that evaporation of the moisture and the melting together of the wax precisely
at these places is the necessary consequence. Furthermore the addition of wax

page_text: by painting or otherwise which is continuously carried on during the heating
always provides sufficient wax to take the place of that absorbed by the filling up
of the interstices in the coil and also provides for the filling up of any fresh
interstices produced by the evaporation of the moisture.
By constructing secondary coils in the manner described that is to say by using
insulated wire, dividing the convolutions thereof by layers of paper, intimately
connecting the convolutions by boiling in wax and pressing, and protecting the
treated coil by outer coatings of paint and varnish or shellac there is produced a
coil which, without becoming in the least hot when in use, can safely withstand
tensions of 30,000 volts and upwards.
Deted this 17th day of March 1901.
Improvements in the Manufacture of Secondary Coils for
Transformers.
We, AUGUST SCHNELLER, of Aarlanderveen-Alfen, near Leyden, Engineer,
and WILLIAM JOHN WISSE, of Haarlem in the Kingdom of Holland, Engineer,
do hereby declare the nature of this invention and in what inauner the same is to
be performed to be particularly described and ascertained in and by the following
statement :-
This invention has reference to improvements in the manufacture of secondary
coils for transformers designed to transform electric currents of low tension into
electric currents of high tension, say for example 30,000 volts and upwards, for
which purpose it is requisite that the insulation at all parts of the coil should be
compact or dense, that is to say without interstices and perfectly dry.
Referring to the drawings filed with our Provisional Specification,
Fig. 1 illustrates a sector-like piece supposed to be cut out of a secondary
transformer-ring or coil constructed according to this invention, and
Fig. 2 represents, to a larger scale, a part cross section of such ring or coil.
The secondary ring or coil is constructed as follows:-Copper-wire a covered
with say four layers of insulating material 6 it may be with layers of silk, cotton,
or tape applied to the wire in the ordinary manner, is wound helically in such a
manner as to produce a ring or coil (hereinafter called á coil) preferably of
rectangular form in cross section. Between the several adjacent layers of wire a,
thin layers of insulating material such as paper, cotton &c., shown only in Fig. 1,
are inserted during the winding, and at greater distances apart there are inserted
thicker layers c' of paper, cotton &c., so that the layers of wire are completely
separated one from the other. The several layers of wire and insulating
material c c¹ composing the coil are tied or fastened securely together by binding
cords d passed several times transversely through the coil as shown in Fig. 1.
The coil thus formed is then boiled in wax or a wax substance such as bees' wax
or ceresine with colophony, or in any other equivalent waxy, cereous or resinous
insulating substance, that is capable of being readily converted into a liquid or
seini-liquid state by heat, but is solid at ordinary temperatures, for say 12 hours,
after which it is dried by pressure. The coil is then put into position for use as a
secondary coil in a transformer, and an electric current of the same strength as
that intended to be finally used in practice, is passed through the primary coil of
the transformer whereby the secondary coil effects the conversion of the main
current into a secondary current of high tension. By this means the coil will be

page_text: heated and the wax or waxy substance therein remelted, the coil being left in
operation until the last trace of moisture has been removed. During this operation
a further quantity of wax or waxy substance is added to the coil, it may be by
means of a brush.
When, finally, the coil is no longer warm, due to the gradual filling up of the
interstices in the coil with wax, and to the removal of moisture, it is given a coat
of paint and then a coat or layer of protecting material such as shellac varnish.
As will be obvious, the main object of the invention is to remove every trace of
moisture from the coils and to avoid the presence of any spaces or cavities however
small in the insulating material. Only in this manner can short circuiting and
heating be avoided.
By the preliminary working of the transformer, moisture, always present in the
coil after the same has been boiled and pressed, is effectually removed, and the
interstices in the coil effectually filled up, since, as is evident where there are
spaces and moisture, short-circuiting and heating of the coil very readily take
place, so that evaporation of the moisture and the melting together of the wax or
waxy substance precisely at these places is the necessary consequence. Furthermore
the addition of wax, or of a waxy substance by painting or otherwise which is
continuously carried on during the heating operation always provides sufficient
wax or waxy substance to take the place of that absorbed by the filling up of the
interstices in the coil and also provides for the filling up of any fresh interstices
produced by the evaporation of the moisture.
By constructing secondary coils in the manner described, that is to say, by using
insulated wire, dividing the convolutions thereof by layers of insulating material
such as paper, cotton and the like, intimately connecting the convolutions by
boiling in wax or a waxy substance, and pressing, and protecting the treated coil
by outer coatings of paint and varnish or shellac there is produced a coil which,
without becoming in the least hot when in use will safely withstand tensions of
30,000 volts and upwards.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
1. The manufacture of secondary transformer coils for use in the production of
high tension electric currents, by boiling coils of insulated wire in wax or a waxy
substance, then pressing them, and then putting them into preliminary use for the
purposes of evaporating moisture therefrom and of filling up the interstices therein,
additional wax or waxy substance being supplied to the coils as long as heating
thereof is produced by the passage of an electric current therethrough, as set
forth.
2. A secondary coil for a transformer, composed of wire covered with several
layers of insulating material, and the convolutions of which are embedded in wax
or a waxy substance, are separated from one another in a circular direction by
strips or layers c c³ of insulating material, and are firmly secured together by
binding cords passed several times transversely through the coil, which is finally
provided with an outer protecting layer of material such as shellac varnish, as set
forth.
Dated this 15th day of December 1894.