Improvements in Electrical Transformers."
Year: 1897

page_text: Date of Application, 19th Oct., 1897-Accepted, 4th Dec., 1897
COMPLETE SPECIFICATION.
"Improvements in Electrical Transformers."
We, THE BRITISH THOMSON-HOUSTON COMPANY, LIMITED, of 83, Cannon Street, in
the City of London, Electrical Engineers, do hereby declare the nature of this
invention (which has been communicated to us from abroad by Walter S. Moody,
of Lynn, in the County Essex, State of Massachusetts, United States of America),
and in what manner the saine is to be performed, to be particularly described and
ascertained in and by the following statement :-
The present invention relates to transformers specially intended for very high
voltages, as 20,000 to 30,000 volts, for example: and has for one of its objects to so
arrange the energizing coils that they are well insulated from the surrounding core
and from each other, at the same time providing suitable means for ventilation.
The invention also has for its object to provide a transformer having two complete
and separately controlled systems of cooling, one being for the coils and the other for
the laminated core.
In the accompanying drawings attached to and made a part of this specification,
Fig. 1 is a vertical section of my improved transformer; Fig. 2 is a plan view with
top removed, and Fig. 3 is an enlarged cross-section taken through a portion of
the coils.
The transformer is supported by a rectangular base A provided with openings B at
its ends to permit inspection of the secondary terminals C. Shoulders B₁ are formed
on the base which support the laminae D which are insulated from the base by
pieces of wood A¹. Extending laterally within the base is a connection board A²
forming a support for the secondary terminals C. The base is provided with an open
bottom chamber R, through which a current of air or other insulating medium enters
the transformer casing, as herein described. On the right and at the upper end of
the chamber R is a passage E communicating with the chamber E¹. To vary the
opening in the passage a regulator F is provided which consists of a rectangular
casting having a number of openings and transverse gates. This casting is adapted
to be moved backward and forward over a similar construction on the base.
The laminae are divided into sections, and the sections separated from each other
by space blocks which are so arranged that ventilating spaces G are left between the
sections. These ventilating spaces extend parallel to the laminae and communicate
with chambers H and E, but are entirely separate from the ventilating spaces
between the coils, as will be hereinafter explained. The chambers E' and H are
formed by sheet iron covers k and which extend from the base A to the top J. The
chamber E is separated from the chamber H by pieces of non-magnetic
material m and situated at opposite ends of the transformer so that the two
chambers communicate only through the ventilating spaces in the core. The casing
which forms chamber H is perforated so that air or other insulating medium reveived
from the chamber E through the spaces G will pass to the outside.
Owing to the large size of the transformer, it has been found desirable to divide
the laminae into two bodies which are separated by a slight space (Fig. 2). Each of
these bodies is built up separately around the coils which form the primary and
secondary.
To secure the laminae together, a cast metal top J is provided, having inwardly

page_text: projecting flanges which are insulated from the laminae by blocks of wood J. To
clamp the top to the base, two vertically extending bolts J2 are employed, one on
each side of the core. The nuts employed to secure the top are situated on the
outside so that they are readily accessible; by this arrangement they may be
adjusted or removed without endangering the insulation of the coils by the use of
wrenches.
Mounted on the top is a removable cover K which is provided with a series of
openings K¹ and a slide K2 adapted to vary the extent of the openings by moving
back and forth like a stove damper. This regulates the amount of air that passes
through the air chambers between the coils.
In transformers intended for very high voltage, a large amount of insulation is
required between the primary and secondary coils, and where this insulation is
applied directly to the coils it is very difficult to keep the temperature of the
transformer down to a proper degree, owing to the slowness with which heat can be
absorbed from the coils through the insulation. To overcome this objection the coils
are formed into any desired shape, the turns being insulated from each other in the
usual manner, and the coil as a whole may be covered by tape or other insulation,
but preferably such insulation is limited in amount. The insulation required to
insulate the turns from one another and any additional insulation applied, when
desired, directly to a complete coil will be relatively small compared with what would
be necessary to form a safe insulation between the primary and secondary coils or
between the primary coils and the core, and will not prevent the absorption of heat
to any considerable extent.
The coils are now mounted in a suitable casing L, extending from the top
lengthwise into the chamber R at the bottom of the transformer, and cutting off the
coils with their system of ventilation from the chambers E' and H and the core
system of ventilation.
The primary and secondary windings are subdivided into a numder of coils which
are distributed in any desired manner. This is best shown in Fig. 1, where there is
first a secondary coil $ in two sections, then another similar primary coil, and lastly
a secondary coil. These windings as a whole are separated from the core by the
casing L, of leatheroid or fibre, as described.
The primary coils are insulated from the secondary coils and case in a novel manner
designed to afford ventilating spaces between the coils and the bulk of the
insulation, and preventing heating of the coils to a very material extent as compared
with previous constructions. This is best. shown in Fig. 3, to which reference is
now made.
The primary coils P consist of a number of turns of flat wire or ribbon with
suitable insulation between the turns. A small amount of insulation a is placed
between the two sections which form one coil, and the two sections are then given a
covering b of tape to hold them together. At the edges of the coils is insulation N
consisting of U-shaped pieces of leatheroid. Outside of this is placed a single layer
of insulation c with its ends overlapping, and the whole bound together by a band
of tape d. The insulation c is separated from the coils by a block of wood g, and a
similar block is placed between the coils. Situated on both sides of the primary coils
are secondary coils S; these are similar in construction to the primary coils. These
coils are insulated at their edges by U-shaped pieces of insulation e and between
this insulation and the enclosing case of the primary is a strip f. A block of wood g
is placed between the coil and the primary case, to hold them in position. It will
be seen that the leatheroid c and the tape d serve as a partition between the
passages O and Q. The insulation thus applied forms a sort of openwork structure
having a number of channels or air passages, preferably closed or substantially closed
from one another, and open top and bottom to allow a free circulation of air between
the different windings and between the coils and insulation. The insulation forming
the walls of these channels preferably extends beyond both ends of the coils so as to
present an extended creeping surface over which current must pass before it can
reach the secondary winding. There being no especial reason for economizing space

page_text: at the ends of a transformer, the casings can be extended to a point where the
insulation will be as high, or even higher, than that at any other point between the
primary and secondary windings.
The enclosing case L consists of sheets of insulating material h, and surrounding
it is a layer of tape ; this completely insulates the coils from the core.
Air or
other insulating Huid, upon entering the chamber in the base, passes upward through
the passages between the coils in a vertical direction, and the amount is regulated
by the damper located in the cover K. At the same time a portion of the air or
other insulating medium passes up through the damper E into chamber E' and
passes through the passages G to the chamber H and to the outside of the case in a
direction transverse to that which flows upward through the coils.
It will be seen that there are two separate ventilating systems for cooling the
transformer, one for the coils, the other for the iron, and that each of them is
controlled independently of the other.
Having now particularly described and ascertained the nature of the said invention
(as communicated to us from abroad) and in what manner the same is to be performed,
we declare that what we claim is :-
1. In a transformer, the combination of a core, primary and secondary windings
and insulation for insulating the primary winding from the secondary winding,
not applied to said windings direct or either of them, but separated from the
windings and permitting a more ready absorption of the heat developed in the
windings, as set forth.
2. In a transformer, a primary or high potential winding surrounded by a heavy
insulation, which is separated from the winding by an air space or spaces, said
insulation serving to insulate the primary from the secondary winding.
3. In a transformer, a primary or high potential winding subdivided into sections
slightly separated from one another, and an insulating casing surrounding said
winding and separated therefrom by an air space or spaces said casing serving to
insulate the primary from the secondary winding, as set forth.
4. In a transformer, the combination of primary and secondary windings with
passages extending between the windings for the circulation of a cooling medium,
and a laminated iron core with a second set of passages, through which circulates an
insulating cooling medium, said sets of passages forming independent cooling and
ventilating systems, one for the coils and one for the core.
5. In a transformer, the combination of primary and secondary windings, a
laminated iron core, passages extending between the windings through which an
insulating medium circulates to cool the windings, a second set of passages extending
through the iron core independent of the first, in which an insulating medium
circulates to cool the iron, and means for regulating the circulation through .both
sets of passages.
6. In a transformer, the combination of primary and secondary windings, a
laminated core, means for maintaining an up and down circulation of air through
the coils, and means for maintaining a transverse circulation of air through the iron
core, both circulations being independent.
7. In a transformer, the combination of primary and secondary windings separated
by air passages, a laminated core divided into sections, and air passages independent
of those between the windings formed between the sections, a common source
of air supply, and means for regulating the flow of air through each set of passages
independently.
8. In a transformer, the combination of primary and secondary windings, divided
into a number of coils, a laminated iron core, an insulating case surrounding one or
more of the coils and provided with open ends at the top and bottom, and spaces
between the coils for the free circulation of an insulating medium.
9. In a high potential transformer, the combination of an insulating casing
surrounding the primary and secondary windings, with vertically extending air spaces
between the coils and the case, an insulating case mounted within the first and
2

page_text: surrounding one of the windings, and air spaces between the last mentioned winding
and its surrounding case, the two sets of air spaces being independent.
10. In a high potential transformer, the combination of primary and secondary
windings, each composed of a number of turns of wire which are sufficiently insulated
to prevent leakage between adjacent turns, but not enough to insulate them from the
core and the other winding, a body of insulating material located between the
windings, and spaces formed between the windings and the insulation for insulating
the coil and permitting the circulation of an insulating and cooling medium.
11. In a high potential transformer, the combination of primary and secondary
windings divided into sections, a laminated core, an insulating case between the core
and the windings, air passages between the case and the windings, insulating cases
surrounding the primary winding and separating it from the secondary, the
cases being provided with open ends which project above and below the ends of the
coils so as to increase the creeping or leakage surface, air passages between
the primary coils and the casings, and a common chamber supplying air for both sets
of passages.
12. In a transformer, the combination of primary and secondary windings separated
by air passages, a laminated iron core divided into sections, a set of air passages
between the sections and independent of the first, an air chamber in the base
supplying air to the passages between the windings, and a chamber located on one
side of the laminae, and connecting with the chamber in the base for supplying air
to the passages between the core sections.
13. In a transformer, the combination of primary and secondary windings, a
laminated iron core, air passages extending in a vertical direction through the
windings, air passages extending through the iron in a direction transverse to and
independent of the first set, an air chamber in the base, a chamber located on one
side of the core communicating therewith and supplying air to the core passages,
and means for regulating the passage of air through both sets of passages
independently.
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