Improvements in Electric Current Transformers, and Method of Cooling the same.
Year: 1896

page_text: Date of Application, 14th Apr., 1896-Accepted, 16th May, 1896
COMPLETE SPECIFICATION.
Improvements in Electric Current Transformers, and Method of
Cooling the same.
I, JAMES DEVONSHIRE, Secretary of The British Thomson-Houston Limited,
of 38 Parliament Street, Westminster, London (a communication from abroad by
Walter S. Moody, Electrical Engineer, of Lynn, State of Massachusetts, United
States of America) 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 present invention is to make use of an oil or other insulating
circulation in a novel manner, and at the same time to do away with the usual
expensive enclosing tank.
With transformers of a very large size it is necessary to provide some means,
such as an oil circulation, for lowering the temperature in order to reduce the loss
of energy due to heating. This I accomplish by constructing the transformer
core in such a manner as to form a practically fluid-tight casing with chambers
extending in an upward direction from the base to the top. In these chambers
are placed the coils of wire forming the primary and secondary windings and
supported in their respective places by means of insulating blocks. Passages are
left between the coils; and the blocks separating the coils from the core are
provided with grooves which also form passages; these extend from a chamber
in the base to the top of the transformer where a flange is provided for maintaining
a head of oil, with means for distributing the oil in an even flow from the
outside.
In the base of the transformer is a suitable chamber connected with a source of
oil supply and with the upwardly extending passages. The oil on entering the
base is forced upward through the passages by a pump or other suitable means,
at a rate sufficient to absorb the. heat generated by the coils; on overflowing the
flange at the top it is allowed to flow down over the sides of the transformer in a
thin film which serves to cool it to a greater or less extent. If the surface over
which the oil is allowed to flow is extended, or it is subjected to streams of cold
air, it will not be necessary to provide other cooling means; but if these are
omitted, it will be necessary to pass the oil through cooling tanks or coils of
pipe.
Between the lamina of which the transformer is composed there is always more
or less space, and a certain amount of the oil will flow through these spaces instead
of being forced upward and flowing down the outside; this is an advantage, for it
serves to cool the lamine at a point not reached by the oil flowing through the
upwardly extending passages.
If a transformer of this kind is to be used in a station where there is much dirt
or dust, it is well to put a dustproof case over it in order to keep the oil free
from impurities; if a number are to be used, it is best to build a separate house
for them, and in that case no dust covers would be used. Preferably in a case of
this kind, an air circulation would be used in connection with the oil, and in
using this, the air should be filtered to free it from all particles of dust, etc.
In the drawings
Fig. 1 is a vertical section of the transformer, on the line 1-1 of Fig. 2 ;

page_text: Fig. 3 is a diagram representing the positions and connections of the cooling
apparatus as applied to one or more such transformers, and
Fig. 4 shows a transformer house with the transformers and cooling appliances
arranged according to the present invention.
In Fig. 1 P, P and S, S represent respectively the primary and secondary
conductors of a large sized transformer, one capable of delivering several thousand
kilowatts; the number of turns of the primary and secondary conductors being
proportioned to receive and deliver alternating currents of the desired potentials.
These primary and secondary conductors have iron lamina built up around them
in a compact inass, in the usual manner, and are maintained at suitable distances
from each other, and from the iron core, by insulating spacing blocks or plugs, as
indicated in Fig. 2. These spaces are so arranged that they constituto vertical
channels extending from the bottom to the top.
The laminae of the transformers are held together by means of upper and lower
caps k, k, which are bolted together by bolts a. The cap k¹ is provided with a
flange k which is fitted to the base B in such a manner as to make a fairly tight
joint. The upper cap k has a flange which projects upward in such a manner
as to form a receptacle for the oil.
The oil flowing through the grooves k 4 and down the sides of the flange is
received in a small catch basin b. The edge of the flange 3 and the outside
edge of the catch basin & are provided with grooves or notches k4, k 5, to prevent
the oil from running over the edge at any one point, which would be the case if
the edges were smooth and the transformer was not perfectly level; the metal
between the grooves tends to keep a slight head of oil, thus allowing an
approximately equal amount to flow down the sides of the transformer at all
points. Small holes are bored in the flanges or any other means of restricting the
How of oil at one point so as to ensure a flow at the higher points in case the
transformer is not standing exactly level, suffice for the sanie purpose.
The base B is provided with a chamber C to which is connected an inlet pipe c.
The flange & fitting closely into its seat forms the balance of the chamber which
is filled with an insulating fluid, such as paraffine oil of high boiling point. The
base B is also provided with a catch basin D extending all the way around and
this channel communicates with the small chamber C 2, also formed in the
base B, and from which leads a pipe c' serving to convey the oil from the
transformer.
The direction of flow of the cooling fluid is indicated by the arrows; it enters
by the pipe e, flows up through the spaces between the coils, and between the coils
and core, and at last overflowing through the notches k 4 and 5, passes to the
outside of the transformer, whence it flows over the exterior surface of the same
in streams and is collected in the catch basin D, and then flows to the
chamber C 2, and afterwards out to the external pipe system.
The lamina being assembled in the manner described, form a practically fluid-
tight casing, and while the greater portion of the oil would flow up through the
vertical passages and down the outside, a certain amount flows through the spaces
between the laminæ in a transverse direction to the main body of the oil. The oil
flowing outward from the centre in this manner, tends to cool the laminae at this
point, and the amount of flow may be regulated by adjusting the pressure between
the lamina.
It will be observed that the transformer is not, as has hitherto been the case,
entirely immersed in a vessel filled with oil, but that the oil simply flows up
through its interior and down its exterior, the circulation being maintained, in
any suitable way, and at such a rate as serves to abstract all the heat necessary
for the safe and economical working of the apparatus.
A casing H is shown in dotted lines, and while this casing would ordinarily be
employed in case the transformers were installed in a station along with other
apparatus, or in situations where dust or dirt abounded, it is much preferred,
especially where a number of such transformers are to be installed to erect a

page_text: separate structure, or provide a separate room for the transformers, and in this
event the casing H is not used, but the transformer is left open to the air.
Fig. 2 shows the mode of supporting the conductors and insulating them from
each other. The wooden spacing blocks d d separate the coils from each other,
but leave open passages ff between them for the circulation of the oil. The
wooden spacing blocks di, d separate the conductors from the iron core and
insulate them therefrom; these blocks .have. grooves-upan opposite sides, as
indicated, the outer one serving as a support and guide for the con luctors, an 1
the inner one serving to form a channel for the circulation of oil in contact with
the iron core.
The circulation of the oil is readily maintained by a pump e, Fig. 3, driven by
any suitable motor M, which lifts the oil from the reservoir R1 after it comes from
the transformer T, and forces it through a coil of pipe having an extended surface
in contact with water or air where it is cooled after which it passes to the elevated
reservoir R and flows by gravity again to the transformer.
In Fig. 4 F is a transformer house or room containing six large transformers like
those shown in Fig. 1, but having the casing omitted. The reservoir R supplies all
the transformers T1 to T6 with cooled oil through the distributing pipes I, I, and
the oil is returned through the pipes I 1, 1 1, valves being provided for shutting
off the supply to the individual transformers.
So far as I am aware. I am the first to lower the temperature of the transformers
by maintaining a body of oil in the interior thereof and allowing it to flow down
the outside in a free and unobstructed manner.
While my invention is especially applicable to transformers, its application
extends to any other electrical apparatus.
Having now particularly described and ascertained the nature of the said inven-.
tion and in what manner the same is to be performed as cominunicated to.me from
abroad, I declare that what I claim is:
1. In a transformer, the combination of coils of wire surrounded by an iron
core, and an insulating medium flowing down the outside of the core in a film.
2. In a transformer, the combination of coils surrounded by an iron core, spaces
in the core, and means for maintaining an upward oil circulation through the
spaces.
3. In a transformer, the combination of coils surrounded by an iron core, spaces.
in the core, an upward oil circulation, and means for carrying the oil to the outside
of the core and allowing it to flow down.
4. In a transformer, the combination of coils surrounded by an iron core, spaces
between the coils and the core and between each other, the spaces forming up and
down passages, an oil circulation flowing through these passages, and means
at the top for distributing the oil down the outside of the core in an even flow.
5. In a transformer, the combination of a core forming a practically fluid-tight
casing, coils surrounded by the core and separated therefrom by up and down
passages extending through the transformer, a cap provided with a flange at the
top maintaining a head of oil, and grooves for distributing the oil in a film down
the outside of the core.
6. In a transformer, the combination of coils surrounded by a core forming a
practically fluid-tight casing with a forced circulation of fluid through openings in
the interior of the transformer.
7. In a transformer, a main up and down circulation of oil, and a circulation
transverse thereto.
8. In a transformer, the combination of up and down passages with oil circulating
therein, with transverse passages between the lamina and a limited circulation
therein.
9. In a transformer, the combination of primary and secondary coils, an iron
core forming practically a fluid-tight casing, a main oil circulation having

page_text: an up and down direction, and a limited circulation in a direction transverse
thereto.
10. In a transformer, the combination of oil passages extending through the
lamine, with a cap provided with means for evenly distributing the flow of oil down
the sides.
.
11. The combination in a transformer, of primary and secondary coils, a laminated
core surrounding the coils, a number of passages through the interior of the
transformer, and means for maintaining an upward circulation of an insulating fluid,
as oil, through said passages, and conveying the oil so that it runs down the outside
of the core.
12. In a transformer, the combination of oil passages extending upward from
the base, a cap formed with a flange to maintain a head of oil, and grooves cut in
the top of the flange to insure an even distribution of the oil down the sides of the
transformer.
13. In a transformer, the combination of a base having a chamber connecting
with the passages extending through the laminæ, a cap provided with a flange and
a catch basin, the latter extending to the edge of the lamina and regulating the
flow of oil down the sides of the transformer.
14. In a transformer, the combination of a receiving chamber in the base, passages
extending through the laminæ, a flange forming a receptacle for the head of oil,
a catch-basin at the top of the transformer to distribute the oil, and a second catch-
basin to receive the oil, formed integral with the base and connecting with an outlet
chamber also located in the base.
15. In a transformer system, the combination of means for cooling the oil, a
reservoir for maintaining a head of oil, a connection between the reservoir and the
chamber in the base of the transformer and the passages extending upward through
the lamina, a cap provided with means for holding a body of oil at the top of the
transformer, means for insuring an even distribution of oil down the sides thereof,
a catch-basin located at the base to receive the oil as it flows down the sides of the
transformer, and a pump to effect the circulation.
16. In a transformer, the combination of primary and secondary coils, a base
provided with a chamber, channels between the coils connected with the chamber
in the base, and forming a passage for an insulating fluid.
17. In a transformer, the combination of top and bottom caps between which the
laminæ are clamped, a base adapted to receive the hottom cap and passages between
the different coils and between the coils and the laminæ, forming channels to receive
an insulating fluid.
18. In a transformer, the combination of primary and secondary coils, lamina
surrounding the coils, insulating blocks between the several coils and the core,
channels cut in the blocks forming passages for the insulating fluid, other blocks
separating the coils and forming a second set of passages, a base having a chamber
connecting with the passages, and a top provided with a flange to maintain a head
of oil sufficient to cover the coils.
19. In a transformer system, the combination of electric coils in inductive
relation to each other, laminæ surrounding the coils, passages between the several
coils and the core, and a pump to maintain a circulation through the interior of the
transformer.
20. In a transformer system, the combination of electric coils surrounded by
lamina separated therefrom and from each other, by oil passages, and means for
circulating the oil through these passages under pressure.
21. In a transformer, the combination of primary and secondary coils, a core
surrounding the coils, passages in the core, and an insulating compound supplied
to these passages under pressure and allowed to flow down the sides of the transformer
in an unobstructed manner.
22. In a transfornier, the combination of coils surrounded by a practically fluid-
tight core, means for forcing oil upward through passages formed in the core,

page_text: and an extended surface over which the oil flows for the purpose of cooling the
same.
Dated this 14th day of April 1896.
J. C. CHAPMAN,
70 Chancery Lane, London, W.C., Chartered Patent Agent..