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Patent 2146474 Summary

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(12) Patent: (11) CA 2146474
(54) English Title: SOLID INSULATION TRANSFORMER
(54) French Title: TRANSFORMATEUR A ISOLANT SOLIDE
Status: Expired
Bibliographic Data
(51) International Patent Classification (IPC):
  • H01F 30/00 (2006.01)
  • H01F 27/02 (2006.01)
  • H01F 27/18 (2006.01)
(72) Inventors :
  • PARADIS, CLAUDE (Canada)
  • FORTIN, MARCEL (Canada)
  • HAAS, MICHAEL EDWARD (United States of America)
  • LANOUE, THOMAS J. (United States of America)
  • PINEAULT, JEAN-GUY (Canada)
  • GUILLEMETTE, ROBERT (Canada)
  • CHAABAN, MOHAMMED (Canada)
(73) Owners :
  • CENTRE D'INNOVATION SUR LE TRANSPORT D'ENERGIE DU QUEBEC (Canada)
(71) Applicants :
(74) Agent: NORTON ROSE FULBRIGHT CANADA LLP/S.E.N.C.R.L., S.R.L.
(74) Associate agent:
(45) Issued: 1999-10-19
(22) Filed Date: 1995-04-06
(41) Open to Public Inspection: 1996-10-07
Examination requested: 1997-04-11
Availability of licence: N/A
(25) Language of filing: English

Patent Cooperation Treaty (PCT): No

(30) Application Priority Data: None

Abstracts

English Abstract

The solid insulation transformer has a rectangular core covered with a compressible closed- cell foam to eliminate stress during curing of the cast dielectric material surrounding the core and during operation. Heat pipes are placed between the inner coil and the core to extract heat before the temperature builds up. For safety and to eliminate the need for a separate enclosure, an outer multi- layer casing having an incorporated grounded conductive layer is provided to cover the sides of the cast body. The outer casing prevents explosion if dielectric break down and arcing occur, and reduces the danger of electric shock.


French Abstract

Le transformateur à isolation solide a une base rectangulaire revêtue d'une mousse alvéolée fermée compressible pour éliminer le stress pendant le durcissement du matériau diélectrique entourant le noyau et au cours de l'opération. Des caloducs sont placés entre la bobine interne et le noyau pour extraire la chaleur avant que la température s'accumule. À des fins de sécurité et pour éliminer le besoin d'un boîtier distinct, un boîtier extérieur multicouche ayant une couche conductrice mise à la terre incorporée est fourni pour couvrir les côtés du corps coulé. L'enveloppe extérieure empêche les explosions en cas de rupture diélectrique et d'arc électrique et réduit le risque d'électrocution.

Claims

Note: Claims are shown in the official language in which they were submitted.


- 11 -
WE CLAIM:
1. A solid insulation transformer comprising:
a core;
a primary coil and a secondary coil wound
around at least one limb of said core;
a solid cast dielectric material filling a
space between said primary coil, said secondary coil
and said core; and
a compressible sheet material provided between
said core and said cast dielectric material;
whereby relative movement between said core and
said cast material is substantially absorbed by said
compressible material.
2. A solid transformer comprising:
a core;
a primary coil and a secondary coil wound
around at least one limb of said core;
a solid cast dielectric material filling a
space between said primary coil, said secondary coil
and said core;
an outer casing covering at least a lateral
exterior surface of said cast material and
incorporating a grounded conductive layer,
whereby said casing contains said cast material
in case said cast material cracks as a result of
thermal stress or arcing, and said grounded conductive
layer prevents an electric shock hazard on an exterior
of said transformer.
3. A solid transformer comprising:
a core;
a primary coil and a secondary coil wound
around at least one limb of said core;

- 12 -
heat exchange means provided between at least
one of said coils and said core for conducting heat to
an outside of said transformer; and
a solid cast dielectric material filling a
space between said primary coil, said secondary coil
and said core.
4. The transformer as defined in claim 1, wherein
said compressible sheet material covers an entire
surface of said core and seals said core from said
cast material.
5. The transformer as defined in claim 4, wherein
a rigid support member is provided to support said
compressible sheet material at least at an underside
of said core, said rigid support member being
connected to a base of said transformer, whereby said
compressible sheet material is substantially evenly
compressed when supporting a weight of said core
before said cast material is solid.
6. A transformer as claimed in claim 1, further
comprising heat exchange means provided between at
least one of said coils and said core for conducting
heat from said at least one coil and said core to an
outside of said transformer.
7. A transformer as claimed in claim 1, further
comprising an outer casing covering at least a lateral
exterior surface of said cast material and
incorporating a grounded conductive layer, said cast
material encasing all of said core and said coils,
said sheet material covering all of said core.
8. A transformer as claimed in claim 1, wherein
said compressible sheet material is a resilient closed
cell foam material.


- 13 -

9. A transformer as claimed in claim 4, wherein
said compressible sheet material is a resilient closed
cell foam material.
10. A transformer as claimed in claim 9, wherein
said core is rectangularly shaped, and said coils are
wound concentrically around one elongated limb of said
core.
11. The transformer as claimed in claim 2, wherein
said casing comprises an upwardly tapered upper
portion and a downwardly tapering lower portion, said
outer casing not covering an upper and lower extremity
of said dielectric material.
12. A solid transformer as claimed in claim 2,
wherein said grounded conductive layer comprises a
carbon fiber material.
13. A transformer as claimed in claim 2, wherein
said outer casing comprises a plurality of multi-layer
fiber reinforced shell members having overlapping
engaging tab portions and including a grounded carbon
fiber conductive layer, said shell members being
cemented together and to said dielectric material.
14. A transformer as claimed in claim 2, wherein
said core is rectangularly shaped, and said coils are
wound concentrically around one elongated limb of said
core.
15. A transformer as claimed in claim 2, wherein a
compressible sheet material is provided between said
core and said cast dielectric material, whereby
relative movement between said core and said cast





- 14 -

material is substantially absorbed by said
compressible material.
16. A transformer as claimed in claim 2, further
comprising heat exchange means provided between at
least one of said coils and said core for conducting
heat from said at least one coil and said core to an
outside of said transformer.
17. A transformer as claimed in claim 3, wherein
said core is a closed rectangular loop, said primary
coil and said secondary coil are concentrically wound
around a same limb of said core.
18. A transformer as claimed in claim 3, wherein
said heat exchange means comprise at least one heat
pipe.
19. A transformer as claimed in claim 18, wherein
said core is a closed rectangular loop, and at least
one said heat pipe is provided on each side of said
core, each said heat pipe having a thermally
conductive blade member for transporting heat from
said core side and an adjacent one of said coils.
20. A transformer as claimed in claim 19, wherein
at least two said heat pipes are provided on each
side, adjacent ones of said blade members being
separated by electrically insulating means.
21. A transformer as claimed in claim 3, wherein a
compressible sheet material is provided between said
core and said cast material, said heat exchange means
being provided between said compressible sheet
material and said one of said coils.


- 15 -

22. A transformer as claimed in claim 17, wherein
said transformer is a distribution transformer, and
said secondary coil is inset within said primary coil,
said heat exchange means removing heat from said limb
and said secondary coil.
23. A solid transformer as claimed in claim 22,
further comprising a compressible sheet material
provided between said core and said cast dielectric
material.
24. A transformer as claimed in claim 23, further
comprising an outer casing covering at least a lateral
exterior surface of said cast dielectric material and
incorporating a grounded conductive layer.

Description

Note: Descriptions are shown in the official language in which they were submitted.


21~6474
. ~
-- 1 --
SOLID INSUL.ATION TRAhj,.,
Field of the Invention
The present invention relates to a solid or dry
5 transformer, i.e a transformer in which the
dielectric insulation is a solid instead of a liquid,
e. g . oil, or gas, e . g . circulated air . The invention
relates further to a solid or dry distribution
transformer .
Ju~d of the InveQtion
It is known in the art to mount a transformer
core along with the primary and secondary coils in a
solid cast material to obtain a "dry" transformer,
i.e. without using a dielectric liquid or gas to
dissipate the heat generated in the coils and in the
transformer core. Success in making such solid or dry
transformers has only been _ound to a limited extent
in relatively low power transformers.
Some of the ~liff;~ ties encountered will be
brie~ly discussed in the ~ollowing. Heat dissipation
through a solid dielectric material is known to be
poor and the result of thermal build-up can create hot
spots or high thermal gradients which can crack the
solid dielectric material . The resulting f issure or
f issures can be dangerous because of mechanical
instability (the transformer body can break apart),
and a break-down in the dielectric medium between the
coils, and the core or ground.
Furthermore, if arcing occurs within the solid
insulation, vaporization of the solid material can
build up gas pressure which can even lead to
fragmentation of the solid material and explosion.
Conventional dry-type transformers require a
grounded enclosure to remove any electrical shock
ha~ard. Such enclosures are typically metal cages
having dimensions much larger than the transformer

2146474
. ~ .
-- 2 --
itself, making installation space requirements
dif f icult .
Another problem in constructing a solid or dry
transformer is that the expansion and contraction of
5 the core as a result of temperature variations and
shrinking of the cast solid insulation material
induces stresses on the cast transformer body.
A further fliff;ci~lty in manufacturing a large
scale transformer, such as a distribution transformer,
10 having a surrounding dielectric cast material lies in
curing or setting the cast material in an even and
homogeneous way to provide for homogeneous physical
properties throughout the solid cast body.
15 Summary of the Invention
It is an object of the present invention to
provide a solid transformer which overcomes the known
difficulties of solid or dry transformer construction
and manufacture. In particular, it is an object of
20 the present invention to provide a safe and functional
solid distribution transformer. It is a further
object of the present invention to provide a solid
insulation distribution transformer that can be
installed in conditions where the transformer may be
25 partially or fully submerged in water, such as in an
underground power distribution vault.
According to the invention, there is provided a
solid insulation transformer comprising a core, a
primary coil and a secondary coil wound around at
30 least one limb of the core, a solid cast dielectric
material f illing a space between the primary coil, the
secondary coil and the core, and a compressible sheet
material provided between the core and the cast
dielectric material. In this way, relative irJv~
35 between the core and the cast material is
substantially absorbed by the compressible material.
Thermal expansions and contractions of the core are

21~474
-- 3 --
also absorbed by the compressible material. The
compressible sheet material is preferably resilient.
For example, a closed cell temperature resistant
foamed rubber or silicone material is suitable. When
5 seams of the compressible sheet material need to be
joined, a silicone sealant which is non-corrosive is
preferably used, i.e. silicone sealant which releases
acetic acid during curing is not r~ P.l since the
acetic acid can corrode the core.
According to the irvention, there is also
provided a solid transformer comprising a core, a
primary coil and a secondary coil wound around at
least one limb of the core, a solid cast dielectric
material filling a space between the primary coil, the
15 secondary coil and the core, an outer casing covering
at least a lateral exterior surface of the cast
material and incorporating a grounded conductive
layer. In this way, the casing contains the cast
material in case the cast material cracks as a result
20 of thermal stress or arcing, and the grounded
conductive layer prevents an electric shock hazard on
an exterior of the transformer Preferably, the outer
casing is made from pieces of preformed multi-layer
fiber reinforced material and resin, the resin
25 preferably not including any filler. Carbon fiber is
included or incorporated inside the shell components,
and the carbon f iber material is a relatively good
conductor. The shell components of the outer casing
are preferably bonded together and provide a tough
30 outer shell. The multi-layer fiber-reinforced
material preferably absorbs the energy of a crack or
fissure in the cast material by deforming and
undergoing layer separation locally while preventing
solid fragments from escaping. This preferred
35 construction provides what is known as a ballistic
quality to the outer casing.

21~6474
-- 4 --
According to the invention, there is also
provided a solid transformer comprising a core, a
primary coil and a secondary coil wound around at
least one limb of the core, heat exchange means
provided between at least one of the coils and the
core for conducting heat to an outside of the
transformer, and a solid cast dielectric material
filling a space between the primary coil, the
secondary coil and the core. Advantageously, when the
coils are concentrically wound for good
electromagnetic coupling, the heat from the outer coil
is dissipated through the surrounding cast material to
the ambient air and the heat from the inner coil and
core is dissipated by the heat exchange means.
Fur~h-o ~, the heat exchange means preferably
comprise a copper or other good thermal conductor heat
pipe system which, by being placed between the coil
and the core instead of between the concentric coils,
does not adversely af f ect the dielectric medium
between the coils. Preferably, the heat exchange
means comprise at least one heat pipe Eleat pipes are
known in the art.
In the present specification, the reference to
"concentric" simply means contained within the
perimeter of one another, it being acknowledged that
the core does not have to be circular and is most
likely to be of a rectangular cross-section and thus
the coils will not have a circular cross-section in
most cases.
In the present invention, the cast dielectric
material f ills a space between the primary and
secondary coils in order to insulate one from the
other. As a result, a mechanical support of the coils
and the core is provided by the cast dielectric
material, although such support is initially provided
by other means until the casting is complete.

~ 2I46q74
-- 5 --
In the present invention, it is important that
at least the primary and secondary coils in their
entirety and at least part of the core be encased in
the cast dielectric material ( as required to provide
good electrical insulation). Preferably, the entire
core as well as the coils are submerged in the
dielectric material as a liquid which is then cured to
become a solid. Similarly, the entire core is
preferably covered with the resilient compressible
material to allow for expansion and contraction of the
core during curing and operation.
Brief De8cription of the Drawings
Other ob~ects and features of the present
invention will be better understood by way of the
following detailed description of a preferred
embodiment with reference to the appended drawings in
which:
Figure 1 is a side cross-sectional view of the
molded solid transformer according to the preferred
embodiment;
Figure 2 is a horizontal cross-section of the
solid transformer illustrated in Figure l;
Figure 3 is a detailed cross-section of the way
in which the core and coils are assembled according to
the preferred embodiment; and
Figure 4 illustrates the molded transformer
with its outer casing members before assembly
according to the pref erred embodiment .
I:!etAilp~l Description of the Ef~f~iLLCil r _ i-- t
Figure 1 illustrates the basic construction of
the solid insulation distribution transformer
according to the preferred embodiment. The
transformer 10 has a core 12 and coils or windings 14.
An outer casing 16 surrounds a molded mass 18. The
molded mass 18 is a dielectric resin which completely

` ~ / 2146474
-- 6 --
encases and surrounds the core 12 and the windings 14.
A bracket ( not shown ) connected to the core exterior
side casing 34 3upports the windings 14. The high
voltaqe and the low voltage ~rm;n~l~ are provided at
5 the front on connectors as shown at 21. Heat
generated by the core 12 and the windings 14 is
extracted by four heat pipes 22 each having conductive
heat sink blades 50 for collecting heat in the region
between the core 12 and the windings 14 to draw the
10 heat up towards radiators 24 The distribution
transformer 10 is mounted on a base 20, the base being
engageable by a forklift for ease of manipulation.
According to a f irst aspect of the present
invention, as shown in Figures 2 and 3, the magnetic
15 core is not directly cast in the solid dielectric
material 18 but rather it is surrounded by a resilient
and compressible sheet material 30. During curing of
the cast material 18, the compressible sheet material
30 is constricted as the cast material shrinks. The
20 core is thus also allowed to vibrate and to undergo
thermal expansion and contraction without breaking
away from the solid cast material 18. A silicone foam
rubber (closed cell) sheet material 30 is wrapped
around all of the core 12. Silicone sealant is used
25 to close together and render resin-tight the
compressible sheet material 30 at the seam or seams
thereof. The laminated core 12 thus does not soak up
the liquid cast dielectric material 18 during molding.
The silicone sealant used to seal up the sheet
30 material 30 is preferably the kind which does not
release acetic acid during curing to avoid subjecting
the laminated core 12 to the acetic acid. As
illustrated in Figure 2, the resilient foam sheet
material 30 is partly surrounded by steel casing
35 plates 34 on its outer sides at the base and free
elongated limb by which the whole of the core 12 and
coils 14 is supported when mounted to base 20. The

21~647~
casing plates 34 may be made of metal of composite
material .
Furth~ , in accordance with the present
invention, any possible cracks due to thermal build-up
in the mass of molded dielectric material 18
surrounding the core 12 are prevented from propagating
radially by a series of concentric dielectric sheets
62 placed between the primary coil 66 and the
secondary coil 64, as well as between the secondary
coil 64 and the grounded outer casing 16. While these
sheets 62 are shown to be concentric square-shaped
tubes, it would, of course, be possible to provide a
spiral of a continuous sheet in order to place a
plurality of sheets between the primary and secondary
coils The molded dielectric material 18 fills the
spacing between the sheets 62 . The sheets 62 ~ e . g .
NOMEXTM paper which is a synthetic fiber paper-like web
material having good dielectric properties as well as
good physical strength and flexibility when provided
in a ~hif~knl~cs not much thicker than standard bond
paper) are held in place by spacers generally
indicated by reference numeral 60. The spacers 60 may
be made of fiberglass strips or the like.
According to a second aspect of the present
invention, the heat pipes 22 as illustrated in Figures
1 and 3, are arranged to extract heat from the core 12
and the secondary low voltage windings 64. Heat
pipes, well known in the art, are heat transfer
devices consisting of a sealed metal tube with an
inner lining of wicklike capillary material and a
3mall amount of fluid in a partial vacuum, in which
heat is absorbed at one end by vapori~ation of the
f luid ana is released at the other end by condensation
of the vapor Ileat absorbed by the pipes 22 within
the distribution transformer 10 causeg the liquid
contained within the wick structure to evaporate. The
vapor in the center of the heat pipes 22 moves through

214647~
the wick-like coating in the radiator end of the pipes
22 to condense and release heat to the radiator fins
24. The wick-like coating transports the liquid by
capillary action from the condenser section outside
the transformer to the evaporator section inside the
transformer where the heat is generated. The blades
50 help collect the heat from within the transformer
for transport by the heat pipes 22. An insulator
strip 52 (e g. a NOMEX strip) is used to separate the
two sets of blades 50 in order to electrically
insulate the two and prevent a current loop.
As can be Seen in Figure 3, the heat pipes are
arranged on the outside of the silicone sheet material
30. Heat is more readily absorbed in this way from
the low voltage windings 64. Heat which builds up in
the core 12 is collected by the heat pipes as it
passes through the sheet material 30. ~he heat
generated by the outer high voltage windings 66 is
dissipated through the cast dielectric 18 to the outer
casing 16 and to the ambient air. In the preferred
embodiment, two heat pipes 22 are provided on each
lateral side of the core 12. ~his has proven to be
efficient for removing the heat that is generated in
the case of a 167 kVA distribution transformer. Of
course, it would be possible to have a heat pipe
inside the sheet material 30. While heat pipes are
preferred because they are passive and maintenance-
free, active fluid circulation heat exchange apparatus
could also be implemented.
With reference to Figures 1 and 4, an aspect of
the present invention will be described. The outer
casing 16 which surrounds the solid body 18 comprises
an outer multi-layer f iberglass shell 42 with an inner
carbon f iber cloth liner 44 . ~he shell members
comprise interlocking tabs 46 which allow the
fiberglass shell members to be glued together to form
a rigid and solid shell completely surrounding the

~ . 2146~74
g
sides of the distribution transformer 10. As
illustrated, thin copper strips 48 are connected to
the cloth liner 44 in order to connect the cloth to
ground . By grounding the carbon f iber cloth liner 44,
5 electric fields within the distribution transformer 10
which emanate f rom the windings 14 will not result in
a shock hazard to workers coming into contact with the
casing 16.
By providing a fiberglass shell to cover the
10 molded dielectric body 18, a very safe structure is
constructed. Thus, if a pressure build-up inside of
the molded body occurs resulting in the body 18
wanting to crack apart under the gas pressure, the
fissure will travel until it reaches the casing 16, at
15 which point its energy will be absorbed. The built-up
gas pressure can then travel upwards towards the top
of the transformer 10 where the casing 16 is not
provided and be safely released there. This
construction is known as a "ballistic armor"
20 construction since it prevents any harmful effects
from an otherwise explosive condition. The tapering
at the top of the transformer both reduces the volume
of the cast dielectric and increases the effectiveness
of the casing 16 by reducing the exposed surface. It
25 is assumed that the exposed surface points in a
direction free from the usual passage of workers.
The cast insulating material 18 may be made
from a resin-filler mixture, such as the Ciba-Geigy
resin sold under the name "Araldite CW229" mixed with
30 a Wollastenite powder filler (CaSiO3). The filler
upgrades the resin structural properties. The
dilation coefficient of the set resin-filler composite
is also close to that of steel. After the shell
members 42 are assembled together to make the casing
35 16, the steel molds are then applied to the casing 16
before the resin filler mixture iS vacuum cast in the
casing 16 and allowed to fully cure. The copper

214647~
-- 10 --
strips 48 are then connected to a ground tprm; ni:ll to
ground the carbon f iber cloth material contained in
the shell members 42.

Representative Drawing
A single figure which represents the drawing illustrating the invention.
Administrative Status

For a clearer understanding of the status of the application/patent presented on this page, the site Disclaimer , as well as the definitions for Patent , Administrative Status , Maintenance Fee  and Payment History  should be consulted.

Administrative Status

Title Date
Forecasted Issue Date 1999-10-19
(22) Filed 1995-04-06
(41) Open to Public Inspection 1996-10-07
Examination Requested 1997-04-11
(45) Issued 1999-10-19
Expired 2015-04-07

Abandonment History

There is no abandonment history.

Payment History

Fee Type Anniversary Year Due Date Amount Paid Paid Date
Application Fee $0.00 1995-04-06
Registration of a document - section 124 $0.00 1995-10-19
Maintenance Fee - Application - New Act 2 1997-04-07 $100.00 1997-04-01
Request for Examination $400.00 1997-04-11
Maintenance Fee - Application - New Act 3 1998-04-06 $100.00 1998-04-01
Maintenance Fee - Application - New Act 4 1999-04-06 $100.00 1999-03-31
Final Fee $300.00 1999-07-22
Maintenance Fee - Patent - New Act 5 2000-04-06 $150.00 2000-03-08
Maintenance Fee - Patent - New Act 6 2001-04-06 $150.00 2001-03-29
Maintenance Fee - Patent - New Act 7 2002-04-08 $150.00 2002-03-27
Maintenance Fee - Patent - New Act 8 2003-04-07 $150.00 2003-03-26
Maintenance Fee - Patent - New Act 9 2004-04-06 $200.00 2004-03-26
Maintenance Fee - Patent - New Act 10 2005-04-06 $250.00 2005-03-24
Maintenance Fee - Patent - New Act 11 2006-04-06 $250.00 2006-03-28
Maintenance Fee - Patent - New Act 12 2007-04-10 $250.00 2007-03-26
Maintenance Fee - Patent - New Act 13 2008-04-07 $250.00 2008-03-31
Maintenance Fee - Patent - New Act 14 2009-04-06 $250.00 2009-03-26
Maintenance Fee - Patent - New Act 15 2010-04-06 $450.00 2010-03-24
Maintenance Fee - Patent - New Act 16 2011-04-06 $450.00 2011-03-24
Maintenance Fee - Patent - New Act 17 2012-04-10 $450.00 2012-03-26
Maintenance Fee - Patent - New Act 18 2013-04-08 $450.00 2013-03-26
Maintenance Fee - Patent - New Act 19 2014-04-07 $450.00 2014-03-24
Owners on Record

Note: Records showing the ownership history in alphabetical order.

Current Owners on Record
CENTRE D'INNOVATION SUR LE TRANSPORT D'ENERGIE DU QUEBEC
Past Owners on Record
CHAABAN, MOHAMMED
FORTIN, MARCEL
GUILLEMETTE, ROBERT
HAAS, MICHAEL EDWARD
LANOUE, THOMAS J.
PARADIS, CLAUDE
PINEAULT, JEAN-GUY
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.
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Document
Description 
Date
(yyyy-mm-dd) 
Number of pages   Size of Image (KB) 
Representative Drawing 1999-10-12 1 16
Abstract 1996-10-07 1 13
Cover Page 1996-10-31 1 13
Description 1996-10-07 10 302
Claims 1996-10-07 5 113
Drawings 1996-10-07 4 181
Cover Page 1999-10-12 1 43
Representative Drawing 1998-04-06 1 27
Correspondence 1999-07-22 1 48
Assignment 1995-04-06 10 326
Prosecution-Amendment 1997-04-11 4 160
Fees 1997-04-01 1 69