Title of Invention	CRYOGEN FREE SUPERCONDUCTING TRANSFORMER
Abstract	A superconducting transformer (1) comprising a core coil assembly (2) comprising superconducting material windings (3) mounted over a magnetic material core (5). The core coil assembly is located in an inner housing (6) of thermal conductor material. The inner housing is located in an outer housing (7) of galvanised fibre reinforced plastic in spaced apart relationship. The space within the inner housing and the space between the inner housing and the outer housing is evacuated and the space between the inner housing and the outer housing is insulated with thermal insulation material (8). The transformer further comprises at least one cryocooler (9) for cooling the core coil assembly at subzero temperatures (Fig 1).

Title of Invention

CRYOGEN FREE SUPERCONDUCTING TRANSFORMER

Abstract

A superconducting transformer (1) comprising a core coil assembly (2) comprising superconducting material windings (3) mounted over a magnetic material core (5). The core coil assembly is located in an inner housing (6) of thermal conductor material. The inner housing is located in an outer housing (7) of galvanised fibre reinforced plastic in spaced apart relationship. The space within the inner housing and the space between the inner housing and the outer housing is evacuated and the space between the inner housing and the outer housing is insulated with thermal insulation material (8). The transformer further comprises at least one cryocooler (9) for cooling the core coil assembly at subzero temperatures (Fig 1).

Full Text	FORM 2 THE PATENTS ACT, 1970 (39 of 1970) As amended by the Patents (Amendment) Act 2005 & The Patents Rules, 2003 As amended by the Patents (Amendment) Rules 2006 COMPLETE SPECIFICATION (See section 10 and rule 13) TITLE OF THE INVENTION Cryogen free superconducting transformer APPLICANTS Indian Institute of Technology, Bombay, an autonomous research and educational institution established in India by a specia Act of Parliament of the Republic of India under the Institutes of Technology Act 1961, Powai Mumbai 400076, Maharashtra, India INVENTOR Atrey Milind Diwakar, Indian Institute of Technology Bombay Department of Mechanical Engineering, Powai, Mumbai 400076, Maharashtra, India, an Indian national PREAMBLE TO THE DESCRIPTION The following specification particularly describes the narure of this invention and the manner in which it is to be performed: FIELD OF THE INVENTION This invention relates to a cryogen free superconducting transformer. BACKGROUND OF THE INVENTION Transformers are conventionally oil filled transformers and dry transformers. Oil filled transformers are bulky and heavy and require protective metallic tanks. They also require periodic maintenance and oil replacement. Oil is expensive, environmentally polluting and capable of causing health hazards and fire accidents. Dry transformers are of reduced size and weight as compared to oil filled transformers. Dry transformers are easy to maintain and are preferred for outdoor applications because of their advantages like resistance to ultra-violet rays and moisture, flame proof nature or insulation characteristics. Dry transformers are preferred in hazardous areas such as mines, densely populated residential areas or hospitals. However, both the conventional transformers comprise copper conductors and suffer from copper losses. They also cannot operate at high temperatures and are of low efficiency. Attempts are being made to replace the conventional transformers by superconducting transformers as the superconducting transformers have a variety of potential advantages over the conventional transformers like compactness, high efficiency, fire safety or over load operation. They use superconducting material windings instead of copper conductors and cryogen like liquid nitrogen to maintain the superconducting windings cooled. However, superconducting transformers require cryostats to store the cryogenic liquid. Besides it is necessary periodically to replenish losses in the cryogenic liquid due to evaporation. This makes it difficult and expensive to maintain the transformer. Also cryogenic liquid cannot be cooled below 2 the freezing temperature thereof ie below 63.2 k in the case of liquid nitrogen as the cryogenic liquid solidifies below the freezing temperature. The efficiency of the superconducting transformer thus depends on the freezing temperature of the cryogenic liquid. OBJECTS OF THE INVENTION An object of the invention is to provide a cryogen free superconducting transformer which eliminates cryogen and disadvantages associated with cryogen. Another object of the invention is to provide a cryogen free superconducting transformer which has high efficiency and which is compact, economical and easy to maintain. Another object of the invention is to provide a cryogen free superconducting transformer which has fire safety and overload operation. Another object of the invention is to provide a cryogen free superconducting transformer which eliminates copper conductors and copper losses. DETAILED DESCRIPTION OF THE INVENTION According to the invention there is provided a superconducting transformer comprising a core coil assembly comprising superconducting material windings mounted over a magnetic material core, the core coil assembly being located in an inner housing of thermal conductor material, the inner housing being located in an outer housing of galvanised fibre reinforced plastic in spaced apart relationship, the 3 space within the inner housing and the space between the inner housing and the outer housing being evacuated and the space between the inner housing and the outer housing being insulated with thermal insulation material, the transformer further comprising at least one cryocooler for cooling the core coil assembly at subzero temperatures. The following is a detailed description of the invention with reference to the accompanying drawings, in which : Fig 1 is a schematic crosssectional view of a superconducting transformer according to an embodiment of the invention; Fig 2 is a schematic crosssectional view of a superconducting transformer according to another embodiment of the invention; Fig 3 is a schematic crosssectional view of a superconducting transformer according to another embodiment of the invention; Fig 4 is a schematic crosssectional view of a superconducting transformer according to another embodiment of the invention; and Fig 5 is a schematic crosssectional view of a superconducting transformer according to another embodiment of the invention. 4 The superconducting transformer 1 as illustrated in Fig 1 of the accompanying drawings comprises a core coil assembly 2 comprising superconducting material windings 3 mounted over a magnetic material core 5. The core coil assembly is located in an inner housing 6 of thermal conductor material. The inner housing is located in an outer housing 7 of galvanised fibre reinforced plastic in spaced apart relationship. The space within the inner housing and the space between the inner housing and outer housing is evacuated. The space between the inner housing and outer housing is insulated with thermal insulation material 8. The transformer further comprises a two stage cryocooler 9, the first stage 9a of which is in contact with the inner housing and the second stage 9b of which is connected to the windings through flexible conductor materia) braids 10 The leads of the windings is marked 11. The inner housing is preferably made of copper but can also be made of any other conductor material. The flexible braids are preferably made of copper but can also be made of other conductor materials. The first stage of the cryocooler keeps the inner housing cooled from outside. The second stage of the Cryocooler keeps the windings cooled through the flexible braids of the transformer. The leads are also kept cooled by the cooling effect of the cryocooler. Because of the insulation material in the space between the inner housing and the outer housing, conduction and radiation of heat into the transformer from the atmosphere outside the transformer via the outer housing is practically eliminated. Evacuation of the space within the inner housing and the space between the inner housing and the outer housing also prevents external heat from the atmosphere being transmitted into the transformer by convection. Because of the outer housing being made of galvanized, fibre reinforced plastic, eddy current losses are also prevented. The outer housing aJso can be made of any other material which prevents eddy current losses. The superconducting transformer 12 as 5 illustrated in Fig 2 of the accompanying drawings comprises two cryocoolers 13 and 14. Cryocooler 13 is a single stage cooler in contact with the inner housing. Cryocooler 14 is a two stage cryocooler, the first stage 14a of which is in contact with the inner housing and the second stage 14b of which is connected to the windings through flexible conductor material braids 10. The superconducting transformer 15 as illustrated in Fig 3 of the accompanying drawings comprises two two stage cryocoolers 16 and 17, the first stages 16a and 17a of which are in contact with the inner housing and the second stages 16b and 17b of which are connected to the windings through flexible conductor material braids 10. The superconducting transformer 18 as illustrated in Fig 4 of the accompanying drawings comprises two single stage cryocoolers 19 and 20. Cryocooler 19 is in contact with the inner housing and cryocooler 20 is connected to the windings through flexible conductor material braids 10. The superconducting transformer 21 as illustrated in Fig 5 of the accompanying drawings comprises a two stage cryocooler 22. the first stage 22a of which is in contact with the inner housing and the second stage 22b of which is connected to the windings through a heat pipe 23. According to the invention cryogen has been eliminated and instead the transformer is kept cooled at subzero temperatures with one or more cryocoolers. As the cryogen has been eliminated there is no need for replacement of the cryogen periodically. There is also no constraint that the subcooling should not be below the freezing temperature of the cryogen. Therefore, the transformer can be cooled at very low subzero temperatures so as to improve the efficiency of the transformer. Heat transfer from outside the transformer into the transformer by conduction, convection and radiation is prevented because of the thermal insulation between the inner and outer housings and the vacuum in the housings. Loss of the cooling effect from within the 6 transformer to the atmosphere outside the transformei- is also prevented because of the thermal insulation and vacuum. Further the inner housing is kept cooled from outside and eddy current losses are reduced. Also the leads of the windings are also kept cooled. All this further improves the efficiency of the transformer. Also the transformer is economical and easy to maintain. Fire safety and overload operation of the transformer are also improved. As the transformer eliminates copper conductors, copper losses are avoided. Instead of flexible braids or heat pipes other cooling effect transmission means can be used to transmit the cooling effect from the cryocooler to the windings. There can be more than two cryocoolers. Besides, superconducting transformers, the invention also encompasses other superconducting electric power devices Jike superconducting motors,, magnets or fault current Jimilers as such other superconducting electric power devices also can be configured and cooled in a similar manner. Such variations of the invention are obvious to those skilled in the art and are to be construed and understood to be within the scope of the invention. 7 We claim: 1) A superconducting transformer comprising a core coil assembly comprising superconducting material windings mounted over a magnetic material core, the core coil assembly being located in an inner housing of thermal conductor material, the inner housing being located in an outer housing of galvanised fibre reinforced plastic in spaced apart relationship, the space within the inner housing and the space between the inner housing and the outer housing being evacuated and the space between the inner housing and the outer housing being insulated with thermal insulation material, the transformer further comprising at least one cryocooler for cooling the core coil assembly at subzero tempeiatoes. 2) The superconducting transformer as claimed in claim 1, wherein the inner housing is made of copper. 3) The superconducting transformer as claimed in claim 2, which comprises one cryocooler which is a two stage cryocooler, the first stage of the cryocooler being in contact with the inner housing and the second stage of the cryocooler being connected to the windings through flexible conductor material braids. 4) The superconducting transformer as claimed in claim 2, which comprises two cryocoolers, one of which is a single stage ciyocooler in contact with the inner housing and the other of which is a two stage cryocooler, the first stage of the two stage cryocooler being in contact with the inner housing and the second stage of the 8 two stage cryocooler being connected to the windings through flexible conductor material braids. 5) The superconducting transformer as claimed in claim 2, which comprises two two stage cryocoolers, the first stages of the two cryocoolers being in contact with the inner housing and the second stages of the two cryocoolers being connected to the windings through flexible conductor material braids. 6) The superconducting transformer as claimed in claim 2, which comprises two single stage cryocoolers, one of which is in contact with the inner housing and the other of which is connected to the windings through flexible conductor materia] braids. 7) The superconducting transformer as claimed in anyone of claims 3 to 6, wherein the flexible braids are made of copper. 8) The superconducting transformer as claimed in claim 2, which comprises a two stage cryocooler, the first stage of which is in contact with the inner housing and the second stage of which is connected to the windings through a heat pipe. (Jose M A) of Khaitan & Co Agent for the Applicants Dated this 4th day of July 2008 9

Full Text

FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
As amended by the Patents (Amendment) Act 2005
& The Patents Rules, 2003
As amended by the Patents (Amendment) Rules 2006
COMPLETE SPECIFICATION (See section 10 and rule 13)
TITLE OF THE INVENTION
Cryogen free superconducting transformer
APPLICANTS
Indian Institute of Technology, Bombay, an autonomous research and educational institution established in India by a specia Act of Parliament of the Republic of India under the Institutes of Technology Act 1961, Powai Mumbai 400076, Maharashtra, India
INVENTOR
Atrey Milind Diwakar, Indian Institute of Technology Bombay Department of Mechanical Engineering, Powai, Mumbai 400076, Maharashtra, India, an Indian national
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the narure of this invention and the manner in which it is to be performed:

FIELD OF THE INVENTION
This invention relates to a cryogen free superconducting transformer.
BACKGROUND OF THE INVENTION
Transformers are conventionally oil filled transformers and dry transformers. Oil filled transformers are bulky and heavy and require protective metallic tanks. They also require periodic maintenance and oil replacement. Oil is expensive, environmentally polluting and capable of causing health hazards and fire accidents. Dry transformers are of reduced size and weight as compared to oil filled transformers. Dry transformers are easy to maintain and are preferred for outdoor applications because of their advantages like resistance to ultra-violet rays and moisture, flame proof nature or insulation characteristics. Dry transformers are preferred in hazardous areas such as mines, densely populated residential areas or hospitals. However, both the conventional transformers comprise copper conductors and suffer from copper losses. They also cannot operate at high temperatures and are of low efficiency. Attempts are being made to replace the conventional transformers by superconducting transformers as the superconducting transformers have a variety of potential advantages over the conventional transformers like compactness, high efficiency, fire safety or over load operation. They use superconducting material windings instead of copper conductors and cryogen like liquid nitrogen to maintain the superconducting windings cooled. However, superconducting transformers require cryostats to store the cryogenic liquid. Besides it is necessary periodically to replenish losses in the cryogenic liquid due to evaporation. This makes it difficult and expensive to maintain the transformer. Also cryogenic liquid cannot be cooled below
2

the freezing temperature thereof ie below 63.2 k in the case of liquid nitrogen as the cryogenic liquid solidifies below the freezing temperature. The efficiency of the superconducting transformer thus depends on the freezing temperature of the cryogenic liquid.
OBJECTS OF THE INVENTION
An object of the invention is to provide a cryogen free superconducting transformer
which eliminates cryogen and disadvantages associated with cryogen.
Another object of the invention is to provide a cryogen free superconducting transformer which has high efficiency and which is compact, economical and easy to maintain.
Another object of the invention is to provide a cryogen free superconducting transformer which has fire safety and overload operation.
Another object of the invention is to provide a cryogen free superconducting transformer which eliminates copper conductors and copper losses.
DETAILED DESCRIPTION OF THE INVENTION
According to the invention there is provided a superconducting transformer comprising a core coil assembly comprising superconducting material windings mounted over a magnetic material core, the core coil assembly being located in an inner housing of thermal conductor material, the inner housing being located in an outer housing of galvanised fibre reinforced plastic in spaced apart relationship, the
3

space within the inner housing and the space between the inner housing and the outer housing being evacuated and the space between the inner housing and the outer housing being insulated with thermal insulation material, the transformer further comprising at least one cryocooler for cooling the core coil assembly at subzero temperatures.
The following is a detailed description of the invention with reference to the accompanying drawings, in which :
Fig 1 is a schematic crosssectional view of a superconducting transformer according to an embodiment of the invention;
Fig 2 is a schematic crosssectional view of a superconducting transformer according to another embodiment of the invention;
Fig 3 is a schematic crosssectional view of a superconducting transformer according to another embodiment of the invention;
Fig 4 is a schematic crosssectional view of a superconducting transformer according to another embodiment of the invention; and
Fig 5 is a schematic crosssectional view of a superconducting transformer according to another embodiment of the invention.
4

The superconducting transformer 1 as illustrated in Fig 1 of the accompanying drawings comprises a core coil assembly 2 comprising superconducting material windings 3 mounted over a magnetic material core 5. The core coil assembly is located in an inner housing 6 of thermal conductor material. The inner housing is located in an outer housing 7 of galvanised fibre reinforced plastic in spaced apart relationship. The space within the inner housing and the space between the inner housing and outer housing is evacuated. The space between the inner housing and outer housing is insulated with thermal insulation material 8. The transformer further comprises a two stage cryocooler 9, the first stage 9a of which is in contact with the inner housing and the second stage 9b of which is connected to the windings through flexible conductor materia) braids 10 The leads of the windings is marked 11. The inner housing is preferably made of copper but can also be made of any other conductor material. The flexible braids are preferably made of copper but can also be made of other conductor materials. The first stage of the cryocooler keeps the inner housing cooled from outside. The second stage of the Cryocooler keeps the windings cooled through the flexible braids of the transformer. The leads are also kept cooled by the cooling effect of the cryocooler. Because of the insulation material in the space between the inner housing and the outer housing, conduction and radiation of heat into the transformer from the atmosphere outside the transformer via the outer housing is practically eliminated. Evacuation of the space within the inner housing and the space between the inner housing and the outer housing also prevents external heat from the atmosphere being transmitted into the transformer by convection. Because of the outer housing being made of galvanized, fibre reinforced plastic, eddy current losses are also prevented. The outer housing aJso can be made of any other material which prevents eddy current losses. The superconducting transformer 12 as
5

illustrated in Fig 2 of the accompanying drawings comprises two cryocoolers 13 and 14. Cryocooler 13 is a single stage cooler in contact with the inner housing. Cryocooler 14 is a two stage cryocooler, the first stage 14a of which is in contact with the inner housing and the second stage 14b of which is connected to the windings through flexible conductor material braids 10. The superconducting transformer 15 as illustrated in Fig 3 of the accompanying drawings comprises two two stage cryocoolers 16 and 17, the first stages 16a and 17a of which are in contact with the inner housing and the second stages 16b and 17b of which are connected to the windings through flexible conductor material braids 10. The superconducting transformer 18 as illustrated in Fig 4 of the accompanying drawings comprises two single stage cryocoolers 19 and 20. Cryocooler 19 is in contact with the inner housing and cryocooler 20 is connected to the windings through flexible conductor material braids 10. The superconducting transformer 21 as illustrated in Fig 5 of the accompanying drawings comprises a two stage cryocooler 22. the first stage 22a of which is in contact with the inner housing and the second stage 22b of which is connected to the windings through a heat pipe 23.
According to the invention cryogen has been eliminated and instead the transformer is kept cooled at subzero temperatures with one or more cryocoolers. As the cryogen has been eliminated there is no need for replacement of the cryogen periodically. There is also no constraint that the subcooling should not be below the freezing temperature of the cryogen. Therefore, the transformer can be cooled at very low subzero temperatures so as to improve the efficiency of the transformer. Heat transfer from outside the transformer into the transformer by conduction, convection and radiation is prevented because of the thermal insulation between the inner and outer housings and the vacuum in the housings. Loss of the cooling effect from within the
6

transformer to the atmosphere outside the transformei- is also prevented because of the thermal insulation and vacuum. Further the inner housing is kept cooled from outside and eddy current losses are reduced. Also the leads of the windings are also kept cooled. All this further improves the efficiency of the transformer. Also the transformer is economical and easy to maintain. Fire safety and overload operation of the transformer are also improved. As the transformer eliminates copper conductors, copper losses are avoided. Instead of flexible braids or heat pipes other cooling effect transmission means can be used to transmit the cooling effect from the cryocooler to the windings. There can be more than two cryocoolers. Besides, superconducting transformers, the invention also encompasses other superconducting electric power devices Jike superconducting motors,, magnets or fault current Jimilers as such other superconducting electric power devices also can be configured and cooled in a similar manner. Such variations of the invention are obvious to those skilled in the art and are to be construed and understood to be within the scope of the invention.
7

We claim:
1) A superconducting transformer comprising a core coil assembly comprising superconducting material windings mounted over a magnetic material core, the core coil assembly being located in an inner housing of thermal conductor material, the inner housing being located in an outer housing of galvanised fibre reinforced plastic in spaced apart relationship, the space within the inner housing and the space between the inner housing and the outer housing being evacuated and the space between the inner housing and the outer housing being insulated with thermal insulation material, the transformer further comprising at least one cryocooler for cooling the core coil assembly at subzero tempeiatoes.
2) The superconducting transformer as claimed in claim 1, wherein the inner housing is made of copper.
3) The superconducting transformer as claimed in claim 2, which comprises one cryocooler which is a two stage cryocooler, the first stage of the cryocooler being in contact with the inner housing and the second stage of the cryocooler being connected to the windings through flexible conductor material braids.
4) The superconducting transformer as claimed in claim 2, which comprises two cryocoolers, one of which is a single stage ciyocooler in contact with the inner housing and the other of which is a two stage cryocooler, the first stage of the two stage cryocooler being in contact with the inner housing and the second stage of the
8

two stage cryocooler being connected to the windings through flexible conductor material braids.
5) The superconducting transformer as claimed in claim 2, which comprises two two stage cryocoolers, the first stages of the two cryocoolers being in contact with the inner housing and the second stages of the two cryocoolers being connected to the windings through flexible conductor material braids.
6) The superconducting transformer as claimed in claim 2, which comprises two single stage cryocoolers, one of which is in contact with the inner housing and the other of which is connected to the windings through flexible conductor materia] braids.
7) The superconducting transformer as claimed in anyone of claims 3 to 6, wherein the flexible braids are made of copper.
8) The superconducting transformer as claimed in claim 2, which comprises a two stage cryocooler, the first stage of which is in contact with the inner housing and the second stage of which is connected to the windings through a heat pipe.

(Jose M A)
of Khaitan & Co
Agent for the Applicants
Dated this 4th day of July 2008
9

Documents:

1401-MUM-2008-ABSTRACT(26-9-2013).pdf

1401-MUM-2008-ABSTRACT(27-2-2015).pdf

1401-mum-2008-abstract.doc

1401-mum-2008-abstract.pdf

1401-MUM-2008-CLAIMS(AMENDED)-(26-9-2013).pdf

1401-MUM-2008-CLAIMS(AMENDED)-(27-2-2015).pdf

1401-MUM-2008-CLAIMS(AMENDED)-(5-8-2014).pdf

1401-MUM-2008-CLAIMS(MARKED COPY)-(5-8-2014).pdf

1401-mum-2008-claims.doc

1401-mum-2008-claims.pdf

1401-MUM-2008-CORRESPONDENCE(01-04-2014).pdf

1401-MUM-2008-CORRESPONDENCE(1-9-2008).pdf

1401-MUM-2008-CORRESPONDENCE(11-9-2014).pdf

1401-MUM-2008-CORRESPONDENCE(17-6-2014).pdf

1401-MUM-2008-CORRESPONDENCE(21-11-2011).pdf

1401-mum-2008-correspondence.pdf

1401-mum-2008-description(complete).doc

1401-mum-2008-description(complete).pdf

1401-MUM-2008-DRAWING(27-2-2015).pdf

1401-MUM-2008-DRAWING(4-7-2008).pdf

1401-MUM-2008-DRAWING(5-8-2014).pdf

1401-mum-2008-drawing.pdf

1401-MUM-2008-FORM 1(1-9-2008).pdf

1401-MUM-2008-FORM 1(21-11-2011).pdf

1401-MUM-2008-FORM 1(21-11-2011).tif

1401-mum-2008-form 1.pdf

1401-MUM-2008-FORM 18(1-9-2008).pdf

1401-MUM-2008-FORM 2(TITLE PAGE)-(26-9-2013).pdf

1401-MUM-2008-FORM 2(TITLE PAGE)-(27-2-2015).pdf

1401-mum-2008-form 2(title page).pdf

1401-mum-2008-form 2.doc

1401-mum-2008-form 2.pdf

1401-MUM-2008-FORM 26(1-9-2008).pdf

1401-MUM-2008-FORM 3(27-2-2015).pdf

1401-MUM-2008-FORM 3(5-8-2014).pdf

1401-mum-2008-form 3.pdf

1401-MUM-2008-FORM 8(1-9-2008).pdf

1401-MUM-2008-MARKED COPY(26-9-2013).pdf

1401-MUM-2008-MARKED COPY(27-2-2015).pdf

1401-MUM-2008-OTHER DOCUMENT(27-2-2015).pdf

1401-MUM-2008-REPLY TO EXAMINATION REPORT(26-9-2013).pdf

1401-MUM-2008-REPLY TO HEARING(27-2-2015).pdf

1401-MUM-2008-REPLY TO HEARING(5-8-2014).pdf

1401-MUM-2008-SPECIFICATION(AMENDED)-(26-9-2013).pdf

1401-MUM-2008-SPECIFICATION(AMENDED)-(27-2-2015).pdf

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Patent Number

265712

Indian Patent Application Number

1401/MUM/2008

PG Journal Number

11/2015

Publication Date

13-Mar-2015

Grant Date

10-Mar-2015

Date of Filing

04-Jul-2008

Name of Patentee

INDIAN INSTITUTE OF TECHNOLOGY, BOMBAY

Applicant Address

POWAI,MUMBAI

Inventors:

#	Inventor's Name	Inventor's Address
1	ATREY MILIND DIWAKAR	INDIAN INSTITUTE OF TECHNOLOGY, BOMBAY, DEPARTMENT OF MECHANICAL ENGINEERING, POWAI, MUMBAI-400076,MAHARASHTRA, INDIA.

PCT International Classification Number

H01F27/24; H01F36/00; H01F6/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA