CA1115792A - Direct current transformer - Google Patents
Direct current transformerInfo
- Publication number
- CA1115792A CA1115792A CA319,634A CA319634A CA1115792A CA 1115792 A CA1115792 A CA 1115792A CA 319634 A CA319634 A CA 319634A CA 1115792 A CA1115792 A CA 1115792A
- Authority
- CA
- Canada
- Prior art keywords
- primary
- conductor
- transformer
- primary conductor
- electrical signal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- Containers, Films, And Cooling For Superconductive Devices (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A direct current transformer in which the primary consists of an elongated strip of superconductive material, across the ends of which is applied a direct current potential. Parallel and closely spaced to the primary is positioned a transformer secondary consisting of a thin strip of magnetoresistive material.
A direct current transformer in which the primary consists of an elongated strip of superconductive material, across the ends of which is applied a direct current potential. Parallel and closely spaced to the primary is positioned a transformer secondary consisting of a thin strip of magnetoresistive material.
Description
157~2 This invention relates to direct current transformer, and particularly to a transformer in which the secondary winding is made of a magnetoresistive material.
The D.C. transformer was invented by Giaever in 1965, and in its simplest form, consists of closely spaced, but insulated, thin films of superconductive material, one constituting a primary and the other the secondary of the transformer. Typically, the windings are magnetically biased by an auxiiiary magnet or electromagnet and the assembly placed in liquid helium to lower the temperature to approximately 4 K (-269C), and thus to produce superconductivity in the transformer windings and in the electro-magnet. Superconductive materials are diamagnetic, and thus initially the magnetic field does not penetrate the windings. However, when the flux level present is raised above a critical value, magnetic vortices pass through the primary. Then, by virtue of the application of current to the primary winding, the magnetic vortices are caused to be moved at right angles to the current flow, and thus there is created a moving magnetic field.
Alternatively in the absence of an auxiliary magnet, the vortices result from the primary current itself. The moving magnetic field is coupled to the secondary by virtue of its close proximity, and it thereby produces an output potential across the secondary which is a function of the applied current.
There are several disadvantages with existing D.C. transformers, and these may be summarized as follows:
1. The vortices in the secondary area experience a pinning force which opposes flux motion in the secondary. As a result, transformer action is restricted to rather high values of current and applied magnetic fields. At low currents and fields, the flux motion of the primary is not as effective in causing flux motion in the secondary.
The D.C. transformer was invented by Giaever in 1965, and in its simplest form, consists of closely spaced, but insulated, thin films of superconductive material, one constituting a primary and the other the secondary of the transformer. Typically, the windings are magnetically biased by an auxiiiary magnet or electromagnet and the assembly placed in liquid helium to lower the temperature to approximately 4 K (-269C), and thus to produce superconductivity in the transformer windings and in the electro-magnet. Superconductive materials are diamagnetic, and thus initially the magnetic field does not penetrate the windings. However, when the flux level present is raised above a critical value, magnetic vortices pass through the primary. Then, by virtue of the application of current to the primary winding, the magnetic vortices are caused to be moved at right angles to the current flow, and thus there is created a moving magnetic field.
Alternatively in the absence of an auxiliary magnet, the vortices result from the primary current itself. The moving magnetic field is coupled to the secondary by virtue of its close proximity, and it thereby produces an output potential across the secondary which is a function of the applied current.
There are several disadvantages with existing D.C. transformers, and these may be summarized as follows:
1. The vortices in the secondary area experience a pinning force which opposes flux motion in the secondary. As a result, transformer action is restricted to rather high values of current and applied magnetic fields. At low currents and fields, the flux motion of the primary is not as effective in causing flux motion in the secondary.
2. The superconductive type transformer will not work at temperatures higher than the transition temperature of the secondary~
It is an object of this invention to overcome the aforesaid difficulties and to generally provide an improved D.C. transformer.
MR/ ~
~ ., illS7~
It is also an object of this invention to provide a D.C.
transformer in which the magnetic flux flow in the primary will result in a space modulated flux motion in a magnetoresistive secondary.
A still further object of this invention is to provide a D.C.
transformer in which there is a net flux flow voltage across both the primary and secondary due to space modulated flux motion across them.
In accordance with this invention, the conventional super-conductive secondary of a D.C. transformer is replaced by a secondary of megnetoresistive material. The secondary is best constructed of a thin film sufficiently close to the primary so that it can substantially ex-perience the flux flow in the primary, the primary and secondary being separated by a thin layer of insulating material. While there is no basic restriction on the particular characteristics of the superconductive pri-mary, it has been determined that thin foils of type 1 superconductive material are good choices, one example being a high purity lead. The secondary may be of any material which i9 magnetoresistive at liquid He temperature, approximately 4 K (-269C), and would include Bi, InSb, Al, In~ and Na. -BRIEF DESCRIPTION OF THE DRAWINGS ~ ~
.
Fig. 1 is a plan view of an arrangement of electrical conduc-tors and a supporting structure for the transformer.
Fig. 2 is a sectional view along l~nes 2-2 of Fig. 1.
Fig. 3 is a pictorial view of the overall structure of a transformer contemplated by this invention.
; Referring Initially to Figs. 1 and 2, transformer primary 10 consists of a thin foil of high purity lead which is mounted on bakelite or other insulator substrate 12. In the illustrated example, the length -of the primary would be approximately 1,250 millimeters, the foil would have a width of 2.5 to 5.0 millimeters and would be of a thickness of 0.250 to 2.5 millimeters. Two steps or notches (not shown) may be cut in sub-strate 12 at locations 14 and 16 of the ends of primary foil 18, in which MR/
, 57~2 case the foil would be bent to conform to the steps. Primar)~ terminals 20 and 22 are formed at the ends of the primary foil. Ne~t, metal secondarv terminal strips 24 and 26 are attached on substrate 12, being insulated from primary 10. Next, an insulating film 27 is coated over the primary, leaving the top of the metal primary terminal strips 20 and 22 bare. Ihe thickness of the insulating film would range from 2,000 to 10,000 angstrom units. Finally, a transformer secondary in the form of a thin film of e.g., InSb, is applied on the insulating layer and just over the primary, and having, as shown, slightly less width than the primary, and being centered with respect to the primary. The dimensions of the secondary film would be approximately 2.5 to 4.0 millimeters in width, approximately 10,000 to 50,000 angstrom units in thickness, and of the same length as the primary in this example, 1,250 millimeters.
As shown in Fig. 3, the sandwich consisting of the primary, insuLation, secondary, and substrate may, if desired, be placed in bias electromagnetic coil assembly 30, consisting of coil halves 32 and 34 (powered by the shown leads). Typically, the conductors of the electro- -magnetic assembly would be made of superconductive material. Actual super-conductivity in coils 32 and 34, primary 10 and a high value of magnetore-sistivity in secondary 28 is effected by placing these elements in liquid helium 36 within container 38. Note that the source of the bias magnetic field, if usedt is not critical to this invention. It could consist of a conventional magnet or electromagnet outside of the liquid helium con-tainer.
As thus effected, primary 10 will have been cooled below its superconductive transision temperature, and in such state will be pene-trated by the magnetic flux from coil assembly 30. Typically, the magni-tude of the bias field applied by magnetic coil assembly 30 i6 such that the so-called pinning forces which inhibit flux motion in the primary are ¦
reduced. When current Ip is applied through primary 10, additional flux (so-called self field) is produced in and around the primary. Also due
It is an object of this invention to overcome the aforesaid difficulties and to generally provide an improved D.C. transformer.
MR/ ~
~ ., illS7~
It is also an object of this invention to provide a D.C.
transformer in which the magnetic flux flow in the primary will result in a space modulated flux motion in a magnetoresistive secondary.
A still further object of this invention is to provide a D.C.
transformer in which there is a net flux flow voltage across both the primary and secondary due to space modulated flux motion across them.
In accordance with this invention, the conventional super-conductive secondary of a D.C. transformer is replaced by a secondary of megnetoresistive material. The secondary is best constructed of a thin film sufficiently close to the primary so that it can substantially ex-perience the flux flow in the primary, the primary and secondary being separated by a thin layer of insulating material. While there is no basic restriction on the particular characteristics of the superconductive pri-mary, it has been determined that thin foils of type 1 superconductive material are good choices, one example being a high purity lead. The secondary may be of any material which i9 magnetoresistive at liquid He temperature, approximately 4 K (-269C), and would include Bi, InSb, Al, In~ and Na. -BRIEF DESCRIPTION OF THE DRAWINGS ~ ~
.
Fig. 1 is a plan view of an arrangement of electrical conduc-tors and a supporting structure for the transformer.
Fig. 2 is a sectional view along l~nes 2-2 of Fig. 1.
Fig. 3 is a pictorial view of the overall structure of a transformer contemplated by this invention.
; Referring Initially to Figs. 1 and 2, transformer primary 10 consists of a thin foil of high purity lead which is mounted on bakelite or other insulator substrate 12. In the illustrated example, the length -of the primary would be approximately 1,250 millimeters, the foil would have a width of 2.5 to 5.0 millimeters and would be of a thickness of 0.250 to 2.5 millimeters. Two steps or notches (not shown) may be cut in sub-strate 12 at locations 14 and 16 of the ends of primary foil 18, in which MR/
, 57~2 case the foil would be bent to conform to the steps. Primar)~ terminals 20 and 22 are formed at the ends of the primary foil. Ne~t, metal secondarv terminal strips 24 and 26 are attached on substrate 12, being insulated from primary 10. Next, an insulating film 27 is coated over the primary, leaving the top of the metal primary terminal strips 20 and 22 bare. Ihe thickness of the insulating film would range from 2,000 to 10,000 angstrom units. Finally, a transformer secondary in the form of a thin film of e.g., InSb, is applied on the insulating layer and just over the primary, and having, as shown, slightly less width than the primary, and being centered with respect to the primary. The dimensions of the secondary film would be approximately 2.5 to 4.0 millimeters in width, approximately 10,000 to 50,000 angstrom units in thickness, and of the same length as the primary in this example, 1,250 millimeters.
As shown in Fig. 3, the sandwich consisting of the primary, insuLation, secondary, and substrate may, if desired, be placed in bias electromagnetic coil assembly 30, consisting of coil halves 32 and 34 (powered by the shown leads). Typically, the conductors of the electro- -magnetic assembly would be made of superconductive material. Actual super-conductivity in coils 32 and 34, primary 10 and a high value of magnetore-sistivity in secondary 28 is effected by placing these elements in liquid helium 36 within container 38. Note that the source of the bias magnetic field, if usedt is not critical to this invention. It could consist of a conventional magnet or electromagnet outside of the liquid helium con-tainer.
As thus effected, primary 10 will have been cooled below its superconductive transision temperature, and in such state will be pene-trated by the magnetic flux from coil assembly 30. Typically, the magni-tude of the bias field applied by magnetic coil assembly 30 i6 such that the so-called pinning forces which inhibit flux motion in the primary are ¦
reduced. When current Ip is applied through primary 10, additional flux (so-called self field) is produced in and around the primary. Also due
- 3 - !:
MR/
-1~5792 to the current I , a force on the total flux in the primary is generated.
When this force exeeds the pinning force, there occurs 2 moving field as described above in accordance with known principles of D.C. transformer effect. In some applications, the applied bias field may be omitted and a force above the pinning force achieved simply by transport direct current Ip through primary winding 10.
In accordance with this invention, the moving field achieved in the primary is coupled to the secondary which, although not a superconductive material, but a magnetoresistive material, responds by the generation of a potentiai across it Vs. To effect different ratios of the voltage transformation, known techniques of adjusting turns ratios and coupling may be employed.
As discussed above, thin films of any type of superconductive material may be used for the primary. Materials with higher critical fields are the most suited. Thus, in addition to Pb, one may also use Sn or In foils for the primary. Similarly, any material which is magnetoresistive at liquid helium temperature in thin film (foil) form may be used for the secondary. Other materials for the secondary may be Bi, InAs, Al, In, Ag, etc.
The basic purpose of this invention is to extend the operation of the D.C. transformer to a new class of materials which leads to several advantages as follows: ;
1. Unlike the earlier conventional D.C. transformer, there is no critical "transition" temperature of the secondary in the new trans- r' former above which the transformer will not work. Thus, the new transformer will function at all temperatures below the superconductive transition temperature of the primary.
2. The secondary material in the new transformer has no vor-tex structure and hence no associated pinning of vortices in it, the principal problem of using superconductive secondaries. In other words, the force which opposes flux motion across the secondary is much reduced in the new transformer. This is in strong contrast to the situation with MR/
I
., ~ , .
~115792 superconductive secondaries wherein the driving force provided by the moving flux pattern in the primary had to exceed the pinning force on the vortices in the secondary for flux motion to occur across it. Such a problem does not exist in the new transformer.
3. Eddy current losses in the regions where flux changes occur during flux motion in the magnetoresistive secondary are much reduced in the new transformer from similar losses in previous supercon-ductive D.C. transformers. Thus this enables a higher efficiency to be -achieved. -having thus discloDed oor invention, what is claimed is: -''' ''' ''.''' '`
., , ;~ .',' :, .
r ,, .
'"', .
MR/
. .
: . ., : ~ . ,
MR/
-1~5792 to the current I , a force on the total flux in the primary is generated.
When this force exeeds the pinning force, there occurs 2 moving field as described above in accordance with known principles of D.C. transformer effect. In some applications, the applied bias field may be omitted and a force above the pinning force achieved simply by transport direct current Ip through primary winding 10.
In accordance with this invention, the moving field achieved in the primary is coupled to the secondary which, although not a superconductive material, but a magnetoresistive material, responds by the generation of a potentiai across it Vs. To effect different ratios of the voltage transformation, known techniques of adjusting turns ratios and coupling may be employed.
As discussed above, thin films of any type of superconductive material may be used for the primary. Materials with higher critical fields are the most suited. Thus, in addition to Pb, one may also use Sn or In foils for the primary. Similarly, any material which is magnetoresistive at liquid helium temperature in thin film (foil) form may be used for the secondary. Other materials for the secondary may be Bi, InAs, Al, In, Ag, etc.
The basic purpose of this invention is to extend the operation of the D.C. transformer to a new class of materials which leads to several advantages as follows: ;
1. Unlike the earlier conventional D.C. transformer, there is no critical "transition" temperature of the secondary in the new trans- r' former above which the transformer will not work. Thus, the new transformer will function at all temperatures below the superconductive transition temperature of the primary.
2. The secondary material in the new transformer has no vor-tex structure and hence no associated pinning of vortices in it, the principal problem of using superconductive secondaries. In other words, the force which opposes flux motion across the secondary is much reduced in the new transformer. This is in strong contrast to the situation with MR/
I
., ~ , .
~115792 superconductive secondaries wherein the driving force provided by the moving flux pattern in the primary had to exceed the pinning force on the vortices in the secondary for flux motion to occur across it. Such a problem does not exist in the new transformer.
3. Eddy current losses in the regions where flux changes occur during flux motion in the magnetoresistive secondary are much reduced in the new transformer from similar losses in previous supercon-ductive D.C. transformers. Thus this enables a higher efficiency to be -achieved. -having thus discloDed oor invention, what is claimed is: -''' ''' ''.''' '`
., , ;~ .',' :, .
r ,, .
'"', .
MR/
. .
: . ., : ~ . ,
Claims (2)
IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A direct current transformer having input terminals adapted to be connected to a source of D.C. electrical signal, Ip , said transformer comprising:
a primary conductor of a superconductive material, said primary conductor having a pair of opposite ends forming transformer input terminals;
a secondary conductor of a magneto-resistive material, said secondary conductor being positioned closely adjacent to, but electrically insulated from, said primary conductor, and having a pair of unbiased end terminals; and environmental means for applying a low temperature to said primary and secondary conductors, said temperature being no higher than the superconducting transition temperature of said primary conductor;
the material of said primary conductor and level of said D.C. electrical signal Ip being such that said primary conductor is super-conductive in the presence of said electrical signal Ip , and that said electrical signal Ip rises at least to a critical level for said super-conductive material, such that a direct magnetic fiekd is induced and moving vortices are created in said primary conductor and a D.C. potential Vp appears across said input terminals of said primary conductors;
whereby a D.C. potential Vs appears across said terminals of said secondary conductor responsive to the application of said D.C.
signal Ip across said input terminals of said primary conductor.
a primary conductor of a superconductive material, said primary conductor having a pair of opposite ends forming transformer input terminals;
a secondary conductor of a magneto-resistive material, said secondary conductor being positioned closely adjacent to, but electrically insulated from, said primary conductor, and having a pair of unbiased end terminals; and environmental means for applying a low temperature to said primary and secondary conductors, said temperature being no higher than the superconducting transition temperature of said primary conductor;
the material of said primary conductor and level of said D.C. electrical signal Ip being such that said primary conductor is super-conductive in the presence of said electrical signal Ip , and that said electrical signal Ip rises at least to a critical level for said super-conductive material, such that a direct magnetic fiekd is induced and moving vortices are created in said primary conductor and a D.C. potential Vp appears across said input terminals of said primary conductors;
whereby a D.C. potential Vs appears across said terminals of said secondary conductor responsive to the application of said D.C.
signal Ip across said input terminals of said primary conductor.
2. A direct current transformer as set forth in claim 1 further comprising bias means for applying a second magnetic field to said primary and secondary conductors, whereby together the applied magnetic fields pro-duce a magnetic field which penetrates said primary and secondary conductors, and said magnetic field do not exceed a value which would render said primary non-superconductive.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA319,634A CA1115792A (en) | 1979-01-15 | 1979-01-15 | Direct current transformer |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA319,634A CA1115792A (en) | 1979-01-15 | 1979-01-15 | Direct current transformer |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1115792A true CA1115792A (en) | 1982-01-05 |
Family
ID=4113327
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA319,634A Expired CA1115792A (en) | 1979-01-15 | 1979-01-15 | Direct current transformer |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1115792A (en) |
-
1979
- 1979-01-15 CA CA319,634A patent/CA1115792A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |