WO2003069687A1

WO2003069687A1 - Method and mold for encapsulating high temperature superconductor coils

Info

Publication number: WO2003069687A1
Application number: PCT/NZ2003/000020
Authority: WO
Inventors: Donald Pooke
Original assignee: Industrial Research Limited
Priority date: 2002-02-11
Filing date: 2003-02-11
Publication date: 2003-08-21
Also published as: AU2003206472A1

Abstract

A method for encapsulating a superconducting coil (5) includes placing a coil (5) of superconducting wire in a mold (2, 3), evacuating the mold cavity, causing a settable material such as an epoxy to flow into the mold cavity from an inlet (15) to an outlet which are separated by the coil (5) so that the settable material flows around the coil (5) and impregnates between the coil windings to impregnate and encapsulate the coil (5) and flows beyond the coil (5), and subsequently removing the coil (5) from the mold. A mold is also disclosed. The resulting encapsulated coil (5) is rigid, robust and hermetically sealed.

Description

METHOD AND MOLD FOR ENCAPSULATING HIGH TEMPERATURE

SUPERCONDUCTOR COILS

FIELD OF INVENTION

The invention relates to a method for use in encapsulating a superconducting coil with a settable material such as an epoxy material, and a mold for the same, useful to produce encapsulated superconducting coils which are rigid, robust and hermetically sealed, substantially free of porous space into which gases or fluids could penetrate.

BACKGROUND

Superconductors have a broad range of technological applications that are either predicated on their ability to conduct electricity with low electrical energy losses or their ability to carry high electrical current densities, or both. The phenomenon of superconductivity is characterised by the possession of zero, or near zero, electrical resistivity to a continuous DC electrical current. Such a state cannot be indefinitely preserved as the electrical current is increased in magnitude and it is common to refer to the maximum current density as the critical current density which is expressed in units of Amps/cm² and is frequently given the symbol J_c. When the current density, J, exceeds the value of J_c the material becomes dissipative and therefore electrically lossy. The value of J_c depends upon the superconducting material, its microstructure and both temperature and magnetic field strength. One of the most important applications of superconductors is in coils for magnets, motors, generators, fault-current limiters, and transformers. Here the motivation for their use may lie mainly in the very high J_c achievable and as a consequence the high magnetic fields that can be obtained or alternatively the fewer number of windings needed to achieve a given magnetic field. Known, useful superconductors include so called low-temperature superconductors such as niobium-tin or niobium-titanium intermerallic alloys. These have low transition temperatures (below which they become superconducting) and thus have to be cooled to very low temperatures, less than 18K and typically to liquid helium temperatures 4.2K, in order to superconduct usefully. In 1986 a new class of materials known as high temperature superconductors (HTS) was discovered. Many HTS are known to have superconducting transition temperatures, T_c exceeding the temperature at which liquid nitrogen boils, 77 K. Such temperatures are more practical because they can be achieved using single stage cryocoolers or by using liquid nitrogen as a coolant. T_c values of exemplary high temperature superconductors may be of the order of 93 K for example for YBa2Cu3θ7_5, 95K for example for Bi2Sr2CaCu2θg, 109 K for example for

Bi2Sr2Ca2Cu3θι o, 120K for example for TlBa2Ca2Cu3θιo or as high as 134 K for

HgBa2Ca2Cu3θι Q. These HTS materials are generally utilised in wires in the form of flat tapes comprising an HTS oxide core or cores, supported in a metal matrix, most often comprised of silver or a suitable alloy of silver. Other known and potentially useful superconductors include magnesium diboride, MgB₂.

The construction of electrical coils, for magnets, motors, generators, fault-current limiters, and transformers for example, must provide for a robust coil which can withstand the electromagnetic forces arising when a large current is passed through the coil. There should be little or no movement of windings relative to each other. The windings should also be hermetically sealed, free of pore space into which ambient gases or fluids could penetrate either during operation or between operational activity. The penetration of gases such as nitrogen or oxygen can cause contraction and expansion during condensation and boiling and can result in bubbles which on warming subject the coil to stresses and possible fracture.

Japanese patent specifications 7077168 and 2211606 disclose prior methods for impregnating superconductor coils.

SUMMARY OF INVENTION

It is an object of the present invention to provide a method for use in producing superconducting coils which are rigid, robust and hermetically sealed, substantially free of pore space into which gases or fluids could penetrate. In one aspect of the invention there is provided a method for encapsulating a superconducting coil which includes placing a coil of superconducting wire in a mold, evacuating the mold cavity, causing a settable material to flow into the mold cavity from an inlet to an outlet which are separated by the coil so that the settable material flows around the coil and impregnates between the coil windings to impregnate and encapsulate the coil and flows beyond the coil, allowing or causing the settable material set, and subsequently removing the coil from the mold.

In another aspect the invention comprises a method for encapsulating a superconducting coil which includes placing a coil of superconducting wire in a mold, evacuating the mold cavity, causing a settable material to flow into the mold cavity from a part of the mold within the inner diameter of the coil so that the settable material flows from within the coil around the coil to impregnate and encapsulate the coil, or causing the settable material to flow into the mold cavity from beyond the outer diameter of the coil so that the settable material flows from outside of the coil around the coil to within the inner diameter of the coil to encapsulate the coil, allowing or causing the settable material set, and subsequently removing the coil from the mold.

In another aspect the invention comprises a method for encapsulating a superconducting coil which includes placing a coil of superconducting wire in a mold, evacuating the mold cavity, causing a settable material to flow into the mold cavity from a part of the mold on one side or end of the coil so that the settable material flows from one side or end of the coil around the coil to the other side or end of the coil to impregnate and encapsulate the coil, allowing or causing the settable material set, and subsequently removing the coil from the mold.

Preferably the method includes causing the settable material after filling the mold cavity to flow from an outlet from the mold cavity until substantially no entrained gas bubbles are present in the flow of settable material flowing from the mold cavity. Most preferably the method includes causing the settable material to flow into the mold cavity from an inlet or inlets, around the coil and from the mold cavity via a multiple number of outlets, monitoring the flow from each of the outlets, and selectively closing each of the outlets when there are substantially no entrained gas bubbles present in the flow of settable material from that outlet.

Preferably the method includes evacuating the mold cavity so that vacuum or relative vacuum draws the settable material into the mold cavity, and then applying pressure to the settable material in the mold cavity.

Preferably the method includes first winding the coil from superconducting wire and co- winding a strip material between the individual windings which separates the individual windings from one another and which on filling of the mold cavity allows the settable material to permeate between individual windings to form on setting an insulation layer between the individual windings. The strip material is a porous or absorbent paper-like material.

In a further aspect the invention includes a mold for encapsulating superconducting coils of superconducting wire, including mold parts which may be assembled together and which define a primary mold cavity for containing a coil and one or more secondary mold volume(s) which enable settable material flowing into the mold from a part of the mold on one side or end of the coil or from within the inner diameter of the coil or beyond the outer diameter of the coil, to flow around the coil and through the coil windings to fill the smaller secondary mold volume(s) to ensure complete encapsulation of the coil.

In another aspect the invention includes mold for encapsulating superconducting coils of superconducting wire, including mold parts which may be assembled together and which define a primary mold cavity for containing a coil and one or more secondary mold volume(s) which enable settable material flowing into the mold from a part of the mold within the inner diameter of the superconducting coil to flow from within the diameter of the coil around the coil and beyond the outer diameter of the coil to fill the smaller secondary mold volume(s) ensure complete encapsulation, or to flow from beyond the outer diameter of the coil around the coil and to within the inner diameter of the coil to fill the smaller secondary mold volume(s) ensure complete encapsulation, and a port or ports to the interior of the mold which enable(s) evacuation of the mold and filling of the mold with the settable material, and wherein the mold is openable to enable the coil to be separated from the mold after encapsulation.

Preferably the secondary mold volume(s) are provided on one or both ends of the primary mold cavity. A multiple number of secondary mold volume(s) on one or both ends of the mold cavity may be arranged radially relative to the orientation of the coil in the mold cavity. The secondary mold volume(s) include one or more grooves on one or both sides of the primary mold cavity.

Preferably the mold includes associated evacuation means arranged to evacuate the mold and cause the settable material to flow into the mold. Such means may enable monitoring of the flow from each of a number mold outlets and selective closing of each of the outlets when there are substantially no entrained gas bubbles present in the flow of settable material from that outlet.

In a further aspect the invention comprises a superconducting coil produced by the method or with the mold described herein.

The superconducting wire preferably contains, as the active superconductor, a high temperature superconductor such as YBa2Cu3θ7__α ^, ₅ Bi2Sr2CaCu2θg,

Bi2Sr2Ca₂Cu3O₁₀, TlBa₂Ca2Cu3θ₁₀, HgBa2Ca Cu₃O_{10 or} some derivative material as is known in the art, for example Bi_2-xPb_xSr₂Ca Cu₃O₁₀₊d or Bi₂.₁-_xPb_xSr₂Ca Cu₃O₁o₊d. Preferably the wire is in the form of a tape.

BRIEF DESCRIPTION OF THE FIGURES

The invention is further described with reference to the accompanying drawings by way of example and without intending to be limiting, in which:

Figure 1 is an exploded view of a preferred form mold, Figure 2 is a cross-section view of the mold components closed, with a coil in the mold,

Figures 3a-3e are schematic diagrams which illustrate use of the mold to produce a coil by the method of the invention, and

Figure 4 shows a device for slicing paper or other separation or insulation material which is wound between the windings of the HTSC conductor during winding of the coil before impregnation with a suitable material.

DETAILED DESCRIPTION OF PREFERRED FORM

Referring to Figure 1 the preferred form mold comprises two mold parts in the form of base 1 and top 2, which sandwich between them ring 3 and centre part 4. When the mold parts are assembled together a primary cavity is defined within the mold. In use a coil 5 (see Figure 2) wound from superconducting wire is placed between the mold parts which are then assembled together so that the coil is positioned within the cavity, as shown in Figure 2.

The mold may be in any form which defines a primary cavity and one or more secondary mold volumes (as will be described) and which is operable so that the coil can be removed after molding, but the advantage of the preferred form mold structure is that different interchangeable rings 3 and centre parts 4 of different diameter may be used for the encapsulation of coils of different thicknesses. In an alternative form the mold may be intended for encapsulating coils of the same diameter and the ring 3 and centre part 4 or equivalent may be an integral part of the mold base 1 or top 2. In the preferred form the ring 3 may be secured to the base 1 (or top 2) by screws or bolts passing through holes, some of which are indicated at 6. O-ring grooves 8 are provided on either side of the outer periphery of the ring 3 for housing O-rings for sealing between the rings and base 1 and top 2.

A vacuum groove 10 is also provided around the periphery of the ring 3 and slots, some of which are indicated at 11, connect the vacuum groove 10 to the coil space in the primary mold cavity. Vacuum ports 12 in the top part 2 connect to the vacuum ring 10 so that in use when vacuum is connected to the ports 12 the mold will be evacuated.

The centre part 4 is located between the base and top parts 1 and 2 by a bolt 13, which is hermetically sealed to the base and top parts 1 and 2 by glue or o-ring seals, and which also serves limit deflection of the base and top parts during vacuum or overpressure operation. The centre part 4 also includes annular epoxy distribution channel 14, and the outer edge 15 is slightly reduced in dimension relative to the centre portion of the part 4 so that the settable material can flow from the epoxy distribution channel 14 into the mold cavity. An inlet port 15 is provided in the base part (or alternatively the top part or at any other convenient location) from which settable material may flow into the mold.

The arrangement of inlet(s) and outlet(s) is preferably such that the inlet(s) and outlet(s) are separated by the coil so that the settable material such as epoxy flows around the coil and preferably between the coil windings, from inlet to outlet. In a preferred form the inlets and outlets are positioned so that the settable material is caused to flow from a part of the mold within the inner diameter of the coil to beyond the outer diameter of the coil as shown, or vice versa. Alternatively the inlets and outlets may be positioned so that the settable material is caused to flow from one end (the axial end of the coil) of the mold cavity around and through the coil to the other end of the mold cavity and beyond the other end of the coil. Alternatively the inlet(s) and outlet(s) of both may be positioned so that the settlable material is caused to flow from one side of the coil to the other.

The surfaces of the interior mold parts may optionally include a coating of a suitable release agent, such as Teflon™, or alternatively a substance which will act as a release agent may for example be brushed or sprayed onto the interior surfaces of the mold before each use.

The superconducting wire which is most preferably in the form of a tape may be co- wound with a strip material between the individual windings which separates the individual windings from one another. The co-wound material may be an insulation material, or may be another porous or absorbent material which allows the epoxy or other settable material to permeate and impregnate between individual windings to form on setting an insulation layer between the individual windings.

Alternatively the superconducting wire may be coated with an insulating layer before winding into a coil. Optionally such an insulating layer may be porous or textured so that the epoxy or other settable material may permeate or impregnate between individual windings.

Another component may be placed in the mold and partially encapsulated along with the coil to fix the other component to the coil. For example such a component may be a heat sink plate or other heat sink component having a part which is encapsulated with the coil while leaving a major part of the heat sink component unencapsulated.

Where in order to insulate coil turns from each other in the HTSC coil for impregnation, the HTSC conductor is co-wound with insulating material such as Nomex™ or other absorbent paper or material which will preferably absorb the epoxy or other settable material, the paper may be cut into strips by a device as shown in Figure 4. The device comprises an array or adjacent blades 20 sandwiched between spacer plates 21, which are in turn sandwiched between side frames 22 and bolted or screwed together by screws or bolts 23. In use a wider length of the insulation material may be cut into strips by drawing the insulation material through the device under tension, preferably by winding the insulation material off one roll, over the blade array, and rewinding the strips on to a spool or drum on the other side of the device. Th^e sheet may be tensioned and pulled over the blades so as to slit a number of tapes side by side from the sheet. In a preferred form rollers, made from rubber for example, may be placed between the blade assembly and the take-up spool, the rollers carrying out the pulling action. This ensures even tension across the width of insulation material for even cutting.

In use a coil is first wound, preferably with material separating the windings of the coil as described. Preferably the superconducting wire is in the form of a tape. Preferably the insulation is also in the form of a tape co-wound with the superconducting tape or in the form of an insulating coating previously applied to the superconducting wire. The electrical insulation is preferably suited for cryogenic applications and may for example be Nomex™ paper available from Du Pont, and which has been slit to strips using a device similar to that of Figure 4. The wound coil may be tied by looping adhesive insulation tape, for example, radially around the windings. This has the added advantage of providing clearance after assembly between the coil and the inside of the base and top of the mold allowing free flow of the settable material such as epoxy during impregnation and encapsulation.

Referring to Figure 3 the ring 3 is placed on the base 1 of the mold with o-rings in place, and preferably screwed down (Figure 3A); the wound coil is placed on the base inside the ring 3 (Figure 3B); the centre part 4 is placed inside the coil; and the mold top 2 is placed on the assembly and fixed in place. The epoxy port 15 in the base-plate is connected via suitable valve or valves to a reservoir of the settable material such as an epoxy resin, and the vacuum port or ports on the top plate are connected via a suitable valve or valves to a vacuum system and pump (Figure 3C). The mixed epoxy may be introduced to the reservoir and preferably pumped for a period of time to remove dissolved and/or entrained gases or other volatile phases that might otherwise cause bubbling after impregnation. Preferably the mold is evacuated for a period of time then the epoxy introduced so as to flow throughout the interior of the mold and around the coil. Where a porous or absorbent material has been co-wound with the coil windings the epoxy impregnates between the coil windings. The flow may be viewed through an optionally transparent top-plate or through optionally transparent riser tubes 20 (see Figures 3C and 3D) or both. Subsequently after the epoxy has set the mold is opened and the coil removed. The flow of the settable material such as epoxy into the mold may be through the same one or more ports by which the interior of the mold is evacuated. The flow of epoxy from the mould may be via one or more outlets. Alternatively the mold cavity may be evacuated by one or more ports and the flow of epoxy into the mold may be via one or more other separate epoxy inlet ports. Preferably the flow is monitored until there are substantially no entrained gas bubbles present in the flow of settable material from the mold cavity via the epoxy outlets. Where a multiple number of epoxy outlets are provided spaced around the mold cavity, a flow control valve may be associated with each outlet or with groups of outlet, so that individual outlets may be closed off when the flow of epoxy from that part of the mold no longer has any entrained gas bubbles. Thus the flow of epoxy from one or more parts of the mold may occur for longer than from one or more other parts of the mold, so as to minimise the use of the settable material while at the same time ensuring that the flow is continued until there are no entrained gas bubbles in epoxy flowing from any of the mold outlets. Optionally the pressure of the epoxy within the mold may then be raised to or above atmospheric pressure. Before or during impregnation the temperature of the mold may be raised using a heating pad. Subsequently the epoxy is cured for a suitable duration, before disassembly of the mold and removal of the coil. Curing may occur where the epoxy material comprises two reactive components which have been mixed immediately prior to use, through allowing the mold to cool where the settable material is a thermoplastic material which has been heated prior to flowing into the mold, or may be caused to occur or initiated by exposing a UV-settable material within the mold to UV through a UV transparent part of the mold, or by heating a settable material which is heat activated to set, for example.

The mold may be optionally placed on a heating pad to raise the temperature of the complete mold in order to lower the viscosity of the epoxy during impregnation and/or to accelerate the curing of the epoxy.

The grooves or slots 11 in the ring 3 provide a smaller secondary mold volume or "accumulation volume" to help ensure complete impregnation. They lie beyond the coil to be impregnated and provide space for the epoxy to flow to beyond the coil for ensuring complete impregnation of the coil. With such an arrangement it may be sufficient to ensure that there are no entrained gas bubbles within the coil, for there to be no flow outlets from the mold but for the epoxy to flow into the mold and around the coil and to fill these "accumulation volume(s)". This effect can be further enhanced by the addition of vacuum tubes between the top-plate vacuum ports and the vacuum valves. This has the added benefit of applying pressure (relative over pressure) to the epoxy once the system is opened to air. In a preferred form these grooves or slots are shallow so that the resultant "fins" of excess epoxy around the outer diameter of the coil are thin and so can easily be cut from the impregnated coil after disassembly.

The invention is further illustrated by the accompanying examples.

Example 1

A double pancake coil of 345 mm outer diameter and 165mm inner diameter was epoxy impregnated using a mold as shown in Figure 1. The inner diameter of the middle outer annulus or ring 3 was 347 mm. The base-plate 1 was constructed from 16mm thick aluminium plate, the middle-layer outer annulus from 10 mm thick aluminium, the middle-layer central disk 4 from 10 mm thick teflon and the top-plate 2 from 24 mm thick perspex sheet. The inner surfaces of all parts of the mold to be exposed to epoxy were painted with two coats of NUPLEX resin release agent 6RAPVA01.

Each coil was constructed from superconducting wire containing the HTS material of approximate composition Bi_1.75Pb₀.₃₅Sr₂Ca₂Cu₃O₁o₊? . The wire was in the form of a tape with dimensions 4mm width and 300μm thickness (including approximately lOOμm of stainless steel strengthening laminations) and rated with a critical current in excess of 100 Amps. To electrically insulate each successive turn from its adjacent turns the tape was co-wound with Nomex™ Type 410 paper insulation having the same width as the tape. Each coil consisted of approximately 240 turns making for a total length of HTS wire of 400 metres. The double pancake coils were mounted face to face, separated by two sheets of Nomex™ insulation paper, on a copper ring forming the inner diameter of the coil and the coils were secured by four radial loops of adhesive Nomex™ paper strip.

The coils were placed between the middle-layer outer-annulus and the central disk in the partially assembled mold, the top plate bolted in place and the assembly was evacuated at the two vacuum ports. After assembly there was approximately 500μm clearance from the top-plate and the bottom-plate above and below the coil. The epoxy port was connected to an epoxy reservoir via a valve and the epoxy reservoir was filled with a well-mixed charge of resin plus hardener. The epoxy reservoir was pumped for 1 hour to remove volatile phases. The epoxy valve in the bottom plate was then opened along with an air bleed valve into the epoxy reservoir to release the epoxy into the coil space. Once the internal volumes were filled with epoxy the vacuum ports and epoxy inlet port were closed; air was then bled slowly into the vacuum ports. Once the internal pressure returned to approximately 1 atmosphere the charged mold was placed on a hot mat and maintained at 50°C while the epoxy cured.

The resultant "potted" coil, on removal and visual inspection, appeared absolutely free of bubbles, pores or cracks and was rigidly bound into a monolithic unit. Evidently a coil or coils of different thickness and radial dimension could be hermetically potted by simply altering the thickness and radii of the outer annulus and the central disk.

Example 2

A reel of 90 mm wide Nomex tape was cut into 16 strips of 4mm wide tape using an array of 17 scalpel blades each mounted on aluminium spacer blocks assembled in linear array in a frame as shown in Figure 4. The slicing frame was mounted on a drawing platform, such that the passage of the paper over the blades was effected by the rotation of a set of rubber rollers placed just after the slicing frame. The Nomex tape was wound off a first drum sited about 600 mm from the blade array, it passed through the blade array then through the set of rubber rollers and onto a second drum sited about 600 mm on the other side of the array. Tension on the tape could be regulated by controlling the friction on the axle of the first drum; tracking of the paper could be controlled by the adjustment of side to side tension on the rollers thus ensuring uniform and straight strips.

The preferred form mold shown in the drawings is for this generally circular, or ringlike coils but thicker version of molds may be used for forming coils having a larger end to end dimension, and the mold may be suitably shaped for forming a coil which is not circular or ring-like in end-on shape but square, hexagonal, or race track in shape for example, for particular applications.

The foregoing describes the invention including a preferred thereof. Alterations and modifications as will be obvious to those skilled in the art are intended to be incorporated within the scope hereof as defined in the accompanying claims.

Claims

CLAIMS:

1. A method for encapsulating a superconducting coil which includes placing a coil of superconducting wire in a mold, evacuating the mold cavity, causing a settable material to flow into the mold cavity from an inlet to an outlet which are separated by the coil so that the settable material flows around the coil and impregnates between the coil windings to impregnate and encapsulate the coil and flows beyond the coil, allowing or causing the settable material to set, and subsequently removing the coil from the mold.

2. A method for encapsulating a superconducting coil which includes placing a coil of superconducting wire in a mold, evacuating the mold cavity, causing a settable material to flow into the mold cavity from a part of the mold within the inner diameter of the coil so that the settable material flows from within the coil around the coil to impregnate and encapsulate the coil, or causing the settable material to flow into the mold cavity from beyond the outer diameter of the coil so that the settable material flows from outside of the coil around the coil to within the inner diameter of the coil to encapsulate the coil, and allowing or causing the settable material to set, subsequently removing the coil from the mold.

3. A method for encapsulating a superconducting coil which includes placing a coil of superconducting wire in a mold, evacuating the mold cavity, causing a settable material to flow into the mold cavity from a part of the mold on one side or end of the coil so that the settable material flows from one side or end of the coil around the coil to the other side or end of the coil to impregnate and encapsulate the coil, allowing or causing the settable material to set, and subsequently removing the coil from the mold.

4. A method according to any one of claims 1 to 3 including causing the settable material after filling the mold cavity to flow from an outlet from the mold cavity until substantially no entrained gas bubbles are present in the flow of settable material flowing from the mold cavity.

5. A method according to any one of claims 1 to 4 including after filling the mold cavity then applying pressure or increased pressure to the settable material within the mold before allowing the impregnating material to set.

6. A method according to any one of claims 1 to 5 including causing the settable material to flow into the mold cavity from an inlet or inlets, around the coil and from the mold cavity via a multiple number of outlets, monitoring the flow from each of the outlets, and selectively closing each of the outlets when there are substantially no entrained gas bubbles present in the flow of settable material from that outlet.

7. A method according to any one of claims 1 to 6 including evacuating the mold cavity so that vacuum or relative vacuum draws the settable material into the mold cavity, and then applying pressure to the settable material in the mold cavity.

8. A method according to any one of claims 1 to 7 including first winding the coil from superconducting wire and co-winding a strip material between the individual windings which separates the individual windings from one another and which on filling of the mold cavity allows the settable material to permeate between individual windings to form on setting an insulation layer between the individual windings.

9. A method according to claim 8 wherein the strip material is a porous or absorbent paper-like material.

10. A method according to any one of claims 1 to 9 including first winding the coil from superconducting wire and co- winding a strip insulation material between the individual windings of the superconducting wire to insulate the coil windings from one another.

11. A method according to any one of claims 1 to 10 including first forming the strip material by slitting from a larger sheet or roll of material by passing the material over a series of blades spaced transversely across the direction of movement of the material so that the material is slit into one or more strips by the blades.

12. A process according to any one of claims 1 to 11 wherein the superconducting wire is in the form of a tape.

13. A method according to any one of claims 1 to 12 wherein the settable material includes an epoxy resin.

14. A method according to any one of claims 1 to 13 including also placing another component in the mold and fixing the other component to the coil by encapsulating a part of the other component with the coil.

15. A method according to claim 14 wherein the other component is a heat sink component which is attached to the coil by encapsulating a part of the heat sink component in the settable material while leaving a major part of the heat sink component unencapsulated by the settable material.

16. A mold for encapsulating superconducting coils of superconducting wire, including mold parts which may be assembled together and which define a primary mold cavity for containing a coil and one or more secondary mold volume(s) which enable settable material flowing into the mold from a part of the mold on one side or end of the coil or from within the inner diameter of the coil or beyond the outer diameter of the coil, to flow around the coil and through the coil windings to fill the smaller secondary mold volume(s) to encapsulate the coil.

17. A mold for encapsulating superconducting coils of superconducting wire, including mold parts which may be assembled together and which define a primary mold cavity for containing a coil and one or more secondary mold volume(s) which enable settable material flowing into the mold from a part of the mold within the inner diameter of the superconducting coil to flow from within the diameter of the coil around the coil and beyond the outer diameter of the coil to fill the smaller secondary mold volume(s), or to flow from beyond the outer diameter of the coil around the coil and to within the inner diameter of the coil to fill the smaller secondary mold volume(s), and a port or ports to the interior of the mold which enable(s) evacuation of the mold and filling of the mold with the settable material, and wherein the mold is openable to enable the coil to be separated from the mold after encapsulation.

18. A mold according to either one of claims 16 and 17 wherein the secondary mold volume(s) are provided on one or both ends of the primary mold cavity.

19. A mold according to claim 18 wherein a multiple number of secondary mold volume(s) on one or both ends of the mold cavity are arranged radially relative to the orientation of the coil in the mold cavity..

20. A mold according to claim 19 wherein the secondary mold volume(s) include one or more grooves on one or both sides of the primary mold cavity.

21. A mold according to any one of claims 16 to 20 wherein at least a part of the mold is formed from a transparent material enabling observation of a coil during encapsulation of the coil in the mold.

22. A mold according to any one of claims 16 to 20 wherein at least a part of the mold is formed from a UV-transparent material enabling setting or initiating setting of a

UV-settable material.

23. A mold according to any one of claims 16 to 22 including evacuation means arranged to evacuate the mold and cause the settable material to flow into the mold.

24. A mold according to any one of claims 16 and 23 including means enabling monitoring of the flow from each of a number mold outlets and selective closing of each of the outlets when there are substantially no entrained gas bubbles present in the flow of settable material from that outlet.

25. A mold according to any one of claims 16 to 24 together with slitting means for slitting larger sheets or rolls of insulating material into strips for co-winding with the superconducting wire in forming a coil before encapsulation in the mold.

26. A mold according to claim 25 wherein the slitting means comprises a series of spaced blades which will slit the insulation material into parallel strips as the insulation material is passed over the blades.

27. A mold according to claim 26 wherein the slitting means also includes a spool for taking up the strips of insulation material after slitting.

28. A superconducting coil produced by the method of any one of claims 1 to 15.

29. A superconducting coil produced by the mold of any one of claims 16 to 27.