Mechanically switched superconducting flux pump

Abstract

The invention relates to a device for inducing current in a load, also referred to as a flux pump. The apparatus may include: a rotor including at least one magnetic field generator configured to rotate with the rotor; one or more segments of superconducting material arranged as an induction coil; a switch; and output terminals configured to be connected to a load, the output terminals being connected in parallel with the switch. Rotation of the rotor may move the at least one magnetic field generator relative to the induction coil and the switch such that the magnetic field is periodically applied to the induction coil and the switch to induce a current through the switch in the induction coil and to reduce a critical current of the material within the switch, the switch is transitioned from a low resistance state to a higher resistance state.

Description

Technical Field

[0001] The present technology relates to the field of superconducting materials, and in particular to a technology for increasing the current in a superconducting material using a flux pumping technique. In particular, the present technology relates to a mechanically switched superconducting flux pump. The technology may be particularly useful in high power motor applications, magnetic resonance imaging, or nuclear fusion. However, this should not be viewed as a limitation of the present technology. Background Art

[0002] High temperature superconducting (HTS) materials, such as wires or ribbons, typically have a superconducting transition temperature above 77 K. Below this temperature, HTS materials can achieve high magnetic fields, which is attributed to extremely low levels of heat dissipation. A key property of superconducting materials is that in the superconducting state, they have zero or very close to zero electrical resistance. This means that once an electric current flows in a superconducting material, it does not decay as it would in a conventional conductor, or at least it decays at a much lower rate.

[0003] However, it is difficult to join HTS materials without using normal (non-superconducting) metal contacts. In the case of using normal contacts, significant resistive losses can be introduced into the superconducting circuit, which means that current must be continuously injected into the circuit to prevent current decay, which can require a large amount of power to operate continuously.

[0004] One way to increase the current within an HTS material is to use a device known as a flux pump. A flux pump can be used to induce current in a superconducting material in a contactless manner using electromagnetic flux. This allows current to flow in an HTS circuit without the need for a normally conducting connection.

[0005] One form of flux pump is described in U.S. Patent No. 9,972,429, which is referred to as a generator flux pump. In this generator flux pump, a magnetic field is periodically applied to a region of the HTS material within the superconducting circuit so that flux eddies are formed within the HTS material. The flux eddies must completely penetrate the HTS material in a direction perpendicular to the desired direction of the net current that will be driven around the superconducting circuit. There is a minimum applied magnetic field strength at which complete flux penetration occurs, and this minimum penetration field is referred to as Bpen. Although the generator structure produces a net DC transmission current, the design typically has high losses because the entire current must pass through the dynamic resistance created by the magnets. In a generator flux pump, the penetrating flux eddies can be moved through the HTS material by moving the applied non-uniform magnetic field relative to the HTS material in a manner that drags the flux eddies in the direction of movement of the applied field.

[0006] Another type of flux pump is a transformer-rectifier flux pump, which typically uses a non-superconducting transformer primary coil magnetically coupled to a superconducting secondary coil. However, the current waveform produced in the superconducting secondary coil still needs to be rectified, and there are significant losses due to the current flowing in the primary coil.

[0007] 3. Purpose of the invention

[0008] It is an object of the technology to provide an improved superconducting flux pump. Alternatively, it is an object of the technology to provide a mechanically switched superconducting flux pump. Alternatively, it is an object of the technology to provide an improved apparatus and / or system for inducing current in a load. Alternatively, it is an object of the technology to provide an improved rectifier. Alternatively, it is an object of the technology to at least provide the public with a useful choice. Summary of the invention

[0009] Aspects of the present technology relate to electrical devices configured to produce a net DC current in one or more segments of superconducting material.

[0010] In one aspect of the present technique, an apparatus configured to induce current in one or more lengths of superconducting material is provided.

[0011] In one aspect of the present technique, a method of inducing current in one or more lengths of superconducting material is provided.

[0012] In one aspect of the present technique, a flux pump configured to induce current in one or more sections of superconducting material is provided.

[0013] In one aspect of the present technology, a device for inducing current in a load is provided, which may be referred to as a flux pump. The device may include a rotor, the rotor including at least one magnetic field generator configured to rotate with the rotor. The at least one magnetic field generator may generate a magnetic field. The device may also include one or more sections of superconducting material, the superconducting material being arranged to provide an induction coil, a switch, and two or more output terminals configured to be connected to a load in use, the two or more output terminals being electrically connected in parallel with the switch, and the rotation of the rotor may cause the at least one magnetic field generator to move relative to the induction coil and the switch, so that: a magnetic field is periodically applied to the induction coil to induce a current in the induction coil, at least a portion of the current being configured to flow through the switch; and the magnetic field is periodically applied to the switch, and a critical current of the superconducting material within the switch is reduced, so that the magnetic field and the current within the switch cause the switch to switch from a low resistance state to a higher resistance state.

[0014] In one aspect of the present technology, a device for increasing current in a load is provided. The device may include a rotor, the rotor including at least one magnetic field generator, the magnetic field generator being configured to rotate with the rotor. The at least one magnetic field generator may generate a magnetic field. The device may further include a stator. The stator may be provided with one or more sections of superconducting material, the superconducting material being arranged to provide an induction coil, a switch, and two or more output terminals configured to be connected to a load in use, the two or more output terminals being electrically connected in parallel with the switch. In use, the rotor may be configured to rotate relative to the stator, and the at least one magnetic field generator may be configured to periodically apply a magnetic field: to the induction coil to induce current in the induction coil; and to the switch to switch the switch between a low resistance state and a higher resistance state for a given current in the switch.

[0015] In one aspect of the present technology, a device for inducing current in a load is provided, which device may be referred to as a flux pump. The device may include a rotor, the rotor including at least one magnetic field generator configured to rotate with the rotor. The at least one magnetic field generator may generate a magnetic field. The device may further include a stator. The stator may be provided with an induction coil. The stator may also be provided with a switch configured to switch between a low resistance state and a higher resistance state. The stator may further be provided with two or more output terminals, the two or more output terminals configured to be connected to the load in use, and the two or more output terminals are electrically connected in parallel with the switch. In use, the rotor may be configured to rotate relative to the stator. The at least one magnetic field generator may be configured to periodically apply a magnetic field to the induction coil and the switch, the induction coil and the switch: inducing current in the induction coil when the magnetic field generator moves relative to the induction coil; and for a given current, switching the switch between a low resistance state and a higher resistance state. The magnetic field may be applied to the switch with a phase delay relative to the magnetic field applied to the induction coil.

[0016] In one aspect of the present technology, a rectifier is provided. The rectifier may include a rotor including at least one magnetic field generator configured to rotate with the rotor. The at least one magnetic field generator may generate a magnetic field. The rectifier may further include an induction coil. The rectifier may further include a switch including one or more sections of superconducting material. In use, the rectifier may be configured to be connected to a load, which is electrically connected in parallel with the switch. In use, the rotor may be configured to rotate to move the at least one magnetic field generator relative to the induction coil and the switch so as to periodically apply a magnetic field to the induction coil and the switch, so that: a current is induced in the induction coil, the current having a positive component and a negative component over time, wherein at least a portion of the current is configured to flow through the switch and the load; and the magnetic field applied to the switch reduces the critical current of the superconducting material within the switch, so that the magnetic field and the current within the switch cause the switch to switch from a low resistance state to a higher resistance state. Application of a magnetic field to the switch may be synchronized with the positive or negative component of the current, causing the switch to transition to a higher resistance state to increase the amount of current flowing in the load during the positive or negative component, thereby providing a net positive or negative current in the load.

[0017] In one aspect of the present technology, a system for increasing current in a load is provided. The system may include a rotor including at least one magnetic field generator configured to rotate with the rotor. The at least one magnetic field generator may generate a magnetic field. The system may also include one or more sections of superconducting material arranged to provide an induction coil and a switch. The system may further include a superconducting load electrically connected in parallel with the switch. The rotation of the rotor may cause the at least one magnetic field generator to move relative to the induction coil and the switch, so that: the magnetic field is periodically applied to the induction coil to induce a current in the induction coil, at least a portion of the current is configured to flow through the switch and the superconducting load; and the magnetic field is periodically applied to the switch and reduces the critical current of the superconducting material within the switch, so that the magnetic field and current within the switch cause the switch to switch from a low resistance state to a higher resistance state, thereby affecting the amount of current flowing in the superconducting load.

[0018] In some forms, the magnetic field generator is configured to generate the magnetic field such that a component of the magnetic field is applied to the switch in a direction perpendicular to a surface of the superconducting material.

[0019] In examples of the present technology, the rotor may have an axis of rotation about which the rotor rotates in use. For example, the rotor may be provided with a drive shaft configured to be attached to a drive source in use to rotate the rotor about the axis of rotation. For example, the longitudinal axis of the drive shaft may substantially define the axis of rotation.

[0020] In an example of the present technology, at least one magnetic field generator may be located radially outside of the axis of rotation. For example, at least one magnetic field generator may be configured to travel in a circular path as the rotor rotates.

[0021] In an example of the present technology, one or more magnetic field generators may be disposed on a side of the rotor closest to the stator.

[0022] In an example of the present technology, the rotor may include at least one support extending outward from the axis of rotation. For example, the support may be configured to extend substantially perpendicular to the axis of rotation. In some examples, the support may include one or more arms, or plates, to which at least one magnetic field generator is disposed.

[0023] In an example of the present technology, the rotor can include a material having a high magnetic permeability. For example, the rotor can be configured to provide a high magnetic permeability path for a magnetic field generated by a magnetic field generator. For example, the rotor can be constructed of a ferromagnetic material such as iron or steel.

[0024] In an example of the present technology, the rotor may be provided with a plurality of magnetic field generators. For example, the rotor may be provided with a first magnetic field generator and a second magnetic field generator, the first magnetic field generator being located at a first radial distance from the axis of rotation, the second magnetic field generator being located at a second distance from the axis of rotation, the first distance being substantially the same as the second distance.

[0025] In examples of the present technology, the switch may be located at substantially the same radial distance from the axis of rotation as the one or more magnetic field generators, when measured from a center point of the switch.

[0026] In examples of the present technology, the induction coil may be located at substantially the same radial distance from the axis of rotation as the one or more magnetic field generators, when measured from a center point of the induction coil.

[0027] In an example of the present technology, the first magnetic field generator may be located between 167 degrees and 193 degrees relative to the second magnetic field generator when measured about the axis of rotation.

[0028] In an example of the present technology, the switch can be located between 167 and 193 degrees relative to the induction coil when measured about the axis of rotation. For example, the first magnetic field generator can be located at approximately 180 degrees relative to the second magnetic field generator, and the switch can be located within 167 and 193 degrees relative to the induction coil, such that when the rotor rotates and moves at least one magnetic field generator past the induction coil and the switch, the magnetic field applied to the induction coil and the switch is provided with a phase shift of up to 13 degrees.

[0029] In examples of techniques using more than two magnetic field generators, the magnetic field generators may be evenly spaced around the rotor. For example, the magnetic field generators may be provided in pairs, such as two, four, six, or eight magnetic field generators. Where each of these pairs of magnetic field generators may be positioned substantially diametrically opposite to each other. In other examples, each of the pairs of magnetic field generators may be located within 167 degrees and 193 degrees of each other relative to the axis of rotation.

[0030] In examples of the present technology, the flux pumps and rectifiers described herein may further include a stator.

[0031] In an example of the present technology, the stator can include a material having a high magnetic permeability. For example, the stator can be configured to provide a high magnetic permeability path for a magnetic field generated by a magnetic field generator. For example, the stator can be constructed of a ferromagnetic material such as iron or steel.

[0032] In examples of the present technology, one or more magnetic field generators may include permanent magnets. For example, one or more magnetic field generators may include samarium cobalt (SmCo), aluminum nickel cobalt alloy (AlNiCo), or neodymium iron boron (NdFeB). In other examples of the present technology, one or more magnetic field generators may include electromagnets.

[0033] In an example of the present technology, one or more sections of superconducting material may include a high temperature superconductor. For example, the high temperature superconducting material may include rare earth barium copper oxide (ReBCO), such as a ReBCO tape.

[0034] In an example of the present technology, the stator may include one or more arms. For example, the stator may include a stator base, and the one or more arms may extend upward from the stator base toward the rotor. For example, the stator arms may be substantially perpendicular to the stator base.

[0035] In examples of the present technology, the induction coil may include one or more segments of superconducting material that are less than one turn. For example, the induction coil may include less than or equal to one turn of superconducting material, such as a quarter turn or a half turn. In other examples of the technology, the induction coil may include one or more turns (including non-integer turns) of one or more segments of superconducting material. For example, the one or more segments of superconducting material may surround one or more arms of the stator. For example, the induction coil may include one turn and a half turn, or two turns or more turns of one or more segments of superconducting material.

[0036] In an example of the present technology, the induction coil may include a portion of superconducting material arranged in a substantially arcuate path, a focus of the arcuate path defining a center of the induction coil, and wherein at least one magnetic field generator has a radial distance from the axis of rotation that is substantially the same as the radial distance of the center of the induction coil from the axis of rotation.

[0037] In an example of the present technology, any one or more of the stator arms can be substantially cylindrical. For example, the stator arms can have a radius greater than or equal to the minimum bending radius of the superconducting material. For example, any one or more of the stator arms can have a radius greater than or equal to 50 mm.

[0038] In examples of the present technology, the switch may be referred to as a "Jc(B) switch." In other words, the switch may be configured or arranged such that the magnetic field generated by the magnetic field generator affects the maximum critical current of the one or more segments of superconducting material, such that for a given current through the switch, the superconducting material switches between a first low resistance state and a second higher resistance state. For example, the switch may be configured or arranged such that at least a portion of the magnetic field applied by the magnetic field generator is perpendicular to the surface of the one or more segments of superconducting material.

[0039] In one example of the present technology, the switch can be located on the same stator arm as the induction coil. In other examples of the present technology, the switch can be located on the opposite stator arm from the induction coil, such as a stator arm within 167 degrees and 193 degrees relative to the stator arm including the induction coil.

[0040] In examples of the present technology, a flux pump may include multiple induction coils, and / or multiple switches.

[0041] In an example of the present technology, the switch can be electrically connected in parallel with the output terminal or load. For example, the load can include a circuit or loop of superconducting material. For example, the loop of superconducting material can include 10 or more turns of high temperature superconductor.

[0042] In an example of the present technology, the switch can be located on one or more stator arms, such as a stator arm between the stator and the rotor. For example, at least a portion of the switch can be configured to extend in a direction substantially perpendicular to the magnetic flux generated by the magnetic field generator.

[0043] In an example of the described technology, a switch may be located between a stator arm and a field spreader. For example, the field spreader may be configured to generate or otherwise cause a uniform magnetic field to act on at least a portion of the switch, such as one or more sections of superconducting material of the switch. For example, the field spreader may include a material having a high magnetic permeability, such as a ferromagnetic material.

[0044] In examples of the present technology, the field spreader may be sized to have substantially the same width as the magnetic field generator, as measured in a radially outward direction of the axis of rotation.

[0045] In examples of the present technology, a field spreader may be substantially centrally located on top of one or more arms of the stator.

[0046] In examples of the present technology, the distance from any edge of the field spreader to the edge of the stator arm on which it is located may be less than the width of the magnetic field generator.

[0047] In an example of the present technology, any one or more of the induction coil, the switch, and the load or terminal can be composed of a single continuous section of superconducting material. For example, a high temperature superconducting tape. In other words, the superconducting material can be configured so that there is no joint between any one or more of the induction coil, the switch, and the load or terminal.

[0048] In other examples of the technology, a joint may be used to connect any one or more of the induction coil, the switch and the load or the terminal. For example, the joint may be a normal conductive connection familiar to those skilled in the art.

[0049] In an example of the present technology, one or more sections of superconducting material can be placed in a cryostat. For example, the stator can be located in a cryostat. For example, the cryostat can include a cryostat refrigeration system familiar to those skilled in the art.

[0050] In examples of the present technology, a cryostat refrigeration system may include a liquid refrigerant operable to cool by latent heat of evaporation, and / or a thermomechanical refrigerator. For example, liquid nitrogen may be used.

[0051] In examples of the present technology, the rotor may also be located within the cryostat. For example, a drive may be provided external to the cryostat, the drive being operably connected to the rotor via a drive shaft extending through a wall of the cryostat.

[0052] In examples of the present technology, the flux gap or other spacing between the magnetic field generator and the stator can be less than 6 mm, for example, the flux gap can be 1 mm or less.

[0053] It should be appreciated that the present technology may provide any one or more of a number of advantages, including:

[0054] · Ability to have a switched rectifier that works across the cryostat wall without penetrating the wall;

[0055] More efficient flux pump technology;

[0056] Flux pump technology operable within or at least partially within a cryostat;

[0057] Lower cooling requirements compared to transformer-based flux pump technology;

[0058] Higher efficiency than generator-based flux pump technologies; and

[0059] Automatic regulation of the induced current in the superconducting material, i.e. without the need for any control circuit regulation.

[0060] Other aspects of the technology, which should be considered in all its novel aspects, will become apparent to those skilled in the art after reading the following description, which provides at least one example of a practical application of the technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] One or more embodiments of the present technology will be described below by way of example only and not intended to be limiting, with reference to the following drawings, in which:

[0062] Figure 1 shows an exemplary electric field versus current graph for a high temperature superconductor;

[0063] Figure 2 shows an exemplary graph indicating the effect of an applied magnetic field on the critical current of a high temperature superconductor;

[0064] Figure 3 shows a simplified schematic diagram of a superconducting flux pump according to the present technology;

[0065] Figure 4A A first example of a superconducting flux pump according to the present technology is shown;

[0066] Figure 4B An alternative superconducting flux pump according to the present technology is shown;

[0067] Figure 5 An alternative superconducting flux pump according to the present technology is shown;

[0068] Figure 6 Shows Figure 5 An exemplary plot of experimental performance of a flux pump as a function of time of increasing current in a high temperature superconductor;

[0069] Fig. 7A A first example is shown of how a power supply is conventionally used to increase the current in a superconducting coil located within a cryostat;

[0070] Figure 7B A second example is shown of how a superconducting flux pump can be used to increase the current in a superconducting coil located within a cryostat;

[0071] Figure 7C A third example is shown of how a superconducting flux pump may be used to increase the current in a superconducting coil positioned within a cryostat;

[0072] Figure 8 A superconducting flux pump device according to an example of the present technology is shown;

[0073] Fig. 9 An example of a switch according to the present technology is shown;

[0074] Fig.10 shows a simplified schematic diagram of a superconducting flux pump with a series shunt resistor;

[0075] Fig.11A shows a magnetic field diagram of a flux pump according to the present technology;

[0076] Fig. 11B Shows Fig.11A A close-up view of the field diffuser within the magnetic field map;

[0077] Fig. 12A An exemplary stator according to the present technology is shown, wherein the switch position is adjustable;

[0078] Fig. 12B A switch keeper according to the present technology is shown which may be adjustably positioned on a stator to vary the phase relationship between the induction coil and the switch;

[0079] Fig. 12C Shown according to Fig. 12A and 12B A graph showing the current and phase relationship between the induction coil and the switch of the adjustable design;

[0080] Fig.12D A graph showing a current versus phase relationship between an induction coil and a switch according to another embodiment of the present technology;

[0081] Fig.13 shows a schematic side view of a flux pump within a housing according to the present technology;

[0082] Fig.14A shows a schematic diagram of a Jc(B) switch device according to the present technology;

[0083] Fig. 14B shows a schematic diagram of a two-wire Jc(B) switch device according to the present technology;

[0084] Fig. 14C A schematic diagram showing another two-wire Jc(B) switch device according to the present technology; and

[0085] Fig.15 A graph summarizing the actual operating voltages of a flux pump constructed in accordance with the present technology is shown.

[0086] 6. Detailed description of the preferred embodiments of the present invention

[0087] 6.1. Principles of superconductivity

[0088] A superconductor or superconducting material is at a temperature known as the critical temperature Tc A material that exhibits zero electrical resistance at a certain temperature. This zero resistance state is often referred to as a superconducting state. This lack of resistance is the result of a phenomenon known as the Meissner Effect, which is the complete expulsion of any magnetic field from a superconductor. A superconductor is a material that is electrically conductive until it reaches a critical field, B. c The critical field also means that there is a limit to the amount of current a superconductor can carry, called the critical current I. c .

[0089] There are two types of superconductors, called Type I and Type II. Type I superconductors are usually pure metals and function as described above. Type II superconductors behave differently. Type II superconductors allow some magnetic fields to be c1 <H c Type II superconductors can therefore carry more current.

[0090] Compared to type I superconductors, this makes them useful for practical applications.

[0091] The critical temperature of a superconductor is generally defined as the temperature below which the resistivity of the superconductor drops to zero or close to zero. In other words, when the temperature of a superconductor is below the critical temperature, the superconductor is said to be in its superconducting state, and when the temperature is above the critical temperature, the superconductor is said to be in a non-superconducting state. Many superconductors have critical temperatures close to absolute zero; for example, mercury is known to have a critical temperature of 4.1 K. However, it is also known that some materials can have much higher critical temperatures, such as 30 K to 125 K; for example, magnesium diboride has a critical temperature of about 39 K, while yttrium barium copper oxide (YBCO) has a critical temperature of about 92 K. These superconductors are generally collectively referred to as high temperature superconductors (HTS).

[0092] 6.1.1. Critical current

[0093] The critical current of a high temperature superconductor wire or strip is usually defined as the current flowing in the superconductor wire / strip that results in an electric field drop of 100 μV / m (=1 μV / cm) along the wire. The critical current is a function of the superconducting material used and the physical structure of the superconducting material. For example, a wider strip / wire can have a higher critical current than a thinner strip / wire made of the same material. However, throughout the specification, reference to the critical current of the superconductor / superconducting material is intended to simplify the discussion.

[0094] In a superconductor, if the current I is approximately equal to the critical current I c , then the resistance of the superconductor is non-zero, but small. However, if I is much larger than the critical current I c , then the resistance of the superconductor becomes large enough to cause heat dissipation, which can heat the superconductor to a temperature above its critical temperature, which in turn makes it no longer superconducting. This situation is sometimes called a "quench" and can damage the superconductor itself.

[0095] Figure 1 An exemplary graph depicting the internal electric field of a high temperature superconductor versus current is shown. The electric field shown in this graph is related to resistance by the following equation:

[0096]

[0097] in:

[0098] E is the electric field;

[0099] I is the current through the superconductor;

[0100] R is the resistance of the wire; and

[0101] L is the length of the wire.

[0102] therefore, Figure 1 The curve of is related to the resistance per unit length of the superconductor, and because the curve depicted is nonlinear, the ultimate resistance of the superconductor is nonlinear with the current.

[0103] exist Figure 1 It can be seen that the electric field strength in the superconductor is below the critical current I c Below this, it is essentially zero. When the current in a superconductor approaches the critical current, the electric field in the superconductor begins to increase. At the critical current, the electric field in the superconductor is 100 μV / m. Further increasing the current in the superconductor above the critical current results in a rapid increase in the electric field strength in the conductor.

[0104] The transition from superconducting state to normal state in HTS materials, such as Figure 1 As shown, it can be described by an empirical law called the EJ power law:

[0105]

[0106] where E is the electric field in the conductor, J is the current density, and n is an experimentally defined unitless parameter that controls the steepness of the transition. In most superconductors, the value of n is between 25-30. The critical current density J c By some arbitrarily chosen threshold electric field E 0Defined, it may be 100 μV / m (= 1 μV / cm), as explained above.

[0107] Throughout this specification, reference may be made to the relative resistances of superconducting materials and components that include superconducting materials. More specifically, this specification relates to superconducting materials in a low resistance or higher resistance state. It will be appreciated that when in a superconducting state, a superconducting material may have zero or substantially zero resistance, and thus these resistances are typically expressed in terms of the electric field that exists across the superconducting material for a given current. However, throughout this specification, in order to simplify the discussion, reference is made to relative resistances, such as low resistance and higher resistance states of superconducting materials.

[0108] The term 'low resistance state' may refer to when the superconducting material has a resistance close to or substantially zero in the superconducting state, or when the material has a low resistance in a partially superconducting state. The term 'higher resistance' state refers to a state in which the superconducting material has a resistance substantially greater than the resistance in the low resistance state, such as a substantially non-zero resistance or a resistance close to zero but substantially greater than the resistance in the low resistance state. For the avoidance of doubt, unless the context clearly indicates otherwise, a higher resistance state referred to in this specification may include a superconducting state.

[0109] Similarly, where reference is made in this specification to a superconductor being in a higher resistance state due to the current carried by the superconductor exceeding the critical current, it should be understood that the higher resistance state can also be achieved if the current carried by the superconductor is close to or substantially equal to the critical current, unless the context clearly indicates otherwise.

[0110] In describing the technology in this specification, materials and components including the materials are referred to as "superconducting". This term is commonly used in the art for such materials and should not be taken to mean that the relevant materials are always in a superconducting state. Under certain conditions, the materials and components including the materials may not be in a superconducting state. That is, the material may be described as superconducting but not superconducting.

[0111] 6.1.2. Superconducting materials

[0112] Certain forms of the present technology may include various types of superconducting materials. For example, forms of the present technology may include high temperature superconducting (HTS) materials. Exemplary HTS materials suitable for use in the described forms of the technology include copper oxide superconductors, for example rare earth barium copper oxides (ReBCO) such as yttrium barium copper oxide, gadolinium barium copper oxide, or bismuth strontium calcium copper oxide (BSCCO) superconductors, and iron-based superconductors. BSCCO superconductors typically have a strong interdependence between critical current and applied magnetic field, which may make them particularly suitable for use in some forms of the present technology. Other types of superconductors may be used in other forms of the present technology.

[0113] Although forms of the technology will be described with respect to high temperature superconductors, it will be appreciated that other forms of the technology may use other types of superconductors, such as low temperature superconductors.

[0114] 6.1.3. Effects of magnetic field on superconducting materials

[0115] The critical current in a superconductor depends on the external magnetic field applied to the superconductor. More specifically, the critical current decreases as higher external magnetic fields are applied to the superconductor, until a value of the critical magnetic field, beyond which the superconductor is no longer in a superconducting (low resistance) state. Figure 2 This relationship is shown in Figure 2 is a graphical representation of the electric field versus current diagram of a superconducting material when three external magnetic fields of different magnitudes are applied. The highest magnitude of the external magnetic field B app1 Leading to the lowest critical current I c1 In some forms, an external magnetic field that achieves this effect may be applied perpendicular to the surface of the segment of superconductor in which the critical current is reduced or suppressed. The applied magnetic field may be in one direction only, which may be referred to as a DC field, compared to a time-varying magnetic field that cycles sinusoidally, for example, which may be referred to as an AC field.

[0116] For all superconductors, the critical current drops sharply only at small applied magnetic fields. This means that small changes in the applied magnetic field can lead to large changes in the critical current. The relationship depends on the superconducting material and the way the section of superconducting material that carries the current is made.

[0117] It should be understood that this mechanism of reducing or suppressing the critical current by applying an external magnetic field (e.g., a DC field) is distinct from the phenomenon of dynamic resistance. This occurs when a superconductor is exposed to a time-varying magnetic field while carrying a DC transmission current. This creates a DC resistance in the superconductor that can be large enough to cause the superconductor to switch to a higher resistance state.

[0118] 6.1.4. Superconducting switch

[0119] Throughout this specification, reference will be made to the relative resistance of superconducting switches and their components. In general, a superconducting switch is a switch that incorporates one or more superconducting materials that can be switched between a low resistance state and a higher resistance state, as described herein. These may not be the open / closed states common to conventional normal conductive switches, and typically, even in the higher resistance state, the resistance may be considered low by the standards of a normal conductive switch, such as a few ohms or less.

[0120] Those skilled in the art will appreciate that superconducting materials can have zero or substantially zero resistance when in a superconducting state, and therefore these resistances are more generally expressed as the electric field present across the superconducting material for a given current. However, throughout this specification, reference has been made to relative resistance, low resistance, and higher resistance states in order to simplify the discussion.

[0121] 6.2. Mechanically switched superconducting flux pump

[0122] 6.2.1. Working principle

[0123] Figure 3 An example of a mechanically switched flux pump 300 according to one form of the present technology is shown. In broad terms, the flux pump 300 includes a rotor 302 configured to rotate about a rotation axis in use. The rotor 302 includes one or more magnetic field generators 306, each configured to generate a magnetic field, such as a permanent magnet or an electromagnet.

[0124] In use, the rotation of the rotor 302 moves one or more magnetic field generators 306 past the induction coil 310 and the switch 312 to periodically apply a magnetic field to the induction coil 310 and the switch 312, for example, the one or more magnetic field generators can move in a substantially circular path. The magnetic field generated by the magnetic field generator 306 is configured to induce a current in the induction coil 310 and apply a magnetic field to the switch 312, such as a magnetic field having a component perpendicular to the surface of the switch, thereby reducing the critical current of the switch due to the effects described above. When the magnetic field is applied, the lower critical current of the switch 312 means that for a given current, the switch 312 has a higher resistance, or when compared to when no magnetic field is applied to the switch, the switch is in a higher resistance state. Throughout this specification, references to switches that transition from a low resistance state to a higher resistance state should be understood to refer to the relative resistance when a given current flows through the switch. For example, the current can be equal to or less than the current induced in the induction coil 310. In some forms, when in the higher resistance state, the switch 312 is in a superconducting state. It should be understood that this may be the case for any form of technology, even if not explicitly stated.

[0125] exist Figure 3 In the example of , a load 314 is provided that is electrically connected in parallel with the switch 312. The load may preferably include a superconducting coil, however, this should not be seen as a limitation of the technology, and the load may be any suitable component or circuit placed in parallel with the switch 312. In some aspects of the present technology, the flux pump 300 described herein may be provided with two or more output terminals 315 that are configured to be connected to the load 314 in use, and the two or more output terminals 315 are electrically connected in parallel with the switch.

[0126] In the example shown, two magnetic field generators 306a, 306b are provided, each positioned diametrically opposite or approximately 180 degrees relative to each other on the rotor 302. The induction coil 310 and the switch 312 are positioned so that during rotation of the rotor 302, the first magnetic field generator 306a passes by the induction coil 310 so that its magnetic field is applied to the induction coil 310 and a current is induced in the induction coil 310. At about the same time, the second magnetic field generator 306b passes by the switch 312 so that its magnetic field is applied to the switch 312, and the magnetic field generated by the second magnetic field generator 306b reduces the critical current of the switch, which, for a given current, switches the switch from a low resistance state to a higher resistance state as described herein. Similarly, after further rotation of the rotor 302, when the second magnetic field generator 306b passes by the induction coil 310, it induces current in the induction coil 310, and the first magnetic field generator 306a passes by the switch, and as described herein, the magnetic field generated by the first magnetic field generator 306a switches the switch from a low resistance state to a higher resistance state. Between these states, the first and second magnetic field generators 306a and 306b are further away from the induction coil 310 and the switch 312, so their magnetic fields do not induce current in the induction coil 310, or reduce the critical current of the switch 312, or at least do so to a lesser extent than when the magnetic field generators are close to the induction coil and the switch. Further rotation of the rotor 302 causes a periodic cycle of the described behavior. For example, the induction coil 310 and the switch 312 can be positioned substantially diametrically opposite to each other relative to the rotor 302.

[0127] Thus, with a single 360° rotation of the rotor 302, current is induced in the induction coil 310 twice, and the switch 312 transitions from a low resistance state to a higher resistance state each time in a synchronized manner. Figure 3 The use of two magnetic field generators 306a, 306b in should not be considered a limitation of the technology, and any number of magnetic field generators 306 may be used. In some examples of the present technology, it may be advantageous to use an even number of magnetic field generators, such that each magnetic field generator 306 may have a position substantially opposite to another of the magnetic field generators, such as, for example, 180° opposite to another magnetic field generator. It should be understood that the greater the number of magnetic field generators used, the greater the number of times current is induced in the induction coil 310, and, in turn, the greater the number of times the switch transitions from a low resistance state to a higher resistance state for every 360 degrees of rotation of the rotor.

[0128] By adjusting the timing and duration of the transition of switch 312 from a low resistance state to a higher resistance state, the current flowing in load 314 can be affected and thereby adjusted so that load 314 has a net DC current, thereby allowing load 314 current to increase on a cycle-by-cycle basis.

[0129] The transition of the switch 312 from the low resistance state to the higher resistance state in phase with the induced current in the induction coil 310 results in an increase in the current delivered from the induction coil 310 to the load 314 during the higher resistance state relative to the current delivered to the load in the low resistance state. This is because the load 314 is electrically connected in parallel with the switch 312, and the current ratio between the load 314 and the switch 312 depends on the relative impedance or resistance of the load 314 to the switch 312.

[0130] It should be understood that the movement of the magnetic field generator 306 relative to the induction coil 310 applies a changing magnetic field to the induction coil 310, which causes current to flow in the induction coil 310. The current in the induction coil 310 generally has a positive component and a negative component. In other words, the current in the induction coil can oscillate between positive current and negative current over time. Therefore, by switching the switch 312 to a higher resistance state during the positive current or negative current, a net positive or negative current can be provided in the load. In other words, the relative timing of the switch switching to the induction current pulse can be adjusted so that the higher resistance state substantially corresponds to the positive component of the current induced in the induction coil, and the lower resistance state substantially corresponds to the negative current induced in the induction coil 310.

[0131] In the examples described herein, the induction coil 310 and the switch 312 are provided by one or more sections of superconducting material, such as a high temperature superconductor as will be discussed herein. In particular, the use of one or more sections of superconducting material can advantageously provide improved efficiency in superconducting flux pump technology. However, this should not be seen as a limitation of the technology, and in other examples, any one or more components of the present technology may be provided with a normal conductive equivalent.

[0132] 6.2.1. Magnetic flux coupling

[0133] One way to increase the induced current in the induction coil 310 is to increase the strength of the magnetic field applied to the induction coil 310. One way to accomplish this is to use a material with high magnetic permeability, such as by using a ferromagnetic material such as steel, to couple the magnetic field to the induction coil.

[0134] Similarly, for various types of superconducting switching mechanisms, such as those described herein, it may be advantageous to increase the strength of the magnetic field acting on the segment of superconducting material because this may result in any one or more of: greater suppression of the critical current, an increase in the current induced in the induction coil 310, and / or an increase in the resistance of the switch 312 in the higher resistance state.

[0135] Figure 4A An example of a flux pump 300 according to one form of the present technology is shown, the flux pump comprising a ferromagnetic stator 304 and a ferromagnetic rotor 302. The stator comprises a first arm 320a on which an induction coil 310 and a switch 312 are disposed. The stator also comprises a second arm 320b which serves as a magnetic return path to minimize the total air gap between the rotor 302 and the stator 304.

[0136] The stator 304 is provided with one or more sections of superconducting material 308, which are configured to provide an induction coil 310 and a switch 312. In the illustrated example, the superconducting material 308 also provides a superconducting load 314 in the form of a load coil, however, this should not be considered a limitation of the technology. For example, two or more output terminals can be provided instead of the load described herein.

[0137] The rotor 302 may include a drive shaft 316 which, in use, is connected to a drive source such as a motor to rotate the rotor 302. Thus, in the illustrated example, the longitudinal axis of the drive shaft 316 defines an axis of rotation 317 of the rotor 302.

[0138] Figure 4A The flux pump 300 operates by rotating the rotor 302 to move the magnetic field generator 306 through one or more stator arms 320a, 320b. This movement generates a changing magnetic field within the stator 304, which passes through the loops of the induction coil 310 and the switch 312, respectively.

[0139] In the illustrated example, the drive shaft 316 is arranged in line with the second arm 320b of the rotor. In other words, the rotation axis 317 is aligned with the second arm 320b so that the second arm remains adjacent to the rotor in use. In this way, the present technology can be configured to generate a changing magnetic field in the stator when the magnetic field generator 306 only passes through the first arm 320a.

[0140] It will be appreciated that, as shown, the rotor is asymmetrical about the axis of rotation 317, which may result in vibration or oscillation during use. Therefore, in some examples of the technology, the rotor may be provided with a generally symmetrical configuration about the axis of rotation, such as in Figure 5 In the example.

[0141] The magnetic field generator 306 may be located on a side of the rotor 302 closest to the stator 304. The magnetic field generator 306 may be arranged at a radial distance from the axis of rotation 317 such that the magnetic field generator travels through an arcuate or circular path in use.

[0142] exist Figure 4A , the magnetic field generators are attached to the rotor by one or more support members 311. In the illustrated example, the support member 311 comprises a plate or a substantially circular support. For example, when the cross section is taken in a plane perpendicular to the rotation axis 317, the support member 311 can have a substantially circular cross-section, or can be a substantially circular plate. The use of a substantially circular support member can advantageously result in reduced drag or air turbulence, particularly in examples of the technology where the rotor is located within a cryostat as described herein. However, this should not be seen as limiting, and in other examples, the support member 311 can include an arm or elongated structure that supports the corresponding magnetic field generator.

[0143] Advantageously, the midpoint of each arm 320 a , 320 b has a radial distance from the axis of rotation 317 that is substantially equal to the radial distance of the magnetic field generator 306 to provide a short magnetic path between the magnetic field generator 306 and the stator 304 .

[0144] In use, Figure 4A The flux pump 300 is operated by rotating the rotor 302 to move the magnetic field generator 306 along an arcuate path through one or more arms 320a, 320b of the stator. The movement of the magnetic field generator through the arms 320a, 320b generates a changing magnetic field in the stator 304, which in turn generates a current in the induction coil 310 and causes the switch to switch between a low resistance state and a higher resistance state.

[0145] exist Figure 4A In the embodiment of the present invention, the switch 312 and the induction coil 310 are disposed on a single arm 320a of the stator. In other examples of the technology, the switch and / or the induction coil can be located at any position on the stator. For example, the switch can be disposed in a portion between the arms 320a, 320b of the stator 304, such as a midpoint between the arms. Similarly, the induction coil can be disposed on either arm, or around a portion of the stator connecting the arms, such as a stator base 321.

[0146] For example, Figure 4B An alternative flux pump 300 according to another form of the present technology is shown in which the induction coil 310 is provided on the second arm 320B of the stator 304 .

[0147] Figure 5Another example of another form of flux pump 500 according to the present technology is shown, which includes a ferromagnetic stator 304 and a ferromagnetic rotor 302. The stator includes a first arm 320a and a second arm 320b, the induction coil 310 is disposed on the first arm (e.g., the induction coil 310 can be wound around the first arm 320a), and the switch 312 is disposed on the second arm (e.g., the switch can be disposed on the top of the second arm 320b). The stator may also include a third central arm 320c to minimize the total air gap between the rotor 302 and the stator 304.

[0148] The stator 304 may be provided with one or more sections of superconducting material 308 configured to provide an induction coil 310 and a switch 312. In the illustrated example, the superconducting material 308 also provides a superconducting load 314 in the form of a load coil, however, this should not be viewed as a limitation of the technology.

[0149] Figure 5 The flux pump 300 operates by rotating the rotor 302 to move the magnetic field generator 306 through one or more stator arms 320a, 320b to provide the magnetic field generated by the magnetic field generator 306 to the induction coil 310 and the switch 312, respectively.

[0150] For example, the rotor 302 may include a drive shaft 316 that, in use, is connected to a drive source such as a motor to rotate the rotor 302. Thus, in the illustrated example, the longitudinal axis of the drive shaft 316 defines an axis of rotation 317 of the rotor 302.

[0151] The magnetic field generator 306 may be located on a side of the rotor 302 closest to the stator 304. The magnetic field generator 360 may be located at a radial distance from the axis of rotation 317 such that each magnetic field generator travels through an arcuate or circular path in use. It is advantageous for each of the one or more magnetic field generators to follow substantially the same arcuate or circular path in use. For example, each of the one or more magnetic field generators may have substantially the same radial distance from the axis of rotation 317.

[0152] exist Figure 5 , the magnetic field generators are connected to the rotor via support members 311. In the illustrated example, the support members 311 can be considered to be arms of the rotor. For example, each support member can be an independent elongated structure that supports a corresponding magnetic field generator. In other examples of the technology, the support member 311 can have a substantially circular cross-section when cut along an axis perpendicular to the rotation axis 317, or can be a substantially circular plate. The use of a substantially circular support member can advantageously result in reduced drag or air turbulence, particularly in examples of the technology where the rotor is located within a cryostat as described herein.

[0153] Advantageously, the midpoint of each arm 320 a , 320 b has a radial distance from the axis of rotation 317 that is substantially equal to the radial distance of the magnetic field generator 306 to provide a short magnetic path between the magnetic field generator 306 and the stator 304 .

[0154] In use, Figure 5 The flux pump 300 is operated by rotating the rotor 302 to move one or more magnetic field generators 306 along an arcuate path through one or more arms 320a, 320b of the stator. The movement of the magnetic field generators through the arms 320a, 320b generates a changing magnetic field in the stator 304, which in turn generates a current in the induction coil 310. The changing magnetic field in the stator 304 further acts on the switch 312, which switches from a low resistance state to a higher resistance state, as described herein.

[0155] In the illustrated example, two magnetic field generators are used and are configured such that when the first magnetic field generator 306a passes over the first stator arm 320A, the second magnetic field generator passes over the second arm 320B. Each magnetic field generator generates a magnetic field such as Figure 5 Thus, the changing magnetic field used to induce current in the induction coil 310 may be different from the magnetic field used to switch the switch from a low resistance state to a higher resistance state.

[0156] Figure 6 Shown according to Figure 5 Measured output of a flux pump prototype constructed in accordance with the design outlined in FIG. The graph shows an example of how the flux pump technique described herein can be used to increase the current in the load 314. Note that over time, the current in the load 314 is positive and increases on a cycle-by-cycle basis, with the current in the load 314 being maintained at a constant level of over 7.5A before decaying when the motor driving the rotor 302 stops (at approximately 650 seconds).

[0157] It should be understood that Figure 6 The results obtained are from experiments performed by the inventors, and therefore, while they demonstrate the principles of the technology, they may not represent the limitations or overall performance of different versions of the technology.

[0158] 6.3. Rotor structure

[0159] Although the concepts of the present technology may be provided using a rotor constructed of any material, it is advantageous to provide a rotor 320 comprising a material having a high magnetic permeability, such as any suitable ferromagnetic material. For example, it may be advantageous to construct the support members 311 (arms or plates) of the rotor from a material having a high magnetic permeability to provide a connection between the rotor and the stator. Figure 4A ,4B and the magnetic circuit indicated by the arrows in 5.

[0160] It should be understood that not all components of the rotor need be constructed from materials having high magnetic permeability, for example the shaft 316 may be constructed from any suitable material, including those that do not have high magnetic permeability.

[0161] The use of materials with high magnetic permeability can improve magnetic field coupling between the magnetic field generator and the induction coil 310 and the switch 312, as described herein. For example, any one or more components of the rotor 302 can be constructed of iron or steel or any other ferromagnetic material to provide an electromagnetic conductive path. The use of steel may be particularly advantageous in some applications of the technology due to its low cost and ready commercial availability.

[0162] In some examples of the technology, the rotor includes a shaft 316 that can be connected to a drive device (not shown), such as a motor, to enable the rotor 302 to rotate.

[0163] It should be understood that in order to maintain the superconducting material 308 in a superconducting state, cryogenic temperatures are required. Therefore, in one example of the technology, the rotor 302 can be located outside of the cryostat containing the stator. In this way, heat generated, for example, due to rotational friction generated by moving the rotor 302 does not cause the temperature of the superconducting material 308 to increase, or the cryogenic cooling requirements to increase.

[0164] 6.3.1. Magnetic field generator

[0165] As previously mentioned Figures 3 to 5 As discussed, the magnetic field generator 306 is located on the rotor 302 such that a corresponding magnetic field is applied to the induction coil 310 and the switch 312 when the magnetic field generator 306 rotates around these components. For example, the magnetic field generator may be located on the side of the rotor 302 closest to the stator 304. However, this should not be seen as limiting, for example, in a low-profile version of the technology, the magnetic field generator 306 may be provided on the distal end of the arm of the rotor 302, or in an example using a circular rotor, the magnetic field generator 306 may be provided on the outer periphery of the rotor 302.

[0166] In some forms, magnetic field generators 360 are located at a radial distance from the axis of rotation 317 such that each magnetic field generator travels through an arcuate or circular path in use. It is advantageous for each of the one or more magnetic field generators to follow substantially the same arcuate or circular path in use. For example, each of the one or more magnetic field generators may have substantially the same radial distance from the axis of rotation 317.

[0167] The magnetic field generators 306 may include any suitable component or system capable of providing or generating a magnetic field. In one example of the technology, each magnetic field generator 306 is a permanent magnet, such as a permanent magnet composed of one or more of samarium cobalt (SmCo), AlNiCo, or neodymium iron boron (NdFeB), or any other suitable magnetic material. The use of permanent magnets can advantageously allow for simpler construction, as well as reduced heat generation, compared to active magnetic field generation systems such as transformer-based flux pumps or electromagnets.

[0168] In an optional example of the present technology, one or more magnetic field generators 306 may include electromagnets. For example, where one or more electromagnets are used, the electromagnets may be configured to continuously generate their respective magnetic fields. In an optional example, one or more electromagnets may be configured to periodically generate their magnetic fields. For example, the position of the rotor 302 may be determined in use, and the electromagnets may be activated at appropriate times based on the position of the rotor 302. For example, the electromagnets may be activated when the electromagnets are near or in proximity to the induction coil 310 or the switch 312. Determining the position of the rotor 302 may be performed using any method known to those skilled in the art, including using a rotary encoder.

[0169] For example, in one form of the technology, it may be advantageous to control the activation of one or more magnetic field generators 306 to adjust the relative timing between the current induced in the induction coil 310 and the timing of the switch 312 switching from a low resistance state to a higher resistance state. For example, where an electromagnetic or transformer-based magnetic field generator is used, the magnetic field may be activated or deactivated by any suitable control circuit familiar to those skilled in the art. Doing so may be beneficial for optimizing the current transfer to the load 314. For example, where an electromagnet is used, the position of the rotor and therefore the position of the electromagnet relative to the stator may be determined using any suitable method, including those described above. Thus, the timing of the electromagnet activation may be adjusted by advancing the activation time or by delaying the activation time. Since the resulting current induced into the load can be measured, these timing adjustments may be related to the current induced into the load in order to determine the optimal electromagnet activation timing.

[0170] In examples of technologies where permanent magnets are used as the magnetic field generator 306 , the flux pump may advantageously be able to operate more efficiently because less heat is generated by the windings than would otherwise be generated by the electromagnetic magnetic field generator 306 .

[0171] Furthermore, in the examples described herein, the present technology may be implemented using any number of magnetic field generators 306. For example, a single magnetic field generator may be used to generate magnetic flux through the stator 304 such that it induces current in the induction coil 310 and activates the switch 312 simultaneously or in a timed relationship with each other.

[0172] 6.3.2. Rotor structure

[0173] The rotor 302 may have any suitable structure known to those skilled in the art. Figure 5 In the illustrated structure, the rotor 306 is a substantially flat cylindrical or circular plate. In other examples, the rotor may include one or more arms extending radially outward from the axis of rotation 317 to provide the support member 311 described herein. Thus, the rotor 302 may have any suitable shape or configuration capable of causing the magnetic field generator to rotate.

[0174] In some examples of the technology, a single magnetic circuit may be provided, such as a configuration in which multiple portions of a rotor and a stator together form a magnetic circuit, as described with respect to Figure 4A and 4B As discussed, or alternatively, two or more magnetic circuits may be provided by multiple portions of the rotor and stator, such as Figure 5 One advantage of configuring the rotor and stator to provide two magnetic circuits is that the time or phase relationship between the changing magnetic field induced in the first circuit relative to the changing magnetic field induced in the second circuit can be different.

[0175] 6.4. Low temperature cooling

[0176] In order to maintain the superconducting material 308 in a superconducting state, a low temperature or cryogenic environment is generally required. Therefore, one advantage of some forms of the present technology is that the rotor 302 can be arranged in a non-contact arrangement with the stator 304. Therefore, the stator 304 can be located within the cryostat 702, and the heat generating components of the rotor 302 are located outside the cryostat 702.

[0177] Fig. 7A A conventional power generation circuit is shown, wherein a power source 301 or other current generating source is located outside of a cryostat 702 and is electrically connected to a load 314 or to a superconducting loop contained within the cryostat 702. For example, in Fig. 7A In the embodiment of the present invention, electrical leads 704 can be configured to penetrate the cryostat 702 to transfer current to the load 314. One disadvantage of using electrical leads 704 is that they provide a thermal conduction path out of the cryostat 702, which can increase the overall cooling requirements of the system.

[0178] Figure 7BAn alternative configuration is shown, for example, according to some forms of the present technology, where the rotor 302, stator 304, and load 314 are located within the chamber, and a drive device 706, such as an electric motor, may be located outside the cryostat 702 to reduce the overall cooling requirements of the system. In this example, the shaft 316 still penetrates the wall of the cryostat, however, unlike Fig. 7A Different from the example of FIG. 3 , the shaft 316 may be formed of a material having relatively low thermal conductivity, or may be formed of a material having insulating properties such as carbon fiber.

[0179] Figure 7C Yet another configuration, for example according to certain forms of the present technology, is shown in which the rotor 302 and drive 706 are located outside the cryostat 702, while the stator 304 and load 314 are located within the cryostat 702. One benefit of this arrangement is that the cryostat 702 can be completely isolated from the heat / flux generating components, thereby potentially reducing the cooling requirements of the system. However, a potential disadvantage of this approach is the reduction of magnetic field coupling, or the increase of the flux gap between the rotor 302 and the stator 304, which will be described in more detail herein.

[0180] In some examples of the present technology, the cryostat 702 includes a cryostat refrigeration system that should be familiar to those skilled in the art. For example, the cryostat refrigeration system can include a liquid cryogen operable to cool by latent heat of evaporation, and / or a thermomechanical refrigerator. For example, liquid nitrogen can be used.

[0181] The cooling chamber 702 may include any suitable insulation, including any one or more of a vacuum, multi-layer insulation, and / or a cooled heat shield. In the case where the walls of the chamber 702 are located between the rotor 302 and the stator 304, it may be advantageous to use a material with low electrical conductivity, such as fiberglass composites, stainless steel, and / or thin / slit multi-layer foils.

[0182] 6.5. Stator structure

[0183] Broadly speaking, the purpose of the stator is to position the induction coil 310 and switch 312 so that the magnetic field generator 306 passing over the rotor 302 provides a changing magnetic field that can induce current in the induction coil 310 and switch the switch 312 from a low resistance state to a higher resistance state.

[0184] In certain forms, the stator 304 may be constructed of any suitable ferromagnetic material or any material with a suitably high magnetic permeability to more effectively couple the magnetic field between the rotor 302 and the stator 304. For example, the stator 304 may be constructed of iron or steel or any other ferromagnetic material to direct the magnetic field from the magnetic field generator through the loop of the induction coil 310 and the switch 312. The use of steel may be particularly advantageous in some applications of the technology due to its low cost and ready commercial availability. The use of a ferromagnetic stator may advantageously induce sufficient current in one or more sections of superconducting material 308 that exceeds the field suppression critical current of the switch 312, and apply a sufficiently strong field to the switch 312 to reduce its critical current to below the induced current, or to switch the switch 312 from a low resistance to a higher resistance state as described herein.

[0185] In some examples of stators described herein, the stator includes one or more arms 320A, 320B, 320C configured to extend upward from a stator base 321 toward the rotor 304. Thus, the use of stator arms 320 can advantageously allow for a smaller air gap between the rotor 302 and the stator 304, thereby improving the efficiency of the transfer of the magnetic field from the magnetic field generator to the stator 304.

[0186] Stator 304 may further include features that allow the relative positioning of induction coil 310 with respect to switch 312 to be adjusted as described herein. For example, switch 312 may be disposed on a switch holder 1212 as described herein, which allows for easy adjustment of the positioning of the switch on the stator.

[0187] 6.5.1. Superconducting materials

[0188] In the examples described herein, one or more segments of superconducting material 308 may include a high temperature superconductor such as rare earth barium copper oxide (ReBCO) tape (including, for example, a superconductor made by SuNam TM However, this should not be viewed as a limitation of the technology, and any suitable superconducting material 308 may be used as described herein.

[0189] The above discussion provides examples of how one or more sections of superconducting material 308 may be configured and / or arranged to provide an induction coil 310, a switch 312, and a load 314. For experimental purposes, the components of the induction coil 310, the load 314, and / or the switch 312 have been electrically connected using conventional connections such as welds. However, this should not be viewed as a limitation of the technology. For example, in some examples of the technology, the superconducting material 308 may include a continuous strip, or other suitable material arranged to provide any one or more of the induction coil 310, the load 314, and / or the switch 312.

[0190] More specifically, in some examples of the technology, the induction coil 310 may be provided by looping a coil of superconducting material 308 around one of the arms 320A, 320B of the stator 304. Similarly, depending on the selected switching configuration (more below), the switch 312 may be formed by positioning a portion of one or more lengths of superconducting material 308 strip in a position where a magnetic field applied to the superconducting material 308 has a component perpendicular to the surface of the length of superconducting material 308 providing the switch 312.

[0191] In the case where the components of the technology are provided in parallel, these components may also be provided by a continuous superconducting material 308 (such as a tape), for example by splitting the tape along its longitudinal axis (or length direction) so as to provide two parallel paths of superconducting material 308, which are integrally connected, i.e. having a superconducting connection between each parallel path.

[0192] 6.5.2. Induction coil

[0193] The reader should be familiar with the concept of an induction coil according to Faraday's law. However, unlike a conventional transformer, the present technology uses a magnetic field generator 306 (such as a permanent magnet or an electromagnet) to generate an electromagnetic field. Therefore, the technology is able to solve many problems of transformer-based flux pumps, such as heat generated due to current in the primary of the transformer.

[0194] It may be advantageous to maximize or otherwise increase the current in the induction coil 310 to induce as much current as possible in the flux pump. Higher currents may result in more current being delivered to the load 314 or output terminal 315, and a higher resistance of the switch in a higher resistance state, since the resistance of the switch depends on the field suppression critical current, as well as the current flowing through the switch, as Figure 2 shown.

[0195] In some forms of the technology, the induction coil 310 may include any number of turns of a superconducting material such as a ribbon, including a partial number of turns (i.e., a non-integer number of turns). Figure 6 The results shown in FIG. 1 are provided with one full turn or less of a 12 mm wide superconducting tape 308. However, any number of turns may be used, and as described above, it may be advantageous to maximize the number of turns provided in the available space. As an example, in a form of the technology described herein, and which provides Figure 6 Based on experimental results, the stator arm 320 has a height of about 50 mm to ensure that there is enough space on the arm 320 to support the belt.

[0196] However, the foregoing should not be considered limiting of the technology, however, more than two windings may be used, for example. In some examples of the technology, it may be advantageous to provide the induction coil 310 from superconducting wire rather than using tape to provide more turns in the available area on the stator arm 320.

[0197] It should also be understood that where superconducting materials are used, these materials may have bending radius limitations, and therefore in preferred examples of the technology, the diameter of the stator arm 320 (around which the length of superconducting material may be wound) may be configured to ensure that the bending radius limitations are not exceeded. For example, the stator arm 320 may have a substantially cylindrical shape with a diameter greater than or equal to the minimum bending radius of the one or more sections of superconducting material 308. In some examples, the superconducting material may have a minimum bending radius of 5 mm or more, and therefore the diameter of the stator arm 320 should be sized accordingly, i.e., greater than or equal to 5 mm. In the example shown, the stator arm 320 has a diameter of approximately 50 mm.

[0198] Figure 8 An example of a stator 304 is shown in FIG. In this example, the stator 304 includes a stator base 312, and a plurality of stator arms 320 extending from the stator base 321 toward the rotor 302 ( Figure 8 321) extends substantially vertically upward away from the stator base 321. For example, Figure 8 In the embodiment, the first stator arm 320a has a cylindrical toroidal structure, and the second stator arm 320b is configured as an annular wall. The second stator arm 320b may form a gap along a section of its circumference, and the first stator arm 320a may be located in the gap, as shown. The third central stator arm 320c provides a return path for the magnetic field, such as Figure 5 As shown. Fig. 12A A similar arrangement is also shown in .

[0199] In an example of the present technology, the second stator arm 320b has a Figure 8 In the annular structure shown, it may be advantageous for the gap between the first stator arm 320a and the second stator arm 320b to be smaller than the width of the magnetic field generator 306. This arrangement may advantageously reduce the effects of cogging torque on the rotor 302. Cogging torque may occur when the magnetic field does not smoothly transition from one flux path to the next. This may cause the rotor 302 to accelerate and decelerate as it passes over the iron teeth, and its motion may become nonlinear.

[0200] The first stator arm 320a may be provided with a coil of one or more sections of superconducting material 308 configured into one or more loops around the arm 320 to provide the induction coil 310. The radius of the cylinder may be selected such that it is greater than or equal to the minimum bending radius of the one or more sections of superconducting material 308 to prevent damage to the one or more sections of superconducting material 308 when the induction coil 310 is wound around the arm 320.

[0201] The stator arm 320a may further be connected to Figure 4A A similar structure as shown supports switch 312. Switch 312 may be a component configured to switch between a low resistance state and a higher resistance state in the presence of a magnetic field as described herein. In the illustrated example, switch 312 may be referred to as a "J c (B) switch”, as will be described in more detail herein. However, this should not be viewed as a limitation of the technology, and suitable superconducting switches 312 may be used in accordance with the present technology.

[0202] The center of the stator 304 is preferably aligned with the rotational axis 317 of the rotor so that the arcuate path of the magnetic field generator 306 travels close to the first and second stator arms 320a, 320b. In other words, it is advantageous for the radial distance of the switch 312 and the induction coil 310 from the rotational axis 317 to be substantially the same as the distance of the one or more magnetic field generators from the rotational axis 317.

[0203] 6.5.3. Switch

[0204] The present technology can be configured for use with any suitable switch 312 that will be familiar to those skilled in the art. In a preferred example of the present technology, the switch may be what may be referred to as a "J c (B) switch. For the purpose of this specification, J c (B) The switch operates by subjecting one or more segments of superconducting material 308 to a magnetic field (e.g., a magnetic field having a direction (or having a component of a direction) perpendicular to the surface of the segment of superconducting material) to change the critical current of the superconducting material 308. The magnetic field acts to suppress the critical current in the segment of superconducting material, which, when the segment of superconducting material carries an appropriate current, can act to switch it to a higher resistance state, thereby acting as a switch. As previously explained, the one or more segments of superconducting material 308 can remain superconducting in the higher resistance state.

[0205] In one form of the technology, the switch 312 includes one or more sections of superconducting material 308 positioned so that a magnetic field generated by a magnetic field generator 306 is applied to the superconducting material such that at least one component of the magnetic field is perpendicular to a surface of the one or more sections of superconducting material. For example, the one or more sections of superconducting material may be located at the ends of a stator arm 320 between a stator and a rotor such that when the magnetic field generator passes over the switch, a magnetic field from the magnetic field generator is applied to the one or more sections of superconducting material 308 such that at least one component of the magnetic field is perpendicular to a surface of the superconducting material. In some forms, the magnetic field may be substantially perpendicular to a surface of the superconducting material 308.

[0206] In one form of the technology, the switch 312 may be located on the stator at a distance from the axis of rotation 317 of the rotor that is substantially equal to the distance of the magnetic field generator 306 from the axis of rotation 317. In some examples, the switch 312 may be located between the arm 320 of the stator 304 and the field spreader 1102, as described herein. However, this should not be viewed as a limitation of the present invention, as the magnetic field generated by the magnetic field generator may be configured to be applied to one or more sections of superconducting material 308 such that at least one component of the magnetic field is perpendicular to the surface of the superconducting material. For example, referring to Figure 4A , the switch can be set on the second arm 320B of the stator, between the rotor 302 and the stator 304.

[0207] In other forms of the technology, the stator may have a multi-component structure. For example, the stator may include a first stator component and a second stator component, wherein the switch is located between the first stator component and the second stator component.

[0208] In some forms of this technology, J can be used due to low circuit complexity, high off-state resistance, and fast response time. c (B) Switch. However, this should not be viewed as a limitation of the technology, and other possible switch mechanisms that may be used in conjunction with features of the technology include:

[0209] • Thermal switching, i.e., a switching mechanism that induces a temperature increase in one or more segments of superconducting material 308 to change the Ej behavior (electric field to current density) and switch 312 from a low resistance state to a higher resistance state.

[0210] ·Low temperature MOSFET.

[0211] Self-rectification, which describes a passive switching process caused by a switching portion of one or more sections of superconducting material 308 having a lower critical current than the rest of the circuit. In use, a current pulse is provided to one or more sections of superconducting material 308 that exceeds the critical current of the switching portion, thereby switching the switching portion from a low resistance state to a higher resistance state.

[0212] • AC field rectifiers, which use electromagnets to generate an AC field oriented in a direction perpendicular to the superconducting tape, thereby increasing its resistance.

[0213] · Shielded current loops, such as those described in PCT Publication No. WO / 2021 / 080443, the contents of which are incorporated herein by reference in their entirety.

[0214] Although these other switching techniques may be used, it should be understood that J c (B) switches, they may have many limitations. For example, thermal switches generally cannot operate at high frequencies and therefore may not be well suited for use in regulation applications. A heat source and control circuit are also required, which generally results in increased cooling requirements. Similarly, the on (low resistance state) resistance of a refrigerant MOSFET is non-zero, which may increase heating of the system. Self-rectifying circuits have a simple overall topology, but they are less flexible and cannot allow full-wave rectification of the current.

[0215] Although AC field rectifiers may be similarly adapted for use with the present technology, we note that some AC field rectifiers rely on dynamic resistance to switch switch 312 to a higher resistance state. c (B) The working principle of the switch is that when the superconducting material 308 is subjected to a vertical magnetic field, the critical current of one or more sections of the superconducting material 308 changes, that is, the EJ characteristics of the switch 312 are changed.

[0216] There is also some evidence that J c (B) The off-state resistance of the switch can be higher than the dynamic resistance caused by the AC field rectifier, which can lead to more efficient regulation.

[0217] This form of technology utilizes different mechanisms that can be used to achieve switching of an electrical switch 312 formed of (including) superconducting materials. The individual mechanisms will now be described, and then examples of how certain forms of technology utilize these mechanisms in combination will be described.

[0218] 6.5.3.1. Effect of magnetic field on critical current of superconducting materials

[0219] The critical current in the superconducting material 308 depends on the external magnetic field applied to the superconducting material 308. More specifically, as a higher external magnetic field is applied to the superconducting material 308, the critical current decreases until a value of the critical magnetic field, beyond which the superconducting material 308 is no longer in a superconducting (low resistance) state. This relationship is Figure 2 , which is a graphical representation of a graph of the electric field versus current in a superconducting material when three different magnitudes of external magnetic field are applied. app1 Leading to the lowest critical current Ic1 .

[0220] Forms of the technology involve electrical switches that exploit the principle that the critical current of a superconducting material is reduced when a higher external magnetic field is applied to the material. By selectively applying a magnetic field to the superconducting material, such as a substantially constant magnetic field over a period of time (i.e., a DC field), the critical current can be raised or lowered relative to the transmission current in order to switch the superconducting material between a low resistance state and a higher resistance state. In some forms, a combination of switching mechanisms may be used. That is, in some forms, a high temperature superconductor (HTS) may need to have an impractically high electric field applied thereto so that the electric field itself switches the superconducting material 308 to a non-superconducting, higher resistance state, but an electric field of practical magnitude may be applied to sufficiently reduce the critical current for another mechanism to achieve switching.

[0221] 6.5.3.2. Effects of time-varying magnetic fields on superconducting materials - dynamic resistance and heating

[0222] Some forms of this technology can exploit the phenomenon of dynamic resistance. This occurs when the superconducting material 308 is exposed to a time-varying magnetic field while carrying a DC transmission current. This creates a DC resistance in the superconducting material 308 that can be large enough to cause the superconducting material 308 to switch to a higher resistance state.

[0223] The DC resistance in the superconducting material 308 caused by this phenomenon may additionally result in energy losses through heating of the superconducting material 308. Heat losses may also occur due to magnetization when a time-varying magnetic field is applied to the superconducting material 308. Losses due to dynamic resistance may occur in regions that carry current, such as the center region of the section of superconducting material, while magnetization losses may occur at the edge regions of the superconducting material. The amount of heating may depend on the frequency and amplitude of the applied time-varying magnetic field.

[0224] The time-varying magnetic field that causes the dynamic resistance phenomenon may be an alternating magnetic field, such as a sinusoidally varying magnetic field.

[0225] In the case of a superconducting material having a length significantly greater than its width or depth (e.g., a wire or ribbon), the dynamic resistance is primarily caused by the component of the time-varying magnetic field applied to the superconducting material that is perpendicular to the direction along the length of the material.

[0226] 6.5.3.3. Heating of superconducting materials

[0227] As mentioned above, the critical current of a superconducting material is a function of the type of superconducting material used and the physical arrangement of the superconducting material. The critical current also depends on the temperature of the superconducting material. As the temperature of the superconducting material increases, the critical current decreases. This relationship persists until a critical temperature, above which the superconducting material is no longer superconducting.

[0228] Forms of the present technology involve electrical switches that exploit the principle that the critical current of a superconducting material decreases as the temperature of the superconducting material increases. By selectively heating the superconducting material, the critical current can be raised or lowered relative to the transmission current in order to switch the superconducting material between a low resistance state and a higher resistance state.

[0229] Different forms of the technology may use different mechanisms to heat the superconducting material in the electrical switch 312, and the forms of the technology may not be limited to the mechanism used to achieve heating. However, two examples of mechanisms for heating superconducting materials are provided in exemplary forms of the technology. These two mechanisms are now briefly explained.

[0230] First, a heating element may be disposed in thermal contact with the superconducting material. The heating element may be, for example, a resistive heating element that converts electrical energy into thermal energy through a process of Joule heating when an electric current flowing through a conductor encounters a resistance. The heating element may be disposed in physical contact with the superconducting material to heat the material primarily by conduction, or spaced apart from the superconducting material to heat the material primarily by convection and / or radiation.

[0231] Second, forms of the present technology may exploit the heating effect induced by applying a time-varying magnetic field (eg, an alternating magnetic field, which may be referred to as an AC field) to a length of superconducting material resulting from dynamic resistance and magnetization phenomena, as explained above.

[0232] 6.5.3.4. Shielding current

[0233] Applying a time-varying magnetic field to a loop of superconducting material causes a screening current to flow around the loop, which, combined with the transmission current carried by the loop, may exceed the critical current of the superconducting material. Thus, by selectively applying a time-varying magnetic field to a loop of superconducting material, the loop can be switched between a low resistance state and a higher resistance state.

[0234] The form of an electrical switch utilizing such a switching mechanism will now be described. It should be understood that where features are described below with respect to an exemplary form of an electrical switch 312 utilizing the mechanism alone, these features may also be used in any form of an electrical switch utilizing a combination of switching mechanisms later in this specification. Further details of such a switching mechanism are provided in PCT Application No. PCT / NZ2020 / 050132, the contents of which are incorporated herein by reference.

[0235] Fig. 9Schematic diagram of a switch 312 operating based on the principle of inductive screening current. The switch 312 includes one or more sections of superconducting material 308 connected between a first terminal 902 and a second terminal 904. The use of terminals in this example should not be considered a limitation of the technology, and the switch can be integrated with other components of the superconducting material 308 described herein, such as a load 314 and an induction coil 310.

[0236] In use, when a magnetic flux is induced in the stator 304 due to the magnetic field generator, for example, a current I t flows between the first terminal 902 and the second terminal 904. It should be understood that the transmission current I t The current induced in the induction coil 310 may be time varying and provided with a phase or time offset relative to the current induced in the induction coil 310 .

[0237] Transmission current I t It is shown as flowing from a first (positive) terminal 902 to a second (negative) terminal 904, as expected for a conventionally defined direct current (DC) voltage. The superconducting material 308 between the two terminals 902, 904 is formed in a ring 906 that includes two parallel superconducting branches 908a, 908b.

[0238] The branches 908a, 908b may be formed using any method that provides a substantially zero resistance joint, such as by splitting the superconducting tape into two parallel branches. Alternatively, a non-zero resistance joint may be used, such as by welding.

[0239] In use, a transmission current is applied between the first terminal 902 and the second terminal 904, and then a time-varying magnetic field B is applied in a direction perpendicular to (or having a direction perpendicular to) the plane of the ring 906, that is, in a direction parallel to the axis of the ring 906. app (t) is selectively applied to or within the ring 906, wherein the axis is perpendicular to the plane of the ring 906. For example, a time-varying magnetic field may be applied to the ring by passing the stator arms 320 through the ring.

[0240] The time-varying magnetic field B app (t) makes the shielding current (I s ) flows between the branches 908a, 908b of the loop 906 to counteract the flux variation in the loop 906. The screening current I s The transmission current flowing around the ring 906 is increased, and as a result, the total current increases. This increase in current may result in a marginal increase in the resistance of the superconducting material (e.g., when the current is less than the critical current I c ) or a significant increase in the resistance of the superconducting material (for example, when the current I c close to, greater than or equal to the critical current of the superconducting material 308).

[0241] 6.5.3.5. Combination of switching mechanisms

[0242] It should be understood that the switch 312 can be constructed using any combination of the above switching mechanisms. For example, the switch 312 can be constructed using a combination of the following:

[0243] • Self-rectification with Jc(B) switching. In other words, the portion of the superconducting material exposed to the perpendicular magnetic field can be configured to have a lower critical current than the rest of the superconducting material.

[0244] • Self-rectification together with screening current loops. In other words, the section of superconducting material used in ring 906 can be configured to have a lower critical current than the rest of the superconducting material.

[0245] • Shielding current loop together with AC field rectifier. In other words, a loop may be formed in the superconducting material 308 to provide a shielding current loop switch 312. In use, a time varying magnetic field may pass through the loop and through a portion of the superconducting material.

[0246] 6.5.4. Load

[0247] In some examples of the technology described herein, a load 314 is connected in parallel with a switch 312. This configuration should not be viewed as limiting the technology, as in some applications it may be desirable to use a flux pump to increase the current in the load before disconnecting the load from the flux pump for use elsewhere. In other words, the technology may include two or more output terminals configured to be connected to a load in use, the two or more output terminals being electrically connected in parallel with a switch.

[0248] The load 314 may be a load coil, or any circuit that receives current from the flux pump described herein in use. In some examples, the load 314 is comprised of a loop of superconducting material, as is familiar to those skilled in the art. In other examples, the load 314 is a portion of a superconducting circuit. Thus, the flux pump configurations described herein may be used to increase the current in one or more sections of superconducting material 308 on a cycle-by-cycle basis, as well as to maintain the current in one or more sections of superconducting material 308 during use.

[0249] 6.6. Improved Flux Pump Device

[0250] While the foregoing discussion may provide a functional flow pump, the inventors have identified further improvements to the technology. These include any one or more of the following:

[0251] Add a shunt resistor between the induction coil 310 and the load 314 and the switch 312;

[0252] Use field spreader 1102 to improve J c (B) flux penetration of switch 312;

[0253] Tuning the flux gap to improve electromagnetic field coupling between the rotor 302 and the stator 304; and

[0254] Adjust the phase angle / timing relationship between the induced current in the induction coil 310 and the activation of the switch 312 .

[0255] Each of the foregoing will now be discussed in more detail.

[0256] 6.6.1. Shunt resistor

[0257] As previously discussed, it is currently impossible or otherwise commercially unfeasible to create superconducting joints in high temperature superconducting materials. Thus, while the present invention may be implemented using a single continuous length of superconducting material 308 that is appropriately configured to provide an induction coil 310, a switch 312, and a load 314, in some examples of the technology, it may be beneficial to include one or more joints, such as normal conducting joints with which those skilled in the art should be familiar.

[0258] Fig.10 Shows Figure 3 A modified version of the schematic diagram of FIG. 3 is shown in which a shunt resistor R is introduced between the induction coil 310 and the parallel switch 312 and the load 314. 2 The shunt resistance may represent the resistance introduced by, for example, a normal conductive joint, such as a solder joint with which one skilled in the art will be familiar. It will be appreciated that by overlapping one or more sections of normal conductive material (otherwise known as a lap joint), the relative resistance of the normal conductive material may be lower than by using a connection method such as an end-to-end or butt joint. In some examples of the technology, a normal conductive material such as copper may be used.

[0259] In other words, in some forms of the technology, the flux pump may include a shunt resistor electrically connected in series between the induction coil 310 and the switch 312. For example, the shunt resistor may be provided by a constant-conductance joint.

[0260] It should be understood that the current entering the load 314 is proportional to the voltage V 2 proportionally, therefore, by increasing the voltage V 2 , it can be expected that the current in the superconducting material 308 should increase. Therefore, conventional wisdom is to use the smallest possible shunt resistance R 2 , to reduce R 2 R 2 and the resulting voltage divider between the combined impedance of the load 314 in parallel with the switch 312Rs. However, the inventors have discovered that increasing the shunt resistor value R 2A higher load current may be generated in the load 314 .

[0261] Assume that the current i 2 In a stable state, the voltage V 2 Defined as:

[0262] V 2 =-i 2 R 2

[0263] Therefore, increasing the shunt resistor value R 2 can result in an increased voltage V 2 Voltage V 2 The higher the current is, the faster the current is delivered to the load 314. Assuming further that I L is the maximum load current:

[0264] V 2 =i L R L

[0265] Further combining the above equations gives:

[0266] i L R L =-i 2 R 2

[0267] Therefore, the maximum load current i L byi 2 and R 2 With R L If R 2 The smaller the maximum load current is, the smaller the maximum load current is. Therefore, it may be beneficial to increase the resistance of the induction coil 310 and the switch. 2 Another advantage is that it can allow easy measurement of the current flowing in a circuit.

[0268] 6.6.2. Field spreader

[0269] Further improvements to the flux pump designs described herein can be provided by improving the flux penetration of switch 312 to allow for a larger resistance difference between the low resistance and higher resistance states. In other words, by exposing switch 312 to a higher strength magnetic field, a higher resistance can be achieved. Figure 2 A greater reduction in the critical current of superconducting material 308 is illustrated.

[0270] Thus, one feature of the present technology is to provide a field spreader 1102 for coupling the magnetic field from the rotor 302 and providing a uniform magnetic field over at least a portion of the switch, such as one or more sections of superconducting material of the switch 312. The term "field spreader" as used in this specification should not be seen as limiting, but should be understood to refer to any component configured to guide a magnetic field through a superconductor, in particular through a switch, such as by providing a uniform field through the switch. The term "spreader" should be interpreted in the context of guiding a magnetic field or otherwise coupling or uniformly distributing a magnetic field. In some examples of the technology, the field spreader can concentrate the magnetic field so as to increase the coupling of the magnetic field to the switch.

[0271] Fig.11A and 11B Shown according to Figure 3 An example of how the magnetic field strength is distributed within the rotor 302 and stator 304 is shown in the form of a flux pump design. As shown, the stator 304 is provided with a field spreader 1102, which is configured to concentrate or otherwise direct the magnetic field from the rotor 302 through the switch 312. To achieve this, preferably, the field spreader 1102 is made of a material having a higher magnetic permeability than the environment surrounding the field spreader 1102, for example, when the field spreader 1102 is in an air environment, the field spreader 1102 should have a higher magnetic permeability than air, for example, iron can be used.

[0272] The field spreader 1102 may be located between the magnetic field generator 306 and the switch 312 on the stator 304 such that when the magnetic field generator moves past the field spreader 1102 , it creates a uniform magnetic field for the switch 312 portion of the superconducting material 308 .

[0273] It is further beneficial to ensure that the field spreader 1102 is substantially located in the center of the stator arm 320A so as to minimize the maximum measurable distance from the edge of the field spreader 1102 to the edge of the stator arm 320, see Fig. 11B D1 and D2 in .

[0274] It may also be advantageous for the field spreader 1102 to have substantially the same width as the magnetic field generator so that the magnetic flux generated from the magnetic field generator is evenly coupled through the field spreader 1102 , through the switch 312 , and into the stator arm 320 .

[0275] 6.6.3. Flux gap

[0276] It will be appreciated by those skilled in the art that the spacing between the magnetic field generator and the stator 304 should preferably be kept to a minimum in order to obtain maximum flux coupling between the rotor 302 and the stator 304. This spacing may be referred to as a flux gap. For example, the inventors have found that a reduction in the flux gap from 6 mm to 1 mm results in a 20% increase in induced current and voltage.

[0277] It should be understood that in examples of techniques where the stator 304 and the rotor 302 are separated by the cryostat 702, such as Figure 7C As shown, there is a tradeoff between the flux gap and the amount of insulation that may be located between the rotor 302 and the stator 304 .

[0278] 6.6.4. Switching phase angle

[0279] In the foregoing examples, the switch 312 has been positioned so that it is activated simultaneously with the induction current in the induction coil 310. For example, the induction coil 310 may be located on the same stator arm 320 as the switch 312, such as Figure 8 In another example, the induction coil 310 can be positioned directly opposite (180 degrees opposite) the switch 312, in which case multiple magnetic field generators 306 are used, which are also positioned opposite to each other on the rotor 302. In this way, when one of the magnetic field generators 306 passes through the induction coil 310, another of the magnetic field generators 306 passes through the switch 312, thereby synchronizing the induced current with the rectification caused by increasing the resistance of the switch 312.

[0280] See also Fig. 12A , the stator arm 320 described herein should be understood to include any component of the stator 304 that is configured to carry the magnetic field from the magnetic field generator on the rotor 302 and couple the magnetic field back to the rotor 302. For example, in Fig. 12A In FIG. 3 , this includes a central magnetic return path 320C, steel / ferromagnetic teeth 320A which are attached to the induction coil 310 in use, and steel walls 320B.

[0281] Stator arm 320B may be configured to provide a wall that allows for continued conduction of magnetic flux generated by magnetic field generator 306, including when switch 312 and / or induction coil 310 are not in the direct presence of the magnetic field. This may advantageously reduce cogging torque as described herein.

[0282] In some forms of the technology, other features of the stator 304 may include an annular bolt hole 1208 which may advantageously allow liquid coolant to flow into the stator 304, as well as be used to secure components of the stator 304 together.

[0283] Optional tape slots may also be provided in the stator 304 through which the superconducting material of the switch 312 passes when in use. In other words, the superconducting material may wrap around the stator arm 320 so that a portion of the tape is located between the stator arm 320 and the magnetic field generator described herein. It should be understood that the use of tape slots is optional, and other switch 312 configurations that do not require tape slots are described herein, including bifilar configurations.

[0284] In some forms of this technology, such as Fig. 12A and 12B In the forms shown in , the flux pump may include a switch holder 1212 configured to adjust the position of the switch 312 relative to the induction coil 310 to be adjusted. For example, the switch holder 1212 may be configured to engage one or more of a plurality of angle marks 1210 corresponding to possible switch 312 positions. For example, the plurality of angle marks may be positioned to each provide an offset of + / - 1 degree. This arrangement allows the relative positioning and therefore the phase relationship of the induced current in the induction coil 310, and the activation of the switch 312 to be adjusted. For example, Fig. 12B A switch holder 1212 is included, whose position is adjustable relative to the stator arm 320. The switch holder 1212 may be configured to slide along the annular stator arm 320. The stator arm 320 may be arcuate in other forms.

[0285] In some forms of the technology, the switch holder 1212 includes an opening that, in use, can receive a field spreader 1102 as described herein, and a slot 1214 that is configured to, in use, receive one or more sections of superconducting material 308. For example, the switch holder 1212 can be configured such that the field spreader 1102 is directly above the one or more sections of superconducting material 308 and directs a magnetic field from a magnetic field generator into the one or more sections of superconducting material 308 to produce the switching action described herein.

[0286] The switch holder is preferably made of a material with low magnetic permeability and low electrical conductivity to reduce the generation of eddy currents. For example, the switch holder 1212 can be made of G10 (high pressure glass fiber laminate).

[0287] Fig. 12C Shown by Fig. 12A and 12B 310 with different angular positions of the switch 312 relative to the induction coil 310. The effect of different rotor 302 speeds in revolutions per minute was also tested and shown in the figure. Note that there are two different zero values ​​recorded on the graph because the system was tested with the rotor 302 rotating in both clockwise and counterclockwise directions.

[0288] The results of the graphs are summarized in the table below:

[0289]

[0290]

[0291] Table 1 - Effect of rotation speed, direction and phase shift on maximum current

[0292] The results indicate that there is some asymmetry within the test device, which the inventors believe can be attributed to the low number of turns used in the induction coil 310, resulting in highly asymmetric areas within the loop.

[0293] Independently of the above, it was found that the peak load 314 current was identified as having a phase offset angle of 10 degrees, and it is believed that a phase offset between 0 and 13 degrees can result in an overall higher load 314 current than a switch 312 and inductive coil 310 having a zero degree offset or being completely opposite (180 degrees opposite) in a flux pump.

[0294] In other words, in certain forms of the technology, the flux pump may include a switch and an induction coil, wherein the switch is configured to activate (switch from a low resistance state to a higher resistance state) with a phase delay or time delay relative to the current induced in the induction coil 310. More specifically, it may be advantageous to locate the switch 312 within the flux pump such that the switch 312 is activated within + / - 13 degrees of the current induced in the induction coil 310. In forms of the technology including two or more magnetic field generators 306, it may be advantageous to locate the switch 312 between 167 degrees and 193 degrees relative to the induction coil 310. In other words, it may be advantageous to provide a phase delay of approximately + / - 3.6% of the period of the current induced in the induction coil.

[0295] The use of phase delays can advantageously allow for the rectification of selective characteristics of the induced current in the induction coil. For example, the phase delay between the induced current in the induction coil and the activation of the switch can be used to select specific characteristics of the induced current characteristic waveform that may be desirable and should therefore be delivered to the load. For example, it may be known that the current induced in the induction coil oscillates between positive and negative values, as described herein with respect to Fig.15 As described, therefore, by controlling the phase delay between the induced current in the induction coil and the activation of the switch, the positive or negative portion of the induced current waveform can be selected for regulation. In other words, certain forms of flux pump devices of the technology described herein can be configured to selectively regulate current in the positive direction and / or the negative direction. In addition, by controlling the phase offset, the polarity of the regulation can be changed during operation of the flux pump.

[0296] While the foregoing examples are described with respect to waveform polarity adjustment, this should not be viewed as limiting, and any desired characteristic of the waveform may be selectively targeted by adjusting the phase relationship as described herein. For example, in other forms, the phase delay may be configured to selectively transfer to the load any one or more of: peak induced current, induced current exceeding a predetermined threshold, and / or frequency characteristics of the induced waveform.

[0297] In another form of this technology, by adjusting the relative sizes of the induction coil 310, the switch 312, and the magnetic field generator 306, it is possible to adjust how long the magnetic field generator acts on the induction coil 310 and the switch 312. For example, a larger magnetic field generator can hold the switch 312 in a higher resistance state for a longer duration and thus change the optimal phase relationship between the induction coil and the switch.

[0298] Fig.12D 310 , which has been configured so that the peak current induced in the load occurs with a substantially zero degree phase offset between activation of the switch 312 and the inductive coil 310. Or more generally, the optimal phase offset between the switch 312 and the inductive coil 310 may be between about -10 degrees and about 5 degrees. Fig.12D The data are summarized in the following table:

[0299]

[0300] Table 2 - Alternative examples of the effects of rotation speed, direction and phase offset on maximum current

[0301] according to Fig.13 In one form of the technology shown, a flux pump is provided that includes a rotor 302 and a stator 304 located within a housing 701. In this example, the housing 701 includes a bearing set that supports a shaft 316 in use. In this example, a first stator arm 320A includes an induction coil 310, while an opposing stator arm 320B includes a switch holder 1212 that allows adjustment of the positioning of the switch 312 relative to the induction coil 310.

[0302] 6.6.5. Induction current frequency

[0303] from Fig. 12C It can also be seen from the graph that in one experimental example, when the flux pump was operated in a first direction, the peak induced current was found at about 150 RPM, and when the flux pump was operated in a second, opposite direction, the peak induced current was found at about 125 RPM. It is believed that these differences are due to the asymmetric nature of the test structure discussed above.

[0304] Thus, for a given rotational speed and / or number of magnetic field generators 306 located on rotor 302 , the phase offsets described herein may be expressed as time offsets.

[0305] It should also be understood that the optimal rotational speed determined in the experiments performed was using a rotor 302 having two magnetic field generators 306. However, this should not be viewed as limiting the technology, for example, in a form of the technology including a single magnetic field generator, a speed at which the peak current is induced can be expected to be between about 250 RPM and 300 RPM. Similarly, in examples of the technology using more magnetic field generators 306 (e.g., 4, 6, or 8 generators), a corresponding reduction in RPM can be expected in order to obtain the peak induced current.

[0306] 6.7. Two-wire switch structure

[0307] exist Fig.14A The J according to the present technology is shown in c (B) An example of a switch 312. In this example, one or more sections of superconducting material 308 surround stator arms 320, such as with Fig. 12A and 12B The switch holder discussed. In other words, in one aspect of the present technology, the switch may include one or more sections of superconducting material 308 disposed in a loop around the stator arms.

[0308] In another aspect of the technique, a switch 312 may be provided by looping one or more sections of superconducting material 308 back onto itself to provide a two-wire arrangement.

[0309] In the context of this specification, unless otherwise stated, a "two-wire arrangement" is understood to mean an arrangement of two conductors, wherein the two conductors are substantially parallel and electrically connected so that current flows through the two strands in opposite directions. The strands may be closely adjacent to each other. The strands may be two sections of a length of superconducting material which is folded in half upon itself. Alternatively, the two strands may be separate lengths of superconducting material which are electrically connected together, for example by welding, diffusion bonding or other suitable form of electrical connection.

[0310] The bifilar arrangement described herein may be located on or adjacent to a ferromagnetic member such as a stator arm to couple the magnetic field from the magnetic field generator through the one or more sections of superconducting material. In some aspects of the present technology, the bifilar arrangement may be disposed between a field spreader as described herein and a stator arm.

[0311] A potential advantage of the two-line construction is that Fig.14ACompared to the loop arrangement of the double wire, the loop area of ​​the superconducting material 308 can be reduced, and thus the inductance can be reduced. In addition, this arrangement reduces the self-field effect of the switch 312, because the fields generated on each side of the double wire arrangement cancel each other.

[0312] This two-wire configuration allows switch 312 to generate voltage without inducing any current. For comparison, known generator flux pumps use a single HTS ribbon that induces current and generates voltage. Other potential advantages of the two-wire configuration include reduced inductance of switch 312 when compared to a similar switch with a single section of superconducting material.

[0313] Another advantage of the switch 312 including a two-wire arrangement of a section of superconducting material is that it helps reduce the suppression of the critical current of the section of superconducting material when the magnetic field applied to the section of superconducting material is low, such as zero. This results in a higher critical current for the low resistance state of the switch 312.

[0314] exist Fig. 14C In another form of the technology shown, a two-wire switch is provided in which two layers of superconducting material 308 are stacked on top of each other and connected by a joint such as a conventional or welded joint 1402. This arrangement can advantageously further reduce loop inductance, as well as address any minimum bend radius issues that may exist in a single length of superconducting material, such as Fig.14A and 14B The example shown in .

[0315] Further examples and applications of two-wire switch structures using superconducting materials are provided in PCT Application No. PCT / NZ2022 / 050009, the entire contents of which are incorporated herein by reference.

[0316] Experimental data

[0317] Fig.15 An example of the present technology in use is shown, where no optical trigger is used in the graphs shown, but the point at which the magnetic field generator 306 is aligned with the induction coil 310 can be determined experimentally. 接头 Represents the voltage drop across the series shunt resistor, V 线圈 is the induced voltage in the induction coil 310, V 桥 represents the voltage across switch 312. Note that the phase offset relative to the light trigger means that switch 312 is activated at approximately the peak of the voltage induced in induction coil 310.

[0318] V 负载 is the measured value of the voltage across the load 314, and V 霍尔 is a measure of the magnetic field within the load 314. Note that the load 314 field remains positive and increases slightly on a cycle-by-cycle basis.

[0319] In summary, the rotation of the one or more magnetic field generators 306 relative to the induction coil 310 causes a current to flow in the induction coil. The current begins before the magnet passes through the induction coil and has a peak induced current (represented by a peak voltage of approximately 1.9 mV) shortly thereafter. The current has a large positive component before swinging negative and decays over time.

[0320] Shortly after the peak current is observed in the induction coil 310 (e.g., approximately 0.01 seconds later), a peak voltage (V 桥 This corresponds to at least one magnetic field generator 306 reducing the critical current of switch 312 and thus switching switch 312 from a low resistance state to a higher resistance state.

[0321] In the example shown, the total period of the waveform is approximately 0.2 seconds, so a 0.01 second delay between the peak current in the induction coil and the peak voltage across the switch corresponds to approximately a 5% delay or 18 degrees of phase shift between the induction coil and the switch.

[0322] The increase in switch resistance corresponds to an increase in the voltage across the load, which can be seen to decay before the switch resistance increases. This causes the voltage measured by the Hall Effect sensor (V 霍尔 ) is indicative of the current in the load. Thus, activating the switch in sync with the peak current induced in the induction coil provides a net DC rectified load 314 current.

[0323] 6.9. Other notes

[0324] Unless the context clearly requires otherwise, throughout the specification and claims, the words "comprise", "comprising", etc. should be construed in an inclusive sense rather than an exclusive or exhaustive sense, ie, in the sense of "including but not limited to".

[0325] The entire disclosures of all applications, patents, and publications cited above and below, if any, are incorporated herein by reference.

[0326] The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that that prior art forms part of the common general knowledge in the field of endeavor anywhere in the world.

[0327] The present technology may also be broadly stated as consisting of the parts, elements and features mentioned or indicated in the specification of the present application, either individually or collectively, in any or all combinations of two or more of said parts, elements or features.

[0328] Where in the foregoing description reference has been made to integers or components having known equivalents thereof, these integers are herein incorporated as if individually set forth.

[0329] It should be noted that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the present technology and without reducing its incidental advantages. Therefore, such changes and modifications are intended to be included in the present technology.

Claims

1. A device for inducing current in a load, the device include: a rotor comprising at least one magnetic field generator configured to rotate with the rotor, wherein the at least one magnetic field generator generates a magnetic field, and one or more lengths of superconducting material arranged to provide an induction coil, a switch, and two or more output terminals configured to be connected to the load in use, the two or more output terminals being electrically connected in parallel with the switch, wherein the rotation of the rotor causes the at least one magnetic field generator to move relative to the induction coil and the switch, such that: The magnetic field is periodically applied to the induction coil to induce a current in the induction coil, at least a portion of the current being configured to flow through the switch, and the magnetic field is periodically applied to the switch and reduces a critical current of a superconducting material within the switch, such that the magnetic field and the current within the switch cause the switch to transition from a low resistance state to a higher resistance state.

2. A device for inducing current in a load, the device include: a rotor comprising at least one magnetic field generator configured to rotate with the rotor, wherein the at least one magnetic field generator generates a magnetic field, and stator, wherein the stator is provided with one or more sections of superconducting material, the superconducting material being arranged to provide an induction coil, a switch, and two or more output terminals configured to be connected to the load in use, the two or more output terminals being electrically connected in parallel with the switch, wherein, in use, the rotor is configured to rotate relative to the stator, and the at least one magnetic field generator is configured to periodically apply the magnetic field: to the induction coil to induce a current in the induction coil, and to the switch to transition the switch between a low resistance state and a higher resistance state for a given current in the switch.

3. A device for inducing current in a load, the device include: a rotor comprising at least one magnetic field generator configured to rotate with the rotor, wherein the at least one magnetic field generator generates a magnetic field, and stator, The stator is provided with: an induction coil, a switch configured to switch between a low resistance state and a higher resistance state, and two or more output terminals configured to be connected to the load in use, the two or more output terminals being electrically connected in parallel with the switch, wherein, in use, the rotor is configured to rotate relative to the stator, and the at least one magnetic field generator is configured to periodically apply the magnetic field to the induction coil and the switch, the induction coil and the switch: inducing a current in the induction coil when the induction coil moves relative to the induction coil, and for a given current, causing the switch to switch between the low resistance state and the higher resistance state, wherein the magnetic field is applied to the switch with a phase delay relative to the magnetic field applied to the induction coil.

4. The device according to any one of claims 1 to 3, in, The magnetic field generated by the magnetic field generator is applied to the switch such that a component of the magnetic field is applied in a direction perpendicular to a surface of the switch.

5. The device according to any one of claims 1 to 4, in, The rotor comprises a drive shaft, and wherein a longitudinal axis of the drive shaft defines an axis of rotation about which the rotor rotates in use.

6. The device according to claim 5, in, The at least one magnetic field generator is located radially outside the rotation axis.

7. The device according to any one of claims 1 to 6, in, The rotor is configured to provide a high magnetic permeability path for a magnetic field generated by the magnetic field generator.

8. The device according to any one of claims 1 to 7, in, The rotor comprises a ferromagnetic material.

9. The device according to any one of claims 1 to 8, in, The rotor includes a plurality of magnetic field generators.

10. The device according to claim 9, in, Each of the plurality of magnetic field generators is located at a position at a substantially same radial distance from the rotation axis of the rotor.

11. The device according to claim 10, in, The plurality of magnetic field generators are substantially evenly distributed about the rotation axis such that angles between each of the plurality of magnetic field generators are substantially the same when measured relative to the rotation axis.

12. The device according to any one of claims 1 to 11, in, The at least one magnetic field generator is located at a radial distance from the rotation axis of the rotor that is substantially the same as the radial distance of the switch from the rotation axis.

13. The device according to any one of claims 1 to 12, in, The at least one magnetic field generator is located on a side of the rotor closest to the induction coil and the switch.

14. The device according to claim 1, in, The induction coil, the switch and the two or more output terminals are arranged on the stator.

15. The apparatus according to any one of claims 2, 3 or 14, in, The stator is configured to provide a high magnetic permeability path for a magnetic field generated by the magnetic field generator.

16. The device according to claim 15, in, The high magnetic permeability path includes ferromagnetic material.

17. The apparatus according to any one of claims 1 to 16, in, The switch is located between about 167 degrees and about 193 degrees relative to the induction coil when measured about the axis of rotation of the rotor.

18. The device according to claim 3, in, The phase delay is between approximately -13 degrees and approximately +13 degrees.

19. The device according to claim 3, in, The phase delay is between about +3.6% and about -3.6%.

20. The apparatus according to any one of claims 1 to 19, in, The magnetic field generator includes a permanent magnet.

21. The apparatus according to any one of claims 1 to 19, in, The magnetic field generator includes an electromagnet.

22. The apparatus according to any one of claims 1 to 21, further comprising a field spreader, in, The field spreader is configured to generate a uniform magnetic field in at least one section of superconducting material of the switch.

23. Apparatus according to any one or more of claims 1 to 21, in, The switch and induction coil are located within the cryostat.

24. A rectifier, the rectifier include: a rotor, the rotor comprising at least one magnetic field generator configured to rotate with the rotor, wherein the at least one magnetic field generator generates a magnetic field, induction coil, and a switch comprising one or more sections of superconducting material, wherein, in use, the rectifier is configured to be connected to a load, the load being electrically connected in parallel with the switch, wherein, in use, the rotor is configured to rotate to move the at least one magnetic field generator relative to the induction coil and the switch to periodically apply the magnetic field to the induction coil and the switch such that: inducing a current in the induction coil, the current having a positive component and a negative component over time, wherein at least a portion of the current is configured to flow through the switch and the load, and a magnetic field applied to the switch reduces a critical current of a superconducting material within the switch such that the magnetic field and the current within the switch cause the switch to transition from a low resistance state to a higher resistance state, wherein the magnetic field is applied to the switch in synchronization with the positive component or the negative component of the current, causing the switch to transition to the higher resistance state to increase the amount of current flowing in the load during the positive component or the negative component, thereby providing a net positive current or a net negative current in the load.

25. A system for increasing current in a load, the system include: a rotor, the rotor comprising at least one magnetic field generator configured to rotate with the rotor, wherein the at least one magnetic field generator generates a magnetic field, one or more lengths of superconducting material arranged to provide an induction coil and a switch, and a superconducting load, the superconducting load being electrically connected in parallel with the switch, wherein the rotation of the rotor causes the at least one magnetic field generator to move relative to the induction coil and the switch, such that: The magnetic field is periodically applied to the induction coil to induce a current in the induction coil, at least a portion of the current being configured to flow through the switch and the superconducting load, and The magnetic field is periodically applied to the switch and reduces the critical current of the superconducting material within the switch so that the magnetic field and the current within the switch cause the switch to transition from a low resistance state to a higher resistance state, thereby affecting the amount of current flowing in the superconducting load.

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