Mechanically switchable superconducting flux pump

Abstract

The present invention relates to a device, also known as a flux pump, for inducing current flow in a load. The device includes at least one magnetic field generator configured to rotate with a rotor, one or more lengths of superconducting material arranged as induction coils, a switch, and an output terminal configured to connect to the load, the output terminal being connected in parallel with the switch. Rotation of the rotor causes the at least one magnetic field generator to move relative to the induction coil and the switch, and a magnetic field is periodically applied to the induction coil and the switch to induce current flow in the induction coil through the switch, thereby reducing the critical current of the material in the switch and transitioning the switch from a low resistance state to a high resistance state.

Description

[Technical Field]

[0001] 1. Field of the Invention The present technology relates to the field of superconducting materials, and in particular to techniques for increasing the flow of electrical current in superconducting materials using flux pumping technology. In particular, the technology relates to mechanically switchable superconducting flux pumps. This technology may find particular application in high power motor applications, magnetic resonance imaging, or nuclear fusion. However, this is not considered a limitation of the present technology. [Background technology]

[0002] 2. Background of the invention High-temperature superconducting (HTS) materials, such as wires and tapes, typically have a superconducting transition temperature above 77 K. Below this temperature, HTS materials can achieve high magnetic fields due to very low heat dissipation. A key property of superconducting materials is that in the superconducting state, their resistance is zero or near zero. This means that when electric current flows through a superconducting material, it does not decay as it does in conventional conductors, or at least decays at a much lower rate.

[0003] However, joining HTS materials without using normally conducting (non-superconducting) metal contacts is difficult: if normally conducting contacts are used, significant resistive losses can be introduced into the superconducting circuit, meaning that current must be continuously injected into the circuit to prevent it from decaying, which can require significant power for continuous operation.

[0004] One method for increasing the flow of electrical current in HTS materials is to use a device called a flux pump, which can be used to induce electrical current flow in superconducting materials without contact using electromagnetic flux, allowing current to flow through HTS circuits without the need for normal conductive electrical connections.

[0005] One type of flux pump, known as a dynamo flux pump, is described in U.S. Patent No. 9,972,429. In this dynamo flux pump, a magnetic field is periodically applied to a region of HTS material within a superconducting circuit, creating flux vortices within the HTS material. The flux vortices must penetrate completely through the HTS material in a direction perpendicular to the desired direction of net current flow around the superconducting circuit. There is a minimum applied magnetic field strength at which complete flux penetration occurs; this minimum penetrating field is known as B 浸透 Dynamo configurations produce a net DC transport current, but the design generally has high losses because all current must pass through the dynamic resistance created by the magnets. In dynamo flux pumps, penetrating flux vortices can be moved through an HTS material by moving an applied non-uniform magnetic field relative to the HTS material such that the flux vortices are dragged in the direction of movement of the applied field.

[0006] Another type of flux pump is the 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 requires rectification, and the current flowing in the primary coil introduces significant losses. 3. Purpose of the invention

[0007] It is an object of the present invention to provide an improved superconducting flux pump. Alternatively, it is an object of the art to provide a mechanically switchable superconducting flux pump. Alternatively, it is an object of the art to provide an improved device and / or system for inducing current flow in a load. Alternatively, it is an object of the art to provide an improved rectifier. Alternatively, it is an object of the art to at least provide the public with a useful choice. Summary of the Invention

[0008] 4. Summary of the Invention Aspects of the technology relate to electrical devices configured to generate a net direct current flow in one or more lengths of superconducting material.

[0009] In one aspect of the present technology, a device is provided that is configured to induce the flow of electrical current through one or more lengths of superconducting material.

[0010] In one aspect of the present technology, a method is provided for inducing electrical current flow in one or more lengths of superconducting material.

[0011] In one aspect of the present technology, a flux pump configured to induce the flow of electrical current through a length of one or more superconducting materials is provided.

[0012] In one aspect of the present technology, a device for inducing current flow in a load is provided, which may also be referred to as a flux pump. The device 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 device further includes an induction coil, a switch, and one or more lengths of superconducting material arranged to provide two or more output terminals configured to connect to a load in use, the two or more output terminals being electrically connected in parallel with the switch. Rotation of the rotor causes the at least one magnetic field generator to move relative to the induction coil and the switch, and a magnetic field is periodically applied to the induction coil to induce a current flow in the induction coil, at least a portion of the current flow being configured to flow through the switch, and the magnetic field is periodically applied to the switch to reduce a critical current of the superconducting material in the switch, causing the switch to transition from a low resistance state to a high resistance state due to the magnetic field and current flow in the switch.

[0013] In one aspect of the present technology, a device for increasing current flow in a load is provided. The device 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 device may further include a stator. The stator is provided with one or more lengths of superconducting material arranged to include an induction coil, a switch, and two or more output terminals configured to connect to a load in use, the two or more output terminals being electrically connected in parallel with the switch. In use, the rotor is 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 a current flow in the induction coil and to apply a magnetic field to the switch to transition the switch between a low resistance state and a high resistance state for a predetermined current flow in the switch.

[0014] In one aspect of the present technology, a device for inducing current flow in a load is provided, which may also be referred to as a flux pump. The device 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 device may further include a stator. The stator may be provided with an induction coil. The stator may further be provided with a switch configured to transition between a low resistance state and a high resistance state. The stator may further be provided with two or more output terminals configured to connect 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. The at least one magnetic field generator is configured to periodically apply a magnetic field to the induction coil and the switch, inducing a current in the induction coil as the induction coil and the switch move relative to the induction coil, causing the switch to transition between a low resistance state and a high resistance state for a predetermined current flow. The magnetic field may be applied to the switch with a phase delay relative to the magnetic field applied to the induction coil.

[0015] In one aspect of the present technology, a rectifier is provided. The rectifier may include a rotor including a rotor and 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 lengths of superconducting material. In use, the rectifier may be configured to connect to a load, the load being electrically connected in parallel with the switch. 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, periodically applying a magnetic field to the induction coil and the switch to induce a current flow in the induction coil, the current flow having positive and negative components over time, at least a portion of the current flow configured to flow through the switch and the load, the magnetic field applied to the switch reducing a critical current of the superconducting material in the switch, and the magnetic field and current flow in the switch causing the switch to transition from a low resistance state to a high resistance state. The application of a magnetic field to the switch can be synchronized with the positive or negative component of the current flow, causing the switch to transition to a high resistance state, increasing the amount of current flowing to the load during the positive or negative component, thereby providing a net positive or negative current flow to the load.

[0016] In one aspect of the present technology, a system for increasing current flow 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 further include one or more lengths 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. Rotation of the rotor causes the at least one magnetic field generator to move relative to the induction coil and the switch, whereby a magnetic field is periodically applied to the induction coil to induce a current flow in the induction coil, at least a portion of the current flow passing through the switch and the superconducting load. The magnetic field is periodically applied to the switch to reduce a critical current of the superconducting material in the switch, whereby the magnetic field and the current flow in the switch cause the switch to transition from a low resistance state to a high resistance state, thereby affecting the amount of current flowing through the superconducting load.

[0017] In a particular embodiment, the magnetic field generator is configured to generate a magnetic field such that a component of the magnetic field is applied to the switch in a direction perpendicular to the surface of the superconducting material.

[0018] In examples of this technology, the rotor may have an axis of rotation about which the rotor rotates during use. For example, the rotor may be provided with a drive shaft, the drive shaft configured to be attached to a drive source during 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.

[0019] In an example of this technology, the at least one magnetic field generator may be disposed radially outward of the axis of rotation, for example, the at least one magnetic field generator may be configured to move in a circular path as the rotor rotates.

[0020] In an example of this technique, one or more magnetic field generators may be provided on the side of the rotor closest to the stator.

[0021] In examples of this 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 on which at least one magnetic field generator(s) is / are provided.

[0022] In an example of this technology, the rotor may include a material having high magnetic permeability. For example, the rotor may be configured to provide a high-permeability path for the magnetic field generated by the magnetic field generator. For example, the rotor may be constructed of a ferromagnetic material such as iron or steel.

[0023] In an example of this technology, a rotor may be provided with a plurality of magnetic field generators, for example, a first magnetic field generator disposed at a first radial distance from the axis of rotation and a second magnetic field generator disposed at a second distance from the axis of rotation, the first distance being substantially the same as the second distance.

[0024] In an example of this technique, the switch may be positioned at substantially the same radial distance from the axis of rotation as the one or more magnetic field generators, measured from a center point of the switch.

[0025] In an example of this technique, the induction coil may be positioned at substantially the same radial distance from the axis of rotation as the one or more magnetic field generators, as measured from a center point of the induction coil.

[0026] In an example of this technology, the first magnetic field generator may be positioned between 167 degrees and 193 degrees relative to the second magnetic field generator as measured around the axis of rotation.

[0027] In an example of this technology, the switch may be positioned between 167 degrees and 193 degrees relative to the induction coil when measured around the axis of rotation. For example, the first magnetic field generator may be positioned approximately 180 degrees relative to the second magnetic field generator, and the switch may be positioned within a range of 167 degrees and 193 degrees relative to the induction coil, such that as the rotor rotates and at least one magnetic field generator passes the induction coil and switch, a phase offset of up to 13 degrees is provided in the magnetic fields applied to the induction coil and switch.

[0028] In an example technique where two or more magnetic field generators are used, 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 pair of magnetic field generators may be positioned substantially opposite each other. In another example, each pair of magnetic field generators may be positioned within 167 degrees to 193 degrees of each other relative to the axis of rotation.

[0029] In examples of this technology, the flux pumps and rectifiers described herein may further include a stator.

[0030] In an example of this technology, the stator may include a material having high magnetic permeability. For example, the stator may be configured to provide a high permeability path for the magnetic field generated by the magnetic field generator. For example, the stator may be constructed of a ferromagnetic material such as iron or steel.

[0031] In an example of this technology, the one or more magnetic field generators may include permanent magnets. For example, the one or more magnetic field generators may include samarium cobalt (SmCo), alnico, or neodymium iron boron (NdFeB). In another example of this technology, the one or more magnetic field generators may include electromagnets.

[0032] In an example of this technology, the one or more lengths 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.

[0033] In an example of this 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.

[0034] In an example of this technology, the induction coil may include less than one turn of the length of one or more superconducting materials. For example, the induction coil may include one turn or less, such as a quarter turn or a half turn of superconducting material. In another example of this technology, the induction coil may include one or more turns (including non-integer numbers of turns) of the length of one or more superconducting materials. For example, the length of one or more superconducting materials may be looped around one or more arms of the stator. For example, the induction coil may include 1.5 turns, or more than two turns of the length of one or more superconducting materials.

[0035] In an example of this technology, the induction coil may include a section of superconducting material arranged in a substantially arcuate path, a focus of the arcuate path defining a center of the induction coil, and a radial distance from the axis of rotation of the at least one magnetic field generator being substantially the same as the radial distance from the axis of rotation of the center of the induction coil.

[0036] In an example of this technology, one or more of the stator arms may be substantially cylindrical. For example, the radius of the stator arms may be equal to or greater than the minimum bending radius of the superconducting material. For example, one or more of the stator arms may have a radius of 50 mm or greater.

[0037] In this example of technology, the switch is called "J c(B) A switch may be referred to as a "switch." In other words, the switch may be configured or arranged such that the magnetic field generated by the magnetic field generator affects a maximum critical current of the one or more lengths of superconducting material, thereby transitioning the superconducting material between a first low resistance state and a second high resistance state for a given current through the switch. 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 a surface of the one or more lengths of superconducting material.

[0038] In one example of this technology, the switch may be located on the same stator arm as the induction coil, while in another example of this technology, the switch may be located on the stator arm opposite the induction coil, such as a stator arm located within 167 degrees to 193 degrees of the stator arm that makes up the induction coil.

[0039] In an example of this technology, the flux pump may include multiple induction coils and / or multiple switches.

[0040] In an example of this technology, the switch(es) may be electrically connected in parallel with the output terminals or a load. For example, the load may include a circuit or loop of superconducting material. For example, the loop of superconducting material may include 10 or more windings of high temperature superconductor.

[0041] In examples of this technology, the switch may be located on one or more stator arms, such as on a stator arm between the stator and the rotor. For example, at least a portion of the switch may be configured to extend in a direction substantially perpendicular to the flux generated by the magnetic field generator(s).

[0042] In an example of this technology, the switch may be disposed between the stator arm and the field spreader. For example, the field spreader may be configured to generate or exert a uniform magnetic field across at least a portion of the switch, such as a length of one or more superconducting materials in the switch. For example, the field spreader may include a material with high magnetic permeability, such as a ferromagnetic material.

[0043] In an example of this technique, the field spreader may be sized to have substantially the same width as the magnetic field generator when measured radially outward from the axis of rotation.

[0044] In an example of this technology, the field spreader may be positioned approximately centrally on top of one or more arms of the stator.

[0045] In an example of this technology, the distance from any end of the field spreader to the end of the stator arm on which it is located may be less than the width of the magnetic field generator. In an example of this technology, any one or more of the induction coil, switch, load, or terminals may be constructed from a single continuous length of superconducting material, such as a high-temperature superconducting tape. In other words, the superconducting material may be configured so that there are no joints between any one or more of the induction coil, switch, and load or terminals.

[0046] In other examples of this technology, one or more of the induction coil, the switch, the load, or the terminals may be connected using a joint, for example, the joint may be a normally conducting joint, as is well known to those skilled in the art.

[0047] In an example of this technology, one or more lengths of superconducting material can be placed in a cryostat. For example, a stator can be placed in the cryostat. For example, the cryostat can include a cryostat cooling system, as is well known to those skilled in the art.

[0048] In an example of this technology, the cryostat refrigeration system may include a liquid cryogen operable to cool by latent heat of vaporization, and / or a thermomechanical refrigerator. For example, liquid nitrogen may be used.

[0049] In an example of this technique, the rotor may be located within the cryostat, although drive means may be provided external to the cryostat, for example, operatively connected to the rotor via a drive shaft passing through the wall of the cryostat.

[0050] In an example of this technology, the flux gap, or separation between the magnetic field generator and the stator, may be less than 6 mm, for example the flux gap may be 1 mm or less.

[0051] This technology is The ability to operate the switch rectifier throughout the wall without penetrating the cryostat wall, ●More efficient flux pump technology, • flux pumping technology capable of operating within or at least partially within a cryostat; Low cooling requirements compared to transformer-based flux pump technology; • Higher efficiency than dynamo-based flux pumping technologies; and It should be appreciated that this can provide one or more of a number of advantages, including automatic control of induced current in the superconducting material, i.e., control without the need for control circuitry. Further aspects of this technology, which should be considered in all its novel aspects, will become apparent to those skilled in the art upon reading the following description, which sets forth at least one example of a practical application of this technology. 5. Brief description of the drawings

[0052] One or more embodiments of the present invention will now be described, by way of example only and not by way of limitation, with reference to the following drawings, in which: [Brief explanation of the drawings]

[0053] [Figure 1] 1 shows an example of a graph of electric field versus current for a high temperature superconductor. [Figure 2] 1 is an exemplary graph illustrating the effect of an applied magnetic field on the critical current of a high temperature superconductor. [Figure 3] 1 shows a simplified schematic diagram of a superconducting flux pump according to the present technology. [Figure 4A] The first example of a superconducting flux pump using this technology is shown. [Figure 4B] 1 shows an alternative superconducting flux pump according to the present technology. [Figure 5] 1 shows an alternative superconducting flux pump according to the present technology. [Figure 6] 6 is an exemplary curve showing the experimental performance of the flux pump of FIG. 5 increasing the current flow in a high temperature superconductor over time. [Figure 7A] A first example of how power supplies have traditionally been used to increase the current flow in superconducting coils placed within a cryostat is shown. [Figure 7B] A second example of how a superconducting flux pump can be used to increase the current flow in a superconducting coil located within a cryostat is shown. [Figure 7C] A third example of how a superconducting flux pump can be used to increase the current flow in a superconducting coil located within a cryostat is shown. [Figure 8] 1 shows a superconducting flux pump arrangement according to an example of the present technology. [Figure 9] 1 illustrates a switch according to an example of the present technology. [Figure 10] 1 shows a simplified schematic diagram of a superconducting flux pump including a series shunt resistor. [Figure 11A] The magnetic field diagram of the flux pump based on this technology is shown. [Figure 11B] 11B shows a close-up view of a field spreader within the magnetic field diagram of FIG. 11A. [Figure 12A] 1 illustrates an exemplary stator with adjustable switch positions in accordance with the present technology. [Figure 12B]1 shows a switch holder that can be adjustably positioned on a stator to change the phase relationship between an induction coil and a switch in accordance with the present technique. [Figure 12C] 12C shows a graph of the current and phase relationship between the induction coil and the switch according to the adjustable design of FIGS. 12A and 12B. [Figure 12D] 10 shows a graph of current versus phase relationship between an induction coil and a switch in accordance with a further embodiment of the present technique; [Figure 13] 1 shows a schematic diagram of an embodiment of a flux pump in a housing according to the present technology. [Figure 14A] 1 shows a schematic diagram of the Jc(B) switch configuration using this technology. [Figure 14B] 1 shows a schematic diagram of a bifilar Jc(B) switch arrangement according to the present technology. [Figure 14C] Figure 1 shows a schematic diagram of an alternative bifilar Jc(B) switch arrangement in accordance with the present technology. [Figure 15] 1 shows a graph summarizing actual operating voltages of flux pumps constructed in accordance with the present technique. BEST MODE FOR CARRYING OUT THE INVENTION

[0054] 6. Detailed Description of the Preferred Embodiments of the Invention

[0055] 6.1. Principles of superconductivity

[0056] A superconductor or superconducting material has a critical temperature, T c A material that has zero electrical resistance below a certain temperature called the critical magnetic field B. This zero resistance state is often called the superconducting state. This lack of resistance is the result of a phenomenon called the Meissner effect, which is the complete exclusion of any magnetic field from a superconductor. A superconductor is a material that has zero electrical resistance below a critical magnetic field B. cIt is a perfect diamagnetic material up to a certain magnetic field strength, called the critical magnetic field. At this point, the superconductor cannot block the magnetic field, and the magnetic field penetrates the superconductor, creating a flux flow within the superconductor, causing it to transition from a superconducting state to a normal conducting state, where electrical resistance is no longer zero. This critical magnetic field also implies a limit to the electrical current that the superconductor can carry, known as the critical current I c It is called.

[0057] There are two types of superconductors: Type I and Type II. Type I superconductors are usually pure metals and behave as described above. Type II superconductors behave differently. For Type II superconductors, the critical magnetic field H c1 <H c Type II superconductors can carry a larger amount of electrical current, allowing a larger magnetic field to penetrate without causing the material to transition out of the superconducting state. It has superior properties to type I superconductors and is therefore useful for practical applications.

[0058] The critical temperature of a superconductor is usually defined as the temperature below which the resistivity of the superconductor is zero or near zero. In other words, when the temperature of a superconductor is below the critical temperature, it is said to be in a superconducting state; when the temperature is above the critical temperature, it is said to be in a non-superconducting state. Many superconductors have critical temperatures close to absolute zero; for example, the critical temperature of mercury is known to be 4.1 K. However, some materials are known to have much higher critical temperatures, ranging from 30 K to 125 K. For example, the critical temperature of magnesium diboride is approximately 39 K, while the critical temperature of yttrium barium copper oxide (YBCO) is approximately 92 K. These superconductors are commonly referred to as high-temperature superconductors (HTS). 6.1.1.Critical current

[0059] The critical current of a high-temperature superconducting wire or tape is typically defined as the current flowing through the superconducting wire / tape that produces an electric field drop of 100 μV / m (=1 μV / cm) along the wire. The critical current is a function of both the superconducting material used and the physical arrangement of the superconducting material. For example, a wider tape / wire may have a higher critical current than a thinner tape / wire made of the same material. However, for simplicity, reference will be made throughout this specification to the critical current of the superconductor / material.

[0060] In a superconductor, the current I reaches the critical current I c When I is approximately equal to the critical current I, the resistance of the superconductor is small but not zero. c If the temperature is much higher than 0.05°C, the resistance of the superconductor becomes large enough to cause heat dissipation, heating it above its critical temperature and causing it to cease to be superconducting. This condition is sometimes called a "quench" and can be damaging to the superconductor itself.

[0061] Figure 1 is an exemplary graph showing the internal electric field versus current curve for a high temperature superconductor. The electric field shown in this graph is related to the resistance by the following equation: E=IR / L where: ●E is the electric field, ●I is the current flowing through the superconductor, ●R is the resistance of the wire, ●L is the length of the wire. Thus, the graph in Figure 1 relates the resistance per unit length of the superconductor, and since the curve drawn is nonlinear, the resulting resistance of the superconductor will be nonlinear with respect to current.

[0062] In Figure 1, the critical current I of a superconductor cBelow we see that the electric field strength in a superconductor is essentially zero. As 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 causes a rapid increase in the electric field strength in the conductor.

[0063] As shown in Figure 1, the transition from the superconducting state to the normal conducting state in HTS materials can be explained by an empirical law known as the EJ power law.

number

[0064] In this specification, reference may be made to the relative resistance of superconducting materials and components that include superconducting materials. More specifically, this specification refers to superconducting materials in a low-resistivity state or a high-resistivity state. It is understood that when in the superconducting state, superconducting materials can have zero or substantially zero resistance, and thus these resistances are often expressed in terms of the electric field that exists across the superconducting material for a given current. However, throughout this specification, for ease of discussion, reference will be made to relative resistances, e.g., low-resistivity and high-resistivity states of a superconducting material.

[0065] The term "low resistance state" may refer to when a superconducting material has near-zero or substantially zero resistance in a superconducting state, or when the material has low resistance in a partially superconducting state. The term "high resistance" state refers to a state in which a superconducting material has a resistance substantially greater than that of the low resistance state, e.g., a resistance that is substantially non-zero, or a resistance that is close to zero but substantially greater than that of the low resistance state. For the avoidance of doubt, the high resistance state referred to herein may include a superconducting state unless the context clearly dictates otherwise.

[0066] Similarly, when reference is made herein to a superconductor being in a high resistance state as a result of the current carried by the superconductor exceeding the critical current, it should be understood that the high resistance state may also be achieved when the current carried by the superconductor approaches or substantially equals the critical current, unless the context clearly indicates otherwise.

[0067] In describing the technology herein, materials and components that include the materials are referred to as "superconducting." This term is used generally in the art for such materials and does not imply that the materials involved are always in a superconducting state. Under certain conditions, materials and components that include the materials may not be in a superconducting state. That is, materials may be described as superconducting but not superconducting.

[0068] 6.1.2. Superconducting Materials

[0069] Particular embodiments of the present technology may include various types of superconducting materials. For example, embodiments of the present technology may include high-temperature superconducting (HTS) materials. Exemplary HTS materials suitable for use in embodiments of the described technology include copper oxide superconductors, such as 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 exhibit a strong interdependence between critical current and applied magnetic field, which may make them particularly suitable for some embodiments of the present technology. Other types of superconductors may be used in other embodiments of the technology.

[0070] Although embodiments of this technology are described in relation to high temperature superconductors, it should be understood that other embodiments of this technology may use other types of superconductors instead, such as low temperature superconductors.

[0071] 6.1.3. Effect of Magnetic Field on Superconductors

[0072] The critical current of a superconductor depends on the external magnetic field applied to the superconductor. More specifically, as a higher external magnetic field is applied to the superconductor, the critical current decreases to the critical magnetic field value, above which the superconductor is no longer in a superconducting (low resistance) state. This relationship is illustrated in Figure 2, which is a graph showing the relationship between electric field and current in a superconducting material when three external magnetic fields of different magnitudes are applied. The maximum external magnetic field B 印加1 is the critical current value I c1 In some forms, an external magnetic field to achieve this effect may be applied perpendicular to the surface of the length of superconductor where critical current is reduced or suppressed. The applied magnetic field may be in only one direction and may be referred to as a direct current magnetic field, while a time-varying magnetic field may cycle in direction, e.g., sinusoidally, and may be referred to as an alternating current magnetic field.

[0073] All superconductors experience a rapid drop in critical current with small applied magnetic fields. This means that small changes in the applied magnetic field can lead to large changes in the critical current. This relationship depends on the manufacturing method of the superconducting material and the length of the superconducting material carrying the current.

[0074] It should be noted that this mechanism of reducing or suppressing the critical current by applying an external magnetic field (e.g., a DC magnetic field) is different from the phenomenon of dynamic resistance, which occurs when a superconductor is exposed to a time-varying magnetic field while carrying a DC transport current. This creates a DC electrical resistance within the superconductor, and if this resistance becomes large enough, the superconductor can switch to a more highly resistive state.

[0075] 6.1.4. Superconducting Switch

[0076] Throughout this specification, reference is made to the relative resistance of superconducting switches and their components. Generally speaking, a superconducting switch is a switch that incorporates one or more superconducting materials that can transition between low and high resistance states, as described herein. These may not be the open / closed circuit states typical of conventional normally conducting switches, and even the high resistance states may typically be considered low resistance (e.g., a few ohms or less) by the standards of normally conducting switches.

[0077] It should be understood by those skilled in the art that superconducting materials in their superconducting state can have zero or substantially zero resistance, and as such, these resistances are represented by the electric field that exists across the superconducting material for a particular current. However, throughout this specification, for ease of discussion, reference is made to relative resistances, low resistance states, and high resistance states. 6.2. Mechanically Switchable Flux Pumps

[0078] 6.2.1. Operating Principle

[0079] 3 shows an example of a mechanically switchable flux pump 300 in accordance with one form of the present technology. Broadly speaking, the flux pump 300 includes a rotor 302 configured to rotate about an axis of rotation during 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.

[0080] During use, rotation of the rotor 302 moves one or more magnetic field generators 306 past the induction coil 310 and the switch 312, periodically applying a magnetic field to the induction coil 310 and the switch 312; for example, the one or more magnetic field generators may move in a generally circular path. The magnetic field generated by the magnetic field generators 306 is configured to induce current flow in the induction coil 310 and apply a magnetic field to the switch 312, e.g., a magnetic field having a component perpendicular to the surface of the switch, thereby lowering the critical current of the switch due to the aforementioned effect. A lower critical current of the switch 312 when a magnetic field is applied means that, for a given current flow, the switch 312 has a higher resistance, or a high resistance state, compared to when no magnetic field is applied to the switch. Throughout this specification, references to a switch transitioning from a low resistance state to a high resistance state should be understood to refer to the relative resistance when a given current is flowing through the switch. For example, the current may be equal to or less than the current induced in the induction coil 310. In some embodiments, switch 312 is superconducting when in a high resistance state, and it should be understood that this may be true for any embodiment of the technology, even if not explicitly stated.

[0081] 3, a load 314 is provided that is electrically connected in parallel with the switch 312. The load preferably comprises a superconducting coil, although this is not a limitation of the technology and the load can be any suitable component or circuit that is placed in parallel with the switch 312. In some aspects of the technology described herein, the flux pump 300 is provided with two or more output terminals 315 that are configured to connect to the load 314 during use, the two or more output terminals 315 being electrically connected in parallel with the switch.

[0082] In the illustrated example, two magnetic field generators 306a, 306b are provided, each positioned diametrically opposite, i.e., approximately 180 degrees apart, on the rotor 302. The induction coil 310 and switch 312 are positioned such that, during rotation of the rotor 302, the first magnetic field generator 306a passes through the induction coil 310, applying its magnetic field to the induction coil 310 and causing a current flow through the induction coil 310. At approximately the same time, the second magnetic field generator 306b passes through the switch 312, applying its magnetic field to the switch 312, and the magnetic field generated by the second magnetic field generator 306b reduces the critical current of the switch, thereby transitioning it from a low resistance state to a high resistance state for a given current flow, as described herein. Similarly, as the rotor 302 rotates further, the second magnetic field generator 306b passes the induction coil 310, causing current to flow through the induction coil 310 and the first magnetic field generator 306a to pass through the switch, and the magnetic field generated by the first magnetic field generator 306a transitions the switch from a low-resistance state to a high-resistance state, as described herein. Between these states, the first and second magnetic field generators 306a and 306b are further away from the induction coil 310 and switch 312, so their magnetic fields do not act to induce current in the induction coil 310 or lower the critical current of the switch 312, or at least to a lesser extent than if the magnetic field generators were closer to the induction coil and switch. As the rotor 302 rotates further, the described operations are periodically repeated. For example, the induction coil 310 and switch 312 may be positioned substantially diametrically opposite each other relative to the rotor 302.

[0083] Thus, for each 360° rotation of the rotor 302, current is induced in the induction coil 310 twice, and the switch 312 transitions from the low resistance state to the high resistance state synchronously each time. The use of two magnetic field generators 306a, 306b in FIG. 3 is not a limitation of the technology; any number of magnetic field generators 306 may be used. In some examples of the technology, it may be advantageous to use an even number of magnetic field generators, with each magnetic field generator 306 positioned substantially opposite, e.g., 180° from, one of the other magnetic field generators. It should be understood that the more magnetic field generators used, the more times current is induced in the induction coil 310, and, consequently, the more times the switch transitions from the low resistance state to the high resistance state per 360° rotation of the rotor.

[0084] By adjusting the timing and duration of the transition of switch 312 from a low resistance state to a high resistance state, the current flow through load 314 can be affected, adjusting the current flow so that a net DC current flow through load 314 increases the current in load 314 with each cycle.

[0085] When switch 312 transitions from a low resistance state to a high resistance state in phase with the induced current in induction coil 310, the current transferred from induction coil 310 to load 314 during the high resistance state increases compared to the current flowing to the load during the low resistance state because load 314 is electrically connected in parallel with switch 312 and the ratio of current between load 314 and switch 312 depends on the relative impedances or resistances of load 314 and switch 312.

[0086] It should be understood that movement of the magnetic field generator 306 relative to the induction coil 310 applies a changing magnetic field to the induction coil 310, resulting in a current flow in the induction coil 310. The current flow in the induction coil 310 typically has a positive and a negative component. In other words, the current flow in the induction coil may oscillate between positive and negative current flow over time. Thus, transitioning the switch 312 to a high resistance state during positive or negative current flow may provide a net positive or negative current flow to the load. In other words, the relative timing of the switches transitioning to the induction current pulses may be adjusted so that a higher resistance state substantially corresponds to a positive component of the current flow induced in the induction coil and a lower resistance state substantially corresponds to a negative current flow induced in the induction coil 310.

[0087] In the examples described herein, the induction coil 310 and switch 312 are provided by one or more superconducting materials, such as the high temperature superconductors described herein. In particular, the use of lengths of one or more superconducting materials may be advantageous in improving the efficiency of the superconducting flux pump technology. However, this should not be considered a limitation of the technology, and in other examples, any one or more components of the technology may be provided with a normally conductive equivalent.

[0088] Flux Coupling

[0089] One way to increase the induced current in induction coil 310 is to increase the strength of the magnetic field applied to induction coil 310. One way to accomplish this is to couple the magnetic field to the induction coil using a material with high magnetic permeability, such as a ferromagnetic material like steel.

[0090] Similarly, in various types of superconducting switch mechanisms such as those described herein, it may be advantageous to increase the strength of the magnetic field acting on the length of superconducting material, as this may cause 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 high resistance state.

[0091] 4A shows an example of a flux pump 300 in accordance with one form of the present technology, including a ferromagnetic stator 304 and a ferromagnetic rotor 302. The stator includes a first arm 320a carrying an induction coil 310 and a switch 312. The stator also includes a second arm 320b that serves as a magnetic return path to minimize the total air gap between the rotor 302 and the stator 304.

[0092] The stator 304 is provided with one or more lengths 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, although this is not to be considered a limitation of the technology. For example, two or more output terminals may be provided in place of the load described herein.

[0093] The rotor 302 may include a drive shaft 316 that, in use, is connected to a drive source, such as a motor, for rotating 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.

[0094] 4A operates by rotating rotor 302 to move magnetic field generator 306 past one or more stator arms 320a, 320b. This movement generates a changing magnetic field within stator 304, which passes through the loops of induction coil 310 and switch 312, respectively.

[0095] In the illustrated example, the drive shaft 316 is aligned with the second arm 320b of the rotor. In other words, the axis of rotation 317 is aligned with the second arm 320b, so that the second arm remains adjacent to the rotor during use. In this manner, the present technology can be configured to generate a changing magnetic field within the stator when the magnetic field generator 306 passes only the first arm 320a.

[0096] It should be noted that, as shown, the rotor is asymmetric about the axis of rotation 317 and may vibrate or wobble during use. Therefore, in some examples of the present technology, the rotor may be provided with a structure that is substantially symmetric about the axis of rotation, such as the example in FIG.

[0097] The magnetic field generator 306 may be located on the side of the rotor 302 closest to the stator 304. The magnetic field generator 306 may be located a radial distance from the axis of rotation 317 so that the magnetic field generator moves through an arcuate or circular path during use.

[0098] In FIG. 4A , the magnetic field generators are attached to the rotor via one or more support members 311. In the illustrated example, the support members 311 comprise plates or substantially circular supports. For example, the support members 311 may have a substantially circular cross-section when cut through a plane perpendicular to the rotation axis 317, or may be substantially circular plates. The use of substantially circular support members may provide the advantage of reduced drag or air turbulence, particularly in examples of techniques in which the rotor is disposed within a cryostat, as described herein. However, this should not be considered limiting, and in other examples, the support members 311 may include arms or elongated structures that support corresponding magnetic field generators.

[0099] It may be advantageous for the radial distance from the axis of rotation 317 of the midpoint of each arm 320 a, 320 b to be 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.

[0100] 4A operates by rotating the rotor 302 to move the magnetic field generator 306 in an arcuate path through one or more arms 320a, 320b of the stator. As the magnetic field generator passes the arms 320a, 320b, it creates a changing magnetic field within the stator 304, which in turn causes current to flow in the induction coil 310, transitioning the switch between a low resistance state and a high resistance state.

[0101] In FIG. 4A, the switch 312 and induction coil 310 are located on a single arm 320a of the stator. In other examples of this technology, the switch and / or induction coil may be located anywhere on the stator. For example, the switch may be located between arms 320a, 320b of the stator 304, such as at the midpoint between the arms. Similarly, the induction coil may be located on either arm or around a section of the stator that joins the arms, such as the stator base 321.

[0102] For example, FIG. 4B shows an alternative flux pump 300 according to another form of technology in which the induction coil 310 is mounted on the second arm 320B of the stator 304.

[0103] 5 illustrates a further example of a flux pump 500 according to another aspect of the present invention, the flux pump 500 including a ferromagnetic stator 304 and a ferromagnetic rotor 302. The stator includes a first arm 320a having an induction coil 310 (e.g., the induction coil 310 may be wound around the first arm 320a) and a second arm 320b having a switch 312 (e.g., the switch may be located on 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.

[0104] The stator 304 may be provided with one or more lengths 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, although this is not considered to be a limitation of the technology.

[0105] The flux pump 300 of FIG. 5 operates by rotating a rotor 302 to move a magnetic field generator 306 past one or more stator arms 320 a, 320 b, providing the magnetic field generated by the magnetic field generator 306 to an induction coil 310 and a switch 312, respectively.

[0106] For example, rotor 302 may include a drive shaft 316 that, in use, is connected to a drive source, such as a motor, to rotate rotor 302. Thus, in the illustrated example, the longitudinal axis of drive shaft 316 defines an axis of rotation 317 of rotor 302.

[0107] Magnetic field generator 306 may be located on the side of rotor 302 closest to stator 304. Magnetic field generators 360 may be located a fixed radial distance from axis of rotation 317, such that each magnetic field generator moves through an arcuate or circular path during use. It may be advantageous for each of the one or more magnetic field generators to follow substantially the same arcuate or circular path during use. For example, each of the one or more magnetic field generators may be at substantially the same radial distance from axis of rotation 317.

[0108] In FIG. 5 , the magnetic field generators are attached to the rotor via support members 311. In the illustrated example, the support members 311 can be considered arms of the rotor. For example, each of the support members can be an independent elongated structure that supports a corresponding magnetic field generator. In other examples of this technology, the support members 311 can have a substantially circular cross-section when cut through an axis perpendicular to the axis of rotation 317, or can be a substantially circular plate. The use of substantially circular support members can provide the advantage of reducing drag or air turbulence, particularly in examples of the technology in which the rotor is disposed in a cryostat as described herein.

[0109] Advantageously, the radial distance from the axis of rotation 317 of the midpoint of each arm 320 a , 320 b is substantially equal to the radial distance of the magnetic field generator 306 , providing a short magnetic path between the magnetic field generator 306 and the stator 304 .

[0110] 5 operates by rotating the rotor 302 to move one or more magnetic field generators 306 in an arcuate path through one or more arms 320 a, 320 b of the stator. As the magnetic field generators pass the arms 320 a, 320 b, a changing magnetic field is generated within the stator 304, which in turn generates a current flow within the induction coil 310. The changing magnetic field within the stator 304 further acts on the switch 312, which transitions from a low resistance state to a high resistance state, as described herein.

[0111] In the illustrated example, two magnetic field generators are used, and the magnetic field generators are configured so that the first magnetic field generator 306a passes over the first stator arm 320A while the second magnetic field generator passes over the second arm 320B. Each magnetic field generator generates a varying magnetic field as indicated by the arrows in Figure 5. Thus, the varying magnetic field used to induce current flow in the induction coil 310 may be different from the magnetic field used to transition the switch from a low resistance state to a high resistance state.

[0112] Figure 6 shows the measured output of a flux pump prototype built according to the design shown in Figure 5. This figure illustrates an example of how the flux pumping techniques described herein can be used to increase the current in load 314. Note that over time, the current in load 314 becomes positive, increases with each cycle, and remains at a constant level above 7.5 A before decreasing (at approximately 650 seconds) when the motor driving rotor 302 stops.

[0113] It should be understood that the results obtained in Figure 6 are from experiments performed by the inventors and therefore, while they are proof of principle of the technique, they may not be representative of the limitations or overall performance of various forms of the technique.

[0114] 6.3.Rotor Configuration

[0115] Although the concepts of the present technology may be implemented using a rotor constructed of any material, it may be advantageous to provide a rotor 320 that includes a material with high magnetic permeability, such as any suitable ferromagnetic material. For example, it may be advantageous to construct the rotor support members 311 (arms or plates) from a material with high magnetic permeability to provide a magnetic path between the rotor and the stator, as shown by the arrows in Figures 4A, 4B, and 5.

[0116] It should be noted that not all components of the rotor need be made from a high magnetic permeability material; for example, shaft 316 may be made from any suitable material, including materials that do not have a high magnetic permeability.

[0117] The use of materials with high magnetic permeability can improve the magnetic field coupling between the magnetic field generator(s) and the induction coil 310 and switch 312, as described herein. For example, any one or more parts of the rotor 302 can be constructed of iron or steel or other ferromagnetic materials to provide an electromagnetic conduction path. Steel's low cost and commercial availability can make it particularly advantageous in some applications of this technology.

[0118] In some examples of this technology, the rotor includes a shaft 316 that may be connected to a drive means (not shown), such as a motor, to enable rotation of the rotor 302 .

[0119] It should be understood that low temperatures are required to maintain the superconducting material 308 in a superconducting state. Therefore, in one example of this technology, the rotor 302 may be located outside of the cryostat, including the stator. In this way, heat generation due to, for example, rotational friction caused by the moving rotor 302 does not increase the temperature of the superconducting material 308 or increase the need for cryogenic cooling.

[0120] 6.3.1. Magnetic Field Generator(s)

[0121] 3-5, the magnetic field generator 306 is positioned on the rotor 302 such that the induction coil 310 and the switch 312 are subjected to their respective magnetic fields as the magnetic field generator 306 rotates around these components. For example, the magnetic field generator may be positioned on the side of the rotor 302 closest to the stator 304. However, this should not be considered limiting; for example, in a low-profile version of this technology, the magnetic field generator 306 may be provided at the distal end of an arm of the rotor 302, or in examples where a circular rotor is used, the magnetic field generator 306 may be provided on the outer periphery of the rotor 302.

[0122] In certain configurations, the magnetic field generators 360 are positioned at fixed radial distances from the axis of rotation 317, with each magnetic field generator moving through an arcuate or circular path during use. It may be advantageous for each of the one or more magnetic field generators to follow substantially the same arcuate or circular path during use. For example, each of the one or more magnetic field generators may be at substantially the same radial distance from the axis of rotation 317.

[0123] The magnetic field generator(s) 306 may include any suitable component or system capable of providing or generating a magnetic field. In one example of this technology, each magnetic field generator 306 is a permanent magnet constructed from one or more of samarium cobalt (SmCo), alnico, neodymium iron boron (NdFeB), or other suitable magnetic materials. The use of permanent magnets may offer advantages of simplified construction and reduced heat generation compared to active magnetic field generation systems such as transformer-based flux pumps or electromagnets.

[0124] In another example of this technology, one or more of the magnetic field generators 306 may include electromagnets. For example, if one or more electromagnets are used, the electromagnets may be configured to continuously generate their respective magnetic fields. In another 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 during 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 approaching or approaching 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 the use of a rotary encoder.

[0125] For example, in one form of 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 at which the switch 312 transitions from a low resistance state to a high resistance state. For example, if an electromagnetic or transformer-based magnetic field generator is used, the magnetic field may be activated or deactivated by any suitable control circuitry familiar to those skilled in the art. Doing so may be advantageous to optimize current transfer to the load 314. For example, if 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's activation may be adjusted by advancing or retarding its activation time. Because the resulting current induced in the load can be measured, these timing adjustments may be correlated with the current induced in the load to determine optimal electromagnet activation timing.

[0126] The example technique of using permanent magnets as the magnetic field generator 306 has the advantage that the flux pump can operate more efficiently because less heat is generated by the windings produced by the electromagnetic magnetic field generator 306 .

[0127] Furthermore, in the examples described herein, the techniques may be implemented using any number of magnetic field generators 306. For example, a single magnetic field generator may be used to generate flux through stator 304, induce current flow in induction coil 310, and activate switches 312 simultaneously or timed to one another.

[0128] 6.3.2. Rotor Structure

[0129] Rotor 302 may have any suitable configuration known to those skilled in the art. For example, in the configuration shown in FIG. 5, rotor 306 is a substantially flat cylindrical or circular plate. In other examples, rotor 306 may include one or more arms extending radially outward from axis of rotation 317 to provide support 311 as described herein. Thus, rotor 302 may have any suitable shape or configuration capable of causing rotation of the magnetic field generator.

[0130] In some examples of this technology, a single magnetic loop may be provided, such as in a configuration where a portion of the rotor and stator together form a magnetic loop, as described in connection with Figures 4A and 4B, or two or more magnetic loops may be provided by portions of the rotor and stator, as shown in Figure 5. One advantage of configuring the rotor and stator to provide two magnetic loops is that the time or phase relationship between the changing magnetic field induced in the first loop and the changing magnetic field induced in the second loop may be different.

[0131] 6.4. Cryogenic Cooling

[0132] A low temperature or cryogenic environment is often required to maintain the superconducting material 308 in a superconducting state. Thus, one advantage of certain forms of the present technology is that the rotor 302 may be provided in a non-contact arrangement with the stator 304. Thus, the stator 304 may be located within the cryostat 702, and the heat-generating components of the rotor 302 may be located outside of the cryostat 702.

[0133] 7A illustrates a conventional power generation circuit in which a power supply 301 or other current generating source is located external to a cryostat 702 and is electrically connected to a load 314 or superconducting loop housed within the cryostat 702. For example, in FIG. 7A, electrical leads 704 may be configured to pass through the cryostat 702 and transfer the current flow to the load 314. One drawback of using electrical leads 704 is that they provide a thermal conduction path from the cryostat 702, which can increase the overall cooling requirements of the system.

[0134] 7B shows, for example, an alternative configuration in accordance with certain forms of the present technology, in which rotor 302, stator 304, and load 314 are located within the chamber, and a drive means 706, such as an electric motor, may be located external to cryostat 702, reducing the overall cooling requirements of the system. In this example, shaft 316 still passes through the wall of the cryostat, but unlike the example of FIG. 7A, shaft 316 could be formed from a material with relatively low thermal conductivity or insulating properties, such as carbon fiber.

[0135] 7C illustrates yet another configuration, e.g., according to certain forms of the present technology, in which the rotor 302 and drive means 706 are located external to the cryostat 702, and the stator 304 and load 314 are located within the cryostat 702. One advantage of this arrangement is that the cryostat 702 can be completely sealed from heat / flux generating components, potentially reducing the cooling requirements of the system. However, one potential drawback of this approach is reduced magnetic field coupling or an increased flux gap between the rotor 302 and stator 304, as will be described in more detail herein.

[0136] In some examples of the present technology, the cryostat 702 includes a cryostat refrigeration system familiar to those skilled in the art. For example, the cryostat refrigeration system may include a liquid cryogen operable to cool by the latent heat of vaporization, and / or a thermomechanical refrigerator. For example, liquid nitrogen may be used.

[0137] Cooling chamber 702 may include any suitable insulation, including one or more of a vacuum, multi-layer insulation, and / or a cooled heat shield. If the walls of chamber 702 are disposed between rotor 302 and stator 304, it may be advantageous to use materials with low electrical conductivity, such as fiberglass composite, stainless steel, and / or thin / slit multi-layer foil.

[0138] 6.5. Stator Configuration

[0139] Broadly speaking, the purpose of the stator is to arrange the induction coil 310 and switch 312 so that a passing magnetic field generator 306 on the rotor 302 generates a changing magnetic field that induces current flow in the induction coil 310 and causes the switch 312 to transition from a low resistance state to a high resistance state.

[0140] In certain configurations, the stator 304 may be constructed of any suitable ferromagnetic material, or any material with a suitably high magnetic permeability, to more efficiently couple the magnetic field between the rotor 302 and the stator 304. For example, the stator 304 may be constructed of iron, steel, or other ferromagnetic material to guide the magnetic field from the magnetic field generator to the loops of the induction coil 310 and the switch 312. Steel may be particularly advantageous in some applications of this technology due to its low cost and commercial availability. The use of a ferromagnetic stator may be advantageous to induce a sufficient current in the length or lengths of the superconducting material 308 that exceeds the field-suppressing critical current of the switch 312, and to apply a sufficiently strong magnetic field to the switch 312 to reduce the critical current below the induced current or to transition the switch 312 from a low-resistance state to a high-resistance state as described herein.

[0141] 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. The use of stator arms 320 therefore advantageously allows for a smaller air gap between the rotor 302 and the stator 304, improving the efficiency of magnetic field transfer from the magnetic field generators to the stator 304.

[0142] Stator 304 may further include features that allow the relative positions of induction coil 310 and switch 312 to be adjusted, as described herein. For example, switch 312 may be mounted on a switch holder 1212, as described herein, which allows for easy adjustment of the position of the switch on the stator.

[0143] 6.5.1. Superconducting Materials

[0144] In the examples described herein, the length or lengths of superconducting material 308 include rare earth barium copper oxide (ReBCO) tapes (e.g., SuNam TM However, this is not a limitation on the technology and any suitable superconducting material 308 may be used as described herein.

[0145] The foregoing description provides examples of how one or more lengths of superconducting material 308 may be configured and / or arranged to provide induction coil 310, switch 312, and load 314. For experimental purposes, the components of induction coil 310, load 314, and / or switch 312 are electrically connected using conventional conductive joints, such as solder joints. However, this is not considered a limitation of the technique. For example, in some examples of the technique, superconducting material 308 may include a continuous tape or other suitable material arranged to provide any one or more of induction coil 310, load 314, and / or switch 312.

[0146] More specifically, in some examples of this technology, induction coil 310 may be provided by looping a coil of superconducting material 308 around one of arms 320A, 320B of stator 304. Similarly, depending on the selected switching configuration (described below), switch 312 may be formed by placing a portion of one or more lengths of tape of superconducting material 308 where a magnetic field applied to the superconducting material 308 has a component perpendicular to the surface of the length of superconducting material 308 that provides switch 312.

[0147] Where components of the technology are provided in parallel, they may be provided from a continuous superconducting material 308, such as a tape, for example by splitting the tape along its longitudinal axis (or lengthwise) to provide two parallel paths of superconducting material 308 that are integrally connected, i.e., with a superconducting connection between each parallel path.

[0148] 6.5.2. Induction Coil

[0149] The reader should be familiar with the concept of induction coils, which obey Faraday's law. However, unlike traditional transformers, this technology uses a magnetic field generator 306, such as a permanent magnet or electromagnet, to generate an electromagnetic field. Therefore, this technology addresses many of the issues of transformer-based flux pumps, such as heat generation due to current flow in the primary side of the transformer.

[0150] It may be advantageous to maximize or increase the current flow in the induction coil 310 to induce as much current flow as possible in the flux pump. The greater the current flow, the more current is delivered to the load 314 or output terminals 315, and the higher the resistance of the switch in the high resistance state, since the resistance of the switch depends on the electric field suppression critical current and the current flow through the switch as shown in FIG.

[0151] In certain forms of this technique, the induction coil 310 may include any number of turns of superconducting material, such as tape, including partial (i.e., non-integer) turns. For example, the results shown in FIG. 6 are for a 12 mm wide superconducting tape 308 wrapped around one or fewer turns. However, any number of turns may be used, and as mentioned above, it may be advantageous to maximize the number of turns within the available space. As an example, in the form of the technique described herein and providing the experimental results in FIG. 6, the height of the stator arms 320 is approximately 50 mm, ensuring sufficient space on the arms 320 to support the tape.

[0152] However, the above is not to be considered limiting of the technology, and for example, more than two windings may be used. In some instances of this technology, it may be advantageous to provide the induction coil 310 from superconducting wire rather than using tape, in order to provide a greater number of turns in the available area on the stator arm 320.

[0153] Furthermore, when superconducting materials are used, it should be understood that these materials have bend radius limitations, and therefore, in preferred examples of the present technology, the diameter of stator arm 320 (around which the length of superconducting material is wrapped) may be configured so as not to exceed the bend radius limitation. For example, stator arm 320 may have a substantially cylindrical shape with a diameter equal to or greater than the minimum bend radius of one or more lengths of superconducting material 308. In some examples, the minimum bend radius of superconducting material may be 5 mm or greater, and therefore the diameter of stator arm 320 should be dimensioned accordingly, i.e., 5 mm or greater. In the example shown, the diameter of stator arm 320 is approximately 50 mm.

[0154] An example of a stator 304 is shown in FIG. 8. In this example, the stator 304 includes a stator base 312 from which multiple stator arms 320 extend generally vertically upward away from the stator base 321 toward the rotor 302 (not shown in FIG. 8). For example, in FIG. 8, the first stator arm 320a has a cylindrical annular structure, and the second stator arm 320b is provided as an annular wall. The second stator arm 320b may form a gap along a portion of its circumference, and the first stator arm 320a may be disposed within the gap, as shown. The third central stator arm 320c provides a return path for the magnetic field, as shown in FIG. 5. A similar arrangement is also shown in FIG. 12A.

[0155] In an example of this technology, if the second stator arm 320b has an annular structure as in FIG. 8, 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 effect of cogging torque on the rotor 302. Cogging torque may occur if the magnetic field does not transition smoothly from one flux path to the next. This may cause the rotor 302 to accelerate and decelerate as it passes the iron teeth, resulting in nonlinear motion.

[0156] The first stator arm 320a is provided with one or more coils of lengths of superconducting material 308 configured in one or more loops around the arm 320 to provide the induction coil 310. The radius of the cylinder may be selected to be equal to or greater than the minimum bend radius of the lengths of superconducting material 308 to prevent damage to the lengths of superconducting material 308 when the induction coil 310 is wound around the arm 320.

[0157] Stator arm 320a may further support switch 312 in a structure similar to that shown in FIG. 4A. Switch 312 may be a component configured to transition between a low resistance state and a high resistance state in the presence of a magnetic field, as described herein. In the illustrated example, switch 312 is a "Jc (B) Switch," which will be described in more detail herein. However, this should not be considered a limitation of the technology, and any suitable superconducting switch 312 may be used in accordance with the technology.

[0158] The center of the stator 304 is preferably aligned with the rotor's axis of rotation 317, such that the arcuate path of the magnetic field generator 306 travels near the first and second stator arms 320 a, 320 b. In other words, it may be advantageous for the switch 312 and induction coil 310 to be radially spaced from the axis of rotation 317 at substantially the same distance as the one or more magnetic field generators are radially spaced from the axis of rotation 317.

[0159] Switch

[0160] The present technology may be configured for use with any suitable switch 312 familiar to those skilled in the art. In a preferred example of this technology, the switch is a "J c (B) switch. For the purposes of this specification, a J c (B) The switch operates by changing the critical current of the superconducting material 308 by applying a magnetic field (e.g., a magnetic field having a direction (or a component of a direction) perpendicular to the surface of the length of superconducting material) to one or more lengths of superconducting material 308. The magnetic field acts to suppress the critical current in the length of superconducting material, and when an appropriate current flows through the length of superconducting material, it acts to transition the superconducting material into a higher resistance state, which can act as a switch. As previously mentioned, the length or lengths of superconducting material 308 can remain superconducting even in the high resistance state.

[0161] In one form of this technology, the switch 312 includes one or more lengths of superconducting material 308 positioned such that a magnetic field generated by a magnetic field generator 306 is applied to the lengths of the superconducting material, with at least one component of the magnetic field being perpendicular to the surface of the one or more superconducting materials. For example, the one or more lengths of superconducting material may be positioned at the ends of the stator arms 320 between the stator and rotor, and when the magnetic field generator passes the switch, the magnetic field from the magnetic field generator may be applied to the lengths of the one or more superconducting materials 308, with at least one component of the magnetic field being perpendicular to the surface of the superconducting materials. In some forms, the magnetic field may be substantially perpendicular to the surface of the superconducting material 308.

[0162] In one form of this technology, the switch 312 may be located on the stator at a distance substantially equal to the distance from the rotor's axis of rotation 317 to the magnetic field generator 306. 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 considered a limitation of the invention, and the magnetic field generated by the magnetic field generator(s) may be configured to be applied to one or more lengths 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, with reference to FIG. 4A , the switch may be provided on the second arm 320B of the stator between the rotor 302 and the stator 304.

[0163] In another form of the present technology, the stator may include multiple parts, for example, a first stator component and a second stator component, with the switch disposed between the first stator component and the second stator component.

[0164] J c (B) Switches may be used due to their low circuit complexity, high off-state resistance, and fast response times in certain forms of technology. However, this is not intended to limit the technology, and other potential switch mechanisms that can be used in conjunction with the functionality of this technology include: • A thermal switch, i.e., a switching mechanism that induces a temperature increase in one or more lengths of superconducting material 308 to change the Ej behavior (electric field vs. current density) and transition the switch 312 from a low resistance state to a high resistance state. ●Cryogenic MOSFET • Self-commutation describes a passive switching process by a switch portion of one or more lengths of superconducting material 308 that has a lower critical current than the rest of the circuit. In use, a current pulse that exceeds the critical current of the switch portion is supplied to the one or more lengths of superconducting material 308, causing the switch portion to transition from a low resistance state to a high resistance state. • An AC magnetic field rectifier uses an electromagnet to generate an AC magnetic field oriented perpendicular to the superconducting tape, thereby increasing the resistance of the superconducting tape. • Screening current loops, such as those described in PCT Publication No. WO / 2021 / 080443, the contents of which are incorporated by reference herein in their entirety. Although these other switching techniques can be used, c (B) Compared to switches, they can have some limitations. For example, thermal switches typically cannot operate at high frequencies and may not be suitable for use in regulation applications. They also often require a heat source and control circuitry, increasing cooling requirements. Similarly, cryogenic MOSFETs have a non-zero conduction resistance (low resistance state), which can increase system heating. Self-rectifying circuits have a simpler overall topology but are less flexible and cannot perform full-wave rectification of current.

[0165] AC field rectifiers may be similarly suitable for use with the present technology, although certain AC field rectifiers rely on dynamic resistance to transition switch 312 to a higher resistance state. c (B) The switch operates on the principle that the critical current of one or more lengths of superconducting material 308 changes when exposed to a perpendicular magnetic field, thus changing the EJ behavior of switch 312 .

[0166] J c (B) There is also evidence suggesting that the off-state resistance of the switch can be higher than the dynamic resistance presented by the AC field rectifier, which may allow for efficient control.

[0167] Forms of this technology utilize a variety of mechanisms that may be used to effect switching of electrical switches 312 formed from (or including) superconducting materials. Individual mechanisms are described first, followed by examples of how particular forms of technology utilize those mechanisms in combination.

[0168] 6.5.3.1. Effect of Magnetic Field on the Critical Current of Superconducting Materials

[0169] The critical current of 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 up to a critical magnetic field value, beyond which the superconducting material 308 is no longer in a superconducting (low resistance) state. This relationship is illustrated in Figure 2, which is a graph showing the relationship between the electric field and the current in a superconducting material when three external magnetic fields of different magnitudes are applied. 印加1 By this, the critical current I c1 will be the lowest.

[0170] This form of technology involves an electrical switch that utilizes the principle that the critical current of a superconducting material decreases when a high external magnetic field is applied to the material. Selective application of a magnetic field, such as a magnetic field that is substantially constant over a period of time (i.e., a direct current magnetic field), to the superconducting material can raise or lower the critical current relative to the transport current, switching the superconducting material between a low-resistivity state and a high-resistivity state. In certain forms, a combination of switching mechanisms may be used. That is, in some forms, a high-temperature superconductor (HTS) may require the application of an impractically high magnetic field to switch the superconducting material 308 to a non-superconducting, high-resistivity state, but may require the application of a practically large magnetic field to reduce the critical current sufficiently to allow another mechanism to perform the switching.

[0171] 6.5.3.2. Effect of a Time-Varying Magnetic Field on Superconducting Materials – Dynamic Resistivity and Heating

[0172] Certain forms of the technology may exploit the phenomenon of dynamic resistance, which occurs when a superconducting material 308 is subjected to a time-varying magnetic field while carrying a direct current transport current. This creates a direct current resistance in the superconducting material 308, and if this resistance becomes large enough, the superconducting material 308 may switch to a higher resistance state.

[0173] The DC electrical resistance created in the superconducting material 308 by this phenomenon can further cause energy loss due to heating of the superconducting material 308. Heat losses due to magnetization can also occur when a time-varying magnetic field is applied to the superconducting material 308. Losses due to dynamic resistance can occur in regions of transport current, e.g., the central region of the length of the superconducting material, while magnetization losses can occur in the edge regions of the superconducting material. The amount of heating can vary depending on the frequency and amplitude of the applied time-varying magnetic field.

[0174] The time-varying magnetic field that causes the dynamic resistance phenomenon can be an alternating magnetic field, such as a sinusoidally varying magnetic field.

[0175] For superconducting materials (e.g., wires or tapes) whose length is much greater than their width or depth, the dynamic resistance arises primarily from the component of the time-varying magnetic field applied to the superconducting material that is perpendicular to the length of the material.

[0176] 6.5.3.3. Heating of Superconducting Materials

[0177] As explained above, the critical current of a superconducting material is a function of both 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 continues up to a critical temperature, above which the superconducting material is no longer superconducting.

[0178] This form of technology involves electrical switches that utilize the principle that the critical current of a superconducting material decreases as its temperature increases. By selectively heating the superconducting material, the critical current can be raised or lowered relative to the transport current, allowing the superconducting material to be switched between low and high resistance states.

[0179] Different forms of the technology may use different mechanisms to heat the superconducting material in electrical switch 312, and forms of the technology may not be limited to the mechanism used to achieve heating. Nevertheless, in exemplary forms of the technology, two example mechanisms for heating the superconducting material are provided. These two mechanisms will now be briefly described.

[0180] First, a heating element may be placed 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 the process of Joule heating when electrical current through a conductor encounters electrical resistance. The heating element may be placed in physical contact with the superconducting material to heat the superconducting material primarily by conduction, or it may be placed remotely from the superconducting material to heat the superconducting material primarily by convection and / or radiation.

[0181] Second, forms of this technology may utilize the heating effect produced by applying a time-varying magnetic field (e.g., an alternating magnetic field, referred to as an AC magnetic field) to a length of superconducting material, which results from the phenomena of dynamic resistance and magnetization, as explained above.

[0182] 6.5.3.4. Screening current

[0183] Application of a time-varying magnetic field to a loop of superconducting material causes a shielding current to flow around the loop, which, combined with the transport current carried by the loop, can 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 transition between low and high resistance states.

[0184] An electrical switch configuration utilizing this switching mechanism will now be described. Note that although features are described below in relation to an exemplary configuration of an electrical switch 312 utilizing only this mechanism, those features may also be used in any of the electrical switch configurations utilizing a combination of switching mechanisms described later in this specification. Details of this switching mechanism are described in PCT Application No. PCT / NZ2020 / 050132, the contents of which are incorporated herein by reference.

[0185] 9 is a schematic diagram of a switch 312 that operates based on the principle of inductive shielding current. The switch 312 includes one or more lengths 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 limiting of the technology, and the switch may be integrated with other components of the superconducting material 308 described herein, such as a load 314 or an inductive coil 310. In use, a flux is induced in the stator 304, for example by the magnetic field generator(s), causing a transport current I between the first terminal 902 and the second terminal 904. t The transport current I tmay vary over time and be provided with a phase or time offset relative to the current induced in the induction coil 310. Transport current I t is shown flowing from a first (positive) terminal 902 to a second (negative) terminal 904, as would be expected for a conventionally defined direct current (DC) voltage. The superconducting material 308 between the two terminals 902, 904 is formed into a loop 906 that includes two electrically parallel superconducting branches 908a, 908b. Branches 908a, 908b may be formed using any method that provides a substantially zero resistance joint, such as splitting a superconducting tape into two parallel branches, or alternatively, a non-zero resistance joint may be used, such as by soldering. In use, a transport current is applied between the first terminal 902 and the second terminal 904, which in turn applies a time-varying magnetic field B app (t) is selectively applied to or within loop 906 in a direction perpendicular (or having a perpendicular component) to the plane of loop 906, i.e., parallel to an axis perpendicular to the plane of loop 906. For example, a time-varying magnetic field may be applied to the loop by passing stator arms 320 through the loop. This time-varying magnetic field B 印加 (t), a shielding current (I s ) flows. This screening current I s adds to the transport current flowing around loop 906, resulting in an increase in the total current flowing. This increase in current causes a slight increase in the resistance of the superconducting material (e.g., when the current exceeds the critical current I c less than 0.05 V), or the resistance of the superconducting material increases significantly (e.g., when the current I c is close to, greater than, or equal to the critical current of the superconducting material 308). 6.5.3.5. Combining Switching Mechanisms

[0186] It should be noted that the switch 312 may be constructed using any combination of the aforementioned switching mechanisms. For example, the switch 312 may be constructed using the following combination: Combining a Jc(B) switch with self-commutation. In other words, the portion of the superconducting material that is exposed to a perpendicular magnetic field can be configured to have a lower critical current than the rest of the superconducting material. Combining a screening current loop with self-commutation. In other words, the section of superconducting material used in loop 906 may be configured to have a lower critical current than the rest of the superconducting material. Combination of Screening Current Loop and AC Field Rectifier In other words, a loop can be formed in the superconducting material 308 to provide a screening current loop switch 312. In use, a time-varying magnetic field passes through the loop and may pass through part of the superconducting material. Load

[0187] In some examples of the technology described herein, the load 314 is connected in parallel with the switch 312. This configuration is not considered a limitation of the technology, as in some applications it may be desirable to use the flux pump to increase the current flow in the load before disconnecting the load from the flux pump and using it elsewhere. In other words, the technology may include two or more output terminals configured to connect to the load in use, the two or more output terminals being electrically connected in parallel with the switch.

[0188] The load 314 may be a load coil or any circuit that receives current from the flux pumps described herein during use. In some examples, the load 314 comprises a loop of superconducting material, as is well known to those skilled in the art. In other examples, the load 314 is part of a superconducting circuit. Thus, the flux pump configurations described herein can be used not only to increase the flow of current through one or more lengths of superconducting material 308 per cycle, but also to maintain the flow of current through one or more lengths of superconducting material 308 during use.

[0189] 6.6. Improved Flux Pump Arrangement

[0190] While the foregoing description may provide a functional flux pump, the inventors have identified further refinements to this technology. These include any one or more of the following: Adding a shunt resistor between the induction coil 310 and the load 314 and switch 312. Use Field Spreader 1102 c (B) Improve flux penetration of switch 312. • Adjust the flux gap to improve the electromagnetic field coupling between the rotor 302 and the stator 304. • Adjusting the phase angle / timing relationship between the induced current in the induction coil 310 and the actuation of the switch 312. Each of the above is explained in more detail below.

[0191] 6.6.1. Shunt Resistor

[0192] As previously mentioned, it is not currently possible or commercially feasible to create superconducting joints with high temperature superconducting materials. Thus, although the present invention may be implemented using a single continuous length of superconducting material 308 suitably configured to provide the induction coil 310, switch 312, and load 314, in some instances of the technology it may be advantageous to include one or more joints, such as conventional conductive joints familiar to those skilled in the art.

[0193] FIG. 10 is a modified version of the circuit diagram of FIG. 3, where a shunt resistor R2 is introduced between the induction coil 310 and the parallel switch 312 and load 314. This shunt resistor may represent the resistance introduced by a normally conductive joint, such as a solder joint, as is well known to those skilled in the art. Note that normally, overlapping one or more lengths of conductive material (also known as a lap joint) may result in a lower relative resistance of the normally conductive material than when using joining methods such as end-to-end joints or butt joints. In some examples of this technique, a normally conductive material such as copper may be used.

[0194] In other words, in a particular form of this 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 normal conductive joint.

[0195] It should be understood that the current into load 314 is proportional to the voltage V2 across the load, and therefore, by increasing voltage V2, the current in superconducting material 308 is expected to increase. Therefore, conventional thinking is to make R2 as small as possible to reduce its effect on the voltage divider between R2 and the combined impedance of load 314 in parallel with switch 312Rs. However, the present inventors have discovered that increasing the shunt resistance R2 can increase the load current in load 314.

[0196] Assuming that the current i2 is in a steady state, the voltage V2 is defined as follows:

[0197] V2=-i2R2

[0198] Therefore, increasing the shunt resistance R2 may increase the voltage V2. The higher the voltage V2, the faster the current may be delivered to the load 314. Furthermore, I L Assuming that is the maximum load current, V2=-i L R L

[0199] The above formula can be further combined as follows: i L R L =-i2R2

[0200] Therefore, the maximum load current i L is i2, R2 and R L The maximum load current is determined by the ratio of R2 to R2. If R2 is small, the maximum load current will also be small. Therefore, it may be advantageous to switch on the induction coil 310 with a large resistance. An additional advantage of introducing the shunt resistor R2 is that the current flowing in the circuit can be easily measured.

[0201] 6.6.2. Field Spreader

[0202] A further improvement to the flux pump design described herein may be provided by improving the flux penetration of switch 312, thereby increasing the resistance difference between the low and high resistance states. In other words, by exposing switch 312 to a stronger magnetic field, a greater reduction in the critical current of superconducting material 308 may be achieved, as shown in FIG. 2.

[0203] Thus, one feature of the present technology is the provision of a field spreader 1102 used to couple the magnetic field from the rotor 302 and provide a uniform magnetic field across at least a portion of the switch, such as one or more lengths of superconducting material in the switch 312. While the term field spreader is used throughout this specification, it should be understood not to be limiting and to refer to any component configured to direct a magnetic field through a superconductor component, particularly a switch, e.g., by providing a uniform magnetic field through the switch. The term "spreader" should be interpreted in the context of directing a magnetic field or coupling or evenly dispersing a magnetic field. In some examples of this technology, the field spreader may concentrate the magnetic field to enhance coupling of the magnetic field to the switch.

[0204] 11A and 11B show examples of how the magnetic field strength is distributed within the rotor 302 and stator 304 according to the flux pump design of the form shown in FIG. 3. As shown, the stator 304 is provided with a field spreader 1102 configured to concentrate or direct the magnetic field from the rotor 302 via switch 312. To achieve this, the field spreader 1102 preferably comprises a material that has a higher magnetic permeability than the environment surrounding the field spreader 1102; for example, if the field spreader 1102 is in an air environment, the field spreader 1102 should have a higher magnetic permeability than air, and may use, for example, iron.

[0205] A field spreader 1102 may be positioned between the magnetic field generator 306 and the switch 312 on the stator 304 such that when the magnetic field generator passes through the field spreader 1102 , a uniform magnetic field is generated in the switch 312 portion of the superconducting material 308 .

[0206] Additionally, it may be advantageous to ensure that the field spreader 1102 is positioned approximately in the center of the stator arm 320A to minimize the maximum measurable distance from the end of the field spreader 1102 to the end of the stator arm 320A, as shown at D1 and D2 in FIG. 11B.

[0207] It is also advantageous for the field spreader 1102 to be approximately the same width as the magnetic field generator so that the flux generated by the magnetic field generator passes through the field spreader 1102, through the switch 312, and is evenly coupled to the stator arm 320.

[0208] 6.6.3.Flux Gap

[0209] Those skilled in the art should understand that it is preferable to keep the distance between the magnetic field generator and the stator 304 to a minimum in order to maximize flux coupling between the rotor 302 and the stator 304. This separation may be referred to as the flux gap. For example, the inventors have discovered that reducing the flux gap from 6 mm to 1 mm increases the induced current and voltage by 20%.

[0210] It should be noted that in an example technology where the stator 304 and rotor 302 are separated by a cryostat 702, as shown in FIG. 7C, there is a trade-off between the flux gap and the amount of insulation that can be placed between the rotor 302 and the stator 304.

[0211] 6.6.4. Switching Phase Angle

[0212] In the aforementioned example, the switch 312 is positioned to operate simultaneously with the induced current in the induction coil 310. For example, as shown in FIG. 8, the induction coil 310 may be positioned on the same stator arm 320 as the switch 312. In another example, the induction coil 310 is positioned directly opposite (180 degrees across from) the switch 312, in which case multiple magnetic field generators 306 may be used, also positioned opposite each other on the rotor 302. In this way, as one of the magnetic field generators 306 passes over the induction coil 310, another of the magnetic field generators 306 passes over the switch 312, thereby synchronizing the induced current with the commutation resulting from the increased resistance of the switch 312.

[0213] 12A, the stator arms 320 described herein should be understood to include any components of the stator 304 configured to transmit a magnetic field from a magnetic field generator on the rotor 302 and return the magnetic field to the rotor 302. For example, in FIG. 12A, these include a central magnetic return path 320C, steel / ferromagnetic teeth 320A that are attached to the induction coil 310 during use, and a steel wall 320B.

[0214] The stator arm 320B may be configured to provide a wall that allows the flux generated by the magnetic field generator 306 to continue to be conducted, including when the switch 312 and / or the induction coil 310 are not in the direct presence of a magnetic field, which may advantageously reduce cogging torque, as described herein.

[0215] Other features of the stator 304 in certain forms of technology include ring bolt holes 1208, which advantageously allow liquid coolant to flow into the stator 304 and also secure the components of the stator 304.

[0216] Stator 304 may also be provided with an optional tape slot through which the superconducting material of switch 312 passes during use. In other words, the superconducting material may be looped around stator arms 320, with a portion of the tape disposed between stator arms 320 and a magnetic field generator as described herein. Note that the use of a tape slot is optional, and other switch 312 configurations are described herein, including bifilar configurations that do not require a tape slot.

[0217] In certain forms of the technology, such as those shown in FIGS. 12A and 12B, the flux pump may include a switch holder 1212 configured to adjust the position of the switch 312 relative to the induction coil 310 being adjusted. For example, the switch holder 1212 may be configured to engage one or more of multiple angle markers 1210 corresponding to potential positions of the switch 312. For example, the multiple angle markers may be arranged to provide an offset of + / - 1 degree each. This arrangement allows for adjustment of the relative position, and therefore the phase relationship, of the induced currents in the induction coil 310 and the activation of the switch 312. For example, FIG. 12B includes a switch holder 1212 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 arc-shaped in other configurations.

[0218] In a particular form of this technology, the switch holder 1212 includes an opening that can accommodate the field spreader 1102 described herein during use, and a slot 1214 that is configured to accommodate the length of one or more superconducting materials 308 during use. For example, the switch holder 1212 can be configured such that the field spreader 1102 can be positioned directly above the length of one or more superconducting materials 308 to direct a magnetic field from a magnetic field generator into the length of one or more superconducting materials 308 to generate a switching action described herein.

[0219] The switch holder is preferably constructed of a material with low magnetic permeability and low electrical conductivity to reduce the generation of eddy currents. For example, the switch holder 1212 may be constructed of G10 (high pressure glass fiber laminate).

[0220] Figure 12C shows examples of the maximum current generated by the designs of Figures 12A and 12B for different angular positions of switch 312 relative to induction coil 310. The effect of different speeds (in turns per minute) of rotor 302 was also tested and shown in the graph. Note that the system was tested with rotor 302 rotating in both clockwise and counterclockwise directions, so two different zero values ​​are recorded on the graph.

[0221] The graphical results are summarized in the table below. Table 1 - Effect of rotation speed, direction and phase offset on maximum current [Table 1] JPEG2025531051000004.jpg31121 This result indicates that there is some asymmetry within the test setup, and the inventors believe that the low number of turns used in the induction coil 310 may be causing the highly asymmetric region within the loop.

[0222] Notwithstanding the above, it has been found that peak load 314 current is identified at a 10 degree phase offset angle, and it is believed that a phase offset between 0 and 13 degrees may result in higher overall load 314 current than a 0 degree offset in the flux pump or when the switch 312 and induction coil 310 are diametrically opposed (180 degree opposite). In other words, in certain forms of this technology, the flux pump includes a switch and an induction coil, where the switch is configured to operate (switch from a low resistance state to a high resistance state) with a phase or time delay relative to the current induced in the induction coil 310. More specifically, it may be advantageous to position the switch 312 within the flux pump such that the switch 312 operates within + / - 13 degrees of the current induced in the induction coil 310. In forms of the technology that include two or more magnetic field generators 306, it may be advantageous to position 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 cycle of the current induced in the induction coil.

[0223] The use of phase delay can be advantageous to rectify selective characteristics of the current induced in the induction coil. For example, a phase delay between the induced current in the induction coil and the activation of a switch can be used to select and transfer to a load certain potentially desirable characteristics of the induced current waveform. For example, the current induced in the induction coil is known to oscillate between positive and negative values, as described herein in connection with FIG. 15 . Therefore, controlling the phase delay between the induced current in the induction coil and the activation of the switch can selectively adjust either the positive or negative portion of the induced current waveform. In other words, flux pump devices of certain forms of the technology described herein can be configured to selectively adjust current flow in a positive and / or negative direction. Furthermore, controlling the phase offset can change the polarity of control during flux pump operation.

[0224] While the foregoing examples are described with respect to adjusting the polarity of the waveform, this should not be construed as limiting, and any desired characteristic of the waveform can 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 one or more of the peak induced current, the induced current above a predetermined threshold, and / or the frequency characteristics of the induced waveform to the load.

[0225] In another form of this technique, the relative dimensions of the induction coil 310, switch 312, and magnetic field generator 306 can be adjusted to adjust the amount of time the magnetic field generator acts on the induction coil 310 and switch 312. For example, a larger magnetic field generator can hold the switch 312 in a high resistance state for a longer period of time, thereby changing the optimal phase relationship between the induction coil and switch.

[0226] 12D shows test results for an example technique configured such that the peak current induced in the load occurs with a substantially 0 degree phase offset between the activation of switch 312 and induction coil 310. Or, more generally, the optimal phase offset between switch 312 and induction coil 310 may be between about -10 degrees and about 5 degrees. The data in FIG. 12D is summarized in the following table: Table 2 - Alternative examples of how rotation speed, direction and phase offset affect maximum current [Table 2]

[0227] According to one form of the technology shown in Figure 13, there is provided a flux pump including a rotor 302 and a stator 304 arranged within a housing 701. In this example, the housing 701 includes a bearing group which supports a shaft 316 during use. In this example, a first stator arm 320A includes an induction coil 310 and an opposing stator arm 320B includes a switch holder 1212 which allows the position of a switch 312 relative to the induction coil 310 to be adjusted.

[0228] 6.6.5. Induced Current Frequency

[0229] The graph in Figure 12C also shows that in one example experiment, the peak induced current was detected at approximately 150 RPM when the flux pump was operating in a first direction, and the peak induced current was detected at approximately 125 RPM when the flux pump was operating in a second, reverse direction. These differences are likely due to the asymmetry of the test configuration, as previously discussed.

[0230] Thus, the phase offsets described herein may be expressed as time offsets for a given rotational speed and / or number of magnetic field generators 306 disposed on the rotor 302 .

[0231] It should also be understood that the optimal rotational speed identified in the experiments conducted was for a rotor 302 that included two magnetic field generators 306. However, this is not to be considered a limitation of the technology. For example, in a version of the technology including a single magnetic field generator, the speed at which peak current is induced is expected to be between approximately 250 RPM and 300 RPM. Similarly, in examples of the technology using more magnetic field generators 306, such as four, six, or eight, the RPM is expected to be correspondingly reduced to achieve peak induced current.

[0232] 6.7.Bifilar Switch Configuration

[0233] This technology c (B) An example of a switch 312 is shown in Figure 14A. In this example, one or more lengths of superconducting material 308 are looped around a stator arm 320, such as using a switch holder, as described in connection with Figures 12A and 12B. In other words, in one aspect of the technology, the switch may include one or more lengths of superconducting material 308 looped around a stator arm.

[0234] In another aspect of this technology, the switch 312 may be provided by looping one or more lengths of superconducting material 308 into a two-wire arrangement.

[0235] In the context of this specification, unless otherwise specified, a "bifilar arrangement" is understood to mean an arrangement of two strands of conductor in which the two strands are substantially parallel and electrically connected so that current flows through the strands in opposite directions. The strands may be adjacent to each other. A strand may be two folded sections of a length of superconducting material. Alternatively, the two strands may be lengths of separate superconducting material electrically connected, such as by soldering, diffusion bonding, or other suitable form of electrical connection.

[0236] The bifilar arrangements described herein may be disposed on or adjacent to a ferromagnetic member, such as a stator arm, and may couple a magnetic field from a magnetic field generator through one or more lengths of superconducting material. In some aspects of this technology, a bifilar arrangement may be provided between a field spreader and a stator arm, as described herein.

[0237] One potential advantage of the bifilar configuration is that it reduces the loop area of ​​the superconducting material 308, reducing inductance compared to the loop arrangement of Figure 14 A. Additionally, this arrangement reduces the self-field effect of the switch 312 because the fields generated on either side of the bifilar arrangement cancel each other.

[0238] This bifilar configuration allows switch 312 to generate voltage without inducing current. By comparison, dynamo flux pumps are known to use a single HTS tape that induces current to generate voltage. Other potential advantages of the bifilar structure include reduced inductance of switch 312 compared to a similar switch using a single length of superconducting material.

[0239] Another advantage of switch 312, where the length of superconducting material is bilinearly arranged, is that it helps reduce the suppression of the critical current of the length of superconducting material when a low, e.g., zero, magnetic field is applied to the length of superconducting material, thereby increasing the critical current in the low resistance state of switch 312.

[0240] 14C, a bifilar switch is provided in which two layers of superconducting material 308 are stacked on top of each other and joined by a joint, such as a normal or solder joint 1402. This arrangement not only further reduces loop inductance, but also has the advantage of eliminating minimum bend radius issues that can arise with a single length of superconducting material such as the example shown in FIGS. 14A and 14B.

[0241] Further examples and applications of bifilar switch configurations using superconducting materials are described in PCT Application No. PCT / NZ2022 / 050009, the entire contents of which are incorporated herein by reference.

[0242] 6.8.Experimental Data

[0243] 15 shows an example of the use of this technique; although an optical trigger is not used in the graph shown, it can be used experimentally to determine the point at which the magnetic field generator 306 aligns with the induction coil 310. The V-joint represents the voltage drop across the series shunt resistor, the V-coil represents the induced voltage in the induction coil 310, and the V-bridge represents the voltage across the switch 312. Note that the phase offset from the optical trigger means that the switch 312 will be active at approximately the peak of the voltage induced in the induction coil 310.

[0244] Vload is a measurement of the voltage across the load 314, and Vhall is a measurement of the magnetic field within the load 314. Note that the field in the load 314 remains positive and increases slightly with each cycle.

[0245] Generally speaking, rotating one or more magnetic field generators 306 relative to the induction coil 310 induces current flow in the induction coil. This current flow begins before the magnet passes the induction coil, with a peak induced current occurring shortly thereafter (represented by a peak voltage of approximately 1.9 mV). This current has a large positive component, then goes negative and decreases over time.

[0246] Shortly after the peak current is observed in induction coil 310 (e.g., after about 0.01 seconds), a peak voltage is observed across switch 312 (V ブリッジ reaches 0.5 mV), which corresponds to the at least one magnetic field generator 306 reducing the critical current of the switch 312, thus transitioning the switch 312 from a low resistance state to a high resistance state.

[0247] 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 degree phase offset between the induction coil and the switch.

[0248] It was found that an increase in switch resistance corresponds to an increase in voltage across the load, and that the voltage across the load decreases before the switch resistance increases. As a result, the voltage measured by the Hall Effect sensor (V hall ) increases visibly, indicating the current in the load. Thus, the net DC rectified load 314 current is provided by activating the switches synchronously relative to the peak current induced in the induction coil.

[0249] 6.9.Other

[0250] Unless the context clearly dictates otherwise, throughout the specification and claims, the words "comprise," "comprising," and the like, are to be construed in their inclusive sense, i.e., "including, but not limited to," rather than in their exclusive or exhaustive sense.

[0251] The entire disclosures of all applications, patents and publications, cited above and below, are hereby incorporated by reference.

[0252] The reference herein to any prior art is not, and should not be construed as, an acknowledgment or in any way an indication that the prior art forms part of the common general knowledge in that field anywhere in the world.

[0253] This technology may be broadly described as consisting of the parts, elements, and features referred to or shown in the specification of the application, individually or collectively, or any or all combinations of two or more of said parts, elements, or features.

[0254] Where reference is made in the foregoing description to integers or components that have known equivalents, those integers are incorporated herein as if individually set forth.

[0255] 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 can be made without departing from the spirit and scope of the technology and without diminishing its attendant advantages. Accordingly, such changes and modifications are intended to be included within the scope of the technology.

Claims

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

2. 1. A device for inducing current flow in a load, comprising: a rotor including at least one magnetic field generator configured to rotate with the rotor, the at least one magnetic field generator generating a magnetic field; a stator; the stator is provided with one or more lengths of superconducting material arranged to provide an induction coil and a switch, and two or more output terminals configured to connect to a load in use, the two or more output terminals being electrically connected in parallel with the switch; In use, the rotor is configured to rotate relative to the stator, and the at least one magnetic field generator comprises: to induce a current flow in the induction coil, and A device configured to periodically apply a magnetic field to transition the switch between a low resistance state and a high resistance state for a given current flow through the switch.

3. 1. A device for inducing current flow in a load, comprising: a rotor including at least one magnetic field generator configured to rotate with the rotor, the at least one magnetic field generator generating a magnetic field; a stator; the stator is provided with an induction coil, a switch configured to transition between a low resistance state and a high resistance state, and two or more output terminals configured to connect to a load in use, the two or more output terminals being electrically connected in parallel with the switch; In use, the rotor is configured to rotate relative to the stator, and the at least one magnetic field generator periodically applies a magnetic field to the induction coil and the switch to: Inducing a current in the induction coil when moved relative to the induction coil; configured to transition the switch between a low resistance state and a high resistance state for a predetermined current flow; The device wherein the magnetic field is applied to the switch with a phase delay relative to the magnetic field applied to the induction coil.

4. A device according to any one of claims 1 to 3, wherein 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. A device according to any preceding claim, wherein the rotor comprises a drive shaft, the longitudinal axis of the drive shaft defining an axis of rotation about which the rotor rotates in use.

6. The device of claim 5 , wherein the at least one magnetic field generator is disposed radially outward of the axis of rotation.

7. A device according to any preceding claim, wherein the rotor is configured to provide a high permeability path for the magnetic field generated by the magnetic field generator.

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

9. The device of any one of claims 1 to 8, wherein the rotor comprises a plurality of magnetic field generators.

10. 10. The device of claim 9, wherein each of the plurality of magnetic field generators is positioned at substantially the same radial distance from the axis of rotation of the rotor.

11. 11. The device of claim 10, wherein the plurality of magnetic field generators are approximately evenly distributed around the axis of rotation, and the angle between each of the plurality of magnetic field generators when measured relative to the axis of rotation is substantially the same.

12. 12. The device of claim 1, wherein the at least one magnetic field generator is positioned at a radial distance from the axis of rotation of the rotor that is substantially the same as a radial distance of a switch from the axis of rotation.

13. A device according to any preceding claim, wherein the at least one magnetic field generator is arranged on a side of the rotor nearest the induction coil and the switch.

14. The device of claim 1 , wherein the induction coil, the switch, and the two or more output terminals are provided on the stator.

15. 15. The device of claim 2, 3, or 14, wherein the stator is configured to provide a high permeability path for a magnetic field generated by the magnetic field generator.

16. The device of claim 15 , wherein the high permeability path comprises a ferromagnetic material.

17. 17. The device of claim 1, wherein the switch is positioned 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 of claim 3 , wherein the phase delay is between about −13 degrees and about +13 degrees.

19. The device of claim 3 , wherein the phase delay is between about +3.6% and about −3.6%.

20. The device of any one of claims 1 to 19, wherein the magnetic field generator comprises a permanent magnet.

21. The device of any preceding claim, wherein the magnetic field generator comprises an electromagnet.

22. 22. The device of any one of claims 1 to 21, further comprising a field spreader, said field spreader configured to generate said uniform magnetic field within a length of superconducting material of said at least one switch.

23. The device of any one of claims 1 to 21, wherein the switch and the induction coil are located in a cryostat.

24. A rectifier, a rotor including at least one magnetic field generator configured to rotate with the rotor, the at least one magnetic field generator generating a magnetic field; An induction coil; a switch comprising one or more lengths of superconducting material; In use, the rectifier is configured to connect to the 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, thereby periodically applying a magnetic field to the induction coil and the switch; a current flow is induced in the induction coil, the current flow having a positive component and a negative component over time, at least a portion of the current flow being configured to flow through the switch and the load; a magnetic field applied to the switch reduces the critical current of a superconducting material in the switch, such that the magnetic field and current flow in the switch causes the switch to transition from a low resistance state to a high resistance state; A rectifier in which application of a magnetic field to the switch is synchronized with a positive or negative component of current flow, causing the switch to transition to a high resistance state, increasing the amount of current flowing to the load during the positive or negative component, thereby providing a positive or negative net current flow to the load.

25. 1. A system for increasing current flow in a load, the system comprising: a rotor including at least one magnetic field generator configured to rotate with the rotor, the at least one magnetic field generator generating a magnetic field; one or more lengths of superconducting material arranged to provide said induction coil and said switch; a superconducting load electrically connected in parallel with the switch; rotation of the rotor causes the at least one magnetic field generator to move relative to the induction coil and the switch; the magnetic field is periodically applied to the induction coil to induce a current flow in the induction coil, at least a portion of the current flow passing through the switch and the superconducting load; The magnetic field is periodically applied to the switch to reduce the critical current of the superconducting material in the switch, such that the magnetic field and current flow in the switch causes the switch to transition from a low resistance state to a high resistance state, thereby affecting the amount of current flowing through the superconducting load.

Images