Improved superconducting switches

Abstract

In some forms, the electrical switch is configured to be controlled between a low resistance state and a high resistance state by selectively applying one or more switching mechanisms. In the high resistance state, the current flowing through the superconducting material segment may be either close to, substantially equal to, or greater than the critical current of the superconducting material segment. In some embodiments, the superconducting material segment is a length of high temperature superconducting material. The switching mechanisms include heating the superconducting material segment, applying a magnetic field to the superconducting material segment, applying a time-varying magnetic field to generate dynamic resistance and / or heat, and / or applying a time-varying magnetic field to a superconducting material loop to generate a screening current around the loop.

Description

[Technical field]

[0001] The present technology relates to superconducting switches, and more particularly to electrical switches that include components formed from superconducting materials, particularly high temperature superconducting materials. [Background technology]

[0002] In superconducting circuits, it is generally difficult to introduce components with similarly low or zero resistance conductive paths. Introducing non-superconducting components can degrade the circuit's performance and reduce the overall efficiency of the circuit. Furthermore, adding resistance to a high-current superconducting circuit requires greater cooling to offset the heating of the resistive components.

[0003] An additional problem with introducing resistive components into a superconducting circuit is that the DC current flowing in that circuit decays quickly when the current source is removed. In a superconducting circuit, the current decays according to the time constant (L / R) of the circuit. In other words, the advantage of a superconducting circuit is that it can support the flow of DC current for a long period of time after the power source is turned off. The rate of current decay in these superconducting circuits is determined by the non-zero resistance in the circuit associated with the normally conducting junctions.

[0004] There is therefore a need to be able to provide components or configurations within superconducting circuits that operate more efficiently, preferably without significantly degrading their performance.

[0005] One of the components used in these superconducting circuits is the variable resistance current switch. However, currently existing switching devices have many known drawbacks. For example, thermally controlled switches are usually slow to respond and are not suitable for high speed switching applications. Current controlled switches usually apply current pulses that exceed the critical current of the superconductor, making these types of switching devices prone to degradation. Existing field controlled switching devices are controlled by high strength magnetic fields, but the resistance per unit length of these field controlled switching devices during actuation is small, and the switching speed is usually limited by the large inductance of the applied magnetic field coil. Summary of the Invention [Problem to be solved by the invention]

[0006] Object of the invention It is an object of the present technology to provide an electrical switch including at least one component made of a superconducting material that meets one or more of the above requirements. Alternatively, one objective of the present technology is to provide the public with at least one useful option. [Means for solving the problem]

[0007] According to one aspect of the invention, an electrical switch is provided that includes a superconducting material segment. In some forms, the electrical switch is configured to be controlled between a low resistance state and a high resistance state by selectively applying one or more switching mechanisms. In the high resistance state, the current through the superconducting material segment may be close to, substantially equal to, or greater than the critical current of the superconducting material segment. In some aspects, the superconducting material segment is a high temperature superconducting material segment.

[0008] In a particular form of the technology, the switching mechanism comprises: 1. Heating a superconducting material segment to reduce a critical current of the superconducting material segment; 2. Applying a magnetic field to the superconducting material segment to reduce a critical current of the superconducting material segment; 3. applying a time-varying magnetic field to the superconducting material segment to generate a dynamic resistance in the superconducting material segment and / or heat the superconducting material segment by the dynamic resistance and / or magnetization; 4. Applying a time-varying magnetic field to a superconducting material loop and generating a screening current around the loop.

[0009] In examples, the electrical switch may include a heating assembly and / or one or more magnetic field generators to achieve any combination of the above switching mechanisms.

[0010] According to one aspect of the present technology, an electrical switch is provided that includes a superconducting material segment configured to carry a transport current and having a critical current and a critical temperature. The electrical switch may further include a magnetic field generator configured to apply a magnetic field to the superconducting material segment. The electrical switch may further include a heating assembly for heating the superconducting material segment. The magnetic field generator and the heating assembly may be configured to be selectively controlled independently or in combination to switch the electrical switch between a low resistance state and a high resistance state. In the low resistance state, the magnitude of the magnetic field may be relatively small and the temperature of the superconducting material segment may be substantially lower than the critical temperature such that the transport current is substantially smaller than the critical current. In the high resistance state, the magnitude of the magnetic field may be relatively large to reduce the critical current and / or the heating assembly may heat the superconducting material segment to reduce the critical current such that the transport current is close to, substantially equal to, or greater than the critical current of the superconducting material segment.

[0011] In some examples, a) the magnetic field generator and the heating assembly may be configured to be selectively activated and deactivated, independently or in combination, to toggle the electrical switch between a low resistance state and a high resistance state; b) the heating assembly is configured to maintain activation, and the electrical switch may be switched between a low resistance state and a high resistance state by selective deactivation and activation of the magnetic field generator; c) the magnetic field applied by the magnetic field generator may be a constant magnetic field; d) the heating assembly may include a resistive heating element disposed in thermal contact with the superconducting material segment; e) the superconducting material may be a high temperature superconducting material; f) the magnetic field generator may be a first magnetic field generator, the magnetic field may be a first magnetic field, and the electrical switch may include a second magnetic field generator configured to apply a second time-varying magnetic field to the superconducting material segment. The second magnetic field generator may be configured to be selectively controlled to switch the electrical switch between a low resistance state and a high resistance state; g) the superconducting material may be a tape having two opposing surfaces; h) the second magnetic field generator may be configured to apply a second magnetic field in a direction substantially perpendicular to the two opposing faces; i) the first magnetic field generator and the second magnetic field generator may be the same magnetic field generator, and the magnitude of the magnetic field applied by the same magnetic field generator varies over time in response to a DC bias; j) the superconducting material segment may include a superconducting material loop configured to carry a transport current between a first terminal and a second terminal, the loop may include a first branch and a second branch electrically connected in parallel between the first terminal and the second terminal, the loop may have an axis substantially perpendicular to a plane of the loop, and k) the electrical switch may further include a third time-varying magnetic field generator configured to apply a third time-varying magnetic field through the loop such that the direction of the third magnetic field through the loop is substantially parallel to the axis of the loop or has a component substantially parallel to the axis of the loop. In a low resistance state, the third magnetic field generator may not apply a third magnetic field through the loop and a transport current may flow through the loop between said two terminals. In a high resistance state, the third magnetic field generator may apply a third magnetic field through the loop and induce a screening current such that a total current in one or more of the first and second branches is close to, substantially equal to, or greater than a critical current of the superconducting material.

[0012] According to one aspect of the present invention, an electrical switch is provided that includes a superconducting material segment configured to carry a transport current and having a critical current and a critical temperature. The electrical switch may include a first magnetic field generator configured to apply a first constant magnetic field to the superconducting material segment. The electrical switch may further include a second magnetic field generator configured to apply a second time-varying magnetic field to the superconducting material segment. The first magnetic field generator and the second magnetic field generator may be configured to be selectively controlled independently or in combination to switch the electrical switch between a low resistance state and a high resistance state. In the low resistance state, the magnitude of the first magnetic field and the second magnetic field may be relatively small and the transport current may be substantially smaller than the critical current. In the high resistance state, the magnitude of the first magnetic field may be relatively large and / or the second magnetic field may generate a dynamic resistance in the superconducting material segment to reduce the critical current such that the transport current is close to, substantially equal to, or greater than the critical current of the superconducting material segment.

[0013] In some examples, a) the first magnetic field generator and the second magnetic field generator may be configured to be selectively activated and deactivated, independently or in combination, to switch the electrical switch between a low resistance state and a high resistance state; b) the first magnetic field generator may be configured to remain activated and the electrical switch may be switched between a low resistance state and a high resistance state by selectively deactivating and activating the second magnetic field generator; c) the second magnetic field generator may be configured to remain activated and the electrical switch may be switched between a low resistance state and a high resistance state by selectively deactivating and activating the first magnetic field generator; d) the superconducting material may be a tape having two opposing faces, and the second magnetic field generator may be configured to apply a second magnetic field in a direction substantially perpendicular to the two opposing faces; e) the first magnetic field generator and the second magnetic field generator may be the same magnetic field generator, and the magnitude of the magnetic field applied by the same magnetic field generator varies over time in response to a DC bias; f) the superconducting material may be a high temperature superconducting material; g) the electrical switch may further include a heating assembly for heating the superconducting material segment, wherein in the high resistance state, the heating assembly may heat the superconducting material segment to reduce the critical current such that the transport current is close to, substantially equal to, or greater than the critical current of the superconducting material segment; h) the heating assembly may include a resistive heating element disposed in thermal contact with the superconducting material segment; i) the superconducting material segment may include a superconducting material loop configured to carry a transport current between a first terminal and a second terminal, the loop including a first branch and a second branch electrically connected in parallel between the first terminal and the second terminal, the loop may have an axis substantially perpendicular to a plane of the loop; j) the electrical switch may further include a third time-varying magnetic field generator configured to apply a third time-varying magnetic field through the loop, the direction of the third magnetic field through the loop being substantially parallel to the axis of the loop or having a component substantially parallel to the axis of the loop. In a low resistance state, the third magnetic field generator may not apply a third magnetic field through the loop and a transport current may flow through the loop between said two terminals. In a high resistance state, the third magnetic field generator may apply a third magnetic field through the loop and induce a screening current such that a total current in one or more of the first and second branches is close to, substantially equal to or greater than a critical current of the superconducting material.

[0014] According to one aspect of the invention, an electrical switch is provided that includes a superconducting material loop configured to pass a transport current between a first terminal and a second terminal, the superconducting material loop having a critical current and a critical temperature. The loop may include a first branch and a second branch electrically connected in parallel between the first terminal and the second terminal, the loop having an axis substantially perpendicular to a plane of the loop. The electrical switch may further include a time-varying magnetic field generator configured to apply a time-varying magnetic field through the loop, the direction of the magnetic field through the loop may be substantially parallel to the axis of the loop or may have a component substantially parallel to the axis of the loop. The electrical switch may further include a heating assembly for heating the superconducting material loop. The time-varying magnetic field generator and the heating assembly may be configured to be selectively controlled independently or in combination to switch the electrical switch between a low resistance state and a high resistance state. In the low resistance state, the time-varying magnetic field generator does not apply a time-varying magnetic field through the loop, a transport current may flow through the loop between the two terminals, the transport current may be substantially less than the critical current, and the temperature of the loop may be substantially less than the critical temperature. In the high resistance state, the time-varying magnetic field generator may apply a time-varying magnetic field through the loop to induce a screening current in the loop, and / or the heating assembly may heat the loop to reduce the critical current such that the total current in one or more of the first branch and the second branch is close to, substantially equal to, or greater than the critical current of the superconducting material.

[0015] In some examples, a) the time-varying magnetic field generator and the heating assembly may be configured to be selectively activated and deactivated, independently or in combination, to toggle the electrical switch between a low resistance state and a high resistance state; b) the heating assembly may be configured to remain activated and the electrical switch may be switched between a low resistance state and a high resistance state by selectively deactivating and activating the time-varying magnetic field generator; c) the heating assembly may include a resistive heating element disposed in thermal contact with the superconducting material loop; d) the first branch may include one or more coils of superconducting material; e) the second branch may include one or more coils of superconducting material; f) the coil of the first branch and the coil of the second branch may be wound around the same axis; g) the coils of the first branch may be wound in a first rotational direction and the coils of the second branch may be wound in a second rotational direction, the first rotational direction and the second rotational direction being different; h) the time-varying magnetic field generator may be magnetically coupled to the superconducting material loop by a core; i) the superconducting material may be a high temperature superconducting material; j) the electrical switch may further include a second magnetic field generator configured to apply a second magnetic field to the superconducting material loop. In the low resistance state, the magnitude of the second magnetic field may be relatively small. In the high resistance state, the magnitude of the second magnetic field may be relatively large to reduce the critical current.

[0016] According to one aspect of the invention, an electrical switch is provided that includes a superconducting material loop configured to carry a transport current between a first terminal and a second terminal, the superconducting material loop having a critical current and a critical temperature. The loop may include a first branch and a second branch electrically connected in parallel between the first terminal and the second terminal. The loop may have an axis substantially perpendicular to the plane of the loop. The electrical switch may further include a first magnetic field generator configured to apply a time-varying magnetic field through the loop, such that the direction of the magnetic field through the loop is substantially parallel to the axis of the loop or has a component substantially parallel to the axis of the loop. The electrical switch may further include a second magnetic field generator configured to apply a second magnetic field to the superconducting material segment. The first magnetic field generator and the second magnetic field generator may be configured to be selectively controlled independently or in combination to switch the electrical switch between a low resistance state and a high resistance state. In a low resistance state, the first magnetic field generator may apply no time-varying magnetic field through the loop, a transport current flows through the loop between said two terminals, and the magnitude of the second magnetic field may be relatively small such that the transport current is substantially less than the critical current. In a high resistance state, the first magnetic field generator may apply a time-varying magnetic field through the loop, induce a screening current in the loop, and / or the magnitude of the second magnetic field may be relatively large to reduce the critical current such that the total current in one or more of the first and second branches is close to, substantially equal to, or greater than the critical current of the superconducting material.

[0017] In some examples, a) the first magnetic field generator and the second magnetic field generator may be configured to be selectively activated and deactivated, independently or in combination, to switch the electrical switch between a low resistance state and a high resistance state; b) the first magnetic field generator may be configured to remain activated and the electrical switch may be switched between a low resistance state and a high resistance state by selectively deactivating and activating the second magnetic field generator; c) the second magnetic field generator may be configured to remain activated and the electrical switch may be switched between a low resistance state and a high resistance state by selectively deactivating and activating the first magnetic field generator; d) the first branch may include one or more coils of superconducting material; e) the second branch may include one or more coils of superconducting material; f) the coil of the first branch and the coil of the second branch may be wound around the same axis; g) the coils of the first branch may be wound in a first rotational direction and the coils of the second branch may be wound in a second rotational direction, the first rotational direction and the second rotational direction being different; h) the first magnetic field generator may be magnetically coupled to the superconducting material loop by a core; i) the second magnetic field applied by the second magnetic field generator may be a constant magnetic field; j) the superconducting material may be a high temperature superconducting material; k) the electrical switch may further include a heating assembly for heating the superconducting material loop. In the low resistance state, the temperature of the loop may be substantially below the critical temperature. In the high resistance state, the heating assembly may heat the loop to reduce the critical current.

[0018] In certain forms of the present technology, the electrical switch of any one or more aspects of the present technology may include superconducting material arranged in a bifilar arrangement. For example, the electrical switch includes a first strand and a second strand of superconducting material, each of the first strand and the second strand configured to carry a transport current and having a critical current. The electrical switch may further include a magnetic field generator configured and arranged to apply a magnetic field to the first strand and the second strand of superconducting material. The magnetic field generator may include a high permeability magnetic core. The magnetic field generator may be configured to be selectively controlled to switch the electrical switch between a low resistance state, where the magnitude of the magnetic field is relatively small, and a high resistance state, where the magnitude of the magnetic field is relatively large. In the low resistance state, the transport current may be significantly less than the critical current. In the high resistance state, the transport current may be close to, substantially equal to, or greater than the critical current. The first and second strands of superconducting material may be spatially arranged substantially parallel to one another within the region of the magnetic field and electrically connected such that a transport current flows in opposite directions through the first and second strands of superconducting material within the region of the magnetic field.

[0019] In some examples, a) a high permeability magnetic core including a first end and a second end separated by a gap, the first and second strands of superconducting material being disposed within the gap; b) the first and second strands of superconducting material may each be in the form of a tape having two opposing surfaces; c) the tape may be arranged such that opposing faces of the first strands of superconducting material are parallel to opposing faces of the second strands of superconducting material; d) the tape may be oriented such that a magnetic field applied to the first and second strands of superconducting material is substantially perpendicular to each of two opposing faces; e) the electrical switch may include a superconducting material segment including a first strand and a second strand of superconducting material, or the first and second strands of superconducting material may be electrically connected by connecting one side of the first strand to one side of the second strand; f) The superconducting material is a high temperature superconducting (HTS) material.

[0020] According to another aspect of the present technology, the electrical switch of any one or more aspects of the present technology may include a superconducting material segment configured to carry a transport current and having a critical current. The electrical switch may further include a magnetic field generator configured and arranged to apply a magnetic field to the superconducting material segment. The magnetic field generator may include a high permeability magnetic core. The magnetic field generator may be configured to be selectively controlled to switch the electrical switch between a low resistance state when the magnitude of the magnetic field is relatively low and a high resistance state when the magnitude of the magnetic field is relatively high. In the low resistance state, the transport current may be substantially less than the critical current. In the high resistance state, the transport current may be close to, substantially equal to, or greater than the critical current. The superconducting material segment may be arranged to substantially cancel a self-magnetic field generated by the transport current flowing through the superconducting material segment as it approaches the high permeability magnetic core.

[0021] Upon reading the following description, which provides at least one example of the practical application of the present technology, other aspects of the present technology should be considered in all its novel aspects. One or more embodiments of the present technology are described below by way of example, and not by way of limitation, with reference to the following drawings: [Brief description of the drawings]

[0022] [Figure 1] 1 shows an exemplary electric field versus current graph for a high temperature superconductor. [Figure 1A] 1 is a graph showing electric field versus current in a superconducting material when three external magnetic fields of different magnitudes are applied. [Figure 2A] 1 shows an electrical switch in accordance with one form of the present technology; [Figure 2B] 2B shows the switch of FIG. 2A in a low resistance state. [Figure 2C] 2B shows the switch of FIG. 2A in a high resistance state. [Diagram 3] 1 illustrates an electrical switch in accordance with another aspect of the present technology; [Figure 4] 1 illustrates a method of coupling a magnetic field generator to a switch in accordance with one form of the present technology. [Diagram 5] 13 shows a graph comparing the voltage measured across a superconducting switch in accordance with one form of the present technology in the presence and absence of a varying magnetic field; [Figure 6] 13 illustrates an alternative method of coupling a magnetic field generator to a switch, in accordance with one form of the present technology. [Figure 7] 1 is a perspective view of an electrical switch in accordance with another aspect of the present technology; [Figure 8A] 1 is a perspective view of an electrical switch in accordance with another aspect of the present technology; [Figure 8B] 1 is a perspective view of an electrical switch in accordance with another aspect of the present technology; [Figure 9] 1 is a graph showing the critical current versus applied electric field for a high temperature superconductor at two different temperatures. [Figure 10A] 1 is a perspective view of an electrical switch in accordance with another aspect of the present technology; [Figure 10B] 1 is a perspective view of an electrical switch in accordance with another aspect of the present technology; [Figure 11] 1 is a graph showing the change in magnetic field strength over time generated by a magnetic field generator in accordance with one form of the present technology; [Figure 12] 1 is a perspective view of an electrical switch in accordance with another aspect of the present technology; [Figure 13A] FIG. 1 is a schematic diagram of an electrical switch in accordance with one form of the present technology; [Figure 13B] 1 is a schematic diagram of an electrical switch in accordance with another aspect of the present technology; [Figure 14]FIG. 1 illustrates a relationship between the critical current of superconducting material segments in various application fields and when the superconducting material segments are arranged in a bifilar configuration and a unifilar configuration in an electrical switch according to one form of technology. [Figure 15A] 1 illustrates a magnetic field distribution of an electrical switch in accordance with one aspect of the present technology. [Figure 15B] 1 illustrates the magnetic field distribution of an electrical switch in accordance with another aspect of the present technology; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] 6.1. Discussion of superconductors To aid in understanding the current technology, the reader should become familiar with superconducting terminology such as the critical temperature of a superconductor and the critical current of a superconductor. However, for the reader's benefit, a brief explanation of these concepts is provided below.

[0024] The critical temperature of a superconductor is generally defined as the temperature at which the resistivity of the superconductor drops to zero or near zero. In other words, a superconductor is superconducting when the temperature of the superconductor is lower than the critical temperature, and non-superconducting when the temperature of the superconductor is higher than the critical temperature. Many of the 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 also known to have much higher critical temperatures, such as from 30 K to 125 K. For example, the critical temperature of magnesium diboride is about 39 K, while the critical temperature of yttrium barium copper oxide (YBCO) is about 92 K. These superconductors are generally called high temperature superconductors (HTS).

[0025] The critical current of a high temperature superconducting wire or tape is typically defined as the current flowing through the superconducting wire / tape that causes an electric field drop of 100 μV / m (=1 μV / cm) along the wire. It should be understood that the critical current is a function of both the superconducting material used and the physical arrangement of the superconducting material. For example, a wide tape / wire may have a higher critical current than a thin tape / wire composed of the same material. However, it should be understood that throughout this specification, references to the critical current of the superconductor / superconducting material are for ease of discussion.

[0026] Current I is the critical current I 臨界 If I is approximately equal to the critical current I, the resistance of the superconductor is not zero, but it is small. 臨界 If the temperature is much higher than 0.05V, the resistance of the superconductor becomes large enough to dissipate heat and heat it above the critical temperature, so that it is no longer superconducting. This condition is sometimes called a "quench" and may even damage the superconductor itself.

[0027] Figure 1 is an example of a plot showing the internal electric field versus current curve for a high temperature superconductor, where it is understood that the electric field shown in this plot is related to the resistance by the following equation:

number

[0028] Thus, the plot in FIG. 1 relates the resistance per unit length of the superconductor, and since the curve shown is nonlinear, the resulting resistance of the superconductor is nonlinear with respect to current.

[0029] From this figure, the critical current I 臨界It can be seen that below this threshold, the electric field strength within the superconductor is practically zero. As the current in the superconductor approaches the critical current, the electric field within the superconductor begins to increase. At the critical current, the electric field within the superconductor is 100 μV / m. As the current in the superconductor is increased further beyond the critical current, the electric field strength within the conductor increases rapidly.

[0030] Throughout this specification, reference is 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 or high resistance state. Because superconducting materials can have zero or substantially zero resistance when in a superconducting state, it should be understood that these resistances are often typically expressed in terms of the electric field present in the superconducting material at a given current. However, throughout this specification, reference is made to the relative resistance of the superconducting material, such as the low and high resistance states, to simplify the foregoing discussion. 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 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 the low resistance state. For the avoidance of doubt, unless the context clearly indicates otherwise, the high resistance state referred to herein may include the superconducting state.

[0031] Similarly, where this specification describes a superconductor as being in a highly resistive state because the current flowing through it exceeds the critical current, it should be understood that the highly resistive state can also be achieved when the current flowing through the superconductor is close to or approximately equal to the critical current, unless the context clearly dictates otherwise.

[0032] In describing the technology described herein, materials and components that include them will be referred to as "superconducting." This term is used as a general term for such materials by those of skill in the art, and is not to be taken to mean that the materials 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, a material may be described as being superconducting, but is not superconducting.

[0033] 6.2.Superconducting materials 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 the described embodiments of the technology include copper oxide superconductors such as rare earth barium copper oxide (ReBCO), such as yttrium barium copper oxide or gadolinium barium copper oxide, and iron-based superconductors. Other types of superconductors may be used in other embodiments of the technology.

[0034] In a particular embodiment, the superconducting material may be provided in the form of a tape, which may be described as a segment of material having a width that is greater (including significantly greater) than its depth and having two opposing faces.

[0035] 6.3.Switching Mechanism Forms of the present technology make use of a variety of mechanisms that can be used to achieve switching of electrical switches formed from (or including) superconducting materials. Individual mechanisms are described herein, followed by examples of how particular forms of the present technology make use of these mechanisms in combination.

[0036] 6.3.1. Superconductors 臨界 Effect of magnetic field on electric current The critical current of a superconductor depends on the external magnetic field applied to the superconductor. More specifically, when a higher external magnetic field is applied to the superconductor, the critical current drops to a critical magnetic field value beyond which the superconductor is no longer in a superconducting (low resistance) state. This relationship is illustrated in Figure 1A, which shows a graph of electric field versus current for a superconducting material when three external magnetic fields of different magnitudes are applied. The maximum magnitude of the external magnetic field B 印加1 is the minimum critical current I 臨界1 results. This form of technology relates to an electrical switch that utilizes the principle that the critical current of a superconducting material decreases when a large external magnetic field is applied to the superconducting material. To switch the superconducting material between a low resistance state and a high resistance state, the critical current can be raised or lowered relative to the transport current by selectively applying a magnetic field, for example a substantially constant magnetic field (i.e., a direct current magnetic field), to the superconducting material. In particular, in high temperature superconductors (HTS), the magnetic field itself must be applied at an unrealistically high magnetic field to switch the superconductor to a higher resistance state, but the critical current can be sufficiently reduced by applying a magnetic field of practical magnitude to enable switching by another mechanism.

[0037] 6.3.2. Effect of time-varying magnetic field on superconductors – dynamic resistance and heating A particular form of the technology exploits the phenomenon of dynamic resistance, which occurs when a superconductor is subjected to a time-varying magnetic field while carrying a direct current transport, which creates a direct current electrical resistance in the superconductor that can be large enough to switch the superconductor into a highly resistive state.

[0038] The DC electrical resistance of a superconductor caused by this phenomenon can also cause energy losses by heating the superconductor. Heat losses due to magnetization can also occur when applying a time-varying magnetic field to a superconductor. Losses due to dynamic resistance may occur in the region of the transporting current, e.g., the central region of the superconducting material segment, while magnetization losses may occur in the end regions of the superconducting material. The amount of heating may depend on the frequency and amplitude of the applied time-varying magnetic field. The time-varying magnetic field that causes the dynamic resistance phenomenon may be an alternating magnetic field, for example a magnetic field that varies sinusoidally.

[0039] When the superconducting material segment is significantly greater than its width or depth (eg, a wire or tape), the dynamic resistance is caused primarily by the component of a time-varying magnetic field applied to the superconducting material that is perpendicular to the direction along the length of the material.

[0040] 6.3.3. Heating of Superconductors As can be seen, 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.

[0041] A form of the present technology relates to an electrical switch that utilizes the principle that the critical current of a superconducting material decreases as the temperature of the superconducting material increases. By selectively heating the superconducting material, the critical current can be increased or decreased relative to the transport current in order to switch the superconducting material between low and high resistance states.

[0042] Different embodiments of the present technology may use different mechanisms for heating the superconducting material in the electrical switch, and embodiments of the present technology may not be limited to the mechanism used to achieve heating. However, in exemplary embodiments of the present technology, two examples of mechanisms for heating the superconducting material are provided. The two mechanisms are briefly described here.

[0043] 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 by the Joule heating process when an electrical current flowing through a conductor encounters resistance. The heating element may be placed in physical contact with the superconducting material and heat the material primarily by conduction, or may be separate from the superconducting material and heat the material primarily by convection and / or radiation. Second, as mentioned above, forms of the present technology can take advantage of the thermal effects caused by the application of a time-varying magnetic field (e.g., an AC magnetic field, which may be referred to as an AC magnetic field) to a superconducting material segment that are generated by dynamic resistance and magnetization phenomena.

[0044] 6.3.4. Screening current When a time-varying magnetic field is applied to a loop of superconducting material, a screening current flows around the loop which, in combination with the transport current flowing through 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 be transitioned between low and high resistance states.

[0045] A form of electrical switch utilising such a switching mechanism is described below. Where features are described below with respect to an exemplary form of electrical switch utilising a mechanism alone, it should be understood that these features may also be used in any form of electrical switch utilising a combination of switch mechanisms as described herein below. Further details of this switching mechanism are provided in PCT Application No. PCT / NZ2020 / 050132, the contents of which are incorporated herein by reference.

[0046] 2A is a schematic diagram of a switch 200 that operates according to a switching mechanism in accordance with the present technology. The switch 200 includes a superconducting material 202 connected between a first terminal 204 and a second terminal 206.

[0047] When in use, the transport current I 輸送 is selectively provided to flow between the first terminal 204 and the second terminal 206. In other words, the transport current I 輸送 can be turned on and off as needed.

[0048] It should be noted that in FIG. 2A, for ease of explanation, the first terminal 204 is shown as a positive terminal and the second terminal 206 is shown as a negative terminal.

[0049] Similarly, the transport current I 輸送 is shown flowing from a first (positive) terminal 204 to a second (negative) terminal 206 as would be expected for a conventionally defined direct current (DC) voltage. However, as is evident from the above discussion, the use of DC voltages should not be considered as a limitation of the present technology. Furthermore, it should be understood that when using DC current, the superconducting material experiences negligible losses due to the low, zero, or near zero resistance of the superconducting material 202. When using AC current, losses are often higher due to parasitic effects, but the total losses are significantly less than an equivalent non-superconducting material.

[0050] The superconducting material 202 between the two terminals 204, 206 is formed into a loop 210 that includes two electrically parallel superconducting branches 212a, 212b.

[0051] These superconducting branches 212a, 212b may be formed by joining two or more superconducting materials together using methods known to those skilled in the art, including methods that provide a non-zero connection resistance. Alternatively, the branches 212a, 212b may be formed using any method that provides a substantially zero resistance joint, such as, for example, splitting a superconducting tape into two parallel branches.

[0052] In use, a transport current is applied between the first terminal 204 and the second terminal 206 using a circuit (not shown) connected between the first terminal 204 and the second terminal 206. The electrical circuit may include a power source, such as a voltage or current source, a transformer, or any other suitable electronic circuit known to those skilled in the art. A time-varying magnetic field B 印加(t)is selectively applied to or within loop 210 in a direction orthogonal to the plane of loop 210 (or having a component orthogonal to the plane of loop 210), i.e., parallel to the axis of loop 210, which axis is orthogonal to the plane of loop 210. In FIG. 2A , a time-varying magnetic field is applied to loop 210 such that the magnetic field passes through loop 210. To reduce losses due to the magnetic field passing or attempting to pass through superconducting material 202, it is advantageous to provide a time-varying magnetic field in a direction substantially or at least partially orthogonal to the plane of the loop.

[0053] This time-varying magnetic field B 印加(t) A screening current (I スクリーニング ) is passed through the screening current I スクリーニング is added to the transport current flowing through loop 210, resulting in an increase in the total current flowing. Such an increase in current can be caused by an increase in the limit of resistance of the superconducting material (e.g., when the current exceeds the critical current I as shown in FIG. 1). 臨界 ), or a significant increase in the resistance of the superconducting material (for example, when the current I 臨界 If is close to or exceeds the critical current of the superconductor, this can result in

[0054] 2B, there is shown how the switch 200 of FIG. 2A operates in the absence of a time-varying magnetic field, or in the presence of a non-time-varying or weak time-varying magnetic field. As can be seen in FIG. 2B, the current flowing through the loop 210 is a transport current I 輸送 When a time-varying magnetic field is applied or the magnetic field increases or decreases in magnitude, a screening current I flows around the loop 210, as shown in FIG. スクリーニング A transport current I 輸送 and the screening current I スクリーニング When the sum of V and V approaches or exceeds the critical current of the superconductor, the effective resistance of the branches 212a, 212b increases. As a result, a time-varying magnetic field can be applied to transition the switch between a low resistance state and a high resistance state.

[0055] The low resistance state of switch 200 can be considered equivalent to a closed state of switch 200, and the high resistance state can be considered equivalent to an open state of switch 200. However, it should be understood that the high resistance state is not an electrical open circuit typical of mechanical switches, but rather a high resistance conductive state representing a loop that will remain superconducting unless subsequent heating above T critical occurs.

[0056] In some embodiments, the low resistance state may be a superconducting state in which the resistance of the branches 212a, 212b of the loop 210 is near or substantially zero. That is, in preferred embodiments, the low resistance state of the switch has at least a portion of the loop 210 in a superconducting state. However, this is not considered a limitation of the technology, and in alternative embodiments, the low resistance state may be a partial superconducting state. For example, soldered joints of normal metals form one or more low resistance junctions between the superconducting elements of the loop.

[0057] Similarly, the high resistance state may be a superconducting state in which the resistance of the branches 212a, 212b of the loop 210 is close to zero, but is greater than the resistance of the low resistance state. In one application of the present technology, the resistance of the branches 212a, 212b of the loop 210 in the high resistance state may be substantially non-zero. For example, the loop 210 may be in a non-superconducting state or a partially superconducting state.

[0058] It should thus be appreciated that the present technology provides a switch that can transition between a low resistance state and a high resistance state when exposed to a time-varying magnetic field or when the amplitude of the time-varying magnetic field is changed. This can advantageously enable the construction of faster switches, non-contact switches, that are more reliable than conventional current switches. Other potential advantages include creating switching elements that: As is clear from the above description, it is more compact than conventional switches. · Switching speeds are faster than thermal switches, especially in applications where the high resistance state of the switch is a superconducting state. A higher off-resistance can be achieved than existing AC field controlled switches. · More efficient than conventional switches as the magnetic field is eliminated from the superconductor, reducing dissipation within the superconductor. The switch is contactless and has low losses, making it more reliable than existing switches; and Since the inductance is low, the power required to drive the magnetic field generator can be reduced.

[0059] 3 illustrates another embodiment of a switch 300 according to the present technology. As with the previous embodiment, the superconducting material 202 is arranged in a loop 310 that includes two electrically parallel branches 312a, 312b. However, in this embodiment, each branch 312a, 312b includes a coil 314a, 314b of superconducting material, each coil including one or more turns.

[0060] With reference to the drawings and the foregoing description, it should be understood that the loops of the present technology include two or more electrically parallel conductive paths, whereas each coil of the present technology has a single conductive path consisting of one or more turns.

[0061] In use, a time-varying magnetic field B is induced through the loop 310 and across both of the two coils 314a, 314b in a direction perpendicular to (or having a component perpendicular to) the plane of the loop 310 and / or the coils 314a, 314b. 印加 This causes a screening current I to flow around the closed loop 310 formed by the two branches 312a, 312b connected in parallel. スクリーニング According to the embodiments described above, this screening current may be used to selectively transition the switch 300 between a low resistance state and a high resistance state.

[0062] The first branch 312a desirably includes one or more coils 314a wound in a clockwise direction and the second branch 312b includes one or more coils 314b wound in a counterclockwise direction, or vice versa. Such an arrangement may be used to ensure that the screening current in the first coil 314a is induced in the same direction as the screening current in the second coil 314b, and may be advantageous in encouraging the screening current to flow around the loop 310. Furthermore, the use of coils 314a, 314b may advantageously facilitate making the inductance of each branch 312a, 312b substantially equal. For example, by using coils 314a, 314b having one or more turns, the geometric difference between each branch 312a, 312b is a smaller fraction of the number of current turns in each branch.

[0063] Another potential advantage of such an arrangement is that it allows for a higher switching resistance than previous embodiments, due to the longer switching length in each branch.

[0064] Figure 4 is a schematic diagram of one implementation of the switch 300 of Figure 3. In this embodiment, the coupling between the variable magnetic field generator 402 and the switch 404 can be improved by directing the magnetic flux into a core 406. In this way, the arrangement of Figure 4 is similar to that of a transformer well known to those skilled in the art.

[0065] Core 406 is preferably a high permeability magnetic core, such as an iron core, although this should not be considered a technological limitation, as will become apparent from the above discussion.

[0066] For simplicity, the magnetic field generator 402 is shown as an AC power source 408 magnetically coupled to a core via a coil 410 containing one or more turns, however, this should not be considered a technology limitation and alternative methods of generating a variable magnetic field may be used, for example, by switching a DC current source.

[0067] To simplify the foregoing discussion, and to distinguish the magnetic field generator coil 410 from the coils 414a, 414b of the switch 402, the magnetic field generator coil 410 will be referred to herein as the magnetic field generator coil 410, or simply as the generator coil.

[0068] It should also be appreciated that the magnetic field generator coil 410 may be constructed from any suitable conductive material, including superconducting materials such as YBCO or non-superconducting materials such as copper or aluminum. In a preferred embodiment, the generator coil 410 is constructed from copper. This advantageously provides a less expensive switch than a similar switch using a superconducting generator coil 410.

[0069] To continue the transformer analogy, the generator coil 410 may be thought of as the primary side of a transformer, and the switch coils 414a, 414b as the secondary side of the transformer.

[0070] Unlike a conventional transformer, however, the superconducting coils 414a, 414b of the switch 404 are wound in counter-rotating directions around the core 406 and electrically connected in parallel with each other. As a result, if the number of turns in the coils 414a, 414b is the same, the secondary turn coil is shorted and the net magnetic flux surrounding the coils 414a, 414b is approximately zero. The core 406 is for coupling an applied magnetic field to the pair of coils 414a, 414b that form a loop 416. This generates a screening current in the loop 416 to oppose the magnetic flux changes from the magnetic field generator 402.

[0071] In use, the magnetic field generator 402 can be selectively enabled or varied in amplitude as required to transition the switch 404 between a low resistance state and a high resistance state.

[0072] In a low resistance state where the magnetic field generator 402 does not generate a variable magnetic field in the core 406 or generates a weak magnetic field in the core 406, a transport current I 輸送In this state, the resistance of the branches 412a, 412b is zero or close to zero, and since the coils 414a, 414b are wound in counter-rotating directions, there is almost no inductance between the terminals 204, 206. Furthermore, even if the coils 414a, 414b are wound in counter-rotating directions and connected in parallel, the magnetic flux induced in the core 406 from the coils 414a, 414b is substantially zero or very small. When the magnetic field generator 402 is activated or the magnitude of the applied magnetic field is increased or decreased, a screening current I flows in the loop 416 of the superconducting wire, as described above. スクリーニング is formed. A transport current I 輸送 and the screening current I スクリーニング If the sum of is close to, equal to, or greater than the critical current of the superconducting material, then a non-zero resistance exists in the branch, which allows the magnetic field generator 402 to be activated and its amplitude to be varied arbitrarily to switch the switch 404 between a low resistance state and a high resistance state.

[0073] 5 shows an example of measuring the voltage across the switch terminals 204, 206 in accordance with one form of the present technology. In this figure, the voltage across the switch is the voltage measured across the switch terminals 204, 206. The magnetic field generator current reflects the amplitude of the current applied by the magnetic field generator 402 to the generator coil 410.

[0074] For completeness, a current source is used to apply a DC current of about 80 amps between terminals 204, 206. The superconducting coils 414a, 414b each consist of a single turn of 4 mm wide YBCO tape, and the generator coil uses 200 turns of copper wire.

[0075] It can be seen that in the absence of a varying magnetic field (after approximately 80.5 seconds), the voltage measured between the terminals 204, 206 is substantially zero. In other words, in the absence of a time-varying magnetic field, the superconducting material is superconducting. This represents a low resistance state of the switch. On the other hand, when a varying magnetic field is applied (before 80.5 seconds), the voltage variation measured between the terminals represents a change in the electrical resistance of the superconducting material. In addition, upon application of such a varying magnetic field, a peak voltage was observed between the terminals. This represents a high resistance state of the switch. It should be understood that such a high resistance state of the switch may represent a superconducting or non-superconducting state depending on the expected application of the switch.

[0076] 6 illustrates yet another embodiment of a switch 600 according to the present technology. In this embodiment, the generator coil 410 of the variable magnetic field generator 402 is coaxially aligned with the coils 414a, 414b of the switch 600. This may advantageously improve the magnetic field coupling between the generator coil 410 and the superconducting coils 414a, 414b of the switch 600.

[0077] In the illustrated embodiment, the number of turns of the superconducting coils 414a, 414b of the switch 600 are staggered with the number of turns of the generator coil 410. However, this should in no way be considered a limitation of the technology. For example, the superconducting coils 414a, 414b may be positioned axially inward of the superconducting coils 414a, 414b of the generator coil 410. Alternatively, the generator coil 410 may be located axially inward of the superconducting coils 414a, 414b. In yet another alternative, the generator coil 410 may be spaced longitudinally from the coils 414a, 414b. It is contemplated that the first superconducting coil 414a may be positioned in an alternative location to the second superconducting coil 414b. For example, the first superconducting coil 414a may be located below the generator coil 410 and the second superconducting coil 414b may be located above the generator coil 410.

[0078] An additional benefit of coaxially aligning the generator coil 410 and the superconducting coils 414a, 414b is that it allows for the use of a non-magnetic or air core 602, which contributes to a smaller, lighter, and less costly switch. Additional benefits of using an air core, such as driving higher screening currents without saturating the core, will be apparent to those skilled in the art.

[0079] 6.4. Combination of switching mechanisms Aspects of the present technology utilize combinations of the above mechanisms that may be used to achieve switching in electrical switches formed from (including) superconducting materials. Aspects of the present technology include all possible combinations of the various mechanisms, including those specifically described below. Additionally, while the operation of different combinations of mechanisms are described with reference to specific examples and configurations of components, other configurations of the technology use other components that achieve switching using the same combinations of mechanisms. For example, configurations of electrical switches that use the "screening current" mechanism described above can include any of the configurations described above, as well as other configurations. Similarly, alternative configurations of other switching mechanisms can be used.

[0080] 6.4.1. Combination 1 - Screening current and resistive heating In a particular form of the present technology, there is provided an electrical switch 700 that operates using a combination of the above-mentioned "screening current" and "heating" switching mechanisms. One form of such an electrical switch 700 is shown in Figure 7, which is a perspective view of the electrical switch 700.

[0081] In the illustrated form, the electrical switch 700 includes a superconducting material segment 710 connected between two terminals 712 and 714. The superconducting material segment 710 includes a loop 716 that includes two electrically parallel branches of superconducting material segments 718 and 719. The loop 716 may be similar to the loop 210 described above with respect to Figures 2A-2C. The superconducting material segment 710 may take the form of a tape having two opposing faces. In use, a transport current is applied between the first terminal 712 and the second terminal 714 using an electrical circuit (not shown) connected between the first terminal 712 and the second terminal 714. The electrical circuit may include a power source, such as a voltage or current source, a transformer, or any other suitable mechanism known to those skilled in the art.

[0082] The electrical switch 700 further includes a time-varying magnetic field generator 720 configured to apply a time-varying magnetic field through the loop 716 in a direction perpendicular to the plane of the loop 716 (or having a component perpendicular to the plane of the loop 716), i.e., in a direction parallel to the axis of the loop 716, which axis is perpendicular to the plane of the loop 716.

[0083] 2A-2C, the time-varying magnetic field applied by time-varying magnetic field generator 720 causes a screening current to flow between branches 718, 719 of loop 716 to oppose the magnetic flux changes in loop 716. This screening current is added to the transport current flowing around loop 716, resulting in an increase in the total current flowing through superconducting material segment 710. Time-varying magnetic field generator 720 can switch superconducting material segment 710 from a low resistance state to a high resistance state when the levels of the transport current and / or screening current are appropriately controlled.

[0084] 7, the time-varying magnetic field generator 720 includes a power source 722, a coil 724, and a magnetic core 726. The power source 722 is configured to generate an alternating current. In one form, the power source 722 is an AC power source, while in other forms the power source 722 may include a suitably switched DC power source.

[0085] Power supply 722 is electrically connected to coil 724. Coil 724 can be formed of any type of conductor, including superconductors, although in certain configurations non-superconductors may be preferred due to lower cost.

[0086] The coil 724 is wound around a magnetic core 726. The magnetic core 726 may be a high permeability magnetic core such as a ferrite core (e.g., iron core) or a laminated steel / iron core. In other configurations, other cores having high relative permeability at the operating frequency may be used, or non-magnetic cores or air cores may be used. In the configuration shown in FIG. 7, the magnetic core 726 is a solid core that is substantially link-shaped, such as a square link with rounded corners. In the illustrated configuration, the coil 724 is wound on one side of the square link core 726.

[0087] The magnetic core 726 also passes through the superconducting material loop 716. For example, the side of the magnetic core 726 opposite the side carrying the coil 724 may pass through the loop 716. This arrangement magnetically couples the coil 724 and the loop 726. Thus, a change in the alternating current flowing through the coil 724 causes a time-varying magnetic field in the magnetic core 726, thereby inducing a screening current in the loop 726.

[0088] The electrical switch 700 further includes a heating assembly 750 for heating the superconducting material loop 716. In the embodiment shown in Figure 7, the heating assembly 750 includes a resistive heating element 752 disposed in thermal contact with the superconducting material loop 716. For example, the resistive heating element 752 may be attached to a surface of the superconducting material loop 716. The heating assembly 750 further includes a power source (not shown) configured to provide an electrical current to the resistive heating element 752.

[0089] The heating assembly 750 is configured to be selectively actuated to heat the superconducting material loop 716, thereby increasing its temperature and reducing its critical current. By controlling the increase and / or decrease in temperature of the loop 716 and appropriately controlling the transport current through the loop 716, the switch 700 can be switched between a low resistance state and a high resistance state. In some forms, the heating assembly 750 may be controlled based on a duty ratio indicating the percentage of time the heating assembly 750 is turned on, i.e., the cycling of the heating assembly 750 on and off may be controlled.

[0090] Two mechanisms are described for the electrical switch 700 to switch the switch 700 between a low resistance state and a high resistance state. If each of the two mechanisms is in a configuration corresponding to a low resistance state of the loop 716, the switch 700 is in a low resistance state. If one or both of the mechanisms are in a configuration that places the loop 716 in a high resistance state, the switch 700 as a whole adopts this high resistance state. Switching by the "screening current" mechanism is controlled by selective control (i.e., activation, deactivation, and / or variation) of the time-varying magnetic field generator 720. Switching by the "heating" mechanism is controlled by selective control of the heating assembly 750. In different forms of the present technology, the time-varying magnetic field generator 720 and the heating assembly 750 may be controlled to be selectively controlled (e.g., activated and deactivated) independently of each other or in combination to enable switching of the switch 700. These two mechanisms, operating in concert, provide advantages over each mechanism operating individually, such as faster and more efficient switching and more flexible switching in response to transport current levels.

[0091] For example, in some forms, one of the time varying magnetic field generator 720 and the heating assembly 750 is configured to remain activated, while controlling the activation and deactivation, or activation level, of the other of the time varying magnetic field generator 720 and the heating assembly 750 allows for switching. In one example of such a form, the heating assembly 750 is configured to remain activated (although the degree of activation of the heating assembly 750 may vary), which reduces the critical current in the loop 716, and switching between low and high resistance states is enabled by activation and deactivation of the time varying magnetic field generator 720.

[0092] Since the energy loss of a superconducting switch is roughly proportional to the critical current at which it switches, using the heating assembly 750 to reduce the value of the critical current at which it switches can reduce losses and improve efficiency compared to a screening current mechanism operating individually. Furthermore, the speed of the switch can be faster than one operating with only the heating mechanism (due to the delay in heating and cooling the superconductor when activating / deactivating the heating assembly) and can be switched with arbitrarily small currents.

[0093] In other forms, the time varying magnetic field generator 720 and the heating assembly 750 may be activated and deactivated together to allow for switching. In other forms, the time varying magnetic field generator 720 and the heating assembly 750 may be activated and deactivated together at some times and individually at other times to allow for switching.

[0094] Suitable control mechanisms for achieving switching between the time-varying magnetic field generator 720 and the heating assembly 750 are not described herein, although suitable forms of control mechanisms will be understood by those skilled in the art.

[0095] 6.4.2. Combination 2 - Screening current and time-varying electric field heating In another form of the present technology, an electrical switch is provided that is similar to the switch 700 shown in FIG. 7, but with an alternative heating assembly. The above description of the switch 700 is also applicable to such a form of the technology, except for the differences described below. In this other form, the heating assembly includes a second time-varying magnetic field generator (separate from the magnetic field generator 720) configured to apply a time-varying magnetic field to the loop 710. As described above, the second magnetic field generator can be controlled (e.g., activated and deactivated) by a suitable control mechanism to apply a time-varying magnetic field to the loop 710 and heat the loop 710 by the effects of application of the time-varying magnetic field, dynamic resistance and magnetization loss.

[0096] Similar to that described above with respect to "Combination 1," in this configuration the heating assembly and magnetic field generator can be controlled individually and / or in combination (e.g., activated, deactivated, and / or varied) to effect the switching of an electrical switch. When each of the two mechanisms is in a configuration that corresponds to a low resistance state for the loop, the switch is in a low resistance state. When the mechanisms are in a configuration that places one or both loops in a high resistance state, the switch as a whole adopts this high resistance state.

[0097] The second magnetic field generator may be positioned such that the direction of the magnetic field applied to the loop 710 is substantially perpendicular to two opposing planes of the tape, thereby increasing the amount of dynamic resistance generated compared to magnetic fields in other directions on the tape surface.

[0098] 6.4.3. Combination 3: Resistive heating and magnetic field In a particular form of the present technology, there is provided an electrical switch 800 that operates using a combination of the "magnetic field" and "heating" switching mechanisms described above. Two forms of such an electrical switch 800 are shown in Figures 8A and 8B, which are perspective views of the electrical switch 800.

[0099] In the form shown in Figure 8A, the electrical switch 800 includes a superconducting material segment 810 connected between two terminals 812 and 814. The superconducting material segment 810 may take the form of a tape having two opposing sides. In use, a transport current is applied between the first terminal 812 and the second terminal 814 using an electrical circuit (not shown) connected between the first terminal 812 and the second terminal 814. The electrical circuit may include a power source, such as a voltage or current source, a transformer, or any other suitable mechanism known to those skilled in the art.

[0100] The electrical switch 800 further includes a magnetic field generator 820 configured to apply a magnetic field to the superconducting material segment 810. When a magnetic field is applied, the critical current of the superconducting material segment 810 is reduced, as described above with respect to FIG. 1A. Thus, a lower transport current is required to approach, equal, and / or exceed the critical current for the superconducting material to transition to a high resistance state than if no magnetic field was applied.

[0101] 8A, a magnetic field generator 820 includes a power source 822 configured to generate an electric current. The power source 822 is electrically connected to a coil 824. The coil 824 can be formed of any type of conductor, including a superconductor, although in some forms a non-superconductor may be preferred due to lower cost.

[0102] The coil 824 is wound around a magnetic core 826. The magnetic core 826 may be a high permeability magnetic core such as a ferrite core (e.g., iron core) or a laminated steel / iron core. In other configurations, other cores having high relative permeability at the operating frequency may be used, or non-magnetic cores or air cores may be used. In the illustrated configuration of FIG. 8A, the magnetic core 826 is a solid core that is substantially link-shaped, such as a square link with rounded corners. In the illustrated configuration, the coil 824 is wound on one side of the square link core 826.

[0103] In the illustrated embodiment, the magnetic core 826 includes a gap 828. The gap 828 may be a space within the solid magnetic core 826, such as on one side of a square link core. In embodiments having an air core, the gap 828 may be any portion of the air core. In the embodiment shown in FIG. 8A, the gap 828 in the magnetic core 826 is the gap on the side of the square ring opposite the side on which the coil 824 is wound.

[0104] In use, coil 824 can have a current flowing through it. The flow of current through coil 824 generates a magnetic field in core 826 and across gap 828. In the illustrated configuration, at least a portion of superconducting material segment 810 is located within gap 828 such that a magnetic field generated by magnetic field generator 820 is applied to superconducting material segment 810. Superconducting material segment 810 can be oriented across gap 828 in a direction perpendicular to the surface of the tape such that the magnetic field is perpendicular to the surface of the tape.

[0105] The electrical switch 800 also includes a heating assembly 850 for heating the superconducting material segment 810. In the embodiment shown in Figure 8A, the heating assembly 850 further includes a resistive heating element 852 disposed in thermal contact with the superconducting material segment 810. For example, the resistive heating element 852 can be disposed on a surface of the superconducting material segment 810. The heating assembly 850 also includes a power source (not shown) configured to provide an electrical current to the resistive heating element 852.

[0106] The heating assembly 850 is configured to be selectively controlled (e.g., actuated) to heat the superconducting material segment 810, thereby increasing the temperature of the superconducting material 810 and reducing the critical current. By controlling the increase and / or decrease in temperature of the superconducting material and appropriately controlling the transport current, the switch 800 can be switched between a low resistance state and a high resistance state. In some forms, the heating assembly 850 may be controlled based on a duty ratio indicating the percentage of time the heating assembly 850 is turned on, i.e., the cycling of the heating assembly 850 on and off may be controlled.

[0107] Figure 8B illustrates an electrical switch 800 that is very similar to the electrical switch illustrated in Figure 8A. However, in the electrical switch 800 illustrated in Figure 8B, the superconducting material segments 810 are arranged in a bifilar arrangement within gaps 828 in a magnetic core 826. The bifilar arrangement is described in more detail later in this specification.

[0108] Two mechanisms are described for the electrical switch 800 to switch the switch 800 between a low resistance state and a high resistance state. If each of the two mechanisms is configured to correspond to a low resistance state of the superconducting material segment 810, the switch 800 is in a low resistance state. If one or both of the mechanisms are configured to place the material in a high resistance state, the switch 800 as a whole adopts this high resistance state. Switching by the "magnetic field" mechanism may be controlled by selective activation, deactivation, and / or variation of the magnetic field generator 820. Switching by the "heating" mechanism is controlled by selective activation, deactivation, and / or variation of the heating assembly 850. In different forms of the present technology, the magnetic field generator 820 and the heating assembly 850 may be controlled (e.g., selectively activated and deactivated) independently or in combination to effect switching of the switch 800.

[0109] For example, in some embodiments, one of the magnetic field generator 820 and the heating assembly 850 is configured to remain activated, while the activation and deactivation, or control of the activation level, of the other of the magnetic field generator 820 and the heating assembly 850 can be switched on and off. In one such embodiment, the heating assembly 850 is configured to remain activated (although the degree of activation of the heating assembly 850 may vary), which reduces the critical current in the superconducting material segment 810, and switching between low and high resistance states is enabled by activating and deactivating the magnetic field generator 820. Since the energy loss of a superconducting switch is approximately proportional to the critical current at the time of switching, using the heating assembly 850 to reduce the value of the critical current at the time of switching can reduce losses and improve efficiency compared to magnetic field mechanisms operating individually.

[0110] In other forms, the magnetic field generator 820 and the heating assembly 850 may be turned on and off together to allow for switching. In other forms, the magnetic field generator 820 and the heating assembly 850 may be turned on and off together at some times and individually at other times to allow for switching.

[0111] These two mechanisms, working in concert, provide advantages over, for example, each mechanism working individually. For example, superconductors typically have different relationships between the critical current and the applied external magnetic field at different temperatures. FIG. 9 is a graph showing the critical current vs. applied electric field of a high-temperature superconductor at two different temperatures, 77K and 85K. As can be seen from the graph, the higher the temperature, the smaller the magnitude of the applied magnetic field required to reduce the critical current of the superconductor to the same magnitude. Thus, by combining the two switching mechanisms, easier and / or faster switching can be achieved at lower temperatures by varying the applied magnetic field, for example, by heating the superconductor a few degrees with the heating assembly 850. This also increases the resistance in the high resistance state compared to using only a magnetic field to reduce the critical current at low temperatures, while maintaining the current carrying capacity in the low resistance state. The absence of a phase transition between these two states allows for faster and easier switching than a switch operated, for example, by turning on and off only the heating assembly. One drawback of this configuration of switch 800 is that it cannot switch arbitrarily small currents unless the temperature exceeds a critical temperature. Suitable control mechanisms for achieving switching between the time-varying magnetic field generator 820 and the heating assembly 850 are not described herein, although suitable forms of control mechanisms will be understood by those skilled in the art.

[0112] 6.4.4. Combination 4 - Resistance heating and additive resistance In another form of the present technology, there is provided an electrical switch that operates using a combination of the "resistive heating" and "dynamic resistance" switching mechanisms described above. Such an electrical switch form is similar to switch 800 shown in Figure 8A or 8B, and the description of switch 800 above is applicable to such a form of technology, except for the differences described below.

[0113] In this embodiment, the magnetic field generator 820 is a time-varying magnetic field generator configured to apply a time-varying magnetic field to the superconducting material segment. For example, the power source 822 may be configured to generate an alternating current, e.g., the power source 722 may be an AC power source or a suitably switched DC power source. The application of the time-varying magnetic field may induce a dynamic resistive phenomenon, and the time-varying magnetic field generator is controlled in conjunction with a heating assembly including a resistive heating element to selectively switch the superconducting material segment between low and high resistance states in a manner similar to that described above with respect to the other embodiments of the technology.

[0114] In one form, the heating assembly 850 is activated to heat the superconducting material segment 810 to reduce its critical current. The time-varying magnetic field generator can then be controlled (e.g., activated and deactivated) to selectively switch the electrical switch 800. Using a resistive heating mechanism to reduce the critical current can reduce losses due to dynamic resistive switching compared to a dynamic resistive switch that reduces the critical current without a resistive heating mechanism.

[0115] 6.4.5. Combination 5 - Magnetic Field and Dynamic Resistance (DC and AC Magnetic Fields) In some forms of the present technology, another electrical switch 1000 is provided that operates using a combination of the "magnetic field" and "dynamic resistance" switching mechanisms described above. Two forms of such an electrical switch 1000 are shown in Figures 10A and 10B, which are perspective views of the electrical switch 1000. The electrical switch 1000 is similar to the switch 800 shown in Figures 8A or 8B, and the description of switch 800 above is applicable to such forms of technology (with appropriate reference numbers), except for the differences described below. 8A and 8B, the electrical switch 1000 does not include a resistive heating element 852. Instead, when the magnetic field generator 1020 applies a time-varying magnetic field, the superconducting material segment 1010 is heated to some extent due to the effects of dynamic resistance and magnetization. Thus, the magnetic field generator 1020 may also be considered to be used as a heating assembly in the present technology.

[0116] Figure 10B illustrates an electrical switch 1000 that is very similar to the electrical switch illustrated in Figure 10A. However, in the electrical switch 1000 illustrated in Figure 10B, the superconducting material segments 1010 are arranged in a bifilar arrangement within gaps 1028 in a magnetic core 1026. The bifilar arrangement is described in more detail later in this specification.

[0117] To achieve two mechanisms of switching of the electrical switch 1000, the magnetic field generator 1020 is configured to generate a magnetic field having a time-varying amplitude in response to a DC bias and apply it to the superconducting material segment 1010. The strength B of the magnetic field generated by the magnetic field generator 1020 is 印加 An example of how V varies with time t is shown in Figure 11. Such a field can be generated by appropriately controlling the current generated by the power supply 1022, for example to generate a current with a waveform as shown in Figure 11.

[0118] In use, the control mechanism is configured to control the magnetic field generator 1020 to vary the magnitude of the magnetic field applied to the superconducting material segment 1010 over time to achieve the desired switching using the two switching mechanisms. That is, the level of the DC bias can be selectively varied to increase or decrease the critical current of the superconductor based on the magnitude of the applied magnetic field. Additionally, the time-varying component of the magnetic field strength can be selectively controlled (e.g., changed, activated, deactivated) to change the amount of dynamic resistance generated and, consequently, the resistance of the superconducting material 1010. The control mechanism is configured to control the magnetic field strength to transition the electrical switch 1000 between low and high resistance states using the two switching mechanisms independently or in combination as required. If each of the two mechanisms is in a configuration corresponding to a low resistance state, the switch 1000 is in a low resistance state. If one or both of the mechanisms are in a configuration that places the superconductor in a high resistance state, the switch 1000 as a whole adopts this high resistance state.

[0119] For example, in some forms, one of the time-varying or DC bias components of the magnetic field applied by the magnetic field generator 1020 is configured to remain activated, while enabling switching to control the activation and deactivation, or activation level, of the other magnetic field component.

[0120] In one example of such an embodiment, the magnetic field generator 1020 is configured to maintain a DC bias component of the magnetic field to reduce the critical current in the superconducting material segment 1010, and the magnetic field generator 1020 activates and deactivates a time-varying component of the magnetic field to selectively trigger the dynamic resistance, thereby enabling switching between low and high resistance states. Using the DC bias component to reduce the critical current results in a smaller amount of heat loss due to dynamic resistance in the superconducting material segment 1010 than would be the case if only the dynamic resistance effect were used as the switching mechanism.

[0121] In another example of such a configuration, the magnetic field generator 1020 is configured to maintain an activated state of a time-varying (e.g., alternating current) component of the magnetic field (although the degree of activation may vary), which creates a dynamic resistance and also reduces the critical current. Current flows through the superconducting material segment 1010 through the dynamic resistance and magnetization-induced heating, and switching between low and high resistance states is enabled by the magnetic field generator 1020 activating and deactivating the DC bias component of the magnetic field.

[0122] Since the energy loss of a superconducting switch is roughly proportional to the critical current in the switch when switching, using the time-varying component of the magnetic field generator 1020 as a heating assembly to reduce the value of the critical current when switching reduces losses and improves efficiency compared to the DC bias components of the magnetic field operating individually. Furthermore, switching speeds are increased compared to the DC bias components operating alone. Additionally, this combination of mechanisms allows arbitrarily small currents to be switched.

[0123] 6.4.6. Combination 6 - Magnetic Field, Resistive Heating and Dynamic Resistance In another form of the present technology, there is provided an electrical switch that operates using a combination of the above-mentioned "resistive heating" switching mechanism, "dynamic resistance" switching mechanism, and "magnetic field" switching mechanism. Such an electrical switch form is similar to switch 800 shown in Figure 8A or 8B, and the description of switch 800 above is applicable to such a form of technology, except for the differences described below.

[0124] In this embodiment, the magnetic field generator is configured to generate a magnetic field having a time-varying amplitude in response to a DC bias and to apply it to the superconducting material segment. 印加 An example of how V varies with time t is shown in Figure 11. Such a field can be generated by appropriately controlling the current generated by the power supply, for example by generating a current with a waveform as shown in Figure 11.

[0125] In use, the control mechanism is configured to control the magnetic field generator to vary the magnitude of the magnetic field applied to the superconducting material, similar to that described with respect to the fifth combination above. In addition, the control mechanism is configured to control the heating assembly to vary the temperature of the superconducting material. In this manner, the switching of the electrical switch can be achieved using three mechanisms, and the magnetic field generator and heating assembly can be controlled to achieve the switching in a desired manner.

[0126] In this configuration, if all three mechanisms are configured to provide a low resistance state, the switch will be in the low resistance state, and if any one or more of the mechanisms are configured to place the superconductor in a high resistance state, the switch as a whole will adopt this high resistance state.

[0127] 6.4.7. Combination 7 - Magnetic field, resistive heating, dynamic resistance and screening current In another form of the present technology, there is provided an electrical switch that operates using a combination of the above-mentioned "resistive heating", "dynamic resistance", "magnetic field" and "screening current" switching mechanisms. One form of such a switch 1200 is shown in Figure 12. Such a form of electrical switch 1200 is similar to switch 700 shown in Figure 7 and, except for the differences described below, the description of switch 700 above is also applicable to such a form of technology (with appropriate reference numbers).

[0128] 7, the electrical switch 1200 further includes a magnetic field generator 1260. The magnetic field generator 1260 is configured to apply a magnetic field to the superconducting material loop 1216. The magnetic field applied by the magnetic field generator 1260 may be time-varying (e.g., alternating), constant (i.e., DC, including a constant DC magnetic field that can vary between constant values), or time-varying in response to a DC bias. This allows the magnetic field generator 1260 to selectively contribute to either or both of a "magnetic field" mechanism or a "dynamic resistance" mechanism to enable switching of the electrical switch 1200.

[0129] The magnetic field generator 1260 may include a power supply 1264 configured to generate a current, such as a direct current, an alternating current, and / or an alternating current with a DC bias. The magnetic field generator 1260 may further include a coil 1262. The coil 1262 may include a conductor wound around the coil and electrically connected to the power supply 1264. The coil 1262 may be positioned and oriented with respect to the loop 1216 to apply a magnetic field to the loop 1216, the direction of the magnetic field being approximately perpendicular to the flat opposing surfaces of the tape of superconducting material forming the loop 1216. For example, the coil 1262 may define an axis perpendicular to the flat opposing surfaces of the tape.

[0130] In use, the control mechanism is configured to control the magnetic field generator 1260 to vary the magnitude of the magnetic field applied to the superconducting material in a manner similar to that described with respect to the fifth combination above. In addition, the control mechanism is configured to control the heating assembly 1250 to vary the temperature of the superconducting material as described with respect to any form of the technique using the "resistance heating" mechanism above. In addition, the control mechanism is configured to control the magnetic field generator 1220 to generate a screening current as described with respect to any form of the technique using the "screening current" mechanism above. In this manner, switching of the electrical switch 1200 can be achieved using four mechanisms, and the magnetic field generators 1260, 1220 and heating assembly 1250 can be controlled independently and / or in any combination to achieve switching in a desired manner using any combination of the four mechanisms.

[0131] In this configuration, if all four mechanisms are configured to provide a low resistance state, the switch will be in the low resistance state, and if any one or more mechanisms are configured to provide a high resistance state for the superconductor, the switch as a whole will adopt this high resistance state.

[0132] The following factors are relevant to the combination of features used in electrical switch 1200 (or any other combination of features described herein). "Magnetic field" mechanisms may not be able to switch arbitrarily small currents by themselves, and in the case of high temperature superconductors (HTS), impractically large currents would be required to achieve switching at all. However, practically large fields can be applied to HTS to reduce the critical current sufficiently to allow other mechanisms to perform switching, which can reduce switching losses by reducing the critical current. "Dynamic resistance" switching mechanisms allow arbitrarily small currents to be switched, resulting in highly controllable resistance in the high resistance state. However, such switches are highly inductive and may require large powers to drive the magnetic field generators quickly. The switching losses may be positively correlated with the critical current of the superconductor. This mechanism generates inductive heating, which increases the temperature of the superconductor, as mentioned above, which may drive the "magnetic field" mechanism. · When using the "Heated Resistance Element" option alone, thermal switching can be very slow and the required temperature changes between high and low resistance states can result in significant heat losses. However, this mechanism can increase the temperature of the superconductor, reducing the magnetic field demands in the "Magnetic Field" mechanism and reducing the critical current, reducing losses in other switching mechanisms (e.g., "Screening Current" and / or "Dynamic Resistance" mechanisms). "Screening current" mechanisms are non-inductive and therefore relatively easy to drive, can be switched quickly, and produce high resistance in the high resistance state. Although switching losses are positively correlated with the critical current of the superconductor, reducing the critical current using "magnetic field" or "resistive element" heater mechanisms helps to reduce switching losses.

[0133] It should be understood that any one or more of the four features described with respect to this form of the technology may be omitted from other forms of the technology, i.e., in a particular form, an electrical switch similar to electrical switch 1200 shown in FIG. 12 is provided, but omitting one or more of the following features (e.g., because the components enabling the feature are not present or are turned off / not used): "magnetic field", "resistive heating", "heating-dynamic resistance", and "screening current".

[0134] 6.4.8. Combination 8 - magnetic field + screening current In one such embodiment, in one form of the present technology, an electrical switch is provided that operates using a "magnetic field" mechanism and a "screening current" mechanism. Such an electrical switch has a similar shape to that of electrical switch 1200 shown in FIG. 12, except that the heating assembly 1250 (including resistive heating element 1252) is omitted.

[0135] In this form, the switch 1200 can be switched by selective control (e.g., varying / activating / deactivating) of one or both of the magnetic field generators 1220 and / or 1260 to increase or decrease the critical current for the transport current. These mechanisms can be controlled independently or in combination. In one example, the magnetic field generator 1220 is configured to remain activated and the magnetic field generator 1260 is selectively activated and deactivated or switched with a varying activation level. In another example, the reverse is true, i.e., the magnetic field generator 1260 is configured to remain activated and the magnetic field generator 1220 is selectively activated and deactivated or switched with a varying activation level.

[0136] 6.5. Bifilar Arrangement A technical form has been described for an electrical switch 210 that utilizes the principle that the critical current of a superconducting material is reduced when a high external magnetic field is applied to the material.

[0137] Figures 8A and 10A show two exemplary such electrical switches, 800 and 1000, respectively, in which the superconducting material segments are arranged in a unifilar arrangement, i.e., an arrangement of segments or strands of conductor. In a similar form of the technology shown in Figures 8B and 10B, electrical switches 800 and 1000 take a similar form to that shown in Figures 8A and 10A, but include superconducting material segments 810 and 1010 arranged in a bifilar arrangement. Figure 13 shows another example of a bifilar arrangement. This aspect of the technology will now be described in more detail.

[0138] Although a bifilar arrangement of superconducting material segments has been described with respect to the configuration of the electrical switch shown in Figures 8B, 10B, 36A, and 36B, it should be understood that a bifilar arrangement is applicable to other configurations of the technology. In particular, any of the electrical switches described herein may, in alternative configurations of the technology, include superconducting material segments arranged in a bifilar arrangement, where appropriate.

[0139] In the context of this specification, unless otherwise stated, a "bifilar arrangement" should be understood to mean an arrangement of two strands of conductor in which the two strands are substantially parallel and electrically connected, with current flowing through the strands in opposite directions. The strands may be in close proximity to each other. The strands may be two segments of superconducting material that are doubled over themselves. Alternatively, the two strands may be separate segments of superconducting material that are electrically connected to each other, such as by solder bonding, diffusion bonding, or other suitable form of electrical connection.

[0140] It should also be understood that in certain forms of the technology, multiple bifilar lands may be used, and thus, unless the context clearly requires otherwise, other forms of the technology may include similar arrangements having multiple bifilar lands where a bifilar arrangement is described.

[0141] More specifically, for example, with reference to the technical form shown in FIG. 13A, the electrical switch 1210 includes a superconducting material segment 1800 in one form of bifilar arrangement. The superconducting material segment 1800 includes two strands (i.e. sub-lengths) 1810a, 1810b of superconducting material. The two strands 1810a, 1810b are connected in series with each other. The superconducting material segment 1800 is arranged to fold back on itself, and the two strands 1810a, 1810b are arranged substantially parallel in space. In such an arrangement, when the superconducting material segment 1800 carries a transport current, the current in the first strand 1810a flows in the opposite direction to the current in the second strand 1810b. A folded region 1820 (which may be in the form of a loop) of the superconducting material segment 1800 may separate the two strands 1810a, 1801b along the length of the superconducting material segment 1800. It should be understood that this description is also applicable to the technical forms shown in Figures 8B and 10B.

[0142] In an alternative embodiment of the technique shown in FIG. 13B, the electrical switch 1210 includes two independent strands 1810a and 1810b of superconducting material. One end of each of the two strands 1810a, 1810b is electrically connected to each other at an electrical joint 1820b, and the two strands are arranged in a bifilar configuration. Similarly, in this configuration, when the superconducting material segment 1800 carries a transport current, the current in the first strand 1810a flows in the opposite direction to the current in the second strand 1810b. The electrical joint 1820b may be a solder joint, a diffusion joint, or any suitable electrical joint.

[0143] In the form of the technology shown in Figures 13A and 13B, the two strands 1810a and 1810b may be positioned close to each other. One or both of the strands 1810a, 1810b may be insulated, and the strands' insulating coatings may be in contact with each other. Alternatively, an insulating layer may be positioned between the two strands 1810a, 1810b, in contact with one strand or both strands. The insulating layer may be formed of an insulating tape, such as Kapton tape or Nomex tape.

[0144] In a particular form of the present technology, the superconducting material segment 1800 can take the form of a tape, which is a material segment having a length that is clearly greater than its width and depth, and a width that is clearly greater than its depth. The tape can have two opposing faces that are substantially parallel, the two faces being separated by the depth of the tape. The strands can be arranged such that the opposing faces of one strand 1810a are parallel to the opposing faces of the other strand 1810b. In the form of the present technology shown in FIG. 13B, each of the two strands 1810a and 1810b can take the form of a tape. The two separate strands can be electrically connected (e.g., soldered) to each other at one end face to form an electrically continuous junction 1820b. Such an arrangement can reduce the inductance of the electrical switch 1210, but such advantage can be achieved at the expense of a slight increase in resistance in the low resistance state. Alternatively, a single superconducting material segment (eg, a tape) may be arranged with the two strands 10a, 810b as adjacent sections of the segment joined end-to-end.

[0145] In certain forms of the present technology, the superconducting material segment 1800 may be a high temperature superconducting (HTS) material segment as previously described.

[0146] As shown in the form of the present technology in Figures 13A and 13B, the electrical switch 1210 in certain forms of the present technology may be arranged such that a magnetic field generator 1310 may be actuated to apply a magnetic field to two strands of superconducting material 1810a and 1810b. The magnetic field generator 1310 may take the form of any of the magnetic field generators previously described herein. The magnetic field generator 1310 may be selectively controlled to selectively generate a magnetic field to move the electrical switch 1210 between a low resistance state and a high resistance state as described above, including in combination with other switching mechanisms described above.

[0147] In a particular embodiment, the magnetic field generator 1310 includes a magnetic core 1320. The core 1320 may be a ferromagnetic core, such as a ferrite core (e.g., an iron core), or a high permeability magnetic core, such as a laminated steel / iron core. The magnetic core 1320a may be a substantially ring-shaped solid core, e.g., a circular ring. In other embodiments, the core may have a different shape, e.g., a square ring with rounded corners. In an exemplary embodiment, the magnetic core 1320 includes a first end and a second end separated by a gap 1330. The gap 1330 may be a space within the solid magnetic core 1320, e.g., a space on one side of a ring core.

[0148] In a particular embodiment, the electrical switch 1210 is positioned such that the magnetic field generated by the magnetic field generator 1310 is substantially perpendicular to the opposing faces of the strands 1810a, 1801b, i.e., the magnetic flux lines of the magnetic field are substantially perpendicular to the faces of the strands 1810a, 1801b where the magnetic flux lines intersect the strands.

[0149] In certain forms of the present technology, the width of the gap 1330 is similar to the combined depth of the two strands 1810a, 1810b, i.e., there is a relatively small air gap separating each of the strands 1810a, 1810b from the corresponding end of the core 1330 closest to the strand.

[0150] It should be understood that the electrical switch configuration shown in Figures 13A and 13B shows only the components necessary to implement the "magnetic field" switching mechanism. This is for purposes of illustrating the bifilar configuration. In certain forms of the present technology, a bifilar configuration electrical switch including superconducting material includes the components necessary to implement second or further switching mechanisms as described above.

[0151] One advantage of the electrical switch 1210 including a bifilar arrangement of one superconducting material segment is that the inductance of the switch is reduced compared to a similar switch having a single superconducting material segment. One practical advantage of this is that the coil 1340 of the magnetic field generator 1310 that applies the magnetic field to the electrical switch 1210 requires fewer turns than would otherwise be required.

[0152] Another advantage of the electrical switch 1210 including a bifilar arrangement of superconducting material segments is that it helps reduce suppression of the critical current of the superconducting material segments when a low (e.g., zero) magnetic field is applied to the superconducting material segments, resulting in a higher critical current for the low resistance state of the switch 1210. This effect will be explained in more detail below.

[0153] The forms of the technology described above include an electrical switch 1210 in which a magnetic field is applied to a superconducting material segment to suppress a critical current in the superconducting material segment. This effect is used in some forms of the technology to transition the superconducting material segment between a low resistance state and a high resistance state. A magnetic field generator 1310 that generates the magnetic field may include a high permeability magnetic core 1320, such as a ferromagnetic core, that can be used to focus the magnetic field on the superconducting material segment.

[0154] It has been observed that the placement of a single superconducting material segment carrying a transport current in the vicinity of a ferromagnetic core further suppresses the critical current even at very low, including zero, magnetic field strengths. In fact, the relative additional suppression of the critical current resulting from this effect is greater at low applied magnetic field strengths. This is due to the self-field amplification effect of the ferromagnetic body in the magnetic core 1320 in close proximity to the superconducting material when a current is passed through it. More specifically, it has been confirmed by experiments and finite element analysis that the presence of a low reluctance return path through the ferromagnetic core 1320 amplifies the self-field of the unifilamentary superconducting material segment, which, when in the form of a tape, is oriented perpendicular to the tape and spans its width. This suppresses the critical current density at each point across the width of the tape, suppressing the overall critical current compared to the absence of a ferromagnetic core.

[0155] Moreover, it has been found that an electrical switch 1210 in which the superconducting material segments are arranged in a bifilar arrangement significantly mitigates this effect, i.e. reduces the suppression of the described critical current. In other words, the self-magnetic field caused by the current flowing through the superconducting material segments, when in close proximity to the ferromagnetic core 1320, is substantially cancelled by the bifilar arrangement. Figure 14 shows the critical current at different applied fields of a section of one superconducting material in an electrical switch 1210 according to the technical form, when the superconducting material of this section is arranged in a bifilar arrangement (blue, top line) and in a unifilar arrangement (orange, bottom line), i.e. one layer of one superconducting material. These experimental results are compared with the reference value of the superconducting material from the database (green dotted line, center line). This shows that in comparison with the unifilar arrangement, the suppression of the critical current under low applied magnetic fields is very low in the bifilar arrangement. This difference is less pronounced at high applied magnetic fields, where the applied magnetic field is significantly larger than any self-field effect. The relatively small difference in critical current at high applied magnetic fields may be due to the increased shielding capability of the two-layer bifilar arrangement compared to the single-layer unifilar arrangement. It should be understood that in certain forms of the present technology, the superconducting material segments may be maintained in a superconducting state at all times.

[0156] The larger difference in critical current for low applied magnetic fields compared to high applied magnetic fields means that the switching performance of an electrical switch 1210 with a bifilar arrangement can be improved compared to one with superconducting material segments in, for example, a unifilar arrangement. The switching performance can be given by the switching factor k, which can be calculated as the ratio of the critical current when the magnetic field is zero to the critical current when a magnetic field is applied, i.e., Ic(0) / Ic,b(Ba). As can be seen from FIG. 14, k for the bifilar arrangement is larger than for the unifilar arrangement. A higher switching factor k means that the current I 臨界 As long as it is lower than (0), it means more efficient switching. Also, a high critical current in the low resistance state allows the electrical switch 1210 to output a higher maximum current.

[0157] 15A and 15B show the magnetic field distribution in the gap between the ends of a ferromagnetic core 1320 for an electrical switch 1210 according to a particular form of the present technology. The electrical switch 1210 includes a superconducting material segment 1810 in the form of a tape located between the ends of the ferromagnetic core 1320. The magnetic field distribution is determined by finite element analysis. In FIG. 15A, the tape is placed in a unifilar arrangement in the gap 1330 between the ends of the magnetic core 1320, i.e., a single tape segment passes through the gap 1330. In FIG. 15A, the tape is modeled to carry a current of 195A and the magnetic field applied to the tape is modeled to have a magnetic field strength of 250mT. In FIG. 15B, the tape is placed in a bifilar arrangement in the gap 1330 between the ends of the core 1320, i.e., two strands of tape are placed parallel and close to each other in the gap 1330. In FIG. 15B, the tape is modeled as carrying a current of 375 A and the magnetic field applied to the tape is modeled as having a field strength of 70 mT.

[0158] 15A and 15B show that the average magnetic field environment of the technique in which the superconducting material segments are arranged in a unifilar arrangement (FIG. 15A) is obviously larger than that of the technique in which the superconducting material segments are arranged in a bifilar arrangement (FIG. 15B). In fact, the bifilar arrangement almost eliminates the self-inductance of the tape, and the magnetic field remaining in the tape is mainly in a direction parallel to the surface of the tape. This explains why the critical current of the bifilar arrangement under zero applied magnetic field is obviously larger than that of the unifilar tape (see FIG. 14).

[0159] It has also been determined that the larger the gap 1330 between the ends of the core 1320, the lower the magnetic field strength of the applied magnetic field. This means that as the gap 1330 increases, a larger current must be provided to the magnetic field generator to maintain the same magnetic field strength. This may be undesirable as it requires additional drive power and dissipates additional heat. Therefore, in certain forms of the present technology, the dimensions of the gap 1330 may be as small as possible, for example, the width of the gap 1330 is similar to the combined depth of the two strands of the superconducting material segment 1810.

[0160] 6.6. Other Notes Unless the context clearly requires otherwise, throughout the specification and claims, the words "comprise", "comprising", and the like are to be interpreted in their inclusive sense, i.e., "including but not limited to", rather than in their exclusive or exhaustive sense.

[0161] The entire disclosures of all applications, patents and publications, cited above and below, if any, are hereby incorporated by reference.

[0162] The citation of any prior art in this specification is not, and should not be, considered as an acknowledgment or implication that the prior art forms part of the public knowledge of any country in the world.

[0163] The technology may also be broadly described as consisting of the parts, elements and features individually or collectively referred to or indicated in the specification of this application, and any and all combinations of two or more of said parts, elements or features.

[0164] In the foregoing description, reference is made to integers or components that have their known equivalents, and these integers are incorporated herein as if separately set forth.

[0165] It should be noted that various changes and modifications of the presently preferred embodiments described herein will be obvious to those skilled in the art, but such changes and modifications can be made without departing from the spirit and scope of the technology and without diminishing its attendant advantages. Therefore, such changes and modifications are intended to be included in the technology. [Explanation of symbols]

[0166] 200 Switch 202 Superconducting Materials 204 1st terminal 206 2nd terminal 210 Loop 212a Superconducting branch 212b Superconducting branch

Claims

1. An electrical switch, a superconducting material segment configured to carry a transport current and having a critical current and a critical temperature; a magnetic field generator configured to apply a magnetic field to the superconducting material segment; a heating assembly for heating the segment of superconducting material; the magnetic field generator and the heating assembly are configured to be selectively controlled, either independently or in combination, to switch the superconducting material segment between a low resistance state and a high resistance state; in the low resistance state, the magnitude of the magnetic field is relatively small such that the transport current is substantially less than the critical current and the temperature of the superconducting material segment is substantially less than the critical temperature; such that in the high resistance state, the transport current is close to, substantially equal to, or greater than the critical current of the superconducting material segment. the magnitude of the magnetic field is relatively large to reduce the critical current; and / or The heating assembly heats the superconducting material segment to reduce the critical current. An electrical switch.

2. 10. The electrical switch of claim 1, wherein the magnetic field generator and the heating assembly are configured to be selectively activated and deactivated, independently or in combination, to switch the electrical switch between the low resistance state and the high resistance state.

3. 3. The electrical switch of claim 2, wherein the heating assembly is configured to maintain an activated state, and the superconducting material segment is switched between a low resistance state and a high resistance state by selectively deactivating and activating the magnetic field generator.

4. The electrical switch according to any one of claims 1 to 3, wherein the magnetic field applied by the magnetic field generator is a constant magnetic field.

5. The electrical switch of any one of claims 1 to 4, wherein the heating assembly includes a resistive heating element disposed in thermal contact with the superconducting material segment.

6. The electrical switch according to any one of claims 1 to 5, wherein the superconducting material is a high temperature superconducting material.

7. 7. The electrical switch of claim 1, wherein the magnetic field generator is a first magnetic field generator, the magnetic field being a first magnetic field, and the electrical switch includes a second magnetic field generator configured to apply a second time-varying magnetic field to the superconducting material segment, the second magnetic field generator configured to be selectively controlled to switch the superconducting material segment between the low resistance state and the high resistance state.

8. 8. The electrical switch of claim 7, wherein the superconducting material is a tape having two opposing faces, and the second magnetic field generator is configured to apply a second magnetic field in a direction substantially perpendicular to the two opposing faces.

9. 9. The electrical switch of claim 7 or 8, wherein the first magnetic field generator and the second magnetic field generator are the same magnetic field generator, and the magnitude of the magnetic field applied by the same magnetic field generator varies over time as a function of a DC bias.

10. the superconducting material segment includes a superconducting material loop configured to carry a transport current between a first terminal and a second terminal, the loop including a first branch and a second branch electrically connected in parallel between the first terminal and the second terminal, the loop having an axis substantially perpendicular to a plane of the loop; The electrical switch is a third time-varying magnetic field generator configured to apply a third time-varying magnetic field through the loop, the direction of the third magnetic field through the loop being substantially parallel to an axis of the loop or having a component substantially parallel to the axis of the loop; In the low resistance state, the third magnetic field generator does not apply the third magnetic field through the loop, and the transport current flows through the loop between the two terminals; 10. The electrical switch of claim 1, wherein in the high resistance state, the third magnetic field generator applies the third magnetic field through the loop to induce a screening current such that a total current in one or more of the first and second branches is close to, substantially equal to, or greater than the critical current of the superconducting material.

11. An electrical switch according to any one of claims 1 to 10, wherein in the high resistance state the superconducting material segment is in a superconducting state.

12. An electrical switch, a superconducting material segment configured to carry a transport current and having a critical current and a critical temperature; a first magnetic field generator configured to apply a first constant magnetic field to the superconducting material segment; a second magnetic field generator configured to apply a second time-varying magnetic field to the superconducting material segment; the first magnetic field generator and the second magnetic field generator are configured to be selectively controlled independently or in combination to switch the superconducting material segment between a low resistance state and a high resistance state; in the low resistance state, the magnitudes of the first magnetic field and the second magnetic field are relatively small and the transport current is substantially less than the critical current; In the high resistance state, the magnitude of the first magnetic field is relatively large to reduce the critical current such that the transport current is close to, substantially equal to, or greater than the critical current of the superconducting material segment; and / or The second magnetic field creates a dynamic resistance in the superconducting material segment.

13. 13. The electrical switch of claim 12, wherein the first magnetic field generator and the second magnetic field generator are configured to be selectively activated and deactivated, independently or in combination, to switch the superconducting material segment between the low resistance state and the high resistance state.

14. 14. The electrical switch of claim 13, wherein either the first or second magnetic field generators are configured to remain activated, and the superconducting material segment is switched between the low resistance state and the high resistance state by selectively deactivating and activating the other of the first and second magnetic field generators.

15. 14. The electrical switch of claim 13, wherein the second magnetic field generator is configured to maintain an activated state, and the superconducting material segment is switched between the low resistance state and the high resistance state by selectively deactivating and activating the first magnetic field generator.

16. 16. An electrical switch according to any one of claims 12 to 15, wherein the superconducting material is a tape having two opposing faces, and the second magnetic field generator is configured to apply the second magnetic field in a direction substantially perpendicular to the two opposing faces.

17. 17. The electrical switch of claim 12, wherein the first magnetic field generator and the second magnetic field generator are the same magnetic field generator, and the magnitude of the magnetic field applied by the same magnetic field generator varies over time as a function of a DC bias.

18. An electrical switch according to any one of claims 12 to 17, wherein the superconducting material is a high temperature superconducting material.

19. 19. The electrical switch of claim 12, further comprising a heating assembly for heating the superconducting material segment, wherein in the high resistance state, the heating assembly heats the superconducting material segment to reduce the critical current such that the transport current is close to, substantially equal to, or greater than the critical current of the superconducting material segment.

20. 20. The electrical switch of claim 19, wherein the heating assembly includes a resistive heating element disposed in thermal contact with the superconducting material segment.

21. the superconducting material segment includes a superconducting material loop configured to carry a transport current between a first terminal and a second terminal, the loop including a first branch and a second branch electrically connected in parallel between the first terminal and the second terminal, the loop having an axis substantially perpendicular to a plane of the loop; The electrical switch is a third time-varying magnetic field generator configured to apply a third time-varying magnetic field through the loop, the direction of the third magnetic field through the loop being substantially parallel to an axis of the loop or having a component substantially parallel to the axis of the loop; In the low resistance state, the third magnetic field generator does not apply the third magnetic field through the loop, and the transport current flows in the loop between the two terminals; 21. The electrical switch of claim 12, wherein in the high resistance state, the third magnetic field generator applies the third magnetic field through the loop to induce a screening current such that a total current in one or more of the first and second branches is close to, substantially equal to, or greater than the critical current of the superconducting material.

22. An electrical switch according to any one of claims 12 to 21, wherein in the high resistance state the superconducting material segment is in a superconducting state.

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