Magnet structure and nuclear fusion reaction device

Abstract

The invention provides a magnet structure and a nuclear fusion reaction device. The magnet structure comprises a first coil, a second coil and a plurality of bridging pieces, wherein the first coil and the second coil are superposed; the first coil and the second coil are both obtained by winding multiple groups of stacked cables in parallel, and the winding directions of the cables in the first coil and the second coil are opposite; in any two adjacent groups of cables in the plurality of groups of cables, the end part of the outer-side cable group extends out relative to the end part of the inner-side cable group along the cable winding direction, and is bent inwards to be flush with the end part of the inner-side cable group; wherein the inner side cable group is a group of cables, which are close to the inner side, in the two groups of cables, and the outer side cable group is a group of cables, which are close to the outer side, in the two groups of cables; and the end parts of each group of cables in the first coil are reversely connected with the end parts of each group of cables in the second coil through the bridging pieces respectively. The magnet structure is low in loss.

Description

Technical Field

[0001] This application relates to the technical fields of electricity and magnetics, and particularly relates to a magnet structure and a nuclear fusion reaction device. Background Art

[0002] Currently, magnets are required in many devices. Especially in some devices that rely on magnetic fields to operate (such as nuclear fusion reaction devices, etc.), a relatively large number of magnets are needed, and it is required that the loss of the magnets is as low as possible to achieve better working performance.

[0003] A commonly used magnet has a double-pancake structure, which uses cables to wind two pancake coils on two superimposed skeletons. During the current-carrying process of this magnet, the magnetic field environments of the cables at different positions in the radial direction are different, and the inductance is unbalanced, resulting in uneven current distribution in each cable, high loss of the magnet, and low overall stability. Summary of the Invention

[0004] This application provides a magnet structure and a nuclear fusion reaction device. In this magnet structure, the current distribution in each cable is relatively uniform, the loss of the magnet is low, and the overall stability is high.

[0005] According to one aspect of this application, a magnet structure is provided, including: a first coil and a second coil that are superimposed, and a plurality of bridging members; Both the first coil and the second coil are obtained by co-winding multiple sets of cables in a stacked manner, and the winding directions of the cables in the first coil and the second coil are opposite; Among any two adjacent sets of cables in the multiple sets of cables, the end of the outer cable group extends relative to the end of the inner cable group along the cable winding direction, and bends inward to be flush with the end of the inner cable group; wherein, the inner cable group is the set of cables closer to the inside among the two sets of cables, and the outer cable group is the set of cables closer to the outside among the two sets of cables; The ends of each group of cables in the first coil are respectively reversely connected to the ends of each group of cables in the second coil through each bridging member.

[0006] In one embodiment, in the stacking direction of the first coil and the second coil, the ends of each group of cables in the first coil are reversely aligned with the ends of each group of cables in the second coil; Each bridging member straddles the first coil and the second coil and covers the ends of a set of cables that are aligned in the first coil and the second coil.

[0007] In one embodiment, the ends of the multiple sets of cables are arranged in sequence along the cable winding direction, and the multiple bridging members are respectively located inside the ends of the multiple sets of cables.

[0008] In one embodiment, each set of cables in the multiple sets of cables includes a stacked multi-layer cable; among any two adjacent layers of cables in the multi-layer cable, the end of the outer-layer cable extends relative to the end of the inner-layer cable along the cable winding direction; wherein, the inner-layer cable is the inner layer of the two layers of cables, and the outer-layer cable is the outer layer of the two layers of cables. The bridging member is located inside the multi-layer cable and extends relative to the end of the innermost cable in the multi-layer cable along the cable winding direction. The magnet structure further includes a conductive member, and the conductive member fills the space between the end of the multi-layer cable and the bridging member.

[0009] In one embodiment, each set of cables in the multiple sets of cables includes a stacked multi-layer cable, and the ends of the multi-layer cables are aligned.

[0010] In one embodiment, in any one of the first coil and the second coil, the ends of the inner cable group and the ends of the outer cable group belong to the cable ends at the inner turns or the outer turns in the any one of the coils.

[0011] In one embodiment, it further includes an insulating layer located between adjacent sets of cables, and both the first coil and the second coil are wound by stacking multiple sets of cables carrying the insulating layer.

[0012] In one embodiment, it further includes a transition member with an arc-shaped surface, and the end of any set of cables extends to the corresponding bridging member through the arc-shaped surface of the transition member.

[0013] In one embodiment, the cable includes a high-temperature superconducting tape.

[0014] According to another aspect of the present application, there is provided a nuclear fusion reaction device, including: a reaction chamber, a central solenoid coil, a poloidal field coil, and a toroidal field coil, wherein at least one of the central solenoid coil, the poloidal field coil, and the toroidal field coil includes the above-mentioned magnet structure.

[0015] In the embodiments of the present application, for a coil obtained by winding multiple groups of cables in a stacked manner, the end of the outermost cable protrudes relative to the end of the innermost cable and is bent inward so that the ends of each group of cables are flush. In this way, the ends of each group of cables in the two coils can approach each other in the reverse direction, and then the ends of each group of cables in the two coils are reversely connected by a bridging member. In this way, it is possible to connect the innermost cable in the first coil to the outermost cable in the second coil, realize the transposition of the inner and outer turn cables in the two coils, balance the overall inductance of the cables at the same radial position within the two coils, make the current distribution more uniform, reduce the loss of the magnet structure, and improve the working stability of the magnet structure. Description of the Drawings

[0016] Figure 1 is a partial structural schematic diagram of a magnet structure provided by an embodiment of the present application; Figure 2 is a partial structural schematic diagram of another magnet structure provided by an embodiment of the present application; Figure 3 is a partial structural schematic diagram of yet another magnet structure provided by an embodiment of the present application; Figure 4 is a partial structural schematic diagram of still another magnet structure provided by an embodiment of the present application; Figure 5 is a simulation result diagram of the hysteresis loss of a different magnet structure provided by an embodiment of the present application; Figure 6 is a simulation result diagram of the coupling loss of a different magnet structure provided by an embodiment of the present application; Figure 7 is a simulation result diagram of the maximum temperature of a different magnet structure provided by an embodiment of the present application. Detailed Embodiments

[0017] In the following description, many specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar generalizations without departing from the spirit of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0018] The terms used in one or more embodiments of the present application are for the purpose of describing specific embodiments only and are not intended to limit one or more embodiments of the present application. The singular forms "a", "the" and "said" used in one or more embodiments of the present application and the appended claims are also intended to include the plural forms unless the context clearly dictates otherwise. It should also be understood that the term "and / or" used in one or more embodiments of the present application refers to and includes any or all possible combinations of one or more associated listed items. The term "at least one" in one or more embodiments of the present application refers to "one or more", and "a plurality" refers to "two or more". The term "comprising" is an open-ended description and should be understood as "including but not limited to", and other contents may also be included based on the described contents.

[0019] It should be understood that although the terms "first", "second", etc. may be used in one or more embodiments of the present application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of one or more embodiments of the present application, "first" may also be referred to as "second", and similarly, "second" may also be referred to as "first". Depending on the context, the word "if" as used herein may be interpreted as "when" or "while" or "in response to determining".

[0020] Currently, the use of various magnets in electrical equipment is very common, and the requirements for the working performance of magnets are also getting higher and higher. During the use of magnets, there will be some losses, resulting in a decrease in the working stability of the magnets and affecting the operation of the equipment. Therefore, improving the stability of the magnets is crucial for the operation of the equipment. A commonly used magnet has a double-pancake structure, which is composed of two flat single-pancake coils stacked on top of each other. During the preparation process of this magnet, a single cable or multiple stacked cables are used to wind two pancake coils on the bobbin starting from the middle respectively. During the process of transmitting alternating current in the coils, certain AC losses will be generated. The AC losses are mainly composed of the hysteresis loss, coupling loss and eddy current loss of the magnet. The AC losses will cause local temperature rise of the magnet, threatening the stability of the magnet and even causing the equipment to which the magnet belongs to fail.

[0021] Specifically, due to the different positions of the inner and outer turns of the coil, the magnetic field intensities and directions they experience are different, and the magnetic field environments of the inner and outer turns are significantly different. For example, the inner turn is closer to the center of the coil and is affected by a stronger magnetic field; the outer turn is relatively farther away and is less affected. Moreover, the inductance of the inner and outer turns in the coil is unbalanced, resulting in uneven current distribution in each turn of the superconducting tape. The inner turn is exposed to a stronger external magnetic field, and its critical current decays more significantly. Since the outer turn is far from the center of the coil, part of the magnetic field will be offset by the reverse eddy current generated by the previous turns of the winding, forming a certain magnetic field shielding effect. Therefore, the outer turn can retain a higher current-carrying capacity. This imbalance will exacerbate local AC losses, form hot spots, and at the same time reduce the overall stability of the coil due to uneven electromagnetic coupling.

[0022] With the rapid development of high-temperature superconducting material technology, it has broad application prospects in modern power systems, magnet devices, and energy storage. For example, high-temperature superconducting coils wound with high-temperature superconducting tapes can be used in nuclear fusion reaction devices to provide the required magnetic field. High-temperature superconducting coils usually need to transmit alternating current during use. High-temperature superconducting coils will generate relatively serious AC losses under alternating current conditions, and this problem has become one of the core challenges restricting their large-scale engineering applications. Based on the electromagnetic induction theory, the inductance effect will cause the current to have a significant skin distribution characteristic in the magnet. For example, the main conduction current will concentrate on the outer turn superconducting tape of the stacked winding closer to the outer diameter. For example, the current in the outer turn superconducting tape accounts for about 75% - 85% of the total current; the outer turn superconducting tape induces a reverse shielding current. For example, the typical value of this reverse shielding current reaches -20% to -30% of the rated current. This asymmetric current distribution will cause the peak value of the local AC loss density to reach 3 - 5 times the average value, forming hot spots exceeding the critical temperature rise threshold, which is extremely likely to cause the magnet to quench; in addition, it will also increase the probability of peeling at the superconducting layer interface due to the stress concentration effect.

[0023] Therefore, there is an urgent need for a solution that can effectively reduce the AC loss of the coil to improve the operating efficiency and reliability of power equipment, and ensure that when this solution is applied to high-temperature superconducting coils, it will contribute to the large-scale engineering application of high-temperature superconducting coils.

[0024] The embodiment of the present application provides a magnet structure, the AC loss of which can be relatively low, and correspondingly, it can have high working stability and improve the working performance of the magnet structure. The embodiment of the present application also relates to a nuclear fusion reaction device, which includes this magnet structure, such as this magnet structure is used to prepare a coil that provides a magnetic field in a nuclear fusion reaction device.

[0025] Figure 1 It is a partial structural schematic diagram of a magnet structure provided by the embodiment of the present application. As Figure 1As shown, the magnet structure includes a superimposed first coil 10 and second coil 20, and a plurality of bridge members 30. Figure 1 Only a partial structure at the ends of the first coil 10 and the second coil 20 is schematically shown. The bridge members 30 are used to connect the two coils at the coil ends.

[0026] The ends of the coil refer to the ends of the cable used to wind the coil. Each cable has two ends, which are located at the outermost side (i.e., the outer turn) and the innermost side (i.e., the inner turn) of the coil respectively. The location where the innermost coil end of the coil is located can be called the cross-turn section of the coil, and the location where the outermost coil end of the coil is located can be called the joint of the coil. In the embodiments of the present application, taking the coil end as the outermost end of the coil, the bridge member 30 is located at the outermost end to connect the two coils, for example, to reduce the AC loss of the coil. In some ways, the bridge member 30 can also be located at the cross-turn section of the coil. Correspondingly, Figure 1 The structure shown can represent the innermost end of the coil.

[0027] Both the first coil 10 and the second coil 20 are pancake coils. A double-pancake coil can be obtained by superimposing them. In one embodiment, the magnet structure can include a plurality of superimposed double-pancake coils. In the embodiments of the present application, only one double-pancake coil is taken as an example for introduction. Adjacent double-pancake coils can also be electrically connected. The specific connection method can refer to the connection method of the first coil 10 and the second coil 20 described in the embodiments of the present application.

[0028] Both the first coil 10 and the second coil 20 are obtained by parallel winding of a stacked plurality of groups of cables, and the winding directions of the cables in the first coil 10 and the second coil 20 are opposite. The winding direction of the coil cable is also the extending direction of the cable end. The parallel winding of the stacked plurality of groups of cables means regarding the stacked plurality of groups of cables as one cable, making the outermost group of cables contact the coil skeleton, and synchronously winding the plurality of groups of cables on the coil skeleton. Each time of winding realizes winding one circle of the plurality of groups of cables, and the outer cables surround the inner cables. The inner and outer described in the embodiments of the present application refer to the inner and outer in the radial direction of the wound annular coil. The outer means the outer in this radial direction, and the inner means the inner in this radial direction.

[0029] The number of cable groups in the first coil 10 and the second coil 20 is the same, and the coil sizes are also the same. In the embodiments of the present application, taking the first coil 10 and the second coil 20 both including three groups of cables as an example for illustration, Figure 1 Each strip structure in represents one group of cables. Figure 1 in the direction from the inside to the outside (such as Figure 1In the direction from bottom to top (in the direction where the paper faces inward in [reference], the three groups of cables included in the first coil 10 are respectively labeled as 101, 102, and 103, and the three groups of cables included in the second coil 20 are respectively labeled as 201, 202, and 203. The ends of the first coil 10 and the second coil 20 can be arranged oppositely. For example, in the stacking direction of the first coil 10 and the second coil 20 (such as Figure 1 in the direction where the paper faces inward in [reference]), the ends of the two coils can be stacked and aligned. For example, Figure 1 in [reference], the winding direction of the cables of the first coil 10 is counterclockwise, and the winding direction of the cables of the second coil 20 is clockwise.

[0030] In the embodiment of the present application, for the multiple groups of cables included in any one of the first coil 10 and the second coil 20, any two adjacent groups of cables include an inner cable group and an outer cable group. Among them, the inner cable group is the group of cables that is closer to the inside among the two groups of cables, and the outer cable group is the group of cables that is closer to the outside among the two groups of cables. The end of the outer cable group extends relative to the end of the inner cable group along the cable winding direction and bends inward to be flush with the end of the inner cable group, that is, the outer cable group and the inner cable group are flush in the cable winding direction of any one of the coils. In the embodiment of the present application, the two groups of cables being flush means that the heights of the two groups of cables are the same; the height refers to the minimum distance between the cable and the center of the coil in the radial direction of the coil.

[0031] In any one of the coils (that is, the first coil 10 or the second coil 20) in the magnet structure provided in the embodiment of the present application, the ends of the inner cable group and the outer cable group among the above-mentioned any two adjacent groups of cables can belong to the cable ends at the outer turn of any one of the coils, that is, they belong to the cable ends at the outermost side of the coil. Correspondingly, the bridging member 30 is located at the position where the outermost cable ends are located, that is, at the coil joint. In one way, the ends of the inner cable group and the outer cable group among the above-mentioned any two adjacent groups of cables can belong to the cable ends at the inner turn of any one of the coils, that is, they belong to the cable ends at the innermost side of the coil. Correspondingly, the bridging member 30 is located at the position where the innermost cable ends are located, that is, at the coil inter-turn section.

[0032] Each two adjacent cable groups in the multiple cable groups are arranged in this way. For any cable group, the cable group adjacent to its inner side is used as the outer cable group, and the cable group adjacent to its outer side is used as the inner cable group. In this way, among the multiple cable groups, the ends of the cable groups other than the innermost cable group are successively bent inward along the cable winding direction until they are flush with the innermost cable group. These other cable groups are in a stepped shape, and the cables closer to the outside have more stepped parts with bends. This can make the ends of the cable groups in the two coils approach in the reverse direction. The end of the cable closer to the outside in the first coil 10 approaches the end of the cable closer to the inside in the second coil 20, and similarly, the end of the cable closer to the outside in the second coil 20 approaches the end of the cable closer to the inside in the first coil 10.

[0033] Hereinafter, the structure of each cable group will be described taking the first coil 10 as an example. The structure of the second coil 20 can refer to the structure of the first coil 10 and will not be described in detail additionally in this specification. For the convenience of description, the three cable groups in the first coil 10 will be respectively referred to as the first cable group 101, the second cable group 102, and the third cable group 103. For the two adjacent cable groups closer to the inside in the first coil 10, the inner cable group of these two cable groups is the first cable group 101, and the outer cable group is the second cable group 102. The end of the second cable group 102 extends to the left (corresponding to the counterclockwise cable winding direction of the first coil 10) relative to the end of the first cable group 101, and the end of the second cable group 102 is bent inward until it is flush with the end of the first cable group 101. For the two adjacent cable groups closer to the outside in the first coil 10, the second cable group 102 serves as the inner cable group, and the third cable group 103 serves as the outer cable group. The end of the third cable group 103 extends to the left relative to the end of the second cable group 102 and is bent inward until it is flush with the end of the second cable group 102, and correspondingly, it is also flush with the end of the first cable group 101.

[0034] The number of the bridging members 30 in the magnet structure can be the same as the number of the cable groups. The ends of the cable groups in the first coil 10 are respectively reversely connected to the ends of the cable groups in the second coil 20 through the respective bridging members 30. Each bridging member 30 is used to bridge two cable groups respectively located in the two coils. The reverse means in the reverse direction of the arrangement direction of each cable group, and each cable group is stacked and arranged in the direction from the inside to the outside along the coil diameter. Through the reverse connection, the cable closer to the outside in the first coil 10 is connected to the cable closer to the inside in the second coil 20.

[0035] The first coil 10 and the second coil 20 both include n sets of cables, where n ≥ 2. The first set of cables to the nth set of cables in the n sets of cables are arranged in sequence in the coils in the direction from the inside to the outside. In the embodiment of the present application, n = 3 is taken as an example. In some ways, n can also be 2, 4, 5 or a larger value. The end of the first set of cables in the first coil 10 is connected to the end of the nth set of cables in the second coil 20 through the bridging member 30, and the end of the second set of cables in the first coil 10 is connected to the end of the (n - 1)th set of cables in the second coil 20 through the bridging member 30, and so on. That is, the end of the ith set of cables in the first coil 10 is connected to the end of the (n - i + 1)th set of cables in the second coil 20 through the bridging member 30, where 1 ≤ i ≤ n. As Figure 1 shown, the first set of cables 101 in the first coil 10 is connected to the third set of cables 203 in the second coil 20 through the bridging member 30, the second set of cables 102 in the first coil 10 is connected to the second set of cables 202 in the second coil 20 through the bridging member 30, and the third set of cables 103 in the first coil 10 is connected to the first set of cables 201 in the second coil 20 through the bridging member 30.

[0036] In the embodiment of the present application, by winding multiple stacked sets of cables on the coil skeleton, the first coil and the second coil are obtained. In the final stage of winding, the ends of each set of cables can be split so that the ends of each set of cables are no longer flush, and the ends of the outer cables protrude a certain length relative to the ends of the inner cables, and the ends of the outer cables are bent downward to a certain extent so that the ends of each set of cables are flush. At this stage, each bridging member is also placed at the end of each set of cables, so that each bridging member is electrically connected to the end of a set of cables in one coil and cross-coil connects the end of a set of cables in the other coil.

[0037] In the embodiment of the present application, for the coils obtained by co-winding multiple stacked sets of cables, the ends of the outer cables protrude relative to the ends of the inner cables and are bent inward so that the ends of each set of cables are flush. The ends of each set of cables in the two coils can approach reversely, and then the ends of each set of cables in the two coils are reversely connected by the bridging member. In this way, the inner cables in the first coil can be connected to the outer cables in the second coil, so that the current of the original inner turn flows to the outer turn, realizing the interchange of the inner and outer turn currents, making the overall inductance of the cables at the same radial position balanced within the two coils, so that the current distribution in the magnet structure is more uniform, effectively reducing the generation of local losses and hot spots, reducing the loss of the magnet structure, and improving the working stability of the magnet structure.

[0038] In one way, the above-mentioned cable includes high-temperature superconducting tapes, that is, the connection method of the above-mentioned cable can be applied to high-temperature superconducting coils. Exemplarily, in a high-temperature superconducting coil, through the structural settings of the ends of each group of cables and the bridging member 30, when the rate of change of current is relatively low during the coil excitation stage, the current exchange between the superconducting tapes of the inner and outer turns in the stacked cables can be realized, enabling the current originally in the inner turn to flow to the outer turn, thereby improving the current distribution uniformity during the operation of the high-temperature superconducting coil.

[0039] In some embodiments, in the stacking direction of the first coil 10 and the second coil 20, the ends of each group of cables in the first coil 10 are aligned reversely with the ends of each group of cables in the second coil 20. Each bridging member 30 straddles the first coil 10 and the second coil 20 and covers the ends of a group of aligned cables in the first coil 10 and the second coil 20. This reverse alignment means that the end of the cable closer to the inside in the first coil 10 is aligned with the end of the cable closer to the outside in the second coil 20. The end of the i-th group of cables in the first coil 10 is aligned with the end of the (n - i + 1)-th group of cables in the second coil 20. The ends of the i-th group of cables in the first coil 10 and the ends of the (n - i + 1)-th group of cables in the second coil 20 have the same height in the radial direction. On the first reference plane perpendicular to this stacking direction, the orthographic projection of the end of the i-th group of cables in the first coil 10 may coincide with the orthographic projection of the end of the (n - i + 1)-th group of cables in the second coil 20.

[0040] Exemplarily, please continue to refer to Figure 1 , the end of the first group of cables 101 in the first coil 10 is aligned with the end of the third group of cables 203 in the second coil 20, the end of the second group of cables 102 in the first coil 10 is aligned with the end of the second group of cables 202 in the second coil 20, and the end of the third group of cables 103 in the first coil 10 is aligned with the end of the first group of cables 201 in the second coil 20. The two groups of cables with aligned ends correspond to each other, and each bridging member 30 is used to connect the corresponding two groups of cables. Each bridging member 30 straddles the first coil 10 and the second coil 20 and covers the ends of the aligned cables in these two coils. On the second reference plane perpendicular to the coil radial direction, the orthographic projection of the bridging member 30 covers the ends of the aligned cables in these two coils. For example, one bridging member 30 simultaneously covers the end of the first group of cables 101 in the first coil 10 and the end of the third group of cables 203 in the second coil 20.

[0041] In the embodiments of the present application, the ends of the cables in each group in the two coils are aligned in the reverse direction. In this way, only by using the bridging member 30 to connect the aligned cables, the cables in each group in the two coils can be reversely connected by using the bridging member 30. In this way, the spatial position between the two groups of cables to be connected is relatively close, and the positional relationship is relatively simple; correspondingly, the structure of the bridging member 30 can be relatively simple. For example, if the bridging member 20 is in a simple sheet shape, the connection of the two groups of cables can be realized without complex structural design of the bridging member 30. In this way, the cable connection method can be simplified, and correspondingly, the preparation process of the magnet structure can be simplified. Moreover, the strength of the bridging member 30 can be relatively high, which can ensure the connection stability and correspondingly ensure the operation stability of the magnet structure.

[0042] In one embodiment, there may also be a height difference between the two groups of cables to be connected in the two coils, or they may not be aligned in the stacking direction of the coils. In this way, certain structural adjustments can be made to the bridging member 30, such as making the bridging member 30 have a bent portion to realize the connection of the two groups of cables.

[0043] In some embodiments, in any one of the first coil 10 and the second coil 20, the ends of multiple groups of cables are arranged in sequence along the cable winding direction, and multiple bridging members 30 are respectively located inside the ends of multiple groups of cables. Correspondingly, the multiple bridging members 30 are arranged in sequence along the circumferential direction of the coil. Each bridging member 30 can be located inside the ends of the two groups of cables to be connected to bridge the ends of the two groups of cables. In this way, only by staggering the ends of each group of cables and directly arranging the bridging member below the ends of each group of cables, the bridging can be realized without further splitting the ends of the originally stacked groups of cables, which can simplify the bridging process.

[0044] As Figure 1 shown, in the first coil 10, the ends of the first group of cables 101, the ends of the second group of cables 102, and the ends of the third group of cables 103 are arranged in sequence along the direction from right to left (i.e., the counterclockwise cable winding direction). In the second coil 20, the ends of the three groups of cables (201, 202, and 203 respectively) from the inside to the outside are arranged in sequence along the direction from left to right. Each bridging member 30 can be located inside the ends of a group of cables. For example, Figure 1 the three bridging members 30 shown are respectively connected to the inside of the ends of the first group of cables 101, the inside of the ends of the second group of cables 102, and the inside of the ends of the third group of cables 103.

[0045] In a possible way, each bridging member 30 can also be located outside the ends of the cables to be connected. For example, the bridging member 30 for connecting the first group of cables 101 is located between the first group of cables 101 and the second group of cables 102, and this is not limited here.

[0046] The bridging member in the embodiment of the present application can be in a sheet shape, and its side surface can be a vertical surface perpendicular to the upper and lower surfaces. Figure 2 It is a partial structural schematic diagram of another magnet structure provided by the embodiment of the present application. As Figure 2 shown, on the basis of the structure shown in Figure 1 the magnet structure can further include a transition member 40 with an arc-shaped surface. The end of any group of cables extends to the corresponding bridging member 30 through the arc-shaped surface of the transition member 40. The bridging member 30 corresponding to each group of cables is the bridging member 30 to which the end of the group of cables is connected.

[0047] Exemplarily, in any coil (such as Figure 2 the first coil 10 in) of the magnet structure, the end of the innermost group of cables (i.e., the first group of cables 101) extends to the corresponding bridging member 30 by using the arc-shaped surface of the transition member 40. In the transition member 40 corresponding to the first group of cables 101, the height of the end close to the bridging member 30 is greater than the height of the end far from the bridging member 30. In this way, after the end of the first group of cables 101 extends to the transition member 40 and then extends to the bridging member 30, it can ensure that the cables rise smoothly to the same height as the bridging member 30, facilitating the smooth transition of the cables to the bridging member 30 and reducing the risk of cable damage caused by the setting of the bridging member 30. The transition member 40 can also ensure that there is support in the transition area where the cables transition to the bridging member 30, ensuring relatively high strength of the cables.

[0048] In some embodiments, in any coil of the magnet structure, the end of each group of cables can extend to the corresponding bridging member 30 by using the transition member 40. Exemplarily, in any coil (such as Figure 2 the first coil 10 in) of the magnet structure, other groups of cables (such as the second group of cables 102 and the third group of cables 103) other than the innermost group of cables also extend to the corresponding bridging member 30 by using the transition member 40. Since the other groups of cables need to be bent inward, correspondingly, the height of the end of the transition member 40 close to the bridging member 30 can be less than the height of the end far from the bridging member 30. The transition member 40 can ensure that the other groups of cables are bent relatively smoothly and support the bent parts of the other groups of cables, ensuring the strength and reliability of the cables after bending.

[0049] In the embodiment of the present application, among multiple groups of cables in each coil of the magnet structure, each group of cables can include only one layer of cables (such as Figure 1Each group of cables therein represents one layer of cables), or may also include multiple stacked layers of cables. Here, an example where each group of cables includes multiple stacked layers of cables will be introduced. In this way, the multiple layers of cables are bent together, which can ensure that the strength of each group of cables is relatively high, avoid damage to the cables caused by bending, and ensure a relatively high reliability of the magnet structure. In one implementation, when each group of cables includes multiple stacked layers of cables, the ends of the multiple layers of cables can be aligned, that is, aligned in the radial direction of the coil. In this way, only a small amount of splitting of the cable ends is required, avoiding increasing the complexity of cable winding.

[0050] In another implementation, when each group of cables includes multiple stacked layers of cables, among any two adjacent layers of cables in the multiple layers of cables, the end of the outer layer cable extends relative to the end of the inner layer cable along the cable winding direction. Here, the inner layer cable is the layer of cable closer to the inside among the two layers of cables, and the outer layer cable is the layer of cable closer to the outside among the two layers of cables. The bridging member 30 is located inside the multiple layers of cables and extends relative to the end of the innermost cable among the multiple layers of cables along the cable winding direction. The magnet structure further includes a conductive member, and the conductive member fills the space between the ends of the multiple layers of cables and the bridging member 30. This space is also the space between the part where the ends of the other layers of cables extend relative to the innermost layer of cable and the bridging member 30. The conductive member is used to electrically connect the other layers of cables to the bridging member 30, and the bridging member 30 can cover the end of the innermost layer of cable and the conductive member. The following will be introduced in combination with the attached Figure 3 This implementation will be introduced.

[0051] Figure 3 is a partial structural schematic diagram of another magnet structure provided by an embodiment of the present application, Figure 4 is a partial structural schematic diagram of yet another magnet structure provided by an embodiment of the present application. Figure 3 can be Figure 1 a refined schematic diagram of the magnet structure shown in Figure 4 can be Figure 3 an enlarged view of the part within the dashed box in the magnet structure shown in Figure 1 For example, each group of cables shown in Figure 3 includes three layers of cables. Correspondingly, the magnet structure can specifically be as shown in Figure 3 where each group of cables includes three layers of cables as an example. In the figure, thick lines are used to distinguish the interfaces of different groups of cables. Please combine Figure 3 with Figure 4, taking the second group of cables 102 in the first coil 10 as an example, the second group of cables 102 includes a first-layer cable 1021, a second-layer cable 1022, and a third-layer cable 1023 arranged in sequence from the inside to the outside. Other groups of cables can refer to the introduction of the second group of cables 102, which will not be elaborated here. In the embodiments of the present application, taking three-layer cables as a group as an example, in some ways, two-layer, four-layer, five-layer, or even more-layer cables can also be used as a group.

[0052] For two adjacent cables in the second group of cables 102 that are closer to the inside, the inner cable of the two cables is the first-layer cable 1021, and the outer cable is the second-layer cable 1022. The end of the second-layer cable 1022 extends to the left (corresponding to the counterclockwise cable winding direction of the first coil 10) relative to the end of the first-layer cable 1021. For two adjacent cables in the second group of cables 102 that are closer to the outside, the second-layer cable 1022 serves as the inner cable, and the third-layer cable 1023 serves as the outer cable. The end of the third group of cables 103 extends to the left relative to the end of the second group of cables 102. The ends of the three-layer cables are stepped along the radial direction of the coil.

[0053] The bridging member 30 connected to the second group of cables 102 can be located inside the second group of cables 102, that is, inside the innermost first-layer cable 1021 of the three-layer cables, and is directly in contact with and connected to the end of the first-layer cable 1021. The bridging member 30 also extends to the left relative to the first-layer cable 1021. For example, the extending part can be aligned with the end of the outermost third-layer cable 1023. A conductive member 50 is provided in the space between the second-layer cable 1022 and the third-layer cable 1023 and the bridging member 30. The second-layer cable 1022 and the third-layer cable 1023 can be spaced from the bridging member 30 through the conductive member 50. The position where the end of the first-layer cable 1021 is vacant relative to the end of the third-layer cable 1023 is filled with the conductive member 50, and the position where the end of the second-layer cable 1022 is vacant relative to the end of the third-layer cable 1023 is also filled with the conductive member 50. The edges of the third-layer cable 1023, the conductive member 50, and the bridging member 30 can be aligned. The second-layer cable 1022 and the third-layer cable 1023 can be electrically connected to the bridging member 30 by using the conductive member 50. Each layer of cable in a group of cables can be electrically connected.

[0054] In the embodiments of the present application, by making multiple layers of cables into a group, and making the cables closer to the outside extend forward, and connecting to the bridging member 30 through the conductive member 50. In this way, the structure of each group of cables can be ensured to be flat, and the bridging member 30 can also have a larger area, so that the contact area between each group of cables and the bridging member 30 is larger. Correspondingly, the resistance between the cables and the bridging member 30 can be reduced, ensuring that the current transmission through the bridging member 30 has a better effect and improving the overall performance of the magnet structure.

[0055] In the embodiments of the present application, when each group of cables includes cables with three or more layers, multiple conductive members 50 can be corresponding. The conductive members 50 arranged beside the cables of different layers can be independent of each other. For example, the space beside the cables of different layers is filled with sheet-shaped conductive members 50 of different lengths. In one way, each group of cables can correspond to only one conductive member 50. When a group of cables includes cables with three or more layers, one side edge of the conductive member 50 can be stepped, and the conductive members 50 arranged beside the cables of different layers are of an integral structure. In the embodiments of the present application, the conductive members 50 corresponding to each group of cables are independent of each other, and the conductive members 50 corresponding to each group of cables in different coils are also independent of each other. The conductive member 50 corresponding to a group of cables refers to the conductive member 50 arranged between the outermost cable in the group of cables and the corresponding connecting member 30.

[0056] The material of the conductive member 50 can be a material with good conductivity. For example, the material can include copper, and the conductive member 50 can be a copper sheet. A copper sheet is arranged beside each layer of cables to make up for the part of the outermost cable that is missing. The material of the conductive member 50 can also include silver, aluminum or other conductive materials, which is not limited here.

[0057] In some embodiments, the magnet structure further includes an insulating layer located between adjacent groups of cables in each coil. The first coil 10 and the second coil 20 are both wound by stacking multiple groups of cables carrying the insulating layer. Please continue to refer to Figures 1 to 4 , an insulating layer (not shown in the figure) is arranged between the first group of cables 101 and the second group of cables 102 in the first coil 10, and an insulating layer is also arranged between the second group of cables 102 and the third group of cables 103. An insulating layer (not shown in the figure) is arranged between the first group of cables 201 and the second group of cables 202 in the second coil 20, and an insulating layer is also arranged between the second group of cables 202 and the third group of cables 203. In one embodiment, an insulating layer can also be arranged on the outermost or innermost side of a group of cables, so as to avoid the electrical connection of the cables in different turns during the stacking and winding process, resulting in too high a current change rate. In the present application, a group of cables wound in a circle in the coil obtained by stacking and winding can be called one turn.

[0058] Exemplarily, the material of the insulating layer can include Teflon or other insulating materials. The insulating layer can be formed by coating, or it can directly be a separate insulating layer sandwiched between two groups of cables.

[0059] In the embodiments of the present application, an insulating layer is provided between adjacent groups of cables, which can block the current flow path between different groups of cables. This can further reduce the influence of the radial current, not only maintaining the relative uniformity of the current distribution, but also achieving the balance of inductance and effective current transposition under a high current change rate, thereby further reducing the AC loss and improving the performance and stability of the magnet structure.

[0060] The embodiments of the present application also provide the results of simulating and testing the operating effects of different magnet structures using an equivalent circuit model, such as simulating and testing the hysteresis loss, coupling loss, and temperature of different magnet structures respectively. Figure 5 It is a simulation result diagram of the hysteresis loss of a different magnet structure provided by the embodiments of the present application. Figure 6 It is a simulation result diagram of the coupling loss of a different magnet structure provided by the embodiments of the present application. Figure 7 It is a simulation result diagram of the highest temperature of a different magnet structure provided by the embodiments of the present application. Among the different magnet structures here, the first magnet is a magnet without transposition of the inner and outer turns of the cable and without inter-turn insulation; the second magnet is a magnet without transposition of the inner and outer turns of the cable but with inter-turn insulation; the third magnet is a magnet with transposition of the inner and outer turns of the cable but without inter-turn insulation; the fourth magnet is a magnet with transposition of the inner and outer turns of the cable and with inter-turn insulation.

[0061] In the embodiments of the present application, it is taken that the first magnet, the second magnet, the third magnet, and the fourth magnet are all high-temperature superconducting magnets, and the high-temperature superconducting magnet is applied to a nuclear fusion reaction device, and it is the transmitted breakdown current after 1500 seconds as an example. Correspondingly, after 1500 seconds, the magnet will generate losses. Figures 5 to 7 It mainly shows the loss situation and temperature situation after 1500 seconds. As Figures 5 to 7 shown, after the treatment of transposition of the inner and outer turns of the cable and insulation between the stacked and wound groups of cables (i.e., inter-turn insulation), the overall hysteresis loss of the high-temperature superconducting magnet is reduced by one order of magnitude, and the coupling loss is also greatly reduced. The most important and intuitive thing is that the temperature rise on the high-temperature superconducting magnet is low, and the highest temperature always remains below 60K (Kelvin). Based on this simulation result, it can be proved that after the treatment of transposition of the inner and outer turns of the cable and inter-turn insulation, the AC loss of the high-temperature superconducting magnet can be greatly reduced, the heat generation during the operation of the magnet can be reduced, and the overall stability of the magnet can be improved.

[0062] The magnet structure of the present application is wound by the method of stacking multiple layers of cables wound side by side, and the number of stacked cable layers can be determined according to actual requirements. At the internal cross-turn section of the double-pancake coil or the joint between the pancake coils in the magnet structure, by adopting a joint structure with a transposition function, the cables of the inner and outer turns of the coil are transposed, so that the currents of the inner and outer turns are interchanged, and the inductance of the cables at the same radial position is balanced within the entire magnet, thereby making the current distribution more uniform and reducing the AC loss. Further, through the collaborative design of the inter-turn insulation, the reverse current can be suppressed, and the failure of the transposition effect can be avoided. When the magnet is a high-temperature superconducting magnet, this method can make full use of the self-screening effect of the superconducting material and the electromagnetic field collaborative regulation mechanism, and significantly reduce the overall AC loss of the magnet, reduce the operation heating, and at the same time improve the dynamic stability and service life of the superconducting magnet without introducing complex auxiliary structures, providing key technical support for the practical application of high-field and high-frequency superconducting power equipment.

[0063] The self-screening effect of the superconducting material stems from the perfect diamagnetism (Meissner effect) of the superconductor and the special nature of the current distribution in the superconductor. This self-screening refers to the phenomenon that when the superconducting magnet enters the superconducting state, its interior can completely repel the penetration of the external magnetic field. When an external magnetic field acts on the superconducting magnet, induced currents (called screening currents) will be automatically generated on the surface of the superconducting magnet. These currents will generate a magnetic field opposite to the direction of the external magnetic field inside the superconducting magnet, thereby offsetting the influence of the external magnetic field, and the result can make the magnetic field inside the superconducting magnet almost zero (ideally completely zero).

[0064] In summary, in the magnet structure provided by the embodiment of the present application, for the coil obtained by winding multiple groups of cables stacked side by side, the end of the outer cable is made to protrude relative to the end of the inner cable and bend inward, so that the ends of each group of cables are flush, and the ends of each group of cables in the two coils can approach reversely, and then the ends of each group of cables in the two coils are reversely connected by a bridging member. In this way, the inner cable of the first coil can be connected to the outer cable of the second coil, realizing the transposition of the inner and outer turn cables in the two coils, making the overall inductance of the cables at the same radial position balanced within the two coils, thereby making the current distribution more uniform and reducing the loss of the magnet structure.

[0065] The embodiment of the present application also provides a nuclear fusion reaction device, such as a tokamak device. The nuclear fusion reaction device includes an annular reaction chamber for carrying out nuclear fusion, as well as toroidal field (TF) coils, a center solenoid (CS) coil, and poloidal field (PF) coils. The CS coil is also called an ohmic coil. At least one of the center solenoid coil, the poloidal field coil, and the toroidal field coil includes the above-mentioned magnet structure. For example, this magnet structure can be used as the center solenoid coil. The center solenoid coil can include a plurality of the above-mentioned magnet structures. The magnet structures are stacked on top of each other, and adjacent magnet structures can be connected. The connection method can refer to the way the first coil and the second coil are connected through a bridging member as described above.

[0066] The number of the center solenoid coil, the poloidal field coil, and the toroidal field coil in the nuclear fusion reaction device can all be multiple. The center solenoid coils are stacked in sequence and are located in the surrounded area of the annular reaction chamber. The change in the current of the center solenoid coil provides the volt-seconds required to generate, establish, and maintain the plasma current (based on the transformer principle, the volt-second is the unit of magnetic flux). A plurality of toroidal field coils respectively surround the reaction chamber along the toroidal direction of the reaction chamber; the poloidal field coils surround the reaction chamber, and a plurality of poloidal field coils are arranged along the axial direction of the reaction chamber. The poloidal magnetic field generated by the poloidal field coils controls the plasma cross-sectional shape and position balance; the toroidal magnetic field generated by the toroidal field coils ensures the macroscopic overall stability of the plasma; the toroidal magnetic field and the poloidal magnetic field generated by the plasma current together constitute a magnetic field configuration with magnetic field line rotational transformation and magnetic surface structure nesting to confine the plasma. Through this series of controls of the plasma by the magnetic field, the plasma can reach the fusion reaction conditions to undergo a nuclear fusion reaction. Since the realization of the nuclear fusion reaction depends on the magnetic fields generated by each coil, the structural stability of each coil and the stability of the magnetic field formed during the working process will directly affect the effect of the nuclear fusion reaction.

[0067] In the embodiment of the present application, since the AC loss of the magnet structure is relatively low and the working stability is relatively high, correspondingly, when the magnet structure is used as the coil in the nuclear fusion reaction device, it can ensure that the coil in the nuclear fusion reaction device has relatively high stability, thereby providing a relatively stable magnetic field and ensuring a better effect of the nuclear fusion reaction.

[0068] The above description is of specific embodiments of the present application. Other embodiments are within the scope of the appended claims. In some cases, the acts or steps recited in the claims may be performed in a different order than in the embodiments and still achieve the desired result. Additionally, the processes depicted in the figures do not necessarily require the particular order or sequential order shown to achieve the desired result. In certain embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0069] Those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the acts and modules involved are not necessarily essential to the present application. In the above embodiments, each embodiment is described with its own emphasis. For parts not detailed in a certain embodiment, reference may be made to the relevant descriptions of other embodiments.

[0070] The preferred embodiments of the present application disclosed above are only used to help explain the present application. The alternative embodiments do not elaborate on all details and do not limit the present application to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of the present application. The present application selects and specifically describes these embodiments to better explain the principles and practical applications of the present application, so that those skilled in the art can well understand and utilize the present application.

Claims

1. A magnet structure, characterized in that: include: A first coil and a second coil are stacked, and a plurality of bridge members; The first coil and the second coil are both obtained by winding a plurality of stacked cables, and the cables in the first coil and the second coil are wound in opposite directions; In any two adjacent groups of cables among the plurality of groups of cables, the end of the outer cable group extends relative to the end of the inner cable group along the cable winding direction, and is bent inwardly to be flush with the end of the inner cable group; wherein the inner cable group is the inner group of cables among the two groups of cables, and the outer cable group is the outer group of cables among the two groups of cables; The ends of each group of cables in the first coil are reversely connected to the ends of each group of cables in the second coil through each bridge component.

2. The magnet structure according to claim 1, characterized in that: In the superimposed direction of the first coil and the second coil, the ends of each group of cables in the first coil are aligned in the opposite direction to the ends of each group of cables in the second coil; Each of the bridges spans across the first coil and the second coil, covering ends of a group of cables aligned in the first coil and the second coil.

3. The magnet structure according to claim 2, characterized in that: The ends of the plurality of cable groups are arranged in sequence along the cable winding direction, and the plurality of bridge members are respectively located inside the ends of the plurality of cable groups.

4. The magnet structure according to any one of claims 1 to 3, characterized in that: Each of the plurality of cable groups comprises stacked multi-layer cables; in any two adjacent layers of cables in the multi-layer cables, the end of the outer layer cable extends out relative to the end of the inner layer cable along the cable winding direction; wherein the inner layer cable is the inner layer of the two layers of cables, and the outer layer cable is the outer layer of the two layers of cables; The bridging member is located inside the multi-layer cable and extends along the cable winding direction relative to the end of the innermost cable in the multi-layer cable; The magnetic structure further includes a conductive member filling a space between an end portion of the multilayer cable and the bridge member.

5. The magnet structure according to any one of claims 1 to 3, characterized in that: Each of the plurality of groups of cables includes multiple layers of cables that are stacked, with ends of the multiple layers of cables aligned.

6. The magnet structure according to any one of claims 1 to 3, characterized in that: In any one of the first coil and the second coil, an end of the inner cable group and an end of the outer cable group belong to cable ends at inner turns in the any one coil, or belong to cable ends at outer turns in the any one coil.

7. The magnet structure according to any one of claims 1 to 3, characterized in that: It also includes an insulating layer located between adjacent groups of cables, and the first coil and the second coil are both obtained by winding a plurality of stacked groups of cables carrying the insulating layer.

8. The magnet structure according to claim 3, characterized in that: It also includes a transition piece with an arcuate surface, and the end of any group of cables extends to the corresponding bridge piece through the arcuate surface of the transition piece.

9. The magnet structure according to any one of claims 1 to 3, characterized in that: The cable includes a high temperature superconducting tape.

10. A nuclear fusion reaction device, characterized in that: include: A reaction chamber, a central solenoid coil, a poloidal field coil and a toroidal field coil, wherein at least one of the central solenoid coil, the poloidal field coil and the toroidal field coil comprises the magnet structure as claimed in any one of claims 1 to 9.

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