Closed superconducting coil magnetic suspension bearing and construction method thereof

Abstract

The invention belongs to the technical field of superconducting electricians, and particularly discloses a closed superconducting coil magnetic suspension bearing and a construction method thereof. The bearing comprises a closed superconducting coil stator, a magnetic flux source rotor and a rotating shaft; the magnetic flux source rotor is used for providing a background magnetic field; the closed superconducting coil stator is used for interlinking in a superconducting state and locking a background magnetic field provided by the magnetic flux source rotor; when the magnetic flux source rotor moves under the action of a load, the closed superconducting coil stator is used for inducing shielding current inside; or the superconducting coil stator is closed to change the internal total magnetic flux by acquiring the transmission current; wherein when the shielding current and / or the transmission current interact with the background magnetic field, the magnetic flux source rotor bears a suspension force opposite to the load direction, and when the suspension force borne by the magnetic flux source rotor is greater than or equal to the load, the magnetic flux source rotor establishes a suspension state; the magnetic suspension bearing provided by the invention can ensure long-term stable operation.

Description

Technical Field

[0001] The present application belongs to the field of superconducting electrical technology, and more specifically, relates to a closed superconducting coil magnetic levitation bearing and a construction method thereof. Background Art

[0002] Magnetic bearings use electromagnetic force to eliminate the mutual contact between the stator and rotor, thereby significantly reducing friction losses and are ideal for high-speed rotating machinery. With the rapid development of type II superconducting materials, superconducting magnetic bearings based on their flux pinning characteristics can achieve three-dimensional passive self-stable suspension and have large suspension stiffness. They have broad development potential in the fields of flywheel energy storage, ultra-high-speed motors, and ship engines. Superconducting magnetic bearing systems usually adopt a superconducting-permanent magnet structure, in which permanent magnets are used as flux sources, and type II superconductors lock the permanent magnet flux that interlinks with them after field cooling. When the superconductor and the permanent magnet are relatively offset in any direction, a high-density shielding current will be induced inside the superconductor due to the flux pinning effect. This current interacts with the magnetic field of the permanent magnet to generate a restoring force opposite to the direction of motion, thereby achieving passive self-stable suspension. At present, the materials used in superconducting magnetic bearings are mainly block materials and stacked strip materials, which have the following limitations: (1) Suspension force attenuation: On the one hand, there is magnetic flux creep inside the high-temperature superconducting material, and the magnetic flux lines will gradually move away from the pinning center over time; on the other hand, there is a certain annular inhomogeneity in the magnetic field of the permanent magnet, and AC loss will occur inside the superconductor when the stator and rotor rotate relative to each other. Both will cause the bearing suspension force to attenuate, thus affecting the long-term stable operation of the system.

[0003] (2) Difficulty in establishing the initial suspension state: Pinned suspension relies on the mutual offset of the stator and rotor after field cooling to establish suspension. For heavy-load equipment, a complex movable support structure is required to ensure the establishment of initial suspension. In order to reduce the initial offset and improve the compactness of the bearing structure and the utilization rate of the permanent magnet magnetic field, the system needs to have greater stiffness, which will greatly increase the cost of using superconductors.

[0004] (3) The suspension state cannot be adjusted: After the initial suspension is established, its suspension position, stiffness, suspension force and other parameters have been determined and are difficult to change, which cannot meet the adjustment requirements, and the tolerance rate of the suspension position is low.

[0005] In summary, the existing superconducting pinned magnetic levitation bearings mainly face the following problems: 1. They cannot meet the requirements of high-speed, long-term and stable operation; 2. The load-bearing capacity is proportional to the stiffness, and it is difficult to establish initial suspension under heavy load conditions, which significantly increases the cost of using superconductors; 3. The suspension cannot be adjusted and has a low fault tolerance. Summary of the invention

[0006] In view of the defects of the prior art, the purpose of this application is to provide a closed superconducting coil magnetic levitation bearing and a construction method thereof, aiming to solve the problems that the existing superconducting magnetic levitation bearings cannot work stably for a long time, cannot be excited and floated, and the suspension state cannot be adjusted.

[0007] To achieve the above-mentioned purpose, in a first aspect, the present application provides a closed superconducting coil magnetic suspension bearing having a three-dimensional self-stabilizing characteristic, comprising: a closed superconducting coil stator, a magnetic flux source rotor and a rotating shaft arranged in sequence from the outside to the inside; The magnetic flux source rotor is used to provide a background magnetic field; The closed superconducting coil stator is used to interlink and lock the background magnetic field provided by the magnetic flux source rotor in the superconducting state; When the magnetic flux source rotor moves under the action of the load, the closed superconducting coil stator induces a shielding current inside to resist the change of the cross-linked magnetic flux; the closed superconducting coil stator changes its internal total magnetic flux by obtaining the transmission current; When the shielding current and / or the transmission current interacts with the background magnetic field, the magnetic flux source rotor is subjected to a suspension force opposite to the load direction. When the magnitude of the suspension force on the magnetic flux source rotor is equal to the load, the magnetic flux source rotor is in a suspended state. The three-dimensional self-stabilization characteristic is a characteristic that after the magnetic flux source rotor is in a suspended state, the magnetic flux source rotor can automatically return to the suspended position after being offset in the axial direction or radial direction.

[0008] Further preferably, the closed superconducting coil stator is wound by superconducting wires, and the superconducting wires include but are not limited to low-temperature superconducting wires or high-temperature superconducting wires; the low-temperature superconducting wires include but are not limited to NbTi or ; High temperature superconducting wires include but are not limited to ReBCO, Bi-2223, Bi-2212, Or iron-based superconductors.

[0009] Further preferably, the magnetic flux source rotor is a permanent magnet, a normal conductive electromagnet or a superconducting magnet; wherein the superconducting magnet includes but is not limited to a superconducting block, a stacked strip or a superconducting coil.

[0010] Further preferably, the closed superconducting coil magnetic bearing suspension works in a pinned suspension without flux control, a magnetic suspension with flux control by PCS+power supply, or a magnetic suspension with flux control by a wireless excitation system.

[0011] Further preferably, the wireless excitation system is various types of transformer-rectifier flux pumps, linear traveling wave flux pumps or rotary traveling wave flux pumps.

[0012] Further preferably, when the wireless excitation system is a transformer-rectifier flux pump, the transformer-rectifier flux pump comprises: an alternating power supply, a transformer core, a primary winding, a secondary winding and a superconducting switch; the superconducting switch is connected to the output end of the secondary winding and serves as part of a closed loop of the closed superconducting coil stator; The alternating power supply is used to provide an asymmetric triangular wave to the primary winding, and the secondary winding is used to induce an asymmetric triangular wave current with an amplitude of n times; Among them, when the instantaneous value of the current in the secondary winding is less than the critical current of the superconducting switch, the superconducting switch remains in the closed state, and the closed superconducting coil stator is short-circuited; when the instantaneous value of the current in the secondary winding is greater than the critical current of the superconducting switch, the superconducting switch is disconnected, and part of the current in the secondary winding flows to the closed superconducting coil stator, pumping the transmission current into the closed superconducting coil stator; by adjusting the positive half-wave amplitude or the negative half-wave amplitude of the secondary winding to be greater than the critical current of the superconducting switch, the direction of the transmission current pumped into the closed coil stator and the movement direction of the magnetic flux on the superconducting switch are changed, thereby realizing the magnetization or demagnetization of the closed superconducting coil stator; When the wireless excitation system is a rotating traveling wave flux pump, the closed superconducting coil magnetic suspension bearing comprises: a closed superconducting coil stator, a flux source rotor, a rotating shaft, a superconducting switch and a rotating motor rotor embedded with a permanent magnet; wherein the superconducting switch is a part of the closed coil stator, so that the stator forms a superconducting closed loop; The superconducting switch is used to control the magnetic flux of the coil; the rotating motor rotor embedded with permanent magnets is used to generate a rotating magnetic field. The rotating magnetic field cuts the superconducting switch, generating a DC voltage at both ends, thereby realizing the magnetic flux control by pumping a transmission current into the superconducting double-disc coil; by changing the rotation direction of the rotating motor rotor, the direction of the transmission current pumped into the stator is changed.

[0013] When the wireless excitation system is a linear traveling wave flux pump, the closed superconducting coil magnetic suspension bearing comprises: a closed superconducting coil stator, a flux source rotor, a rotating shaft, a superconducting switch and a linear traveling wave winding; wherein the superconducting switch is a part of the closed coil stator, so that the stator forms a superconducting closed loop; The superconducting switch is used to control the magnetic flux of the coil; the linear traveling wave winding is used to generate a traveling wave magnetic field with planar motion in the air gap when a phase sequence current is passed through it; the traveling wave magnetic field acts on the superconducting switch to generate a rectified voltage at its two ends, thereby realizing the magnetic flux control by pumping a transmission current into the superconducting double-disc coil; by changing the direction of the current in the traveling wave winding, the direction of the transmission current pumped into the stator is changed.

[0014] Further preferably, when the magnetic suspension working mode of magnetic flux regulation is adopted using PCS+power supply, it includes: a closed superconducting coil stator, a rotating shaft, a magnetic flux source rotor, a superconducting constant current switch, a current lead and an external power supply; The magnetic flux source rotor is located inside the closed superconducting coil stator; the superconducting constant current switch is connected to the closed superconducting coil stator; the external power source is connected to the superconducting constant current switch through the current lead; When the magnetic flux of the closed superconducting coil is regulated, the superconducting constant current switch is turned off, and the closed superconducting coil stator is directly connected in parallel to the two ends of the external power supply; the external power supply is used to magnetize or demagnetize the closed superconducting coil stator.

[0015] In a second aspect, the present application provides a method for constructing a suspended state of a closed superconducting coil magnetic bearing, which specifically comprises the following steps: Step 1: The magnetic flux source rotor remains stationary under the initial support device, the closed superconducting coil stator is cooled to a superconducting state, and the closed superconducting coil stator is used to lock the background magnetic field provided by the magnetic flux source rotor at the current position; Step 2: Remove the initial support device, so that the magnetic flux source rotor moves under the action of the load, and the closed superconducting coil stator induces a shielding current; Alternatively, the initial support device is retained and the transmission current is pumped into the closed superconducting coil stator; Step 3: The shielding current or the transmission current interacts with the background magnetic field, so that the magnetic flux source rotor is subjected to a suspension force opposite to the load direction, until the magnitude of the suspension force on the magnetic flux source rotor is equal to the load, and the magnetic flux source rotor is in a suspended state. Further preferably, if a wireless excitation system is provided in the closed superconducting coil magnetic bearing, step 2 is specifically as follows: The flux source rotor is in a stationary state under initial support, and a wireless excitation system is used to pump transmission current into the closed superconducting coil stator. The transmission current interacts with the background magnetic field, so that the closed superconducting coil stator is subjected to a Lorentz force in the same direction as the load, and the flux source rotor is subjected to a suspension force in the opposite direction to the load. When the suspension force increases to be equal to the load, the flux source rotor establishes a suspended state. Further preferably, the method for obtaining the suspension state further includes adjusting the suspension force and the suspension position, and the specific implementation steps are: Step 4: After the magnetic flux source rotor establishes a suspended state, a wireless excitation system is used to pump a transmission current in the same direction as the initial current into the closed superconducting coil stator. The total current inside the closed superconducting coil increases, and the suspension force on the magnetic flux source rotor is greater than the load, so the magnetic flux source rotor moves in the direction of the suspension force. Step 5: When the magnetic flux source rotor moves in the direction of the suspension force, a shielding current in the opposite direction to the pumped transmission current is induced inside the coil. When the shielding current increases to offset the transmission current pumped in step 4, the magnetic flux source rotor re-establishes the suspension state at the new position; or Step 4: After the magnetic flux source rotor establishes a suspended state, a wireless excitation system is used to pump a transmission current in the opposite direction of the initial current into the closed superconducting coil stator. The total current inside the closed superconducting coil is reduced, and the suspension force on the magnetic flux source rotor is smaller than the load, so the magnetic flux source rotor moves in the direction of the load. Step 5: As the flux source rotor moves toward the load direction, a shielding current in the opposite direction to the pumped transmission current is induced inside the coil. When the shielding current increases to offset the transmission current pumped in step 4, the flux source rotor re-establishes a suspended state at a new position.

[0016] In general, the above technical solutions conceived by this application have the following beneficial effects compared with the prior art: The present application provides a magnetic levitation bearing, which adopts a closed superconducting coil stator to induce shielding current or pump in transmission current. On the one hand, since the superconducting coil stator is in a closed state and the superconducting tape is simple to wind and has an extremely high current density, the bearing can achieve a higher force density and has the characteristics of a compact structure and easy axial and radial expansion. On the other hand, it supports passive induction shielding current or active pumping of transmission current in the closed superconducting coil stator. The working mode of the bearing can be pinned suspension without flux regulation, magnetic levitation with PCS+power supply for flux regulation, or magnetic levitation with wireless excitation system for flux regulation. Compared with the use of block materials and stacked strips in current superconducting magnetic levitation bearings, the magnetic levitation bearing provided by the present application can avoid the attenuation of suspension force caused by flux creep, joint resistance and AC loss, and can ensure long-term stable operation.

[0017] The present application provides a magnetic levitation bearing, which can continue to change the total current inside the closed superconducting coil stator by adjusting the transmission current pumped into the closed superconducting coil stator after the magnetic flux source rotor establishes a suspended state; when the pumped transmission current is in the same direction as the current for establishing the suspended state, the suspension force on the magnetic flux source rotor is greater than the load, and the magnetic flux source rotor moves in the direction of the suspension force, and finally re-establishes the suspended state at a higher position; when the pumped transmission current is in the opposite direction of the current for establishing the suspended state, the suspension force on the magnetic flux source rotor is less than the load, and the magnetic flux source rotor moves in the direction of the load, and finally re-establishes the suspended state at a lower position. Therefore, the magnetic levitation bearing provided by the present application can not only establish a suspended state, but also adjust the size of the suspension force and the suspension position.

[0018] The present application provides a magnetic levitation bearing. When a wireless excitation system is used to pump a transmission current into a closed superconducting coil stator, compared with pinned suspension without flux regulation, the excitation levitation eliminates the initial displacement of the suspension, does not require complex movable mechanical support, and can achieve stable levitation when the magnetic flux source rotor is stationary; at the same time, the transmission current is only limited by the critical current of the closed superconducting coil stator, which can greatly improve the load capacity of the bearing and overcome the problem that the size of the induced shielding current is limited by the gradient of the magnetic field change, making it difficult to achieve levitation under high load. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1( a ) is a structural diagram of a magnetic bearing provided in an embodiment of the present application; FIG1( b ) is a cross-sectional view of a magnetic bearing provided in an embodiment of the present application; Figure 2 It is a schematic diagram of a superconducting closed coil magnetic suspension bearing provided in an embodiment of the present application that relies on shielding current to establish a suspension state; Figure 3 is a schematic diagram of the induced axial stabilizing force generated when the magnetic bearing system provided by the embodiment of the present application is axially offset; FIG4 (a) is a schematic diagram of the initial suspension position of the rotor provided in an embodiment of the present application; FIG4( b ) is a schematic diagram of the induced radial stabilizing force generated when the rotor is radially offset according to an embodiment of the present application; Figure 5 It is a typical transformer-self-rectifier type wireless excitation system structure and equivalent circuit diagram provided in the embodiment of the present application; FIG6 (a) is a schematic diagram of the electric-magnetic-force distribution of the rotor at the initial position when the wireless excitation system is used to pump the transmission current to realize the excitation floating according to an embodiment of the present application; FIG6 (b) is a schematic diagram of the electric-magnetic-force distribution of the rotor suspension position when the wireless excitation system is used to pump the transmission current to realize the excitation levitation according to an embodiment of the present application; FIG. 7 ( a ) is a schematic diagram of the electric-magnetic-force distribution of the initial suspension position for flux regulation using a wireless excitation system according to an embodiment of the present application; FIG7( b ) is a schematic diagram of the distribution of electric-magnetic-force for achieving the rise of the suspension position by regulating the magnetic flux using a wireless excitation system provided in an embodiment of the present application; FIG7 (c) is a schematic diagram of the distribution of electric-magnetic-force for lowering the suspension position by using a wireless excitation system to control magnetic flux, as provided in an embodiment of the present application; FIG8 (a) is an overall structural diagram of a high-load closed superconducting coil magnetic suspension bearing controlled by a transformer-rectifier wireless excitation system provided in an embodiment of the present application; FIG8( b ) is a cross-sectional view of the bearing shown in FIG8( a ) provided in an embodiment of the present application; Fig. 9 Schematic diagram of a closed superconducting coil magnetic suspension bearing using a rotating traveling wave wireless excitation system provided in an embodiment of the present application; Fig.10 Schematic diagram of a closed superconducting coil magnetic suspension bearing using a linear traveling wave wireless excitation system provided in an embodiment of the present application; Fig.11 Schematic diagram of a closed superconducting coil magnetic bearing using a PCS+power excitation system provided in an embodiment of the present application; Fig.12 It is a schematic diagram of a flywheel energy storage system of a closed superconducting coil magnetic bearing based on wireless excitation provided in an embodiment of the present application. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0021] The term "and / or" in this article is a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. The symbol " / " in this article indicates that the associated objects are in an or relationship, for example, A / B means A or B.

[0022] The terms “first”, “second” and the like in the specification and claims herein are used to distinguish different objects rather than to describe a specific order of the objects.

[0023] In the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0024] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application.

[0025] As shown in FIG. 1 (a) and FIG. 1 (b), the present application provides a magnetic suspension bearing, comprising a closed superconducting coil stator 11, a magnetic flux source rotor 12 and a rotating shaft 13, wherein the closed superconducting coil stator is wound by a superconducting wire, and the superconducting wire includes but is not limited to a low-temperature superconducting wire (such as NbTi, ) and high-temperature superconducting wires (ReBCO, Bi-2223, Bi-2212, , iron-based superconductor), the closure mode can be jointless closure or superconducting joint closure; the magnetic flux source rotor 12 can be a permanent magnet, a normal conductive magnet and a superconducting magnet, including but not limited to superconducting blocks, stacked strips and superconducting coils; the working mode of the bearing can be pinned suspension without flux control, magnetic suspension with PCS+power supply for flux regulation, or magnetic suspension with flux regulation by a wireless excitation system; wherein the wireless excitation system includes but is not limited to various types of transformer-rectifier flux pumps, linear traveling wave flux pumps and rotating traveling wave flux pumps; the rotating shaft 13 realizes the torque transmission between the rotor and the rotating system; Under working conditions without flux modulation, the present application relies on shielding current to achieve suspension and maintain self-stability of suspension; Figure 2 As shown, Figure 2 The left side represents the state where the rotor remains stationary under the initial support before suspension is established. In order to enhance the contrast, the support system and the supporting force to balance gravity are not drawn here; the superconducting coil stator is cooled to a superconducting state, and the superconducting coil will lock the background magnetic field through which the flux source rotor passes at this position; after the support device is removed, the flux source rotor moves downward under the action of the load (gravity or thrust); in order to maintain the unchanged cross-linked magnetic field, a shielding current in the corresponding direction will be induced inside the coil, and the interaction between this current and the magnetic field causes the coil to be subjected to a downward force, while the rotor is subjected to an upward suspension force; when it descends a certain distance dz After that, the suspension force increases to be equal to the gravity, and the rotor is in suspension state; Figure 3 The left side shows the initial rotor suspension position. At this time, the axial suspension force on the permanent magnet rotor is F z With axial load F Balance; Figure 3 As shown on the right, when the rotor is axially offset dz After that, the upward magnetic flux linked with the closed coil stator decreases, causing the coil cross section to induce a shielding current in the same direction as the original current to maintain the interlinked magnetic flux unchanged; the original current and the shielding current work together to cause the rotor to be subjected to a suspension force of F z Greater than its load F ;Under the combined force, the rotor will move upward until it returns to its initial equilibrium position; Figure 4 (a) shows the initial rotor suspension position, and Figure 4 (b) shows the suspension position after the rotor is radially offset to the right. Since the axial magnetic fields on the upper and lower sections of the coil are in opposite directions, the coil section is divided into different areas for discussion. As shown in Figure 4 (a), in the initial position, the cross-sectional current is symmetrical up and down, and the interaction with the magnetic field generates radial forces of equal magnitude and opposite directions. F r1 and F r2, the rotor will move to the left under the action of the resultant force until it returns to the initial equilibrium position; The above analysis shows that the bearing structure can achieve suspension and maintain three-dimensional self-stability without the existence of an excitation system; since the superconducting tape is easy to wind and has an extremely high current density, the bearing can achieve a high force density, has a compact structure, and is easy to expand in the axial and radial directions; however, in the case of working without flux modulation, the bearing still cannot avoid the attenuation of the suspension force caused by flux creep, joint resistance and AC loss, and cannot achieve long-term stable operation; using a PCS+ power supply system or a wireless excitation system to modulate the flux of a closed superconducting coil can avoid this problem, and it also has the functions of adjustable suspension and excitation levitation; Figure 5 The first typical transformer-self-rectifier type wireless excitation system structure and equivalent circuit diagram 55; the transformer-self-rectifier type wireless excitation system includes a transformer core 51, a primary winding 52, a secondary winding 53 and a superconducting switch 54; the primary winding 52 can be a normal conductive material or a superconducting material; the secondary winding 53 is wound by a superconducting material; in the equivalent circuit diagram 55 of the wireless excitation system, the alternating power supply provides an asymmetric triangular wave to the primary winding 52 , a current with an amplitude n times that of ;when When the instantaneous value is less than the critical current of the superconducting switch, the superconducting switch remains closed and the closed superconducting coil stator is short-circuited; When the positive half-wave amplitude is greater than the critical current of the superconducting switch, resistance will appear on the superconducting switch 54, and part of the secondary current will flow to the closed coil load, thereby realizing load excitation; from the perspective of magnetism, when the current flowing through the superconducting switch When the current is greater than the critical current, the magnetic flux pinning force on the magnetic induction line will be smaller than the Lorentz force, resulting in the movement of the magnetic flux, and the magnetic induction line crosses the superconducting bridge and interlinks with the closed superconducting coil loop; on the contrary, if The instantaneous value of the negative half-wave is greater than the critical current of the superconducting switch, and the magnetic flux linked with the closed superconducting coil loop moves outward across the superconducting bridge, and the coil current decreases; Figures 6 (a) and 6 (b) show schematic diagrams of realizing magnetic flux source rotor excitation levitation using a wireless excitation system. In order to distinguish the shielding current, double lines are used to represent the transmission current. The coil is cooled to a superconducting state at the position shown in Figure 6 (a), and the coil locks the background magnetic field provided by the magnetic flux source rotor at this position. The wireless excitation system is used to pump the transmission current into the coil. The transmission current interacts with the background magnetic field, causing the coil to be subjected to a downward Lorentz force. ; At the same time, the permanent magnet rotor will be subjected to an upward suspension force As shown in Figure 6 (b), when Increased to the load of the permanent magnet rotor FAt the same time, the support device no longer provides support, and the bearing reaches the suspension condition; at this time, the power supply to the wireless excitation system is stopped, the superconducting switch returns to the superconducting state, and together with the coil and forms a superconducting closed loop. The suspension state is essentially the same as Figure 2 The right side is the same and also has Figure 3 , the three-dimensional passive self-stabilization characteristics shown in Figure 4 (a) and Figure 4 (b); compared with Figure 2 The floating method shown in the figure, the excitation floating eliminates the initial displacement of the suspension dz , without the need for complex movable mechanical support, stable floating can be achieved at a precise position; in addition, the size of the induced shielding current is limited by the gradient of the magnetic field change, making it difficult to achieve floating under high loads; while in theory, the size of the transmission current is only limited by the critical current of the coil, which can greatly improve the load capacity of the bearing.

[0026] The magnetic flux control function can also be used to change the suspension position, as shown in Figure 7 (a) to Figure 7 (c). Figure 7 (a) represents the initial suspension equilibrium state, at which the rotor axial suspension force is With Chenghe F Balance, the suspension height remains unchanged; Figure 7 (b) shows that the wireless excitation system is used to pump the transmission current in phase with the initial current into the closed coil stator, and the total coil current increases, making > F , the rotor moves upward; in the process of upward movement, there is a shielding effect, and the reverse shielding current gradually increases until it offsets the pumped transmission current, and finally the rotor establishes a new balance at a higher suspension position; Figure 7 (c) shows that the wireless excitation system is used to pump a transmission current in the opposite direction of the initial current into the closed coil stator, and the total coil current decreases, making < F , the rotor moves downward; during the downward movement, the same-direction shielding current gradually increases until it offsets the pumped transmission current, and the rotor establishes a new balance at a lower suspension position; it is worth mentioning that during the flux control process, the superconducting switch is not completely open, and the suspension is still passively self-stable. Therefore, the present application can realize convenient and flexible control of the suspension height without destroying the passive self-stable suspension.

[0027] Example FIG8 (a) and FIG8 (b) are an embodiment of the present application, which is a high-load superconducting closed coil magnetic suspension bearing controlled by a transformer-rectifier wireless excitation system. FIG8 (a) is an overall structural diagram of the bearing, and FIG8 (b) is a cross-sectional diagram of the bearing. The bearing includes a coil skeleton 81, two high-temperature superconducting double-pancake coils 82 connected in series, a permanent magnet rotor 83, an auxiliary bearing stator 84, a superconducting joint 85 of the series coils, a lead-out terminal 86 of the closed coil, a transformer-rectifier type wireless excitation system 87 and a low-temperature dewar 88. The permanent magnet rotor 83 is composed of six NdFeB permanent magnet rings fixed on an aluminum alloy liner. Each magnetic ring is composed of 18 tile-type magnets, and the polarization direction of the magnetic tiles of the same magnetic ring is the same. The magnetic poles of the six magnetic rings are arranged in the axial direction according to the Halbach array structure to concentrate the magnetic field on the outer surface of the rotor and increase the strength and gradient of the background magnetic field where the coil is located. The radial magnetic poles of the magnetic array are aligned with the cross sections of the two closed coils respectively. Improve the axial suspension force density and radial suspension stiffness; the auxiliary bearing stator 84 is wound by an open-loop superconducting coil and does not form a closed loop, so it is impossible to induce the net shielding current flowing in the annular direction, and thus has little effect on the control of the axial suspension force; since the radial stability force is generated by the shielding current on the width surface of the strip, there is no need to form a closed loop, so the auxiliary bearing is intended to improve the radial stability of the system; the stator coil and the secondary side of the wireless excitation system are cooled by immersion in liquid nitrogen; in the structure shown in Figures 8 (a) and 8 (b), an upper and lower symmetrical configuration is adopted, which is axially expanded relative to Figures 1 (a) and 1 (b), increasing the system's load capacity while enhancing the axial torsion resistance; when the working direction is axial, the excitation floating method can be used, and the current interacts with the radial magnetic field of the permanent magnet to generate an axial suspension force; by increasing the transmission current and the number of turns of the coil, the system can easily achieve a load capacity of tons; Fig. 9 Another embodiment of the present application is a superconducting closed coil magnetic suspension bearing with a rotating traveling wave flux pump for wireless excitation control, comprising a superconducting double-pancake coil 91, a flux source rotor 92, a superconducting closed joint 93 of the coil and a rotating motor rotor 94 inlaid with a permanent magnet; wherein the superconducting closed joint of the coil also serves as an excitation switch of the flux pump; when the stator coil needs to be excited, the permanent magnet generates a rotating magnetic field driven by the motor, and the magnetic field cuts the superconducting switch strip; under the AC magnetic field, magnetic flux movement will be generated on both sides of the thickness surface of the superconducting switch strip, and the direction of the magnetic flux movement is related to the direction of the rotating magnetic field, thereby increasing or reducing the magnetic flux interlinked by the closed coil loop; in terms of the circuit, a DC electromotive force is generated on the switch strip, and a DC current is generated in the closed coil loop; the advantage of this system is that a traveling wave magnetic field is generated in the form of mechanical rotation, the wireless excitation system can be placed in a normal temperature zone, and the bearing structure can be more compact; Fig.10Another embodiment of the present application is a closed superconducting coil magnetic bearing system with a linear traveling wave flux pump for wireless excitation control, comprising: a superconducting double-pancake coil 101, a flux source rotor 102, a superconducting closed joint 103 of the coil, and a linear traveling wave winding 104; wherein the superconducting closed joint of the coil is also an excitation switch of the flux pump; the principle of the linear traveling wave winding is similar to that of a three-phase motor generating a rotating magnetic field; when a current with a certain phase sequence is passed through the linear traveling wave winding 104, a traveling wave magnetic field with a planar motion is generated in the air gap, and the magnetic field acts on the excitation switch 103 of the flux pump and generates a rectified voltage at both ends, thereby realizing the excitation of the superconducting coil stator; the advantage of this system is that the traveling wave magnetic field is generated in the form of electricity, and the excitation system is more compact; Fig.11 Another embodiment of the present application is a closed superconducting coil magnetic suspension bearing that uses a PCS+ power supply for excitation control, including: a closed superconducting coil 111, a magnetic flux source rotor 112, a superconducting constant current switch 113, a current lead 114 and an external power supply 115; the switch control mode of the superconducting constant current switch 113 includes but is not limited to magnetic control, thermal control or flow control; when the superconducting coil is excited, the superconducting switch is turned off by a control device, and the superconducting coil is directly connected in parallel to both ends of the power supply; at this time, the stator coil is directly charged by the power supply to realize rotor suspension; when the rotor reaches the target suspension position, the control system is turned off, the switch returns to the superconducting state, the superconducting coil operates in a closed loop, and the suspension state is maintained; Fig.12Another embodiment of the present application is a high-temperature superconducting flywheel energy storage system, including a high-speed electric motor / generator 121, a magnetic coupling 122, a vacuum chamber 123, a low-temperature liquid inlet channel 124, a low-temperature liquid outlet channel 125, a closed superconducting coil magnetic bearing 126 controlled by wireless excitation, and a low-temperature chamber 127; the working principle of the system is: in the energy storage stage, the high-speed electric motor / generator 121 operates as a motor, accelerates the flywheel to the rated speed through the magnetic coupling, and then turns off the magnetic coupling through the magnetic switch device, and the flywheel rotates under the support of the superconducting magnetic bearing; since the entire rotating system is placed in the vacuum chamber and the magnetic bearing eliminates mechanical friction, energy is stored in the flywheel for a long time in the form of rotational kinetic energy; in the energy release stage, the magnetic coupling is opened; the high-speed electric motor / generator 121 operates as a generator, and the flywheel drives the generator rotor to rotate through inertia, and the stored mechanical energy is gradually released in the form of electrical energy. The advantages of the flywheel energy storage system are: 1. No complicated floating mechanical device is required. The flywheel can float smoothly at the initial support position by exciting the high-temperature superconducting closed coil through the wireless excitation system; 2. The structure is compact; in order to achieve high energy storage density, the mass of the flywheel can reach hundreds of tons; the superconducting pinned suspension bearing based on induced current requires a large amount of superconducting material to achieve high load-bearing capacity, which will result in a large bearing volume; the present application can pump transmission current into the closed coil through wireless excitation, thereby breaking through the limitation of the induced current size, improving the suspension force density, and reducing the stator superconductivity under the same load-bearing condition. The amount of permanent magnets used in the guide and rotor makes the structure more compact; 3. Long-term stable operation: Traditional superconducting pinned suspension bearings inevitably face the problem of suspension force attenuation. The flywheel cannot be suspended for a long time and the stored energy needs to be released in time; the present application can compensate for the suspension force through a wireless excitation system, maintain the suspension height of the flywheel, and realize long-term energy storage; 4. The suspension position is adjustable: The flywheel system structure is usually compact and the working area is limited; the present application can adjust the suspension height through wireless excitation, which can not only improve the fault tolerance of the floating position, but also achieve a smooth landing without shutting down the cooling system.

[0028] It should be understood that expressions such as "including" and "may include" that may be used in the present application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In the present application, terms such as "including" and / or "having" may be interpreted as indicating specific characteristics, numbers, operations, constituent elements, components, or combinations thereof, but may not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0029] In addition, in the present application, the expression "and / or" includes any and all combinations of the associated listed words. For example, the expression "A and / or B" may include A, may include B, or may include both A and B.

[0030] In the description of the embodiments of the present application, it should be noted that, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. Among them, "fixed connection" means that the relative position relationship after connection remains unchanged. "Rotational connection" means that the two are connected to each other and can rotate relative to each other after connection. "Sliding connection" means that the two are connected to each other and can slide relative to each other after connection. The directional terms mentioned in the embodiments of the present application, such as "top", "bottom", "inside", "outside", "left", "right", etc., are only reference directions of the accompanying drawings. Therefore, the directional terms used are for better and clearer explanation and understanding of the embodiments of the present application, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0031] In addition, in the embodiments of the present application, the mathematical concepts mentioned are symmetry, equality, parallelism, verticality, etc. These limitations are all for the current state of the art, rather than being absolutely strict definitions in a mathematical sense, and allow a small amount of deviation, approximation to symmetry, approximation to equality, approximation to parallelism, approximation to verticality, etc. are all possible. For example, A and B are parallel, which means that A and B are parallel or approximately parallel, and the angle between A and B can be between 0 and 10 degrees. A and B are perpendicular, which means that A and B are perpendicular or approximately perpendicular, and the angle between A and B can be between 80 and 100 degrees.

[0032] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A closed superconducting coil magnetic bearing, characterized in that: It has three-dimensional self-stabilizing characteristics, including: a closed superconducting coil stator, a magnetic flux source rotor and a rotating shaft arranged in sequence from the outside to the inside; The magnetic flux source rotor is used to provide a background magnetic field; The closed superconducting coil stator is used to interlink and lock the background magnetic field provided by the magnetic flux source rotor in the superconducting state; When the magnetic flux source rotor moves under the action of the load, the closed superconducting coil stator induces a shielding current inside to resist the change of the cross-linked magnetic flux; the closed superconducting coil stator changes its internal total magnetic flux by obtaining the transmission current; When the shielding current and / or the transmission current interacts with the background magnetic field, the magnetic flux source rotor is subjected to a suspension force opposite to the load direction. When the magnitude of the suspension force on the magnetic flux source rotor is equal to the load, the magnetic flux source rotor is in a suspended state. The three-dimensional self-stabilization characteristic is a characteristic that after the magnetic flux source rotor is in a suspended state, the magnetic flux source rotor can automatically return to the suspended position after being offset in the axial direction or radial direction.

2. The closed superconducting coil magnetic bearing according to claim 1, characterized in that: The closed superconducting coil stator is wound by a superconducting wire, and the superconducting wire is a low-temperature superconducting wire or a high-temperature superconducting wire; Low temperature superconducting wire is NbTi or ; High temperature superconducting wires are ReBCO, Bi-2223, Bi-2212, Or iron-based superconductors.

3. The closed superconducting coil magnetic bearing according to claim 1 or 2, characterized in that: The magnetic flux source rotor is a permanent magnet, a normal conductive electromagnet or a superconducting magnet; wherein the superconducting magnet is a superconducting block, a stacked strip or a superconducting coil.

4. The closed superconducting coil magnetic bearing according to any one of claims 1 to 3, characterized in that: The working modes of the closed superconducting coil magnetic bearing suspension are pinned suspension without flux control, magnetic suspension with PCS+power supply for flux control, or magnetic suspension with wireless excitation system for flux control.

5. The closed superconducting coil magnetic bearing according to claim 4, characterized in that: The wireless excitation system is a transformer-rectifier flux pump, a linear traveling wave flux pump or a rotary traveling wave flux pump.

6. The closed superconducting coil magnetic bearing according to claim 5, characterized in that: When the wireless excitation system is a transformer-rectifier flux pump, the transformer-rectifier flux pump includes: an alternating power supply, a transformer core, a primary winding, a secondary winding and a superconducting switch; The superconducting switch is connected to the output end of the secondary winding and also serves as a part of the closed loop of the superconducting coil stator; The alternating power supply is used to provide an asymmetric triangular wave to the primary winding, and the secondary winding is used to induce an asymmetric triangular wave current with an amplitude of n times; Among them, when the instantaneous value of the current in the secondary winding is less than the critical current of the superconducting switch, the superconducting switch remains in the closed state, and the closed superconducting coil stator is short-circuited; when the instantaneous value of the current in the secondary winding is greater than the critical current of the superconducting switch, the superconducting switch is disconnected, and part of the current in the secondary winding flows to the closed superconducting coil stator, pumping the transmission current into the closed superconducting coil stator; by adjusting the positive half-wave amplitude or the negative half-wave amplitude of the secondary winding to be greater than the critical current of the superconducting switch, the direction of the transmission current pumped into the closed coil stator and the movement direction of the magnetic flux on the superconducting switch are changed, thereby realizing the magnetization or demagnetization of the closed superconducting coil stator; When the wireless excitation system is a rotating traveling wave flux pump, the closed superconducting coil magnetic suspension bearing includes: a closed superconducting coil stator, a flux source rotor, a rotating shaft, a superconducting switch and a rotating motor rotor embedded with a permanent magnet; the superconducting switch is a part of the closed coil stator, so that the stator forms a superconducting closed loop; The superconducting switch is used to control the magnetic flux of the closed coil stator; the rotating motor rotor embedded with permanent magnets is used to generate a rotating magnetic field, which cuts the superconducting switch and generates a DC voltage at both ends, thereby realizing the magnetic flux control by pumping a transmission current into the stator coil; by changing the rotation direction of the rotating motor rotor, the direction of the transmission current pumped into the stator is changed; When the wireless excitation system is a linear traveling wave flux pump, the closed superconducting coil magnetic suspension bearing includes: a closed superconducting coil stator, a flux source rotor, a rotating shaft, a superconducting switch and a linear traveling wave winding; the superconducting switch is a part of the closed coil stator, so that the stator forms a superconducting closed loop; The superconducting switch is used to control the magnetic flux of the coil; the linear traveling wave winding is used to generate a traveling wave magnetic field with planar motion in the air gap when a phase sequence current is passed through it; the traveling wave magnetic field acts on the superconducting switch to generate a rectifier voltage at both ends, thereby realizing the magnetic flux control by pumping a transmission current into the stator coil; the direction of the transmission current pumped into the stator is changed by changing the direction of the current in the traveling wave winding.

7. The closed superconducting coil magnetic bearing according to claim 2, characterized in that: When the magnetic suspension working mode of magnetic flux control is adopted by PCS+ power supply, it includes: closed superconducting coil stator, rotating shaft, magnetic flux source rotor, superconducting constant current switch, current lead and external power supply; The magnetic flux source rotor is located inside the closed superconducting coil stator; the superconducting constant current switch is connected to the closed superconducting coil stator; the external power source is connected to the superconducting constant current switch through the current lead; When the closed superconducting coil is used for flux control, the superconducting constant current switch is turned off, and the closed superconducting coil stator is directly connected in parallel to both ends of an external power supply; the external power supply is used to magnetize or demagnetize the closed superconducting coil stator.

8. A method for constructing a suspended state of a closed superconducting coil magnetic bearing according to any one of claims 1 to 7, characterized in that: The specific steps include: Step 1: The magnetic flux source rotor remains stationary under the initial support device, the closed superconducting coil stator is cooled to a superconducting state, and the closed superconducting coil stator is used to lock the background magnetic field provided by the magnetic flux source rotor at the current position; Step 2: Remove the initial support device, so that the magnetic flux source rotor moves under the action of the load, and the closed superconducting coil stator induces a shielding current; Alternatively, the initial support device is retained and the transmission current is pumped into the closed superconducting coil stator; Step 3: The shielding current or the transmission current interacts with the background magnetic field, so that the magnetic flux source rotor is subjected to a suspension force opposite to the load direction, until the magnitude of the suspension force on the magnetic flux source rotor is equal to the load, and the magnetic flux source rotor is in a suspended state.

9. The method for constructing a suspended state according to claim 8, characterized in that: If a wireless excitation system is provided in the closed superconducting coil magnetic bearing, step 2 is specifically as follows: The flux source rotor is in a stationary state under initial support, and a wireless excitation system is used to pump transmission current into the closed superconducting coil stator. The transmission current interacts with the background magnetic field, so that the closed superconducting coil stator is subjected to a Lorentz force in the same direction as the load, and the flux source rotor is subjected to a suspension force in the opposite direction to the load. When the suspension force increases to be equal to the load, the flux source rotor establishes a suspended state.

10. The method for constructing a suspended state according to claim 9, characterized in that: It also includes adjusting the suspension force and suspension position, and the specific implementation steps are: Step 4: After the magnetic flux source rotor establishes a suspended state, a wireless excitation system is used to pump a transmission current in the same direction as the initial current into the closed superconducting coil stator. The total current inside the closed superconducting coil increases, and the suspension force on the magnetic flux source rotor is greater than the load, so the magnetic flux source rotor moves in the direction of the suspension force. Step 5: When the magnetic flux source rotor moves in the direction of the suspension force, a shielding current in the opposite direction to the pumped transmission current is induced inside the coil. When the shielding current increases to offset the transmission current pumped in step 4, the magnetic flux source rotor re-establishes the suspension state at a higher position; or Step 4: After the magnetic flux source rotor establishes a suspended state, a wireless excitation system is used to pump a transmission current in the opposite direction of the initial current into the closed superconducting coil stator. The total current inside the closed superconducting coil is reduced, and the suspension force on the magnetic flux source rotor is smaller than the load, so the magnetic flux source rotor moves in the direction of the load. Step 5: As the flux source rotor moves toward the load direction, a shielding current in the opposite direction to the pumped transmission current is induced inside the coil. When the shielding current increases to offset the transmission current pumped in step 4, the flux source rotor re-establishes the suspended state at a lower position.

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