A self-coupled superconducting magnet quench protection system and method

Abstract

The application provides a self-coupling superconducting magnet quench protection system and method, comprising: a plurality of protection units and a decision unit; each superconducting coil in a superconducting magnet system is connected with a protection unit; the protection unit is used for providing a protection action for the superconducting coil in quench; the decision unit is connected with a main loop switch of the superconducting magnet system and the protection unit; the decision unit is used for detecting the superconducting coil and controlling the protection unit. The application solves the problems in the prior art, such as that the quench protection strategy cannot only discharge the quench coil quickly, that an additional secondary coil needs to be wound, and that the coupling degree between the secondary coil and the superconducting coil is insufficient, and the like, and the application utilizes the electromagnetic coupling between the superconducting coils in the magnet to transfer part of the energy stored in the quench coil to the non-quench loop, effectively accelerates the discharge process of the quench coil, and takes into account the rapidity, flexibility and safety of the protection.

Description

Technical Field

[0001] This invention belongs to the field of superconducting magnet protection technology, and particularly relates to a self-coupled superconducting magnet quench protection system and method. Background Technology

[0002] Compared to conventional conductors, superconductors exhibit zero resistance in their superconducting state, allowing them to withstand large direct currents without generating Joule heat. Superconducting magnets, made from superconducting tapes, offer advantages that conventional magnets cannot match, and are widely used in scientific research, medicine, energy, and other fields.

[0003] The superconducting state of a superconductor is subject to numerous constraints. When any one of its parameters—current, temperature, or magnetic field—exceeds a critical value, or when external disturbances cause structural damage, the superconductor transitions from a superconducting state to a resisted normal state. This transition is called quench loss. When a disturbance causes localized quench loss in a superconducting magnet, the magnet's stored energy concentrates in a very small quench region, resulting in a large amount of Joule heating and becoming a hot spot. If protective measures are not taken in time, the high temperature at the hot spot will cause irreversible damage and degradation to the superconductor, and in severe cases, lead to magnet burnout, endangering the magnet system and the safety of operators. Therefore, quench protection is a crucial issue in the application of superconducting magnets.

[0004] The core of quench protection lies in taking timely and effective measures to reduce the hot spot temperature and prevent the magnet from burning out. Based on the balance and transfer of energy stored in the magnet during quench, common quench protection schemes can be divided into two categories. Energy balance refers to accelerating the propagation of quench within the magnet, dispersing the energy originally concentrated at the quench point evenly throughout the entire magnet. However, for high-temperature superconducting materials with high minimum quench energy and slow quench propagation speed, accelerating the propagation of quench within the magnet is quite difficult. Therefore, the energy balance scheme is not very applicable to quench protection of high-temperature superconducting magnets.

[0005] Energy transfer refers to the transfer of stored energy out of a magnet using an external energy release circuit. Compared to energy balance, energy transfer schemes are applicable to both low-temperature and high-temperature superconducting magnets. From an energy transfer perspective, the scheme using a storage resistor as the energy release element is the foundation of many protection schemes. Its principle is to use a resistor-inductor circuit to rapidly transfer stored energy from the magnet to the storage resistor. Based on the storage resistor scheme, the storage scheme based on secondary coil coupling has been widely studied. This scheme includes two circuits: a primary circuit consisting of a superconducting coil and a storage resistor connected in parallel, and a secondary circuit consisting of a secondary coil and a storage resistor connected in parallel. Its core is to utilize the tight magnetic coupling between the superconducting coil and the secondary coil to transfer part of the stored energy to the secondary circuit. Studies have shown that the addition of the secondary circuit absorbs part of the stored energy of the superconducting coil, effectively accelerating the discharge process of the magnet, significantly reducing the hot spot temperature, and achieving a better protection effect.

[0006] Most commonly used secondary coil coupling protection schemes currently employ additional secondary coils, which can be categorized as follows: (1) a secondary coil made of superconducting or other metallic materials is wound around the protected superconducting coil. (2) other metallic materials are co-wound with superconducting tape to serve as a secondary coil. (3) structures such as copper rings, copper disks, and core rods in the coil frame are used as secondary coils. Problems that have not yet been solved by existing secondary coil coupling schemes include: (1) the coupling tightness between the additionally wound secondary coil and structures such as copper disks, copper rings, and core rods and the superconducting coil is insufficient, resulting in a generally poor acceleration effect on discharge. (2) the co-winding of other metallic materials with superconducting tapes reduces the current density of the coil and increases the complexity of magnet design and manufacturing. Superconducting magnets are generally composed of multiple superconducting coils stacked together. In actual operation, local quenching caused by disturbances usually occurs only within one coil and rarely occurs simultaneously in multiple coils. Existing secondary coil coupling protection schemes use identical secondary circuits for each superconducting coil in the magnet. In the event of a quench, all coils discharge at almost the same rate. This rapid overall discharge of the magnet causes drastic changes in the magnetic field, posing a potential risk of damage to other equipment operating within the magnetic field. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention proposes a self-coupled superconducting magnet quench protection system and method. Utilizing the tight magnetic coupling between superconducting coils within the magnet, the non-quenching superconducting coil acts as a secondary coil, absorbing part of the energy stored in the quenching coil and accelerating its discharge process. Compared to traditional transfer resistor methods, due to the self-coupling between the superconducting coils, the quenching coil discharges faster in this method, and only the quenching coil discharges rapidly, minimizing the impact of the protection device on the magnet and other equipment. Unlike traditional secondary coil coupling schemes, the self-coupled protection scheme described in this paper also has significant advantages such as low protection cost and tight coupling. For engineering applications of superconducting magnets, this method fully considers the safety redundancy during magnet operation and intelligently selects the transfer resistor value of the secondary circuit based on the different safety margins of the coils at various locations. This ensures that the current increase time in the non-quenching coil is short and the increase is within the safety redundancy range, balancing the speed, selectivity, and safety of the protection.

[0008] To achieve the above objectives, the present invention provides a self-coupled superconducting magnet quench protection system, comprising: a protection unit and a decision unit;

[0009] The protection unit is provided in several parts, and each superconducting coil in the superconducting magnet system is connected to one of the protection units; the protection unit is used to provide protection for the superconducting coil when it loses quench;

[0010] The protection unit is connected to the superconducting coil in the superconducting magnet system, and the number of the protection units is adapted to the number of the superconducting coil;

[0011] The decision unit is connected to the main circuit switch of the superconducting magnet system and the protection unit, respectively; the decision unit is used to detect the superconducting coil and control the protection unit.

[0012] Optionally, the protection unit includes: a variable dump resistor and a controllable unidirectional switch;

[0013] The variable storage resistor and the controllable one-way switch are connected and form a circuit with the superconducting coil; the variable storage resistor and the controllable one-way switch are respectively connected to the decision unit;

[0014] The variable storage resistor is used to consume the energy stored in the magnet when the superconducting coil fails to quench.

[0015] The controllable one-way switch is used to provide a discharge circuit for the superconducting coil.

[0016] Optionally, the decision unit detects the superconducting coil and controls the protection unit, specifically including: the decision unit detects the quench position of the superconducting coil, sets the resistance value of the variable transfer resistor corresponding to the superconducting coil; generates a trigger signal, and controls the on / off state of the controllable unidirectional switch and the main circuit switch.

[0017] Optionally, the decision unit is further configured to acquire the voltage and current quantities in the discharge circuit, and determine whether the discharge circuit has completed discharging based on the voltage and current quantities.

[0018] On the other hand, to achieve the above objectives, the present invention also provides a self-coupled superconducting magnet quench protection method, which applies the quench protection system described above, including:

[0019] A circuit is set up for the superconducting coil, and the resistance value of the circuit is obtained;

[0020] When the superconducting coil fails to quench, a resistance is set in the circuit; the circuit includes: a quench circuit and a non-quench circuit;

[0021] The non-quench circuit is used to assist the superconducting coil of the quench circuit in discharging. 。

[0022] Optionally, each of the circuits includes: a superconducting coil, a variable dump resistor, and a controllable unidirectional switch.

[0023] Optionally, setting a resistor for the circuit includes:

[0024] Set the variable transfer resistor in the quench circuit corresponding to the quench-out superconducting coil to the value corresponding to the quench-out superconducting coil, and set the resistance value in the non-quench circuit corresponding to the non-quench-out superconducting coil to the value corresponding to the non-quench-out superconducting coil.

[0025] Optionally, discharging the superconducting coil in the quench circuit includes:

[0026] A portion of the energy of the superconducting coil in the quench circuit is released in the quench circuit and converted into heat energy of the variable storage resistor in the quench circuit;

[0027] Another portion of the energy of the superconducting coil in the quench-out circuit is transferred to the non-quench-out circuit through electromagnetic coupling, and is converted into heat energy of the variable storage resistor in the non-quench-out circuit.

[0028] Optionally, the discharge of the superconducting coil assisting the quench circuit further includes:

[0029] If the quench circuit has not completed its discharge, no action is taken; if the quench circuit has completed its discharge, the quench circuit is disconnected and the resistance value of the non-quench circuit is increased to complete the quench discharge of the superconducting magnet.

[0030] Compared with the prior art, the present invention has the following advantages and technical effects:

[0031] This invention addresses the problems in existing technologies where quench protection strategies cannot target only the rapid discharge of the quench coil, require the winding of an additional secondary coil, and have insufficient coupling between the secondary coil and the superconducting coil. By utilizing the electromagnetic coupling between the superconducting coils within the magnet, a portion of the energy stored in the quench coil is transferred to the non-quench circuit, effectively accelerating the discharge process of the quench coil and balancing the speed, flexibility, and safety of the protection. Attached Figure Description

[0032] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0033] Figure 1 This is a schematic diagram of the self-coupling quench protection circuit for a multi-coil superconducting magnet system according to Embodiment 1 of the present invention;

[0034] Figure 2 This is a schematic flowchart of the self-coupling quench protection method for a multi-coil superconducting magnet system according to Embodiment 2 of the present invention;

[0035] Figure 3 The diagram shows the protection circuit of Embodiment 3 of the present invention and a conventional dump resistor; wherein, (a) is a self-coupled protection circuit and (b) is the protection circuit of the conventional dump resistor method.

[0036] Figure 4 This is a schematic diagram showing the discharge effect of the self-coupling protection method of Embodiment 3 of the present invention and the traditional transfer resistor method. Detailed Implementation

[0037] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0038] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0039] This invention proposes a self-coupled superconducting magnet quench protection system, comprising: a protection unit and a decision unit;

[0040] The protection unit comprises several units, and each superconducting coil in the superconducting magnet system is connected to one of the protection units.

[0041] The decision unit is connected to the main circuit switch of the superconducting magnet system and the protection unit, respectively; the decision unit is used to detect the superconducting coil and control the protection unit.

[0042] Furthermore, the protection unit includes: a variable dump resistor and a controllable unidirectional switch;

[0043] The variable storage resistor and the controllable one-way switch are connected and form a circuit with the superconducting coil; the variable storage resistor and the controllable one-way switch are respectively connected to the decision unit;

[0044] The variable storage resistor is used to consume the energy stored in the magnet when the superconducting coil fails to quench.

[0045] The controllable one-way switch is used to provide a discharge circuit for the superconducting coil.

[0046] The decision unit is connected to the main circuit switch to control its opening and closing. The decision unit is also connected to the controllable transfer resistor of the protection unit to change the transfer resistor value according to the quench status. Finally, the decision unit is connected to the controllable unidirectional switch in the protection unit to control the activation of the protection unit.

[0047] Furthermore, the decision unit detects the quench position of the superconducting coil; sets the resistance value of the variable storage resistor corresponding to the superconducting coil; generates a trigger signal to control the on / off state of the controllable unidirectional switch and the main circuit switch.

[0048] Furthermore, the decision unit is also used to obtain the voltage and current quantities in the discharge circuit, and to confirm whether the discharge circuit has completed discharging based on the voltage and current quantities.

[0049] Example 1

[0050] This embodiment proposes a self-coupled quench protection system for a superconducting magnet. Based on the coupling between superconducting coils within the magnet and considering the safety margin during magnet operation, the system intelligently selects the resistance value of the secondary circuit's storage resistor to transfer part of the energy stored in the quench coil to the secondary circuit, accelerating the discharge of the quench coil. To this end, a quench protection device for a superconducting magnet is designed. The superconducting magnet includes several superconducting coils, and the protection system includes several protection units and a decision unit. Each coil within the magnet is connected in parallel with a protection unit, and each protection unit consists of a variable resistor and a controllable switch connected in series. The decision unit is electrically connected to each protection unit and the main circuit switch. Upon quench, it intelligently controls the storage resistor value corresponding to each protection unit and switches the main circuit and protection unit switching states.

[0051] The overall technical solution of this embodiment is as follows:

[0052] Step 1: The decision unit pre-calculates the transfer resistor value in the protection unit based on the magnet parameters;

[0053] Based on self-coupling, the storage resistance values ​​of each protection unit during timeout are pre-calculated, including the values ​​corresponding to the timeout coil and the values ​​corresponding to the non-timeout coil.

[0054] (1) Value corresponding to the quench coil: As the primary circuit, the storage resistor connected in parallel with the quench coil undertakes most of the coil energy storage. Its value is calculated based on the magnet parameters, including the superconducting coil inductance and the primary circuit time constant that meets the protection requirements. It is calculated according to the relationship between the storage resistor, the coil inductance and the time constant.

[0055] (2) Value corresponding to the non-overrun coil: As a secondary circuit, the storage resistor connected in parallel with the non-overrun coil absorbs part of the energy stored in the overrun coil, accelerating its discharge process. Its value is calculated based on the coupling coefficient between this coil and the overrun coil, considering the safety margin for the operation of each coil. It should be noted that: <1> The different relative positions of the coils that have not lost quench and the coils that have lost quench result in different coupling coefficients. <2> The vertical field at the location of each non-overrun coil is different, resulting in different safety margins. Therefore, the dump resistance value corresponding to each non-overrun coil is different.

[0056] Step 2: The decision unit collects the detection results of the overrun detection device. If an overrun occurs, proceed to Step 3; otherwise, no action is taken.

[0057] Step 3: The decision unit selects the transfer resistor value and switch status in each protection unit based on the quench location determined by the quench detection device;

[0058] Based on the actual operation of the magnet, the selection of the dump resistor value and switching state includes:

[0059] (1) When more than one coil fails simultaneously, the working mode of the failure protection system is as follows: If multiple coils fail, the resistance value of the protection unit connected in parallel with the failure coil is set to the value corresponding to the failure coil; the resistance value of the remaining units is set according to the coupling coefficient between the coil connected in parallel with the unit and the nearest failure coil and the safety margin of the coil, and the setting method is as described in step 1.

[0060] (2) Considering that the vertical field is largest and the safety margin is smallest at the positions of the coils at both ends of the magnet, the system operates as follows to avoid the risk of quenching caused by short-term current increase:

[0061] <1> If the safety margin of the end coil is sufficient, the transfer resistor value and switch status shall be set normally according to the pre-calculation results in step 1.

[0062] <2> If the safety margin of the first and last coils is insufficient, the protection device of the end coil will not operate when the first and last coils have not exceeded the calf limit; that is, the switch status of the first and last protection units will be set to off. If one of these two coils is an overrun coil, the protection unit connected in parallel with the overrun coil will be normally activated, and the storage resistor value will be the corresponding value of the overrun coil. If both coils exceed the calf limit, the corresponding protection units will be normally activated, and the storage resistor value will be the corresponding value of the overrun coil.

[0063] Step 4: The decision unit sends a trigger signal to the main circuit, driving the main circuit switch and protection unit to take corresponding actions to perform magnet protection.

[0064] like Figure 1 As shown, taking a superconducting magnet system consisting of N high-temperature superconducting coils (coil 1-coil N) as an example, the current flow direction is indicated by arrows in the figure. 12 is the main circuit switch, and 13 is the lead connecting the magnet and quench protection system to the power system. This can also be combined with the traditional transfer resistor method to form a dual protection system with main protection and backup protection, further ensuring the safety of the magnet in the event of quench. The quench protection device in this embodiment mainly includes protection units 101-10N, which are connected in parallel with each superconducting coil, and a decision unit 11.

[0065] Each protection unit consists of a variable storage resistor and a controllable unidirectional switch connected in series. The storage resistor dissipates the energy stored in the magnet during quench, while the controllable unidirectional switch provides a discharge circuit for the superconducting coil, including a main discharge circuit through which the quench current flows and an auxiliary discharge circuit through which the current from the non-quench coil flows. To prevent current from flowing through the protection system during normal operation, the switch is unidirectional. The decision unit determines the resistance value of the storage resistor in each protection unit based on the quench position detected by the quench detection system, and generates a trigger signal to control the switching on and off of the switch in each protection unit and the main circuit switch. Furthermore, the decision unit measures the voltage and current in each discharge circuit to confirm whether each circuit has completed discharging.

[0066] This invention also provides a method for protecting a self-coupled superconducting magnet from quenching, comprising:

[0067] A circuit is set up for the superconducting coil, and the resistance value of the circuit is obtained;

[0068] When the superconducting coil fails to quench, a resistance is set in the circuit; the circuit includes: a quench circuit and a non-quench circuit;

[0069] Based on the resistance of the quenched and non-quenched circuits, the superconducting coil that has quenched is discharged.

[0070] Furthermore, each of the circuits includes: a superconducting coil, a variable dump resistor, and a controllable unidirectional switch.

[0071] Furthermore, setting a resistor for the circuit includes:

[0072] Set the variable transfer resistor in the quench circuit corresponding to the quench-out superconducting coil to the value corresponding to the quench-out superconducting coil, and set the resistance value in the non-quench circuit corresponding to the non-quench-out superconducting coil to the value corresponding to the non-quench-out superconducting coil.

[0073] Furthermore, the discharge of the superconducting coil assisting the quench circuit includes:

[0074] A portion of the energy of the superconducting coil in the quench circuit is released in the quench circuit and converted into heat energy of the variable storage resistor in the quench circuit;

[0075] Another portion of the energy of the superconducting coil in the quench-out circuit is transferred to the non-quench-out circuit through electromagnetic coupling, and is converted into heat energy of the variable storage resistor in the non-quench-out circuit.

[0076] A portion of the energy in the quench coil is released in the quench circuit, where it is converted into heat energy in the quench circuit's storage resistor. This process can be approximated as the discharge process of an RL circuit.

[0077] Another portion of the energy from the quench coil is transferred to the non-quench coil circuit via electromagnetic coupling, ultimately transforming into heat energy in the storage resistor of the non-quench circuit. This energy transfer process via electromagnetic coupling accelerates the discharge of the quench coil.

[0078] Furthermore, the discharge of the superconducting coil assisting the quench circuit also includes:

[0079] If the quench circuit has not completed its discharge, no action is taken; if the quench circuit has completed its discharge, the quench circuit is disconnected and the resistance value of the non-quench circuit is increased to complete the quench discharge of the superconducting magnet.

[0080] Example 2

[0081] like Figure 2 As shown in the figure, a typical workflow of the self-coupled superconducting magnet quench protection method provided in this embodiment applied to a multi-coil superconducting magnet system is as follows:

[0082] (1) Pre-calculate the resistance values ​​of the quench circuit and the non-quench circuit. To ensure discharge speed, the resistance value of the quench circuit is relatively large and is calculated according to the time constant requirements of the primary circuit. The resistance value of the non-quench circuit is divided into multiple levels according to the distance between the coils and is calculated based on the coupling coefficient and safety margin. Pre-calculation refers to calculating the optimal resistance value in advance for different quench occurrence locations. When a quench occurs, the corresponding resistance value is applied based on the location detected by the quench detection system.

[0083] (2) When the system is running, the main circuit switch is closed and all protection circuit switches are turned off. The decision unit reads the monitoring results of the overrun detection system in real time. If there is no overrun, no action is taken and the magnet works normally. If there is an overrun, the main circuit switch is first controlled to open and the power supply to the magnet is stopped.

[0084] (3) While disconnecting the power supply, the decision unit sets the resistance of each circuit according to the location of the quench. The transfer resistor in the protection unit connected in parallel with the quench coil is set to the value corresponding to the quench coil, and the transfer resistor value in the protection unit connected in parallel with the non-quench coil is set according to the calculation result in (1).

[0085] The main criteria for setting the resistors in each circuit are as follows:

[0086] The purpose of setting different values ​​for the transfer resistors in each loop is to accelerate the discharge of the quench coil. Therefore, the transfer resistor value of the quench loop is larger than that of the non-quench loop, so as to transfer some of the stored energy to the non-quench loop.

[0087] When setting the resistance value, the current safety margin of the superconducting coil must be considered. During superconducting magnet operation, the operating current must be ensured to be below the critical current of each coil; the difference between the critical current and the operating current is called the safety margin. After the self-coupling protection system is activated, the current in the non-overrunning loop will experience a short-term rise; its peak value must be ensured to remain below the critical current, i.e., there must still be a certain safety margin.

[0088] The specific setup of the dump resistor generally involves the following steps:

[0089] The quench loop resistance is set according to the safety requirements of magnet protection. For example, to reduce the hot spot temperature to a safe range, the quench coil must release at least 90% of its energy within 2ms after the protection system activates. Ignoring the non-quench coil circuit for now, assuming all energy is released in the quench loop, the quench loop discharge time constant has a maximum value requirement, denoted as τmax. From the characteristics of the RL circuit, τ = L / R. Based on the maximum time constant requirement and the coil inductance, the minimum value Rmin of the quench loop storage resistance can be determined.

[0090] The quench circuit resistance is tentatively set to Rmin as mentioned above. To transfer some of the quench energy to the non-quench circuit, the non-quench circuit resistance needs to be smaller than that of the quench circuit. According to the coupling coefficient between each coil and the quench coil, the non-quench circuit resistance is first set in stages, for example, successively set to values ​​of 0.2Rmin, 0.1Rmin, etc.

[0091] Based on the above settings, a discharge process simulation is performed to calculate the current safety margin and peak voltage across each coil during discharge. Then, according to the safety margin requirements and peak voltage requirements, the resistances of the non-quench circuit and the quench circuit are optimized. The optimization aims to accelerate the discharge of the quench coil as much as possible, while ensuring that each coil has a sufficient current safety margin and that the peak voltage remains within a safe range during discharge.

[0092] Considering various quench scenarios, the optimal resistance parameter selection scheme corresponding to each quench scenario is finally obtained.

[0093] Note: The specific figures mentioned above (releasing at least 90% of the energy within 2ms, setting the non-quench circuit resistance to values ​​such as 0.2Rmin and 0.1Rmin) are for illustrative purposes only and are not actual engineering requirements.

[0094] (4) After the transfer resistor values ​​of each protection unit are set, the switching transistors of each unit are turned on, and the quench coil discharges rapidly through the quench circuit and the non-quench secondary circuit. It is worth noting that the time required from the occurrence of quench to the discharge of each circuit is very short, and will not cause the magnet to burn out.

[0095] (5) While discharging, the decision unit monitors the discharge status of each circuit in real time. If the overrun circuit has not completed the discharge, no action is taken; if the overrun circuit has completed the discharge, the switch of that circuit is disconnected and the resistance value of each non-overrun circuit is increased to accelerate the discharge speed of the non-overrun circuit.

[0096] (6) After increasing the resistance of the non-overrunning circuit, the decision unit monitors the discharge status of each circuit in real time. If there is still a circuit that has not completed the discharge, no action is taken. Once all circuits have completed the discharge, a signal is sent. At this time, the magnet can be repaired and the fault can be eliminated.

[0097] (7) After all faults are eliminated, the magnet and quench protection system are put back into operation as described in (1), and the system operates normally.

[0098] This embodiment utilizes the tight magnetic coupling between multiple superconducting coils in the magnet and considers the safety redundancy of the superconducting coil operation, using the non-quenching superconducting coil as a secondary coil to accelerate the discharge of the quenching coil. To achieve the above objective, the present invention adopts the following technical solution: a protection unit is connected in parallel across both ends of each coil. This unit consists of a variable storage resistor and a controllable switch connected in series. A decision unit is set up to read the output results of the quenching detection device, mainly including the magnet's operating status and the quenching coil position, and thereby control the resistance value of the storage resistor and the switch state in each protection unit. The basic working logic is: during normal operation, the switches of all protection units are turned off; when a quench is detected, on the one hand, the storage resistor connected in parallel with the quenching coil is set to a larger resistance value and the switch is turned on, so that the resistor-inductor discharge circuit where the superconducting coil is located has a smaller time constant, ensuring a faster discharge speed; on the other hand, the resistance value of the storage resistor connected in parallel with the non-quenching superconducting coil is set to a smaller value, and the switch is turned on. By leveraging strong electromagnetic coupling between the non-quench coil and the quench coil, a portion of the energy stored in the quench coil is transferred to the non-quench coil, accelerating the discharge process of the quench coil. Considering the varying coupling coefficients between the coils and the quench coil at different locations, and the varying operational safety redundancy, the energy release resistor values ​​for the non-quench coils at different locations are different and adjustable. The specific resistance value is adjusted by the decision-making unit based on the current position of the quench coil and the actual operating conditions. This method, based on the self-coupling of the coils inside the magnet, accelerates the magnet's discharge and storage process while eliminating the need for a separate secondary coil, simplifying magnet design and manufacturing, and reducing costs. Based on the coupling coefficient and safety redundancy, by setting flexible and variable storage resistor values, this method also achieves rapid discharge specifically for the quench coil, effectively reducing the safety risks and excitation costs associated with rapid discharge of the entire multi-coil magnet system.

[0099] Example 3

[0100] In this embodiment, the superconducting magnet is a small magnet containing three superconducting coils. The three coils are identical in size, each being a 40-turn insulated superconducting coil with an inner diameter of 3.5 cm. The strip width is 6 mm, the thickness is 0.185 mm, and the distance between adjacent coils is 1 mm. Figure 3 As shown in (a), the coils are numbered 1, 2, and 3 sequentially. Under these parameters, the self-inductance of each coil is calculated to be approximately 0.22 mH, the coupling coefficient between two adjacent coils is approximately 0.67, and the coupling coefficient between coil 1 and coil 3 is approximately 0.44. Based on the actual parameters of the magnet, the pre-calculated quench circuit resistance is 0.21 Ω, and the non-quench resistance is divided into two levels: level one resistance is 12 mΩ, and level two resistance is 10.2 mΩ. To demonstrate the comparison of the discharge effect of the method described in this paper with the traditional dump resistor method, a simulation model of the traditional dump resistor method is also built, and its circuit structure is as follows. Figure 3 As shown in (b), when the quench occurs, switch S is opened, allowing the energy stored in the magnet to be released in the dump resistor. In this embodiment, the dump resistor value is set to 0.63Ω, which is three times the resistance value of the quench coil in the self-coupling method of this embodiment.

[0101] Under the above parameters, the magnet operating current is set to 60A, at which point the central magnetic field is approximately 110mT. The critical current I for coils 1 and 3 is... c Approximately 131A, with a safety margin of 71A; the critical current I of coil 2. c It is approximately 86A, with a safety margin of 26A.

[0102] The magnet is initially set to normal operating condition with a steady-state operating current of 60A. At 8 seconds, the quench protection system detects a quench in coil 1 and sends a signal to the decision unit. Simultaneously, the protection system activates, disconnecting the main circuit switch and activating the switches of the three protection circuits. The resistance of circuit 1 is set to the quench resistance value, the resistance of circuit 2 is set to the first-level non-quench resistance value, and the resistance of circuit 3 is set to the second-level non-quench resistance value. Figure 4 The diagram illustrates the current changes in each superconducting coil within 6 ms after quench loss. Curves for coils 1-3 demonstrate the current changes in the three superconducting coils when using the method described in this invention. Furthermore, the coil current under the conventional dump resistor method also... Figure 4 As shown in the diagram, when using the traditional dump method, the current in each coil is the same, therefore... Figure 4 It is represented by a single curve.

[0103] Reference Figure 4As a result, when using the method described in this invention, the current in the quench coil rapidly decreased from 60A to 12.6A within 1ms, while the traditional transfer resistor method required 1.6ms to achieve the same effect. It is evident that the method described in this invention, by utilizing the self-coupling between superconducting coils, can achieve a faster discharge speed, rapidly releasing the energy stored in the quench coil shortly after a quench occurs, thus reducing the hotspot temperature. The current in the non-quench coil experienced a brief rise before beginning to decrease. During the protection process, the peak current in coil 2 was approximately 89A, and the peak current in coil 3 was approximately 61A, both within safe limits.

[0104] The results of this embodiment demonstrate that the self-coupling between superconducting coils can effectively accelerate the discharge of the quench coil. By selecting an appropriate dump resistor value, the current in each coil during the discharge process can be controlled within a safe range, ensuring the safety of the protection.

[0105] The self-coupled superconducting magnet quench protection system and method proposed in this invention utilizes the mutual inductance between superconducting coils to accelerate the discharge of the quench coil, and can select different protection unit activation schemes according to the quench location, achieving rapid and selective protection. Its main advantages are as follows:

[0106] (1) Compared with the traditional superconducting magnet discharge strategy, the method of the present invention has a faster discharge speed for the superconducting coil due to the utilization of the mutual inductance between superconducting coils.

[0107] (2) By intelligently selecting the resistance value of the storage resistor in the protection unit, the method of the present invention achieves rapid discharge only for the quench coil. After the energy stored in the quench coil is released, the resistance of the non-quench circuit is increased to release the energy in the non-quench coil at an appropriate speed. This avoids the risk of equipment damage caused by sudden changes in the magnetic field and the impact of overall rapid discharge on the lifespan of the magnet.

[0108] (3) The device of the present invention achieves protection through an external protection unit without structurally modifying the coil, thus reducing protection costs and ensuring the current density and mechanical strength of the coil. The addition of the protection unit is flexible and can be selected according to actual operating requirements. If it is desired to enhance the heat dissipation capacity of the dump resistor, the protection unit can be placed in the low-temperature zone; if it is desired to improve the convenience of maintenance of the protection system, the protection unit can be placed in the normal temperature zone. The protection device of the present invention can also be combined with a traditional quench protection device based on a dump resistor as a backup protection to improve the operational safety of the magnet system.

[0109] (4) The method described in this invention is flexible in operation and takes into account practical factors such as multi-coil quenching and the influence of the vertical field of the coils at both ends on the critical current in the actual operation of the superconducting magnet.

[0110] (5) The method described in this invention takes into account the safety margin during the operation of the superconducting magnet, and balances the safety and speed of protection.

[0111] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A self-coupled superconducting magnet quench protection system, characterized in that, include: Protection unit and decision-making unit; The protection unit is provided in several parts, and each superconducting coil in the superconducting magnet system is connected to one of the protection units; The protection unit is used to provide protection for the superconducting coil in the event of quench failure; The protection unit is connected to the superconducting coil in the superconducting magnet system, and the number of the protection units is adapted to the number of the superconducting coil; The decision-making unit is connected to the main circuit switch of the superconducting magnet system and the protection unit, respectively. The decision-making unit is used to detect the superconducting coil and control the protection unit; The protection unit includes: a variable dump resistor and a controllable one-way switch; The variable storage resistor and the controllable one-way switch are connected and form a circuit with the superconducting coil; the variable storage resistor and the controllable one-way switch are respectively connected to the decision unit; The variable storage resistor is used to consume the energy stored in the magnet when the superconducting coil fails to quench. The controllable one-way switch is used to provide a discharge circuit for the superconducting coil; The decision unit detects the superconducting coil and controls the protection unit, specifically including: the decision unit detects the quench position of the superconducting coil, sets the resistance value of the variable transfer resistor corresponding to the superconducting coil, generates a trigger signal, and controls the on / off state of the controllable one-way switch and the main circuit switch. It is also used to obtain the voltage and current quantities in the discharge circuit, and to confirm whether the discharge circuit has completed discharging based on the voltage and current quantities.

2. A self-coupled superconducting magnet quench protection method, employing the quench protection system as described in claim 1, characterized in that, include: A circuit is set up for the superconducting coil, and the resistance value of the circuit is obtained; When the superconducting coil fails to quench, a resistance is set in the circuit; the circuit includes: a quench circuit and a non-quench circuit; The superconducting coil in the non-quench circuit is assisted in discharging by the quench circuit.

3. The self-coupled superconducting magnet quench protection method according to claim 2, characterized in that, Each of the circuits includes: a superconducting coil, a variable dump resistor, and a controllable unidirectional switch.

4. The self-coupled superconducting magnet quench protection method according to claim 3, characterized in that, Setting a resistor for the circuit includes: Set the variable transfer resistor in the quench circuit corresponding to the quench-out superconducting coil to the value corresponding to the quench-out superconducting coil, and set the resistance value in the non-quench circuit corresponding to the non-quench-out superconducting coil to the value corresponding to the non-quench-out superconducting coil.

5. The self-coupled superconducting magnet quench protection method according to claim 3, characterized in that, The discharge of the superconducting coil assisting the quench circuit includes: A portion of the energy of the superconducting coil in the quench circuit is released in the quench circuit and converted into heat energy of the variable storage resistor in the quench circuit; Another portion of the energy of the superconducting coil in the quench-out circuit is transferred to the non-quench-out circuit through electromagnetic coupling, and is converted into heat energy of the variable storage resistor in the non-quench-out circuit.

6. The self-coupled superconducting magnet quench protection method according to claim 3, characterized in that, The superconducting coil assisting the quench circuit in discharging also includes: If the quench circuit has not completed its discharge, no action is taken; if the quench circuit has completed its discharge, the quench circuit is disconnected and the resistance value of the non-quench circuit is increased to complete the quench discharge of the superconducting magnet.

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