Loss of superconductivity protection circuit

Abstract

The application provides a quench protection circuit, which is suitable for quench protection of a superconducting device. The quench protection circuit comprises: a diode branch, which is connected in parallel with a superconducting coil branch in the superconducting device, and comprises a plurality of forward diodes and at least one reverse diode; the plurality of forward diodes are connected in series and connected in parallel with the reverse diode; and the sum of voltage drops of the forward diodes is greater than or equal to an operating voltage between the superconducting coil branch; and a release branch, which is connected in parallel with the diode branch and the superconducting coil branch. The quench protection circuit can protect both insulated superconducting coils and uninsulated superconducting coils, and can be suitable for quench protection of different types of superconducting coils.

Description

Technical Field

[0001] This application relates to the field of superconducting magnet technology, specifically to a quench protection circuit. Background Technology

[0002] Superconducting coils may experience quench events during operation due to inhomogeneities in the superconducting material, thermal disturbances, and mechanical disturbances. Superconducting coils are often expensive and complex; effective quench protection can prevent damage, thereby improving their safety and cost-effectiveness.

[0003] Superconducting coils are generally classified into insulated superconducting coils and non-insulated superconducting coils. The quenching processes of insulated and non-insulated superconducting coils differ. In an insulated superconducting coil, when quenching occurs, the current is confined to the original turn by the insulating layer, and the electromagnetic energy is concentrated at the quenching point and converted into heat, leading to a rapid local temperature rise. In a non-insulated superconducting coil, when quenching occurs, the current is shunted through the inter-turn conductive material, and the heat is dispersed across multiple turns, resulting in a more uniform temperature rise. Based on these different quenching processes, different types of superconducting coils have different protection mechanisms. Insulated superconducting coils primarily rely on external protection, i.e., they depend on external parallel energy-releasing resistors to quickly release energy. Non-insulated superconducting coils primarily rely on self-protection, i.e., the turn current is shunted through the conductors between adjacent turns to suppress local temperature rise.

[0004] However, the quench protection scheme for superconducting coils in related technologies is generally applied to a single type of superconducting coil and is not practical for routine testing of different types of superconducting coils.

[0005] Therefore, how to expand the scope of application of quench protection has become an urgent technical problem to be solved. Summary of the Invention

[0006] This application provides a quench protection circuit, which at least solves the technical problem of how to increase the applicability of quench protection in related technologies.

[0007] According to a first aspect, embodiments of this application provide a quench protection circuit suitable for quench protection of a superconducting device. The quench protection circuit includes: a diode branch connected in parallel with the superconducting coil branch in the superconducting device, comprising a plurality of forward diodes and at least one negative diode, wherein the plurality of forward diodes are connected in series and in parallel with the negative diode, and the sum of the voltage drops of the forward diodes is greater than or equal to the operating voltage across the superconducting coil branch; and an energy release branch connected in parallel with the diode branch and the superconducting coil branch.

[0008] In one embodiment, the superconducting coil branch includes an adjustable boost resistor connected in series in the superconducting coil branch.

[0009] In one embodiment, the superconducting coil branch further includes a superconducting coil and current leads.

[0010] In one embodiment, the superconducting coil includes an insulated superconducting coil or a non-insulated superconducting coil.

[0011] In one embodiment, the diode branch further includes a diode branch switch, wherein the positive diode and the negative diode are connected in parallel and then connected in series with the diode branch switch.

[0012] In one embodiment, the forward diode and the negative diode are modular diodes, each including a diode body and a diode support for supporting the diode body; the modular diodes can be used to construct diode arrays of any series and parallel configuration via the diode support.

[0013] In one embodiment, the diode array has multiple current lead connection points.

[0014] In one embodiment, the energy release branch includes an energy release switch and an energy release resistor connected in series.

[0015] In one embodiment, the quench protection circuit further includes a quench detection module connected to the energy release switch, used to control the energy release switch to close when a quench is detected in the superconducting coil.

[0016] In one embodiment, the quench protection circuit further includes an excitation switch connected in series between the excitation power supply and the superconducting coil branch.

[0017] This application has at least the following beneficial effects:

[0018] The quench protection circuit in this application is applicable to quench protection of a superconducting device. The superconducting device includes a superconducting coil branch connected in series across the excitation power supply. The excitation power supply and the superconducting coil branch constitute an excitation circuit. The superconducting coil branch includes a superconducting coil and current leads connected in series. The quench protection circuit includes: a diode branch connected in parallel with the superconducting coil branch, comprising at least one negative diode and multiple positive diodes. The multiple positive diodes are connected in series and in parallel with the negative diode. The sum of the forward voltage drops of the positive diodes is greater than or equal to the operating voltage across the superconducting coil branch; and an energy release branch connected in parallel with the diode branch and the superconducting coil branch. The quench protection circuit in this application can protect both insulated and non-insulated superconducting coils. When protecting a non-insulated superconducting coil, the diode branch conducts when the voltage across the non-insulated superconducting coil rises due to quench, preventing the excitation power supply from continuing to flow into the non-insulated superconducting coil. The current from the excitation power supply flows through the diode branch, thus protecting the non-insulated superconducting coil, the current lead, and the excitation power supply. When protecting an insulated superconducting coil, the energy release branch discharges the energy of the insulated superconducting coil when quench occurs, protecting the insulated superconducting coil. It can protect both insulated and non-insulated superconducting coils and also provides some protection for the power supply system and the superconducting current lead, making it applicable to quench protection for different types of superconducting coils. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the circuit principle of an exemplary quench protection circuit according to an embodiment of this application;

[0022] Figure 2 This is a schematic diagram of the diode module in an exemplary quench protection circuit according to an embodiment of this application.

[0023] Figure 3 This is a schematic diagram of the diode array in an exemplary quench protection circuit according to an embodiment of this application. Detailed Implementation

[0024] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0025] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, including a series of units, systems, products, or devices is not necessarily limited to those explicitly listed, but may include units, systems, products, or devices not explicitly listed.

[0026] This application provides a quench protection circuit suitable for quench protection of a superconducting device. The superconducting device includes a superconducting coil branch 20 connected in series across an excitation power supply 40. The excitation power supply 40 and the superconducting coil branch 20 form an excitation circuit. The superconducting coil branch 20 includes a superconducting coil and a current lead connected in series. The quench protection circuit of this application can protect against quenching of the superconducting coil or the current lead. The quench protection circuit includes: a diode branch 10 connected in parallel with the superconducting coil branch 20, including at least one negative diode D1 and multiple positive diodes D2. The multiple positive diodes D2 are connected in series and in parallel with the negative diode D1. The sum of the forward voltage drops of the positive diodes D2 is greater than or equal to the operating voltage across the superconducting coil branch 20; and an energy release branch 30 connected in parallel with the diode branch 10 and the superconducting coil branch 20.

[0027] When the superconducting coil is energized and in operation, it is in a superconducting state. The resistance of the superconducting coil is very small. Therefore, the voltage across the superconducting coil branch 20 and the diode branch 10 is very small, less than the forward voltage of the forward diode D2. Thus, the diode branch 10 is in the off state, and the energizing circuit can work normally.

[0028] In this embodiment, when the superconducting coil is in normal working condition, the voltage across the superconducting coil branch 20 is Uc, and the forward voltage of a single forward diode D2 is Vd. In order to ensure that the diode branch 10 is in the off state when the superconducting coil is in normal working condition, the data amount n of the forward diode D2 needs to be set to be greater than or equal to Uc / Vd.

[0029] Since the quenching process is different for different types of superconducting coils, in this embodiment, the diode branch 10 also includes a diode branch switch Kd, and the positive diode D2 and the negative diode D1 are connected in parallel and then connected in series with the diode branch switch Kd.

[0030] When performing quench protection on an uninsulated superconducting coil, the diode branch switch Kd is closed. The voltage across diode branch 10 is very small, less than the forward voltage of multiple forward diodes D2, and diode branch 10 is in the off state.

[0031] When the non-insulated superconducting coil fails to quench, the voltage across the superconducting coil branch 20 increases, which means the voltage across the diode branch 10 increases. This causes multiple forward diodes D2 to conduct, and the current from the excitation power supply 40 flows through the forward diodes, reducing or even stopping the current to the non-insulated superconducting coil. The remaining energy in the non-insulated superconducting coil is dissipated inside the coil through the conductors between adjacent turns. The heat is evenly distributed inside the non-insulated superconducting coil, thereby protecting the non-insulated superconducting coil, the current leads, and the excitation power supply 10.

[0032] Furthermore, when the heat generated by the non-insulated superconducting coil is small, the inter-turn resistance rises slightly, and the value of the inter-turn resistance is also small. The energy release of the non-insulated superconducting coil is slow, and the coil is relatively safe. However, if the temperature of the non-insulated superconducting coil rises due to heat generated by the inter-turn resistance, it will further increase the inter-turn resistance of the coil, and the energy release of the non-insulated superconducting coil will accelerate. At this time, the negative diode D1 conducts as a shunt branch of the non-insulated superconducting coil, carrying a portion of the current in the non-insulated superconducting coil, thereby reducing the heat generated by the coil and protecting the coil.

[0033] In one embodiment, an excitation switch is also connected in series in the excitation circuit. When the uninsulated superconducting coil fails to quench, the excitation switch can be disconnected to break the connection between the excitation power supply 40 and the uninsulated superconducting coil.

[0034] To accommodate testing of non-insulated superconducting coils with a wider range of operating currents, in this embodiment, the superconducting coil branch 20 further includes an adjustable boosting resistor Ra connected in series with the superconducting coil branch 10. The voltage across the superconducting coil branch 20 is then given by: Uc = Ec*L + k*Lc + R1*I + Ra*I, where R1 is the resistance of the non-insulated superconducting coil branch, Ra is the resistance of the adjustable boosting resistor, Lc is the inductance of the non-insulated superconducting coil, I is the operating current of the non-insulated superconducting coil, Ec is the critical electric field, L is the strip length of the non-insulated superconducting coil, and k is the excitation rate of the non-insulated superconducting coil.

[0035] To improve the sensitivity of the protection against uninsulated superconducting coils, with a fixed number of forward diodes D2, the voltage across the superconducting coil branch 20 under normal operating conditions is adjusted by adjusting the adjustable boosting resistor Ra. Specifically, when the operating current of the tested uninsulated superconducting coil is low, the voltage across the superconducting coil branch 20 is low, and even with n=1, the forward diodes D2 cannot be triggered to conduct. Therefore, the resistance of the adjustable boosting resistor Ra needs to be increased. When the operating current of the tested uninsulated superconducting coil is high, the voltage across the superconducting coil branch 20 is high, and the resistance of the adjustable boosting resistor Ra can be decreased. This ensures that the sum of the conduction voltages of the multiple forward diodes D2 is critically greater than the voltage across the superconducting coil branch 20. At the moment the uninsulated superconducting coil experiences a quench, and the voltage across the superconducting coil branch 20 increases instantaneously, the forward diodes D2 can conduct promptly, quickly shunting the current of the excitation power supply 40 and protecting the uninsulated superconducting coil.

[0036] Because of the inter-turn insulation, when a quench occurs in the insulated superconducting coil, the energy inside the coil needs to be released through the energy release branch 30 connected in parallel outside the insulated superconducting coil. In this embodiment, the energy release branch 30 may include an energy release switch Ks and an energy release resistor Rs connected in series.

[0037] When protecting the insulated superconducting coil, disconnect the energy release switch Ks and close the diode branch switch Kd. Under normal operating conditions, the voltage across diode branch 10 is very small, less than the forward voltage of multiple forward diodes D2, and diode branch 10 is in the off state.

[0038] When the insulated superconducting coil loses its quench, the energy release switch Ks is closed, the excitation power supply 40 is disconnected, and the diode branch switch Kd is disconnected. The energy release branch 30 forms a circuit with the insulated superconducting coil, and the current in the insulated superconducting coil is conducted through the energy release branch, releasing the energy of the insulated superconducting coil in the form of Joule heating, thereby protecting the insulated superconducting coil from burning out.

[0039] The energy release resistor Rs has the following resistance: Rs = Vmax / I - R1 - Ra, where Vmax is the maximum insulation withstand voltage of the insulated superconducting coil, I is the operating current of the insulated superconducting coil, R1 is the coil branch resistance, and Ra is the resistance of the adjustable positive voltage resistor. When the insulated superconducting coil loses quench, the total energy deposited on the energy release resistor Rs is W = 0.5 * Lc * I * I, where Lc is the inductance of the insulated superconducting coil; the current flowing through the energy release resistor Rs is the operating current of the insulated superconducting coil decaying exponentially to 0, with a decay time constant of Lc / Rs. The energy release resistor can also be limited by the energy release time, i.e., R = 4.605 * Lc / ts, where ts is the energy release time.

[0040] In another embodiment, when the insulated superconducting coil does not quench and the voltage across the insulated superconducting coil increases, the forward diode D2 conducts, and the voltage across the diode branch 10 is clamped to the total forward voltage drop n*Vd of the multiple forward diodes D2, ensuring that the coil voltage does not exceed the safety threshold, thereby ensuring that the coil voltage is within the limit range and protecting the insulated superconducting coil, the superconducting current lead and the excitation power supply 40.

[0041] In one embodiment, the quench switch Ks can be automatically triggered to close when the insulated superconducting coil fails. In this embodiment, the quench protection circuit further includes a quench detection module connected to the quench switch Ks, used to control the quench switch Ks to close when a quench is detected in the insulated superconducting coil. In this embodiment, the quench detection module may include a voltage acquisition circuit and a comparison circuit. The voltage acquisition circuit can be connected to the superconducting coil branch 20 to detect the voltage across the superconducting coil branch 20. The output terminal of the voltage acquisition circuit is connected to the input terminal of the comparison circuit. After receiving the voltage across the superconducting coil branch 20 acquired by the voltage acquisition circuit, the comparison circuit compares it with a reference voltage. When the voltage across the superconducting coil branch 20 is greater than the reference voltage, the comparison circuit outputs a trigger signal for the quench switch Ks, triggering the quench switch Ks to close.

[0042] To further enhance the application range and scalability of quench protection circuits, quench protection can be implemented for coils ranging from small to large. Figure 2 and Figure 3 As shown, in one embodiment, the forward diode D2 and the negative diode D1 are diode modules 50. The diode module 50 includes a diode body 51 and a diode support 52 for supporting the diode body 51. The diode module 50 can construct a diode array 500 of arbitrary series and parallel configuration through the diode support 52.

[0043] Each diode body 51 is supported by an independent diode bracket 52 to form a diode module 50. Each diode module 50 also includes an independent heat dissipation device 53 for dissipating heat from the diode body. The diode module 50 can function as either a forward diode D2 or a reverse diode D1.

[0044] Multiple diode modules 50 are connected in series and / or in parallel via diode bracket 52 to form multiple forward diodes D2. At least one diode module 50 is connected in series and / or in parallel via diode bracket 52 to form at least one negative diode D1. Multiple forward diodes D2 and at least one negative diode D1 are then connected in parallel via diode bracket 52 to form a diode array 500. Through modular diode design, the diode array 500 can be built based on the diode forward voltage drop required by the superconducting coil to be tested, which can meet the testing needs of more types of superconducting coils and improve the application range and expansion capability of quench protection circuit.

[0045] In the above embodiments of this application, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0046] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A quench protection circuit, characterized in that, This circuit is suitable for providing quench protection for a superconducting device, which includes a superconducting coil branch connected in series across the excitation power supply. The quench protection circuit includes: A diode branch, connected in parallel with the superconducting coil branch, includes multiple forward diodes and at least one negative diode. The multiple forward diodes are connected in series and in parallel with the negative diode. The sum of the voltage drops of the forward diodes is greater than or equal to the operating voltage across the superconducting coil branch. The energy release branch is connected in parallel with the diode branch and the superconducting coil branch.

2. The quench protection circuit as described in claim 1, characterized in that, The superconducting coil branch includes an adjustable boosting resistor connected in series in the superconducting coil branch.

3. The quench protection circuit as described in claim 1, characterized in that, The superconducting coil branch also includes a superconducting coil and current leads.

4. The quench protection circuit as described in claim 3, characterized in that, The superconducting coil includes an insulated superconducting coil or a non-insulated superconducting coil.

5. The quench protection circuit as described in claim 1, characterized in that, The diode branch also includes a diode branch switch, wherein the positive diode and the negative diode are connected in parallel and then connected in series with the diode branch switch.

6. The quench protection circuit as described in claim 1, characterized in that, The forward diode and the negative diode are modular diodes, each including a diode body and a diode support for supporting the diode body; the modular diodes can be used to construct diode arrays of any series and parallel configuration via the diode support.

7. The quench protection circuit as described in claim 6, characterized in that, The diode array has multiple current lead connection points.

8. The quench protection circuit as described in claim 1, characterized in that, The energy release branch includes an energy release switch and an energy release resistor connected in series.

9. The quench protection circuit as described in claim 8, characterized in that, Also includes: A quench detection module, connected to the energy release switch, is used to control the energy release switch to close when a quench is detected in the superconducting coil.

10. The quench protection circuit as described in claim 1, characterized in that, Also includes: An excitation switch is connected in series between the excitation power supply and the superconducting coil branch.

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