A superconducting magnet constant current control demagnetization circuit and method

Abstract

This invention provides a constant current control demagnetization circuit and method for superconducting magnets. The circuit includes an excitation power supply, a demagnetizing load, and a cable. The excitation power supply, the demagnetizing load, and the superconducting coil are connected in series via the cable to form a loop. The excitation power supply increases its output voltage when the loop current decreases, thereby maintaining a constant demagnetization rate. The circuit satisfies U2 > U + V0; U2 represents the rated voltage of the demagnetizing load, U represents the voltage of the superconducting coil, and V0 represents the maximum voltage drop across the cable when the superconducting coil is at full current. This invention solves the technical problems of existing demagnetizing equipment being unable to achieve stable constant-rate demagnetization, or having complex designs and high costs associated with constant-rate demagnetizing equipment.

Description

Technical Field

[0001] This invention relates to the field of superconducting magnet technology, and in particular to a constant current control demagnetization circuit and method for superconducting magnets. Background Technology

[0002] Superconducting magnets, made from superconducting materials, can generate strong magnetic fields by applying large currents, and have been widely used in medical magnets, plasma confinement, and magnetic levitation. Before becoming a superconducting magnet, the superconducting coil needs to be current-loaded (excited), injecting current into the coil to make it carry a large current and thus generate a strong magnetic field. Conversely, after the superconducting magnet has completed its function, the superconducting coil needs to be current-unloaded (demagnetized), removing the current from the superconducting coil and thus eliminating the strong magnetic field.

[0003] The excitation and demagnetization of superconducting magnets are generally performed using specialized excitation power supplies and demagnetization loads. To avoid eddy current heating caused by excessively high or unstable current variations, and to ensure stable operation of the superconducting magnet, the excitation and demagnetization processes require a constant rate of current change. Excitation power supplies input grid energy into the superconducting coils; therefore, most excitation power supplies have good current rate of change control capabilities. However, demagnetization loads are generally used only as energy dissipation modules. While their control over constant voltage, constant current, and constant resistance is relatively mature, they lack control over parameters such as the rate of current change.

[0004] Currently, there are two common methods for constant current rate-of-change demagnetizing superconducting magnets: setting the demagnetizing load to a constant voltage mode and using a dedicated development power supply. However, while setting the demagnetizing load to a constant voltage mode ensures a constant voltage across its terminals, the resistance of the cables in the circuit acts as a voltage divider. As the current in the superconducting coil decreases and the circuit current decreases, the voltage drop across the demagnetizing cable resistance also decreases, while the voltage drop across the coil increases. This results in a continuously increasing current rate of decrease throughout the demagnetizing process, making it impossible to stably control the rate. On the other hand, using a dedicated development power supply for constant current rate-of-change demagnetizing increases both the equipment development and production costs, as well as the equipment complexity and reduced reliability. Summary of the Invention

[0005] This invention provides a demagnetizing circuit and method for constant current control of superconducting magnets, which can solve the technical problems of existing demagnetizing equipment being unable to achieve stable constant rate demagnetization, or having complex design and high cost of constant rate demagnetizing equipment.

[0006] According to one aspect of the present invention, a constant current control demagnetizing circuit for a superconducting magnet is provided. The circuit includes an excitation power supply, a demagnetizing load, and a cable. The excitation power supply, the demagnetizing load, and the superconducting coil are connected in series via the cable to form a loop. The excitation power supply is used to increase its output voltage when the loop current decreases, thereby maintaining a constant demagnetizing rate. The circuit satisfies U2 > U + V0, where U2 represents the rated voltage of the demagnetizing load, U represents the voltage of the superconducting coil, and V0 represents the maximum voltage drop across the cable when the superconducting coil is at full current.

[0007] Preferably, during the demagnetization process, U2 = U + (U1 + V) is satisfied;

[0008] In the formula, U represents the voltage of the superconducting coil, U1 represents the output voltage of the excitation power supply, V represents the voltage division of the cable, U2 and U are constants, and U1 and V are variables.

[0009] Preferably, during the demagnetization process, when V changes from V0 to 0, U1 changes from X to X+V0, where U 1，max >X+V0; where X represents the initial output voltage of the excitation power supply, and U 1，max This indicates the maximum output voltage of the excitation power supply.

[0010] Preferably, X is not higher than 1V.

[0011] According to another aspect of the present invention, a constant current controlled demagnetization method for a superconducting magnet is provided, the method employing any of the circuits described above for demagnetization, the method comprising:

[0012] During demagnetization, the circuit's loop current decreases, causing the voltage drop across the cable to decrease.

[0013] The excitation power supply increases its own output voltage to compensate for the voltage drop in the cable, so as to maintain the voltage of the superconducting coil constant and thus maintain a constant demagnetization rate.

[0014] By applying the technical solution of this invention, the excitation power supply, demagnetizing load, and superconducting magnet are connected in series. During the demagnetizing process, the excitation power supply increases its output voltage as the loop current decreases, thereby maintaining a constant demagnetizing rate and achieving effective and stable control over the rate of change of the demagnetizing current of the superconducting magnet. This invention achieves controllable demagnetizing rate of the superconducting magnet through the coordinated functions of different devices. Furthermore, this invention does not require the addition or development of new equipment; it only requires the use of existing conventional equipment, reducing equipment costs and improving equipment reliability. Attached Figure Description

[0015] The accompanying drawings, which form part of this specification, are provided to further illustrate embodiments of the invention and, together with the textual description, explain the principles of the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0016] Figure 1 A diagram of a superconducting magnet constant current control demagnetization circuit according to an embodiment of the present invention is shown. Detailed Implementation

[0017] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0019] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0020] like Figure 1As shown, this invention provides a constant current control demagnetizing circuit for a superconducting magnet. The circuit includes an excitation power supply, a demagnetizing load, and a cable. The excitation power supply, the demagnetizing load, and the superconducting coil are connected in series via the cable to form a loop. The positive terminal of the excitation power supply is connected to the superconducting coil, and the negative terminal is connected to the demagnetizing load. The excitation power supply is used to increase its output voltage when the loop current decreases, thereby maintaining a constant demagnetizing rate. The circuit satisfies U2 > U + V0, where U2 represents the rated voltage of the demagnetizing load, U represents the voltage of the superconducting coil, and V0 represents the maximum voltage drop across the cable when the superconducting coil is at full current.

[0021] This invention connects the excitation power supply, demagnetizing load, and superconducting magnet in series. During demagnetization, the excitation power supply increases its output voltage as the loop current decreases, thereby maintaining a constant demagnetizing rate and achieving effective and stable control over the rate of change of the demagnetizing current in the superconducting magnet. This invention achieves controllable demagnetizing rate of the superconducting magnet through the coordinated functions of different devices. Furthermore, this invention requires no new equipment or research and development; it only requires the use of existing conventional equipment, reducing equipment costs and improving equipment reliability.

[0022] According to one embodiment of the present invention, during the demagnetization process, U2 = U + (U1 + V) is satisfied;

[0023] In the formula, U represents the voltage of the superconducting coil, U1 represents the output voltage of the excitation power supply, V represents the voltage division of the cable, U2 and U are constants, and U1 and V are variables.

[0024] The voltage U of the superconducting coil is controlled by the constant current rate of the excitation power supply, thus ensuring a constant current drop rate. Changes in V caused by variations in cable current are constantly compensated for by U1, which is automatically controlled by the excitation power supply.

[0025] Specifically, during the demagnetization process, when V decreases from V0 to 0, U1 increases from X to X+V0, where U 1，max >X+V0; where X represents the initial output voltage of the excitation power supply, and U 1，max This indicates the maximum output voltage of the excitation power supply.

[0026] X should not exceed 1V to avoid excessive voltage increase, which would increase the power supply output power, load capacity, and overall circuit power load.

[0027] Essentially, in the entire circuit, the excitation power supply is responsible for controlling the current rate, while the demagnetizing load is responsible for dissipating energy in the circuit. The two devices, connected in series, each perform their respective functions. During the entire demagnetizing process, the current rate control flow is as follows: circuit current decreases → cable voltage V decreases → due to the constant load U2, the voltage U across the coil increases → coil demagnetizing rate increases → power supply increases its own voltage U1 to stabilize the demagnetizing rate → the increase in U1 compensates for the decrease in V → coil U remains stable → demagnetizing rate stabilizes.

[0028] In this embodiment, the excitation power supply has excellent control capability over the constant current change rate, meaning that the power supply can stably maintain the superconducting coil voltage U by controlling its own output current. The power supply output voltage U1 is not a fixed value, but is automatically adjusted according to the impedance of the entire circuit to match the cable voltage divider V, thereby achieving a superconducting coil voltage U that is not affected by the cable resistance voltage divider.

[0029] Generally, without considering energy-related factors, the excitation power supply can effectively control both the rise rate and fall rate of the power supply simultaneously.

[0030] 1. Current rise rate: It can effectively control the rise rate, that is, the energy from the grid is transferred to the superconducting magnet;

[0031] 2. Current Decrease Rate: Since the power supply is generally an energy-supplying device, it cannot process the energy released during the demagnetization of the superconducting coil. Therefore, during the demagnetization process, if the demagnetization circuit of this invention is not used, the current decrease rate of the excitation power supply is low because the energy cannot be effectively released, and the control of the current decrease rate fails.

[0032] The demagnetizing load is essentially a discharge resistor. The current in the superconducting magnet flows through the discharge resistor, releasing energy and reducing the current. The demagnetizing load can achieve stable control of the constant voltage U2. Without the demagnetizing circuit of this invention, it lacks control over changing parameters such as the current rate.

[0033] The present invention also provides a constant current controlled demagnetization method for superconducting magnets, wherein the method employs any of the circuits described above for demagnetization, and the method includes:

[0034] During demagnetization, the circuit's loop current decreases, causing the voltage drop across the cable to decrease. In the absence of control, since the rated voltage of the demagnetizing load is constant, the voltage of the superconducting coil will increase, thereby increasing the demagnetization rate of the superconducting coil.

[0035] The excitation power supply increases its own output voltage to compensate for the voltage drop in the cable, so as to maintain the voltage of the superconducting coil constant and thus maintain a constant demagnetization rate.

[0036] In summary, this invention provides a constant current control demagnetization circuit and method for superconducting magnets. By connecting the excitation power supply, demagnetizing load, and superconducting magnet in series, during the demagnetization process, the excitation power supply increases its output voltage as the loop current decreases, thereby maintaining a constant demagnetization rate and achieving effective and stable control of the demagnetization current change rate of the superconducting magnet. This invention achieves controllable demagnetization rate of the superconducting magnet through the coordinated functions of different devices. Furthermore, this invention does not require the addition or development of new equipment; it only requires the use of existing conventional equipment, reducing equipment costs and improving equipment reliability.

[0037] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0038] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0039] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0040] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A constant current control demagnetizing circuit for a superconducting magnet, characterized in that, The circuit includes an excitation power supply, a demagnetizing load, and cables. The excitation power supply, the demagnetizing load, and the superconducting coil are connected in series via the cables to form a loop. The excitation power supply is used to increase its output voltage when the loop current decreases, thereby maintaining a constant demagnetizing rate. The circuit satisfies U2>U+V0, where U2 represents the rated voltage of the demagnetizing load, U represents the voltage of the superconducting coil, and V0 represents the maximum voltage drop across the cables when the superconducting coil is at full current.

2. The circuit according to claim 1, characterized in that, During the demagnetization process, U2 = U + (U1 + V) is satisfied; where U represents the voltage of the superconducting coil, U1 represents the output voltage of the excitation power supply, V represents the voltage drop across the cable, U2 and U are constants, and U1 and V are variables.

3. The circuit according to claim 1, characterized in that, During demagnetization, when V decreases from V0 to 0, U1 increases from X to X+V0, where U 1，max >X+V0; where X represents the initial output voltage of the excitation power supply, and U 1，max This indicates the maximum output voltage of the excitation power supply.

4. The circuit according to claim 3, characterized in that, X is no higher than 1V.

5. A method for demagnetizing a superconducting magnet under constant current control, characterized in that, The method employs the circuit described in any one of claims 1-3 for demagnetization, and the method includes: During demagnetization, the circuit's loop current decreases, causing the voltage drop across the cable to decrease. The excitation power supply increases its own output voltage to compensate for the voltage drop in the cable, so as to maintain the voltage of the superconducting coil constant and thus maintain a constant demagnetization rate.

Images