Device and method for measuring alternating current loss of large-diameter high-temperature superconducting coil by utilizing self-excitation compensation

Abstract

The invention belongs to the field of high-temperature superconducting, and particularly relates to an alternating-current loss measuring device and method for a large-diameter high-temperature superconducting coil by utilizing self-excitation compensation, and the device comprises a power supply loop and a measuring loop. The power supply loop comprises an alternating current power supply and a large-caliber high-temperature superconducting coil; the measuring loop comprises a compensating coil, a current sensor, a voltage lead and a signal collector; the AC power supply, the large-caliber high-temperature superconducting coil and the current sensor are connected in series; the current sensor is connected with the signal collector; the large-caliber high-temperature superconducting coil, the signal collector and the compensation coil are connected in series through a voltage lead; the compensation coil and the large-diameter high-temperature superconducting coil are arranged close to each other, so that the compensation coil and the large-diameter high-temperature superconducting coil are mutually coupled. Compared with the prior art, the method solves the problems that in the prior art, a conventional thermal measurement method and an indirect electrical measurement method need to be calibrated more complicatedly, and a direct electrical measurement method is high in requirement and large in implementation difficulty; the alternating current magnetization loss test with a simple scheme and relatively high flexibility and feasibility is realized.

Description

Technical Field

[0001] The invention belongs to the field of high-temperature superconductivity, and in particular relates to an AC loss measuring device and method for a large-caliber high-temperature superconducting coil using self-excitation compensation. Background Art

[0002] In recent years, high-temperature superconducting materials have become a research hotspot in the field of power equipment due to their characteristics of no DC resistance loss and high conduction current density. Related applications have developed rapidly, such as superconducting cables, superconducting energy storage, superconducting transformers, superconducting current limiters, superconducting motors, etc. However, high-temperature superconducting tapes are highly sensitive to external magnetic fields, that is, the superconducting tapes will produce critical current attenuation and annular eddy currents under the influence of external magnetic fields, which makes the superconducting tapes have significant resistive AC losses under AC conditions. And this AC loss will increase exponentially with the increase in the size of the superconducting magnet wound with superconducting tapes. This is because of the superposition of the spatial magnetic field of the superconducting magnet and the mutual influence between adjacent tapes. Therefore, for superconducting magnets, it is necessary to accurately evaluate, simulate and measure the AC loss of superconducting magnets, so as to equip the superconducting magnets with a suitable refrigeration system to improve the operating stability and safety of superconducting equipment.

[0003] For the AC loss test of superconducting tapes, coils and other samples, the commonly used test methods in the industry are thermal measurement and electrical measurement. The thermal measurement method is to place the superconducting magnet in a low-temperature sealed container and convert the AC loss of the superconducting magnet into the evaporation rate of the heat transfer medium (liquid nitrogen, liquid helium, etc.) for measurement. The thermal measurement method is significantly affected by additional losses such as heat leakage loss of the low-temperature container and resistance loss of the current lead. It is necessary to calibrate the natural evaporation rate of the heat transfer medium under no-load conditions. Therefore, the absolute error of the thermal measurement method due to environmental interference is large, and it is suitable for working conditions where the AC loss of the superconducting magnet itself is large. In contrast, the electrical measurement method collects the current and voltage signals of the superconducting coil and processes the electrical signals to obtain the AC loss. The methods for collecting electrical signals in the electrical measurement method are divided into direct method and indirect method. The most commonly used indirect electrical measurement method with good repeatability is to place a Rogowski coil near the sample, but this method is more complicated and also requires calibration. For different test objects, it is often necessary to obtain the corresponding conversion constants in different ways. The direct electrical measurement method is significantly affected by the inductance of the superconducting magnet itself, and it is necessary to compensate for the inductive voltage in the collected voltage signal. Usually, a compensation coil is connected in series in the measurement loop where the voltage lead is located, and the mutual inductance generated by the compensation coil and the current lead is used to offset the inductive voltage in the voltage signal. However, this method has high requirements on the compensation range of the compensation coil, so the direct electrical measurement method is usually suitable for testing superconducting tapes, superconducting cables with small inductance, and small superconducting coils with small AC losses.

[0004] After searching, it is found that the existing public patents and documents related to the AC loss electrical measurement method for superconducting coils all have the inconveniences mentioned above. The main contents of typical patents and documents are as follows:

[0005] Patent 1: Shi Zhengjun et al., a high-temperature superconducting winding AC loss test device, application publication number CN110988488A, application publication date 2020.04.10. This patent is for high-temperature superconducting windings, using Rogowski coils to sense the voltage of superconducting coils, using excitation coils and compensation coils to generate reverse mutual inductance, and subtracting the voltage and reverse mutual inductance of the Rogowski coils in a differential manner to obtain the final voltage signal. This solution combines the complexity of the indirect electrical measurement method that requires calibration and the high requirements of additional excitation coils and compensation coils for large-diameter high-temperature superconducting coils, and the engineering implementation is difficult.

[0006] Patent 2: Zhu Jiahui et al., A method for measuring AC loss compensation of a high-temperature superconducting unit, application publication number CN105277798A, application publication date 2016.01.27. This patent is similar to Patent 1, and also uses a Rogowski coil to sense the voltage of the superconducting coil and a compensation coil to generate reverse mutual inductance, and it also has the above-mentioned problems.

[0007] Literature: W.Yuan et al., "Measurements and calculations of transport ACloss in second generation high temperature superconducting pancake coils," Journal of Applied Physics, vol.110, no.11, 2011, Art no.113906.

[0008] In 2011, this document proposed a direct electrical measurement method for superconducting coils. A compensation coil is connected in series in the measurement loop where the voltage lead is located. The position of the compensation coil is adjusted to change the mutual inductance between the compensation coil and the current lead, thereby compensating the voltage signal of the superconducting coil. However, this solution has high requirements for the current lead and the compensation coil.

[0009] Taking the above working conditions into consideration, large-diameter (meter-level) high-temperature superconducting coils have relatively large inductance, and using the above-mentioned existing technologies to measure their AC losses faces a relatively awkward situation: it is difficult to compensate for the inductance using conventional direct electrical measurement methods and indirect electrical measurement methods; and the thermal measurement method has a large error and is not suitable for working conditions where the coil AC loss is small; at the same time, the preparation work for the thermal measurement method and the indirect electrical measurement method is complicated and requires preliminary calibration. When using the direct electrical measurement method, it is also limited by the adjustment range of the current lead and the corresponding compensation coil.

[0010] Therefore, it is necessary to consider designing a more convenient and flexible AC loss electrical measurement method suitable for large-diameter high-temperature superconducting coils. Summary of the invention

[0011] The purpose of the present invention is to provide an AC loss measurement device and method for a large-diameter high-temperature superconducting coil using self-excitation compensation in order to solve at least one of the above problems, so as to solve the problem that the direct electrical measurement method and the indirect electrical measurement method are difficult to compensate the inductance and the thermal measurement method has large errors for the AC loss measurement of large-diameter high-temperature superconducting coils in the prior art. The present invention directly couples the compensation coil and the large-diameter high-temperature superconducting coil to be tested, and generates reverse mutual inductance in the compensation coil by self-excitation of the large-diameter high-temperature superconducting coil, thereby realizing an AC magnetization loss test with a simple solution, high flexibility and feasibility.

[0012] The purpose of the present invention is achieved through the following technical solutions:

[0013] The first aspect of the present invention discloses an AC loss measuring device for a large-caliber high-temperature superconducting coil using self-excitation compensation, comprising a power supply circuit and a measurement circuit;

[0014] The power supply circuit includes an AC power supply and a large-diameter high-temperature superconducting coil;

[0015] The measuring circuit comprises a compensation coil, a current sensor, a voltage lead and a signal collector;

[0016] The AC power supply, the large-diameter high-temperature superconducting coil and the current sensor are connected in series to form a loop; the current sensor is connected to a signal collector to collect current signals passing through the large-diameter high-temperature superconducting coil;

[0017] The large-diameter high-temperature superconducting coil, the signal collector and the compensation coil are connected in series through a voltage lead to form a loop for collecting voltage signals at both ends of the large-diameter high-temperature superconducting coil; and the compensation coil is arranged close to the large-diameter high-temperature superconducting coil so that the compensation coil and the large-diameter high-temperature superconducting coil are coupled to each other for compensating the inductive voltage.

[0018] Preferably, the compensation coil is wound with enameled wire.

[0019] Preferably, the diameter of the enameled wire is 0.05-0.6 mm, which reduces the eddy current loss of the compensation coil to the milliwatt level to reduce the absolute error of the measurement.

[0020] More preferably, the diameter of the enameled wire is 0.1-0.25 mm. Small diameter enameled wire is preferred, but considering its brittleness limit and number of turns requirement, 0.1 mm can be selected for a small number of turns, and 0.25 mm can be used for a large number of turns.

[0021] Preferably, the device further comprises a three-axis positioning system, and the compensation coil is connected to the output end of the three-axis positioning system through a mechanical support component. The three-axis positioning system can adopt a structure such as a three-axis mechanical arm.

[0022] Preferably, the portion of the mechanical support component close to the large-diameter high-temperature superconducting coil is made of non-metallic material, which reduces the interference of metal eddy current loss while ensuring mechanical strength.

[0023] Preferably, the phases of the voltage signal and the current signal of the compensation coil are consistent with those of the large-diameter high-temperature superconducting coil to complete the compensation.

[0024] Preferably, the signal collector includes an oscilloscope.

[0025] Preferably, the current sensor comprises a current transformer.

[0026] The second aspect of the present invention discloses a method for measuring AC loss using a large-diameter high-temperature superconducting coil using self-excitation compensation as described above, wherein the AC power supply supplies power to the large-diameter high-temperature superconducting coil to be tested, the generated current signal is collected by the current sensor and transmitted to the signal collector, the generated voltage signal is collected through the voltage lead and transmitted to the signal collector, the compensation coil is self-excited by the large-diameter high-temperature superconducting coil and generates reverse mutual inductance to compensate for the inductive voltage; the signal collector obtains the AC loss by integrating the product of the current and the voltage.

[0027] Preferably, the temperature of the large-diameter high-temperature superconducting coil in the test is controlled to be below the superconducting critical temperature.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention designs an AC loss measurement device and method for self-excitation compensation of large-diameter high-temperature superconducting coils. The advantage is that the compensation coil is directly coupled to the large-diameter high-temperature superconducting coil to be tested, and reverse mutual inductance is generated in the compensation coil by self-excitation of the superconducting coil, which reduces the complexity and size of the test system construction, and the test scheme is simple, flexible and feasible. At the same time, in this scheme, the compensation coil is wound with the thinnest enameled wire, and the eddy current loss of the compensation coil is reduced to the milliwatt level, which greatly reduces the absolute error of the scheme. This scheme also uses the compensation coil three-axis positioning system to accurately position and adjust the compensation coil, thereby increasing the possibility of the test system to achieve complete compensation. Therefore, this scheme has both accuracy and engineering feasibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a structural schematic diagram of an AC loss measuring device for a high-temperature superconducting coil in the prior art;

[0031] Figure 2 It is a structural schematic diagram of an AC loss measuring device for a large-caliber high-temperature superconducting coil of the present invention;

[0032] Figure 3 It is a structural schematic diagram of the arrangement of the three-axis positioning system, the compensation coil and the large-caliber high-temperature superconducting coil of the present invention;

[0033] In the figure: 1-power supply circuit; 2-measurement circuit; 3-AC power supply; 4-large-diameter high-temperature superconducting coil; 5-compensation coil; 6-current sensor; 7-voltage lead; 8-signal collector; M-mutual inductance; 10-current lead; 11-three-axis positioning system; 12-mechanical support components. DETAILED DESCRIPTION

[0034] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and specific operation process are given. It should be pointed out that for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

[0036] Figure 1 The structure diagram of the existing AC loss measurement device (direct electrical measurement method) is shown in FIG. In order to provide a reverse mutual inductance M to the large-diameter high-temperature superconducting coil 4 and eliminate the inductive voltage, the compensation coil 5 needs to be coupled with an inductor formed by an additional current lead 10. Usually, the current lead 10 exists in the form of a transformer or other large inductor. Figure 1 The conventional AC loss electrical measurement method shown has high requirements on the adjustment range of the current lead 10 and the compensation coil 5, and the overall system is large and complex, and inconvenient to use.

[0037] Example

[0038] An AC loss measuring device for a large-diameter high-temperature superconducting coil 4 using self-excitation compensation, such as Figure 2 , 3 As shown, it includes a power supply circuit 1 and a measurement circuit 2;

[0039] The power supply circuit 1 includes an AC power supply 3 and a large-diameter high-temperature superconducting coil 4;

[0040] The measuring circuit 2 comprises a compensation coil 5, a current sensor 6, a voltage lead 7 and a signal collector 8;

[0041] The AC power supply 3, the large-diameter high-temperature superconducting coil 4 and the current sensor 6 are connected in series to form a loop; the current sensor 6 is connected to the signal collector 8 to collect the current signal passing through the large-diameter high-temperature superconducting coil 4;

[0042] The large-diameter high-temperature superconducting coil 4, the signal collector 8 and the compensation coil 5 are connected in series through the voltage lead 7 to form a loop, which is used to collect the voltage signal at both ends of the large-diameter high-temperature superconducting coil 4; and the compensation coil 5 is arranged close to the large-diameter high-temperature superconducting coil 4, so that the compensation coil 5 and the large-diameter high-temperature superconducting coil 4 are coupled to each other to compensate for the inductive voltage.

[0043] More specifically, in this embodiment:

[0044] like Figure 2 As shown, the device includes a power supply circuit 1 and a measurement circuit 2.

[0045] First, in the power supply circuit 1, the AC power supply 3 and the large-diameter high-temperature superconducting coil 4 are connected in series.

[0046] Then, in the measurement loop 2, the compensation coil 5 is placed near the large-diameter high-temperature superconducting coil 4 and directly coupled with the superconducting coil. The current sensor 6 (using a current transformer) is placed in series in the power supply loop 1 to collect the current signal, and the voltage lead 7 and the compensation coil 5 are connected in series to collect the voltage signal. The current signal and the voltage signal are input into the signal acquisition instrument (using an oscilloscope) to obtain the AC loss experimental measurement value.

[0047] Furthermore, the superconducting coil self-excites the compensation coil 5 to generate a mutual inductance M for eliminating the inductive voltage.

[0048] Furthermore, the compensation coil 5 should be wound with the thinnest enameled wire available on the market (e.g., 0.05-0.6 mm, specifically, 0.1 mm / 0.25 mm), and the eddy current loss of the compensation coil 5 should be reduced to the milliwatt level to reduce the absolute error of the measurement. The specific wire diameter should be determined according to the actual number of turns and the brittleness of the enameled wire. When the number of turns meets the requirements and the compensation coil 5 (enameled wire) is intact and not broken, a smaller wire diameter is preferred.

[0049] Furthermore, if Figure 3As shown, a three-axis positioning system 11 can also be installed in the device to accurately position and adjust the compensation coil 5. Then, the compensation coil 5 is moved by the three-axis positioning system 11, and the current signal I and the voltage signal U in the oscilloscope are synchronously observed. When the two signals are in a state of completely consistent phase, the compensation is completed. The three-axis positioning system 11, the compensation coil 5 and the large-diameter high-temperature superconducting coil 4 are arranged vertically, and the three-axis positioning system 11 drives the compensation coil 5 to be accurately positioned and adjusted above the large-diameter high-temperature superconducting coil 4 until the voltage signal and the current signal are in a state of completely consistent phase.

[0050] Furthermore, the three-axis positioning system 11 is connected to the compensation coil 5 via a mechanical support component 12. The mechanical support component 12 is made of non-metallic material at one end close to the large-diameter high-temperature superconducting coil 4 to ensure mechanical strength while reducing interference from metal eddy current loss.

[0051] The specific implementation of the measurement method of the measurement system is: through the AC power supply 3, current signals of different amplitudes and frequencies are generated to power the large-diameter high-temperature superconducting coil 4 to be tested. The current signal flowing through the superconducting coil is collected by the current transformer, and the voltage signal is collected by the voltage lead 7. In particular, a compensation coil 5 is connected in series in the measurement loop 2 where the voltage lead 7 is located to compensate for the inductive voltage and retain the resistive component. The voltage and current signals are filtered and amplified and then output to the oscilloscope. The voltage and current signals are intuitively obtained and can be observed at the same time using a high-performance oscilloscope. Finally, the AC loss is obtained by integrating the product of current and voltage. During the measurement process, the temperature of the large-diameter high-temperature superconducting coil 4 is controlled to be lower than its superconducting critical temperature, so that the test can be carried out normally and stably.

[0052] In summary, the present invention designs an AC loss electrical measurement method for self-excitation compensation of large-diameter high-temperature superconducting coils 4 and a corresponding measurement device. Its advantage is that the compensation coil 5 is directly coupled with the large-diameter high-temperature superconducting coil 4 to be measured, and a reverse mutual inductance is generated in the compensation coil 5 by self-excitation of the superconducting coil, which reduces the complexity and size of the test system construction, and has high flexibility and feasibility. At the same time, in this scheme, the compensation coil 5 is formed by winding an enameled wire with a wire diameter as thin as possible, and the eddy current loss of the compensation coil 5 is reduced to the milliwatt level, which greatly reduces the absolute error of the scheme. This scheme also accurately positions and adjusts the compensation coil 5 through a three-axis positioning system 11 to ensure that the current and voltage signals of the large-diameter high-temperature superconducting coil 4 and the compensation coil 5 are in a completely consistent state during the test, thereby increasing the possibility of the test system achieving complete compensation. Therefore, this scheme has both accuracy and engineering feasibility.

[0053] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. An AC loss measuring device for a large-diameter high-temperature superconducting coil using self-excitation compensation, characterized in that: It comprises a power supply circuit (1) and a measurement circuit (2); The power supply circuit (1) comprises an AC power supply (3) and a large-diameter high-temperature superconducting coil (4); The measuring circuit (2) comprises a compensation coil (5), a current sensor (6), a voltage lead (7) and a signal collector (8); The AC power source (3), the large-diameter high-temperature superconducting coil (4) and the current sensor (6) are connected in series to form a loop; the current sensor (6) is connected to a signal collector (8) for collecting current signals passing through the large-diameter high-temperature superconducting coil (4); The large-diameter high-temperature superconducting coil (4), the signal collector (8) and the compensation coil (5) are connected in series via a voltage lead (7) to form a loop for collecting voltage signals at both ends of the large-diameter high-temperature superconducting coil (4); and the compensation coil (5) is arranged close to the large-diameter high-temperature superconducting coil (4) so ​​that the compensation coil (5) and the large-diameter high-temperature superconducting coil (4) are coupled to each other for compensating for inductive voltage.

2. The AC loss measuring device of a large-diameter high-temperature superconducting coil using self-excitation compensation according to claim 1, characterized in that: The compensation coil (5) is wound with enameled wire.

3. The AC loss measuring device of a large-diameter high-temperature superconducting coil using self-excitation compensation according to claim 2, characterized in that: The diameter of the enameled wire is 0.05-0.6 mm.

4. The AC loss measuring device of a large-diameter high-temperature superconducting coil using self-excitation compensation according to claim 1, characterized in that: The device also includes a three-axis positioning system (11), and the compensation coil (5) is connected to the output end of the three-axis positioning system (11) through a mechanical support component (12).

5. The AC loss measuring device of a large-diameter high-temperature superconducting coil using self-excitation compensation according to claim 4, characterized in that: The portion of the mechanical support component (12) close to the large-diameter high-temperature superconducting coil (4) is made of non-metallic material.

6. The AC loss measuring device of a large-diameter high-temperature superconducting coil using self-excitation compensation according to claim 1, characterized in that: The phases of the voltage signal and the current signal of the compensation coil (5) and the large-caliber high-temperature superconducting coil (4) are consistent.

7. The AC loss measuring device of a large-diameter high-temperature superconducting coil using self-excitation compensation according to claim 1, characterized in that: The signal collector (8) comprises an oscilloscope.

8. The AC loss measuring device of a large-diameter high-temperature superconducting coil using self-excitation compensation according to claim 1, characterized in that: The current sensor (6) comprises a current transformer.

9. A method for measuring AC loss using the large-diameter high-temperature superconducting coil using self-excitation compensation as claimed in any one of claims 1 to 8, characterized in that: The AC power source (3) supplies power to the large-diameter high-temperature superconducting coil (4) to be tested, the generated current signal is collected by the current sensor (6) and transmitted to the signal collector (8), the generated voltage signal is collected through the voltage lead (7) and transmitted to the signal collector (8), the compensation coil (5) is self-excited by the large-diameter high-temperature superconducting coil (4) and generates reverse mutual inductance to compensate for the inductive voltage; the signal collector (8) obtains the AC loss by integrating the product of the current and the voltage.

10. The method for measuring AC loss of a large-diameter high-temperature superconducting coil using self-excitation compensation according to claim 9, characterized in that: In the test, the temperature of the large-diameter high-temperature superconducting coil (4) is controlled to be lower than the superconducting critical temperature.

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