Thermally isolated superconducting coil current measurement circuit, apparatus and magnetic levitation train

Abstract

A thermally isolated superconducting coil current measurement circuit, an apparatus, and a magnetic levitation train. The thermally isolated superconducting coil current measurement circuit comprises: a current sensor, used to measure an operating current of a superconducting coil; an electrical-acoustic-electrical conversion circuit, used to first convert an output signal of the current sensor into an ultrasonic wave, and then, after the ultrasonic wave passes through a magnetic pole housing of the superconducting coil, capture the ultrasonic wave outside the magnetic pole housing, convert the captured ultrasonic wave into an electrical signal, and finally transmit the electrical signal to a subsequent circuit. Thus, it is possible for a result collected by the sensor to be transmitted to the outside of the magnetic pole housing of the superconducting coil without requiring wires. The magnetic pole housing can remain sealed, and there is no electrical connection between the high- and low-temperature environments inside and outside, effectively avoiding heat loss caused by physical wiring. Using a sound wave as a signal conversion carrier is not easily affected by the magnetic field of the environment, which can effectively ensure the accuracy of current monitoring data and the reliability of the measurement process.

Description

A thermal isolation type superconducting coil current measurement circuit, device and maglev train TECHNICAL FIELD

[0001] The present application claims priority to the domestic application filed on August 15, 2024 with the China Patent Office and with application number CN202411123861.9, and with the title of "A thermal isolation type superconducting coil current measurement circuit, device and maglev train", the entire content of which is incorporated herein by reference. BACKGROUND

[0002] With the continuous improvement of the speed level of high-speed trains, the traditional wheel-rail system is increasingly close to its upper limit of running speed due to limitations such as friction loss, vibration and safety. The maglev vehicle uses electromagnetic force to replace the wheel-rail contact force to achieve support, guidance, traction and braking, has no direct mechanical contact with the track, and is not limited by the traditional wheel-rail adhesion limit, has the advantages of low vibration and noise, smooth running, small turning radius, strong climbing ability, etc., and can achieve higher running speed.

[0003] High-temperature superconducting maglev technology uses the relative motion between the magnet and the conductor to generate eddy currents, i.e., induced magnetic fields, in the conductor. The induced magnetic field and the magnetic field of the magnet interact to generate electromagnetic force, thereby achieving levitation. During the development, testing and operation of high-temperature superconducting magnets, effective monitoring of the current in the superconducting coil is one of the key technical links. Since the superconducting coil operates in a low-temperature environment, traditional current monitoring devices generally need to use a lead to transmit signals from the inside of the superconducting magnet to the outside. Due to the large temperature difference between the inside and outside of the magnet, heat conduction during monitoring is difficult to avoid, which affects the temperature of the magnet and thus deteriorates the working characteristics of the superconducting magnet. Therefore, how to effectively output the sensing signals inside the magnet without losing heat is an important means to improve the research, testing and application capabilities of high-temperature superconducting maglev technology.

[0004] SUMMARY

[0005] Therefore, the embodiments of the present application provide a thermal isolation type superconducting coil current measurement circuit, device and maglev train to effectively output the sensing signals inside the magnet without losing heat.

[0006] To achieve the above object, the embodiments of the present application provide the following technical solutions:

[0007] A thermal isolation type superconducting coil current measurement circuit, comprising:

[0008] a current sensor, configured to measure the operating current of the superconducting coil;

[0009] An electro-acoustic-electric conversion circuit is used to convert the output signal of the current sensor into ultrasonic waves, capture the ultrasonic waves outside the magnetic pole shell after the ultrasonic waves pass through the magnetic pole shell of the superconducting coil, convert the captured ultrasonic waves into an electric signal, and finally send the electric signal to a subsequent circuit.

[0010] Optionally, in the above-mentioned thermal isolation type superconducting coil current measurement circuit, the electro-acoustic-electric conversion circuit comprises:

[0011] A current converter is connected to the output end of the current sensor, used to convert the output signal of the current sensor into an alternating current signal.

[0012] An excitation ultrasonic transducer is connected to the output end of the current converter.

[0013] A receiving ultrasonic transducer is connected to the output end of the excitation ultrasonic transducer.

[0014] Optionally, in the above-mentioned thermal isolation type superconducting coil current measurement circuit, the current converter is a voltage-controlled oscillator.

[0015] Optionally, in the above-mentioned thermal isolation type superconducting coil current measurement circuit, further comprising:

[0016] A power amplifier is arranged between the current converter and the excitation ultrasonic transducer.

[0017] Optionally, in the above-mentioned thermal isolation type superconducting coil current measurement circuit, further comprising:

[0018] The power amplifier is a power amplifier with adjustable amplification.

[0019] Optionally, in the above-mentioned thermal isolation type superconducting coil current measurement circuit, the excitation ultrasonic transducer and the receiving ultrasonic transducer are embedded on both sides of the magnetic pole shell.

[0020] Optionally, in the above-mentioned thermal isolation type superconducting coil current measurement circuit, the subsequent circuit comprises:

[0021] A monitor is connected to the output end of the electro-acoustic-electric conversion circuit, used to acquire and process the voltage signal collected by the output end of the electro-acoustic-electric conversion circuit to obtain the operating current of the superconducting coil.

[0022] Optionally, in the above-mentioned thermal isolation type superconducting coil current measurement circuit, further comprising:

[0023] An inductive power receiver cooperates with an inductive power transmitter to couple the obtained AC power to a power module;

[0024] An AC / DC power module for powering the power consuming modules inside the magnetic pole housing.

[0025] A thermal isolation type superconducting coil current measurement device, comprising:

[0026] A superconducting magnet, a magnetic pole housing, and the thermal isolation type superconducting coil current measurement circuit of any one of the above.

[0027] A magnetic levitation train comprising the thermal isolation type superconducting coil current measurement device.

[0028] Based on the above technical solutions, the present application processes the output voltage of the current sensor through an electric-acoustic-electric conversion circuit, and transmits the collection results of the sensor to the outside of the magnet housing of the superconducting magnet through an electric-acoustic-electric conversion mode without a wire, so that the magnet housing of the superconducting magnet can be kept in a sealed state, and the high and low temperature environments inside and outside the magnet housing are not electrically connected, which can effectively avoid heat loss caused by physical leads. As a signal conversion carrier, the acoustic wave is not easily affected by the environmental magnetic field, and can effectively ensure the accuracy of the current monitoring data and the reliability of the measurement process. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiment or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the present application, and those skilled in the art can obtain other drawings according to the provided drawings without creative labor.

[0030] Fig. 1 is a structural schematic diagram of a thermal isolation type superconducting coil current measurement circuit disclosed by an embodiment of the present application;

[0031] Fig. 2 is a structural schematic diagram of a thermal isolation type superconducting coil current measurement circuit disclosed by another embodiment of the present application;

[0032] Fig. 3 is a signal conversion schematic diagram between a current sensor and a current converter;

[0033] Fig. 4 is a signal conversion schematic diagram between an excitation ultrasonic transducer and a receiving ultrasonic transducer;

[0034] Fig. 5 is a signal conversion schematic diagram between a current sensor, a current converter and a power amplifier;

[0035] Fig. 6 is a schematic diagram of the relationship between the sound pressure output by the excitation ultrasonic transducer and the frequency of the excitation signal;

[0036] Fig. 7 is a schematic diagram of the sound pressure amplitude in the ultrasonic waves received by the receiving ultrasonic transducer when the measured current is 0 ampere-hour;

[0037] Fig. 8 is a schematic diagram of the sound pressure amplitude in the ultrasonic waves received by the receiving ultrasonic transducer when the measured current is 100 ampere-hour;

[0038] Fig. 9 is a schematic diagram of the sound pressure amplitude in the ultrasonic waves received by the receiving ultrasonic transducer when the measured current is 200 ampere-hour. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0040] The purpose of the present application is to provide a thermal isolation type superconducting coil current measurement scheme, which takes the electric-acoustic conversion as the core idea, converts the voltage signal output by the current sensor into an ultrasonic level vibration signal, transmits the vibration signal to the outside of the magnetic pole through the magnetic pole shell, and restores it into a processable electric signal, so as to achieve the purpose of online monitoring the running current of the magnetic pole coil under the condition of no heat loss.

[0041] Referring to Fig. 1, the vehicle-mounted air conditioner detection device disclosed in the embodiments of the present application can include a current sensor 100 and an electric-acoustic-electric conversion circuit 200.

[0042] A current sensor 100 is used to measure the operating current of the superconducting coil, and specifically, the current sensor 100 can convert the operating current in the superconducting coil into a direct current voltage signal through the principle of electromagnetic induction. The current sensor 100 is in a ring structure and surrounds the monitored superconducting coil. When the superconducting coil has current inside, according to the principle of electromagnetic induction, there is a corresponding magnetic field around the superconducting coil. The magnetic field acts on the current sensor 100, so that the sensitive element inside the current sensor 100 generates an induced electromotive force. The induced electromotive force is linearly related to the operating current in the measured superconducting coil. As the operating current in the measured superconducting coil increases, the induced electromotive force also increases, and the induced electromotive force is output in the form of a direct current voltage by the current sensor 100. Because the superconducting coil usually operates in extreme environmental conditions, the current sensor 100 capable of measuring the operating current of the superconducting coil needs to meet the requirements of high precision, high stability and anti-electromagnetic interference, etc. In the embodiment, the type of the current sensor 100 can be a Hall current sensor 100, an optical fiber current sensor 100, a fluxgate current sensor 100, an electronic current transformer, and a Rogowski coil. The range of the current sensor 100 can be selected according to the design requirements. In the technical solution disclosed in the embodiment, the range of the current sensor 100 can be 0-200A, and the corresponding output voltage is 0-10V.

[0043] An electro-acoustic-electric conversion circuit 200 is used to convert the output signal of the current sensor 100 into an ultrasonic wave first, capture the ultrasonic wave outside the magnetic pole shell of the superconducting coil after the ultrasonic wave passes through the magnetic pole shell, and convert the captured ultrasonic wave into an electric signal. Finally, the electric signal is sent to the rear circuit, so that the rear circuit obtains the operating current of the superconducting coil based on the obtained electric signal.

[0044] As can be seen from the above scheme, the output voltage of the current sensor 100 is processed by the electro-acoustic-electric conversion circuit 200. Through the electro-acoustic-electric conversion mode, the collection result of the sensor can be transmitted to the outside of the magnet shell of the superconducting magnet without a wire, so that the magnet shell of the superconducting magnet can maintain a sealed state, and there is no electrical connection between the inside and outside of the magnet shell. The high and low temperature environments can effectively avoid heat loss caused by physical leads. As a signal conversion carrier, the acoustic wave is not easily affected by the environmental magnetic field, which can effectively ensure the accuracy of the current monitoring data and the reliability of the measurement process.

[0045] The structure of the electro-acoustic-electric conversion circuit 200 can be set by itself according to design requirements, and the structure of the electro-acoustic-electric conversion circuit 200 mainly relates to an electro-acoustic transducer, which is a device for converting electrical energy into acoustic energy or converting acoustic energy into electrical energy. Specifically, referring to FIG. 2, the electro-acoustic-electric conversion circuit 200 disclosed by the embodiment of the present application can include: a current converter 201, an excitation ultrasonic transducer 202, and a receiving ultrasonic transducer 203.

[0046] The input end of the current converter 201 is connected with the output end of the current sensor 100, referring to FIG. 3, for converting the output signal of the current sensor 100 into an alternating current signal. A voltage-controlled oscillator can be used as the current converter 201 in the present application. The direct current voltage signal output by the current sensor 100 is modulated into a high-frequency alternating current signal by the voltage-controlled oscillator, and the frequency of the alternating current signal output by the voltage-controlled oscillator has a linear relationship with the input direct current voltage. The greater the input direct current voltage, the higher the frequency of the alternating current signal output, and vice versa. Corresponding to the current sensor 100, the input voltage range of the voltage-controlled oscillator is 0-10V, and the corresponding output signal frequency is 0-500kHz.

[0047] The input end of the excitation ultrasonic transducer 202 is connected with the output end of the current converter 201. Referring to FIG. 4, the excitation ultrasonic transducer 202 is used for converting the alternating current signal output by the current converter 201 into an ultrasonic wave signal. The excitation ultrasonic transducer 202 can emit ultrasonic waves under the excitation of a high-frequency and high-voltage signal. Referring to FIG. 2, according to the working principle of a piezoelectric crystal, when the frequency of the excitation signal is equal to the natural frequency of the crystal, the ultrasonic vibration amplitude generated under the action of the excitation signal is maximum. With the deviation of the excitation signal frequency from the natural frequency of the piezoelectric crystal, the ultrasonic vibration amplitude generated decreases. When the operating current of the measured superconducting coil is the upper limit of the range of the current sensor 100, that is, Imax, the induced voltage Vmax output by the current sensor 100, and the frequency fmax of the output signal of the current converter 201 are equal to the natural frequency f0 of the excitation ultrasonic transducer 202 (the natural frequency of the piezoelectric crystal in the excitation ultrasonic transducer 202). At this time, the sound pressure amplitude Amax of the ultrasonic wave emitted by the excitation ultrasonic transducer 202 is maximum. With the decrease of the operating current of the measured superconducting coil, the sound pressure amplitude of the ultrasonic wave emitted by the excitation ultrasonic transducer 202 decreases. When the operating current of the measured superconducting coil is 0, the output voltage of the current sensor 100 is 0V, and the current converter 201 does not generate any alternating current signal. At this time, the excitation ultrasonic transducer 202 also does not emit ultrasonic waves. Therefore, the operating current value of the measured superconducting coil represented by the sound pressure amplitude in the ultrasonic monitoring signal can be obtained, and the operating current value of the measured superconducting coil and the sound pressure amplitude of the ultrasonic wave output by the excitation ultrasonic transducer 202 satisfy the following relationship: I=kxA

[0048] In the formula, I is the operating current value of the measured superconducting coil, A is the sound pressure amplitude of the ultrasonic wave output by the excitation ultrasonic transducer 202, and k is a preset linear constant.

[0049] The input end of the receiving ultrasonic transducer 203 is connected to the output end of the excitation ultrasonic transducer 202, as shown in FIG. 4, which is used to convert the received vibration signal (ultrasonic wave in the form of vibration signal sent to the receiving ultrasonic transducer 203) into an electric energy signal by using the piezoelectric effect, and send the electric energy signal to the subsequent circuit, so that the subsequent circuit calculates the operating current of the measured superconducting coil based on the electric energy signal. In the technical solution disclosed in the embodiment of the present application, corresponding to the above-mentioned voltage-controlled oscillator, the natural frequency of the excitation ultrasonic transducer 202 and the receiving ultrasonic transducer 203 is 500 kHz.

[0050] Further, in the technical solution disclosed in the embodiment of the present application, in order to adapt the output signal of the current converter 201 to the excitation ultrasonic transducer 202, a power amplifier 204 can also be arranged between the output signal of the current converter 201 and the excitation ultrasonic transducer 202, as shown in FIG. 5, the power amplifier is used for characteristic modulation and power amplification of the output signal of the current converter 201, amplifying the signal from millivolt voltage to 100V or more, and applying the amplified signal to the excitation ultrasonic transducer 202. Further, in order to make the heat-isolated superconducting coil current measurement circuit have a wider application scenario, the power amplifier in the present application is a power amplifier with adjustable amplification multiple, by adjusting the amplification multiple of the power amplifier, the heat-isolated superconducting coil current measurement circuit can measure the operating current of the superconducting coil more accurately.

[0051] In the technical solution disclosed in the embodiment of the present application, the interaction signal between the excitation ultrasonic transducer 202 and the receiving ultrasonic transducer 203 is an ultrasonic wave, the ultrasonic wave signal can be transmitted by vibration, and the magnetic pole shell of the superconducting coil can be used as the transmission medium of the ultrasonic wave signal. At this time, in the embodiment, the excitation ultrasonic transducer 202 and the receiving ultrasonic transducer 203 can be fixed on both sides of the magnetic pole shell, wherein the excitation ultrasonic transducer 202 is embedded on the inner side of the magnetic pole shell, and the receiving ultrasonic transducer 203 is embedded on the outer side of the magnetic pole shell. The ultrasonic wave signal is transmitted from the excitation ultrasonic transducer 202 end to the receiving ultrasonic transducer 203 end through the magnetic pole shell. At this time, there is no need to set a threading hole on the magnetic pole shell, so that the sealing of the internal space of the magnetic pole shell is maintained.

[0052] As to the post-stage circuit, the application can select a suitable device as the post-stage circuit according to different design requirements. In the technical solution disclosed in the embodiment, the post-stage circuit can be a monitor, a processor or other devices. Taking the monitor as an example, the monitor is connected with the output end of the electro-acoustic-electric conversion circuit 200, used for acquiring and processing the voltage signal collected by the output end of the electro-acoustic-electric conversion circuit 200, and calculating the operating current of the superconducting coil. At this time, the monitor is responsible for the control of the whole system and the processing of monitoring information.

[0053] In the technical solution disclosed in the embodiment, in order to facilitate the power consumption of the electrical devices inside the magnetic pole shell in the heat-isolated superconducting coil current measurement circuit, the application can set a power module 300 inside the magnetic pole shell, and the power module 300 is used for supplying power to the electrical modules inside the magnetic pole shell, which include but are not limited to the current sensor 100, the current converter 201 and the power amplifier.

[0054] In the embodiment, the power module 300 can be an AC / DC power module, which is used for converting the acquired alternating current into direct current suitable for each electrical module.

[0055] In order to charge the AC / DC power module and ensure the reliable work of the heat-isolated superconducting coil current measurement circuit, the heat-isolated superconducting coil current measurement circuit can further include an inductive power receiver 400 and an inductive power transmitter 500. The inductive power receiver 400 and the inductive power transmitter 500 cooperate with each other to couple the acquired alternating current (which can be provided by the post-stage circuit) to the power module. At this time, the AC / DC power module, the inductive power receiver 400 and the inductive power transmitter 500 are responsible for the power supply of each electrical module inside the magnetic pole shell. The AC / DC power module and the inductive power receiver 400 are located inside the magnetic pole shell, and the inductive power transmitter 500 is located outside the magnetic pole shell. The inductive power receiver 400 and the inductive power transmitter 500 are located opposite to each other and on both sides of the magnetic pole shell. The external alternating current is coupled to the inductive power receiver 400 through the inductive power transmitter 500, and is converted into direct current by the AC / DC power module. At this time, the inductive power transmitter 500, the inductive power receiver 400 and the magnetic pole shell jointly constitute a voltage transformer. The magnetic pole shell serves as the core of the voltage transformer. Thus, the alternating current outside the magnetic pole shell can be transmitted to the inside of the magnetic pole shell in an isolated manner without damaging the magnetic pole shell, thereby maintaining the sealing property of the magnetic pole shell.

[0056] The working process of the present solution will be described in detail below by taking the complete structure in FIG. 2 and the specific configuration parameters as examples.

[0057] (1) The range of current sensor 100 is 0-200A, and the corresponding output voltage is 0-10V. The input voltage range of voltage-controlled oscillator is 0-10V, and the corresponding output signal frequency is 0-500kHz. The inherent frequency of both the excitation ultrasonic transducer 202 and the receiving ultrasonic transducer 203 is 500kHz, and the corresponding relationship between the sound pressure and the excitation signal frequency is shown in Fig. 6.

[0058] (2) As shown in Fig. 7, when the operating current of the measured superconducting coil is 0, the current sensor 100 outputs a 0V voltage signal, the voltage-controlled oscillator does not produce any alternating output, and the excitation ultrasonic transducer 202 does not emit ultrasonic waves. At this time, the amplitude of the sound pressure in the ultrasonic signal received by the receiving ultrasonic transducer 203 is 0. Referring to Fig. 8, when the operating current of the measured superconducting coil is 100A, the current sensor 100 outputs a 5V voltage signal, the voltage-controlled oscillator produces an alternating signal with a frequency of 250kHz, and the excitation ultrasonic transducer 202 emits ultrasonic waves with a corresponding intensity. At this time, the amplitude of the sound pressure in the ultrasonic signal received by the receiving ultrasonic transducer 203 is 0.25MPa. Referring to Fig. 9, when the operating current of the measured superconducting coil is 200A, the current sensor 100 outputs a 10V voltage signal, the voltage-controlled oscillator produces an alternating signal with a frequency of 500kHz, and the excitation ultrasonic transducer 202 emits ultrasonic waves with a corresponding intensity. At this time, the amplitude of the sound pressure in the ultrasonic signal received by the receiving ultrasonic transducer 203 is 0.5MPa. The operating current I of the measured superconducting coil and the amplitude P of the ultrasonic signal satisfy the following relationship: I = 400P. After P is determined, the operating current I of the superconducting coil can be obtained by back calculation.

[0059] As can be seen from the above embodiments, the thermal isolation type superconducting coil current measurement circuit provided by the present application is composed of a current sensor 100, a voltage-controlled oscillator, a power amplifier 204, an excitation ultrasonic transducer 202, a receiving ultrasonic transducer 203, an AC / DC power supply module, an inductive power receiver 400, an inductive power transmitter 500, and a monitor.

[0060] The current sensor converts the current in the superconducting coil into a direct current voltage signal through electromagnetic induction principle. The direct current voltage signal is modulated into a high-frequency alternating current signal by the voltage-controlled oscillator, and is applied to the excitation ultrasonic transducer after being amplified by the power amplifier. The excitation ultrasonic transducer emits ultrasonic waves with a specific frequency and energy under the action of high-frequency and high-voltage electric signals. The ultrasonic waves are conducted from the inside to the outside through the magnetic pole shell and are captured by the receiving ultrasonic transducer, which converts them back into voltage signals through inverse piezoelectric effect. Finally, the monitor processes the signals to complete the online monitoring of the operating current of the superconducting coil.

[0061] The application takes the signal conversion of electricity-sound-electricity as the core, and transmits the sensing signal in the low-temperature environment inside the superconducting magnetic pole to the high-temperature environment outside the magnetic pole. The high-temperature and low-temperature environments inside and outside the magnetic pole are not electrically connected, so that heat loss caused by physical leads can be effectively avoided. As the carrier of signal conversion, the ultrasonic wave is not easily affected by the environmental magnetic field, and the accuracy of current monitoring data and the reliability of the measurement process can be effectively ensured.

[0062] The application also discloses a thermal isolation type superconducting coil current measurement device, which comprises a superconducting magnet, a magnetic pole shell and the thermal isolation type superconducting coil current measurement circuit.

[0063] The application also discloses a magnetic levitation train comprising the thermal isolation type superconducting coil current measurement device.

[0064] For the convenience of description, the above system is described in various modules in terms of functions. Of course, the functions of the modules can be realized in one or more software and / or hardware when the application is implemented.

[0065] Each embodiment in the specification is described in a progressive manner, and the same and similar parts of each embodiment can be referred to each other. Each embodiment mainly describes the difference from other embodiments. The above-described system and system embodiments are only illustrative, and the units described as separate components can be or can not be physically separated, and the components shown as units can be or can not be physical units, that is, they can be located in one place or distributed on multiple network units. Part or all of the modules can be selected to achieve the purpose of the embodiment scheme according to actual needs. Those skilled in the art can understand and implement without creative labor.

[0066] It should also be noted that in this document, the relationship terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment. Without more limitations, the element defined by the statement "including a" does not exclude the presence of another identical element in the process, method, article or equipment including the element.

[0067] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Modifications of these embodiments will occur to persons of skill in the art, and that the appended claims are intended to cover all such modifications that do not depart from the true spirit and scope of the application. Therefore, the application is not limited to the embodiments shown but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A thermally isolated superconducting coil current measurement circuit, comprising: It comprises: a current sensor for measuring the operating current of the superconducting coil; an electro-acoustic-electric conversion circuit for converting the output signal of the current sensor into ultrasonic waves first, capturing the ultrasonic waves outside the magnetic pole shell after the ultrasonic waves pass through the magnetic pole shell of the superconducting coil, and converting the captured ultrasonic waves into an electric signal, and finally sending the electric signal to a subsequent circuit.

2. The thermally isolated superconducting coil current measurement circuit of claim 1, wherein, The electro-acoustic-electric conversion circuit comprises: a current converter, the input end of which is connected to the output end of the current sensor, for converting the output signal of the current sensor into an alternating current signal; an excitation ultrasonic transducer, the input end of which is connected to the output end of the current converter; a receiving ultrasonic transducer, the input end of which is connected to the output end of the excitation ultrasonic transducer.

3. The thermally isolated superconducting coil current measurement circuit of claim 2, wherein, The current converter is a voltage-controlled oscillator.

4. The thermally isolated superconducting coil current measurement circuit of claim 2, wherein, It further comprises: a power amplifier arranged between the current converter and the excitation ultrasonic transducer.

5. The thermally isolated superconducting coil current measurement circuit of claim 4, wherein, It further comprises: The power amplifier is a power amplifier with adjustable amplification factor.

6. The thermally isolated superconducting coil current measurement circuit of claim 2, wherein, The excitation ultrasonic transducer and the receiving ultrasonic transducer are embedded on both sides of the magnetic pole shell.

7. The thermally isolated superconducting coil current measurement circuit of claim 1, wherein, The subsequent circuit comprises: a monitor connected to the output end of the electro-acoustic-electric conversion circuit, for acquiring and processing the voltage signal collected by the output end of the electro-acoustic-electric conversion circuit to obtain the operating current of the superconducting coil.

8. The thermally isolated superconducting coil current measurement circuit of claim 1, wherein, It further comprises: an inductive power receiver and an inductive power transmitter, which cooperate with each other to couple the acquired alternating current to a power module; an AC / DC power module for supplying power to the power-consuming modules inside the magnetic pole shell.

9. A thermally isolated superconducting coil current measurement device, characterized by, It comprises: a superconducting magnet, a magnetic pole shell, and a thermally isolated superconducting coil current measurement circuit according to any one of claims 1-8.

10. A magnetic levitation train characterized by comprising: It comprises the thermally isolated superconducting coil current measurement device according to claim 9.

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