Test tool for magnetic field distribution test verification

Abstract

According to the test tool for magnetic field distribution test verification, each measuring point of the to-be-tested sample on the magnetic field measuring platform is fixedly provided with a set of double-probe structure, two probes of each set of double-probe structure are composed of magneto-optical crystals with different Verdet constants, and when an alternating-current magnetic field is generated in the to-be-tested sample, the magneto-optical crystals are separated from each other, and the magneto-optical crystals are separated from each other. After light intensity output by the light source is equally divided into multiple paths of optical fibers by the optical fiber coupler, light intensity signals carrying magnetic field information in the two paths of optical fibers are respectively received and converted into voltage signals by each group of double-probe structures, the voltage signals are input into the signal processing system, and the signal processing system outputs corresponding magnetic field distribution conditions; the installation position of the sensor is obtained in a more scientific and rigorous mode, judgment basis for different operation conditions is provided, accurate measurement and analysis of the magnetic field distribution condition are achieved, and more reliable data support is provided for research and application in related fields.

Description

Technical Field

[0001] This application relates to the technical field of magnetic field distribution measurement, and particularly to a test tool for magnetic field distribution test and verification. Background Art

[0002] Magnetic field distribution testing is of great significance in many fields, and thus is widely used in fields such as motors, sensors, and magnetic storage devices. In order to accurately evaluate the magnetic field distribution, it is necessary to design an effective test tool for test and verification. Traditional magnetic field test tools have some limitations, such as only considering the accuracy of normal operation and not considering the accuracy during faults, lacking more accurate analysis in the verification process, and having limited precision. In order to overcome these problems, a new type of test tool needs to be proposed to make it have higher precision and rigor to meet the requirements of magnetic field distribution testing.

[0003] The existing implementation solutions are as follows: Scholars such as Zhu Jun used a fixed single magneto-optic crystal probe in the article "Research on Fiber Optic Magnetic Field Vector Measurement Based on Magneto-optic Crystals" to simultaneously measure the transverse and longitudinal magnetic fields, thereby realizing the measurement of magnetic field distribution. When linearly polarized incident light passes through a magneto-optic crystal under an external magnetic field bias, due to the combined action of the Faraday effect and the magneto-induced linear birefringence effect, the polarization state of the outgoing light will change elliptically. By measuring the magnitude of the change in the polarization state, the measurement of magnetic field distribution can be realized; Scholars such as Yu Wenbin used a dual magneto-optic crystal probe in the article "Field Operation Stability Test of Self-Healing Optical Current Transformers" to compensate for the influence of temperature changes on the measurement results. The measurement system involved in this article includes a continuously operating main sensor and an intermittently operating auxiliary sensor. By using the independent output of the auxiliary sensor and calculating the correction coefficient, the influence of temperature on the main sensor can be eliminated.

[0004] As can be seen from the above content, the measurement platforms of the existing solutions are relatively complex, there is redundancy between the measurement parts, lacking a more reasonable device arrangement method, and the measurement accuracy is low; in addition, the existing technology lacks the analysis of the magnetic field distribution in different test environments, so the measurement accuracy of its measurement results is low in the case of environmental factor interference. Summary of the Utility Model

[0005] The purpose of this application aims to solve at least one of the above technical defects, especially the technical defect that the measurement accuracy of the magnetic field distribution obtained by the measurement platform in the existing technology is low.

[0006] This application provides a test tool for magnetic field distribution test and verification. The test tool includes a magnetic field measurement platform with a variable test environment and an optical magnetic field sensor. The optical magnetic field sensor includes a light source, an optical fiber coupler, a photoelectric converter, and a signal processing system connected in sequence through an optical flange.

[0007] The optical-electric converter includes at least one set of dual-probe structures. Each set of dual-probe structures includes a measurement probe and a compensation probe. Optical fiber penetrators are connected to both the left and right sides of the measurement probe and the compensation probe. The two optical fiber penetrators on the left are both connected to the opto-electric coupler, and the two optical fiber penetrators on the right are respectively connected to the signal processing system through opto-electric detectors;

[0008] Both the measurement probe and the compensation probe include a probe bracket, a magneto-optic crystal located at the center of the probe bracket, polarizers located on both sides of the magneto-optic crystal, and collimators respectively located on the sides of the two polarizers away from the magneto-optic crystal. The ends of the two collimators both extend outside the probe bracket. The magneto-optic crystal, the two polarizers, and the two collimators are bonded together with optical glue. The included angle between the two polarizers is 45°, and both the bonded measurement probe and compensation probe meet the measurement requirements under different test environments;

[0009] Among them, a set of dual-probe structures is fixed at each measurement point of the specimen to be tested on the magnetic field measurement platform. The two probes of each set of dual-probe structures are respectively composed of magneto-optic crystals with different Verdet constants.

[0010] Optionally, the output light intensity of the light source and the splitting number of the optical fiber coupler are proportional to the number of measurement points of the specimen to be tested.

[0011] Optionally, the working wavelength of the light source is 1310 nm, the output light intensity is adjustable from 0 to 50 mW, the fluctuation of the output light intensity within 24 hours is less than 0.2%, and the output connector is an FC / PC connector.

[0012] Optionally, the connectors on both sides of the optical fiber penetrator are both FC / PC connectors, and the light transmission efficiency is greater than 80%.

[0013] Optionally, the maximum outer diameter of the glass tube of each collimator is 2.78 mm, the length is 14 mm, and the optical fiber connector is an FC / PC connector.

[0014] Optionally, the working distance between the two collimators in the measurement probe or the compensation probe is 15 mm.

[0015] Optionally, the diameter of each polarizer is 5 mm, the thickness is 2 mm, the working wavelength is 750 - 1400 nm, the light transmittance is greater than 83%, and the extinction ratio is greater than 104:1.

[0016] Optionally, the measurement probe is made of a TSAG crystal;

[0017] The compensation probe is made of a TGG crystal.

[0018] Optionally, the optical adhesive is a two-component epoxy resin optical adhesive, and its light transmittance at 1310 nm is greater than 90%.

[0019] Optionally, the outer diameter of each probe holder is 8 mm and the length is 30 mm.

[0020] As can be seen from the above technical solutions, the embodiments of the present application have the following advantages:

[0021] An experimental tooling for magnetic field distribution test and verification provided by the present application. The experimental tooling includes a magnetic field measurement platform with a variable test environment and an optical magnetic field sensor. Among them, the optical magnetic field sensor includes a light source, an optical fiber coupler, a photoelectric converter, and a signal processing system that are sequentially connected through an optical flange. The photoelectric converter contains at least one set of dual-probe structures. Each set of dual-probe structures includes a measurement probe and a compensation probe. Fiber optic penetrators are connected to both the left and right sides of the measurement probe and the compensation probe. The two fiber optic penetrators on the left are both connected to the optoelectronic coupler, and the two fiber optic penetrators on the right are respectively connected to the signal processing system through photodetectors. The measurement probe and the compensation probe both include a probe bracket, a magneto-optic crystal located in the center of the probe bracket, polarizers located on both sides of the magneto-optic crystal, and collimators respectively located on the sides of the two polarizers away from the magneto-optic crystal. The ends of the two collimators both extend outside the probe bracket. The magneto-optic crystal, the two polarizers, and the two collimators are bonded together with optical glue. The included angle between the two polarizers is 45°. The overall structure of the optical magnetic field sensor of the present application can, to a certain extent, have both a large measurement range and high resolution, and improve the measurement accuracy. The present application uses a dual-probe structure for measurement. The two probes can measure simultaneously, and temperature compensation can be achieved through the compensation probe, with higher measurement accuracy. The sensor structure is designed to be more easily adjusted and expanded, that is, the light source can be replaced and a fiber optic coupler with more branches can be used to expand the number of sensing probes to achieve synchronous measurement of magnetic fields at more positions. In addition, the bonded measurement probe and compensation probe of the present application both meet the measurement requirements in different test environments, which can better ensure the accuracy of magnetic field measurement results in different situations. Further, the magnetic field measurement platform of the present application can change the test environment according to different test requirements, and thus can verify the magnetic field distribution under different requirements without considering environmental impact, considering environmental vibration impact, and considering environmental temperature impact. A set of dual-probe structures is fixed at each measurement point of the specimen to be tested on the magnetic field measurement platform. The two probes of each set of dual-probe structures are respectively composed of magneto-optic crystals with different Verdet constants. When an alternating magnetic field is generated in the specimen to be tested, the light intensity output by the light source is equally divided into multiple optical fibers by the fiber optic coupler, and then received by each set of dual-probe structures and converted into voltage signals of the light intensity signals carrying magnetic field information in the two optical fibers and input into the signal processing system, so that the signal processing system outputs the magnetic field distribution of the specimen to be tested in different test environments, and then obtains the sensor installation position and provides a judgment basis for different operating conditions in a more scientific and rigorous manner, realizing accurate measurement and analysis of the magnetic field distribution and providing more reliable data support for research and application in related fields. Description of the Drawings

[0022] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0023] Figure 1 It is a schematic structural diagram for testing the magnetic field distribution of a sample to be tested in a non-interference magnetic field measurement platform provided by an embodiment of the present application;

[0024] Figure 2 It is a schematic structural diagram for the magnetic field distribution of a sample to be tested considering the influence of environmental vibration provided by an embodiment of the present application;

[0025] Figure 3 It is a schematic structural diagram for the magnetic field distribution of a sample to be tested considering the influence of environmental temperature provided by an embodiment of the present application;

[0026] Figure 4 It is a schematic structural diagram of an optical magnetic field detector including a dual-probe structure provided by an embodiment of the present application;

[0027] Figure 5 It is a schematic structural diagram of an optical magnetic field detector including multiple dual-probe structures provided by an embodiment of the present application;

[0028] Figure 6 It is a schematic structural diagram of a measurement probe or a compensation probe provided by an embodiment of the present application;

[0029] Figure 7 It is a schematic structural diagram of a performance test platform for an optical magnetic field sensor provided by an embodiment of the present application;

[0030] Figure 8 It is a schematic structural diagram for testing and verifying the magnetic field distribution of a transformer under two winding faults of winding deformation and inter-turn short circuit provided by an embodiment of the present application. Detailed implementation manners

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, rather than all embodiments. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0032] In one embodiment, the present application provides a test tooling for magnetic field distribution test and verification. The test tooling includes a magnetic field measurement platform with variable test environment and an optical magnetic field sensor. The optical magnetic field sensor includes a light source, an optical fiber coupler, a photoelectric converter, and a signal processing system connected in sequence through an optical flange.

[0033] The photoelectric converter includes at least one group of dual-probe structures. Each group of dual-probe structures includes a measurement probe and a compensation probe. Optical fiber penetrators are connected to both the left and right sides of the measurement probe and the compensation probe. The two optical fiber penetrators on the left are both connected to the photoelectric coupler, and the two optical fiber penetrators on the right are respectively connected to the signal processing system through photodetectors.

[0034] Both the measurement probe and the compensation probe include a probe bracket, a magneto-optic crystal located in the center of the probe bracket, polarizers located on both sides of the magneto-optic crystal, and collimators respectively located on the sides of the two polarizers away from the magneto-optic crystal. The ends of the two collimators extend outside the probe bracket. The magneto-optic crystal, the two polarizers, and the two collimators are bonded together with optical glue. The included angle between the two polarizers is 45°. After bonding, both the measurement probe and the compensation probe meet the measurement requirements under different test environments.

[0035] Among them, a group of dual-probe structures is fixed at each measurement point of the test sample on the magnetic field measurement platform. The two probes of each group of dual-probe structures are respectively composed of magneto-optic crystals with different Verdet constants.

[0036] It should be noted that the improvement of the present application lies in the structure of the system. The descriptions of methods involved in the following examples are only to prove that the system can achieve effects in applications. These effects in the system are realized depending on the hardware structure. Based on different objects and in different operation processes, the method steps and detection effects may or may not be different, and no limitation is made here.

[0037] In this embodiment, when configuring the test tooling for magnetic field distribution test and verification, a magnetic field measurement platform and an optical magnetic field sensor can be set. The magnetic field measurement platform can change the test environment according to different test requirements, so as to test the magnetic field distribution of the test sample on the magnetic field measurement platform under different test environments. Moreover, the present application can also determine the measurement points of the test sample in advance through simulation technology and other means, so that the optical magnetic field sensor can be installed at the corresponding measurement points for multi-point measurement, thereby effectively improving the measurement accuracy of the test sample.

[0038] For example, as Figure 1 shown, Figure 1Schematic diagram of the structure for testing the magnetic field distribution of a sample to be tested in a non-interference magnetic field measurement platform provided by an embodiment of the present application; Figure 1 In this application, when testing the magnetic field distribution of a sample to be tested, environmental factors such as environmental vibration and environmental temperature are not considered. The magnetic field measurement platform can be called a non-interference magnetic field measurement platform. This platform mainly consists of a sample to be tested and a developed optical magnetic field sensor. Among them, the sensing probe of the optical magnetic field sensor is placed in the sample to be tested. The sample to be tested is connected to an AC power supply. After adjusting the output voltage of the AC power supply to generate an AC magnetic field in the sample to be tested, measurement is carried out through the optical magnetic field sensor of this application, and then the magnetic field distribution of the sample to be tested can be determined.

[0039] When considering the influence of environmental vibration, a magnetic field measurement platform including the influence of vibration needs to be built, such as Figure 2 shown. Figure 2 Schematic diagram of the structure of the magnetic field distribution of a sample to be tested considering the influence of environmental vibration provided by an embodiment of the present application; Figure 2 In this, the magnetic field measurement platform can be adding a vibration platform on the basis of a non-interference platform. The sensing probe is placed in the sample to be tested and fixed on the vibration platform together. The optical fiber between the light source and the sensing probe can also be fixed on the vibration platform. In addition, since the light carrying magnetic field information does not change in light intensity no matter how the optical fiber passing through the collimator is disturbed, the optical fiber from the sensing probe to the photodetector will not affect the measurement result of the self-developed sensor. Therefore, it is not fixed on the vibration platform during the test. In addition, the vibration frequency of the vibration platform of this application can be set to 100 Hz, and the amplitude can be divided into two cases: low amplitude and high amplitude. The specific values can also be adjusted according to the actual situation and are not limited here.

[0040] When considering the influence of environmental temperature, a magnetic field measurement platform including the influence of temperature needs to be built. This platform adds a heating platform on the basis of a non-interference platform and uses a temperature sensor to monitor the temperature. After the sensing probe is heated to different temperatures by the heating platform, it is placed inside the sample to be tested for magnetic field measurement. The magnetic field measurement platform including the influence of temperature in this application is as Figure 3 shown. Figure 3 Schematic diagram of the structure of the magnetic field distribution of a sample to be tested considering the influence of environmental temperature provided by an embodiment of the present application; It can be seen from Figure 3 that this application can measure the magnetic field distribution inside the sample to be tested at different environmental temperatures, thereby effectively improving the diversity and accuracy of the measurement results.

[0041] It can be understood that the present application can change the test environment of the current magnetic field measurement platform according to different test requirements. The test environment includes, but is not limited to, the above-mentioned interference-free test environment, the test environment when the environmental vibration has an impact, and the test environment when the environmental temperature has an impact. It can also be the test environment in other scenarios, which can be specifically set according to the actual situation and is not limited here.

[0042] Furthermore, as Figures 4 - 5 shown, Figure 4 is a schematic structural diagram of an optical magnetic field detector including a dual-probe structure provided by an embodiment of the present application, Figure 5 is a schematic structural diagram of an optical magnetic field detector including multiple dual-probe structures provided by an embodiment of the present application; the optical magnetic field detector of the present application includes a light source, an optical fiber coupler, a photoelectric converter, and a signal processing system that are sequentially connected through an optical flange. Among them, the photoelectric converter of the present application includes at least one group of dual-probe structures. Each group of dual-probe structures includes a measurement probe and a compensation probe. Optical fiber penetrators are connected to the left and right sides of the measurement probe and the compensation probe. The two optical fiber penetrators on the left are both connected to the optoelectronic coupler, and the two optical fiber penetrators on the right are respectively connected to the signal processing system through photodetectors. In this way, on the basis of the normal use of the optical magnetic field sensor of the present application, the number of sensing probes can also be expanded by replacing the light source with a larger output light intensity and the optical fiber coupler with more branches, realizing distributed magnetic field measurement. In one example, the present application can select an optical fiber coupler with a corresponding number of branches according to the number of measurement points required for distributed measurement. Each measurement point uses two branches for measurement, and the optical fiber coupler is still selected according to the principle of equal splitting ratio. In order to ensure that the probe can still obtain sufficient light intensity, a light source with a larger output light intensity can be selected, and the signal processing system adopts a multi-point parallel processing method and can process the signals of multiple branches simultaneously.

[0043] Even further, as Figure 6 shown, Figure 6 is a schematic structural diagram of the measurement probe or the compensation probe provided by an embodiment of the present application; Figure 6 In, the measurement probe and the compensation probe of the present application both include a probe bracket, a magneto-optical crystal located in the center of the probe bracket, polarizers located on both sides of the magneto-optical crystal, and collimators respectively located on the sides of the two polarizers away from the magneto-optical crystal. The ends of the two collimators extend to the outside of the probe bracket. The magneto-optical crystal, the two polarizers, and the two collimators are bonded together with optical glue. The included angle between the two polarizers is 45°, and the bonded measurement probe and compensation probe both meet the measurement requirements in different test environments.

[0044] Among them, the manufacturing process of the measurement probe and the compensation probe of the present application is as follows:

[0045] (1) Collimator alignment: Fix the collimator on the five-dimensional optical translation stage using a fixture, and keep the axial distance between the two collimators fixed. First, preliminarily align using a visible light source, and then use a 1310 nm light source and a photodetector to finely adjust the five-dimensional translation stage to maximize the output of the photodetector.

[0046] (2) Insert the probe holder: Adjust the translation stage to increase the axial distance of the collimator, insert the probe holder, and keep the transmission efficiency between the collimators unchanged and the adjustment of the five-dimensional optical translation stage unaffected.

[0047] (3) Polarizer adjustment: Insert a polarizer and a magneto-optic crystal, rotate the polarization of the optical detector, and when the output light intensity is half of the maximum output light intensity, fix the positions of the polarizer and the magneto-optic crystal.

[0048] (4) Optical glue bonding: Add optical glue, adjust the translation stage to make the end faces of the collimator, polarizer, and magneto-optic crystal have optical glue. The optical glue should be appropriate and should not overflow from the round holes on both sides of the probe holder, causing the collimator to bond with the fixture.

[0049] (5) Optical glue protection: After the optical glue in (4) cures, remove the fixture, cover the devices inside the probe holder and the collimator exposed outside the probe holder with optical glue to protect the optical devices from external factors such as oil erosion.

[0050] In addition, to ensure the accuracy and rigor of magnetic field measurement, the performance of the optical magnetic field sensor of the present application can also be tested before the magnetic field test. The test platform is as Figure 7 shown. Figure 7 is a schematic structural diagram of the performance test platform of the optical magnetic field sensor provided by the embodiment of the present application; Figure 7 In, the test platform may include devices such as the sensor under research, a magnetic field source, and a magnetometer. If the length of the magneto-optic crystal in the present application is set to 8 mm, in order to more accurately verify the sensor parameters, it is required that the magnetic field generated by the magnetic field source has at least an 8 mm long uniform region, and there are two options: a solenoid and a permanent magnet. The magnetic field generated by the solenoid has good uniformity, but it is difficult to generate a magnetic field of 100 mT. The maximum magnetic field of the existing solenoid in the laboratory is about 40 mT. Although the uniformity of the magnetic field of the permanent magnet is slightly weaker, the uniform magnetic field generated can reach 110 mT. The present application comprehensively considers the advantages and disadvantages of the solenoid and the permanent magnet, and finally selects the permanent magnet with slightly weaker uniformity but a larger magnetic field as the magnetic field source.

[0051] Figure 7In [the situation], the magnetic field distribution is relatively uniform at a certain distance from the side surface of the permanent magnet. By adjusting the distance d between the sensing probe and the surface of the permanent magnet, the magnetic field strength at the sensing probe can be controlled. In the testing process, first adjust the optical probe gear and light intensity output to reach the required theoretical magnetic field resolution, such as 0.14 mT. At this theoretical resolution, measure the data within the required magnetic field range, such as the magnetic flux density data within the magnetic field range of 30 - 110 mT. If the maximum measurement error within this range meets the requirements, it can be verified that the actual measurement range of the self-developed sensor includes the required magnetic field measurement range and can be used for subsequent magnetic field distribution test verification.

[0052] For example, before officially measuring the magnetic field distribution of the sample to be tested under the influence of environmental vibration, this application can first test whether the self-developed optical magnetic field sensor can accurately measure the magnetic field under the required vibration influence. The specific test method is as follows: Apply only high-amplitude vibration with a frequency of 100 Hz to the optical magnetic field sensor. In this case, the influence of vibration on the optical magnetic field sensor is manifested as the sensor output containing AC components with a frequency of 100 Hz and integer multiples of 100 Hz. If the vibration frequency of the magnetic field to be tested is not greater than the set frequency, it can be considered that this vibration will not affect its accuracy, that is, the magnetic field distribution can still be verified under the influence of vibration.

[0053] Before officially measuring the magnetic field distribution of the sample to be tested under the influence of environmental temperature, it is also possible to first test whether the self-developed sensor can accurately measure the magnetic field under the required environmental temperature influence. The specific test method is as follows: Within the required environmental temperature range after appropriate expansion, measure the Verdet constant of the magneto-optical crystal every 10 °C. The measurement results show that if only considering the action of a single probe, the maximum changes in the Verdet constants of the TSAG crystal and the TGG crystal are approximately 22% and 19% respectively, and the magnetic field measurement error reaches 22%. If a dual-probe compensation is adopted, the magnetic field measurement error is less than 4%. Therefore, it can be considered that the magnetic field distribution can still be verified under the influence of temperature when using a dual-probe structure.

[0054] It should be noted that the process of testing whether the self-developed sensor can accurately measure the magnetic field under the required environmental influence is a prior art. The specific test method adopted can be selected according to actual needs. In this embodiment, an experimental fixture is used to achieve accurate measurement of the magnetic field, and the measurement method of the magnetic field is not improved and is not limited here.

[0055] Finally, in the present application, a set of dual-probe structures can be fixed at each measurement point of the specimen to be tested on the magnetic field measurement platform. The two probes of each set of dual-probe structures are respectively composed of magneto-optical crystals with different Verdet constants. When an alternating magnetic field is generated in the specimen to be tested, the light intensity output by the light source is evenly divided into multiple optical fibers through an optical fiber coupler, and then received by each set of dual-probe structures as the light intensity signals carrying magnetic field information in two optical fibers. The photodetector of the present application is a photodetector integrating photoelectric conversion and voltage amplification. This photodetector can be directly connected to the optical fiber of the FC / PC connector through an adapter, convert the light intensity signal carrying magnetic field information in the optical fiber into a current signal first, then into a voltage signal, and then output it to the signal processing system through a BNC connector. The signal processing system outputs the magnetic field distribution of the specimen to be tested under different test environments based on the voltage signals of each path. Moreover, the signal processing system can also send the measurement results to a computer for the user to view on the computer. It should be noted that the present application does not improve the working process of the signal processing system. Among them, the process of the signal processing system outputting the corresponding magnetic field distribution based on the voltage signals of each path can be realized by the prior art, and the specific implementation process will not be elaborated here.

[0056] Furthermore, the present application can also illustrate the usage process of the present application through a related example. The usage process of the specific measurement platform can be as follows: (1) First, determine the positions to be measured in the specimen to be tested, that is, the measurement points. The selection method is not limited. For example, the optimal measurement points can be determined through simulation; (2) If the influence of environmental vibration or environmental temperature needs to be considered during the specific measurement process, then before measurement, apply environmental vibration or environmental temperature to the sensing probe through a vibration platform or a heating platform. If environmental factors do not need to be considered, an interference-free magnetic field measurement platform can be directly used. (3) In order to more accurately verify the magnetic field distribution, the magnetic field can be measured 10 times in parallel using the magnetic field measurement platform. If the measurement results show that for each optical magnetic field sensor, the fluctuations of the 10 magnetic field measurement results are small, then it is considered that the magnetic field measurement results of this group are credible, and the average value of the measurement results is used as the actual measurement result of the magnetic field measurement. (4) Compare and analyze the actual measurement result with the magnetic field distribution result to be verified. The specific analysis method is not unique. It can be analyzed by the magnitude of the error, or by converting the measurement results into index numbers. Through the analysis results, the verification of the magnetic field distribution test can be achieved.

[0057] In a specific embodiment, as Figure 8 shown, Figure 8 is a schematic structural diagram for testing and verifying the magnetic field distribution of a transformer under two winding faults of winding deformation and inter-turn short circuit provided by an embodiment of the present application; Figure 8In the process of testing and verifying the magnetic field distribution of a transformer under two types of winding faults, namely winding deformation and inter-turn short circuit, it is first necessary to prepare the sensor equipment and assemble it into a sensor according to the requirements. After assembly, the performance of the sensor is tested according to the measurement range requirements. After passing the test, a test platform can be selected and the magnetic field distribution measurement and verification can be carried out. The specific measurement and verification steps are as follows: first, simulate the magnetic field distribution of the transformer under the two faults of winding deformation and inter-turn short circuit respectively to select the measurement points. Finally, considering the simulation results and the structural characteristics of the transformer comprehensively, in order to realize the magnetic field distribution test and verification for both winding deformation and inter-turn short circuit faults simultaneously, sensor probes need to be installed inside the winding end insulation and in the middle of the outside of the low-voltage winding. Among them, the two sensor probes inside the winding end insulation are at the corresponding positions of the low-voltage winding and the high-voltage winding. And due to the symmetry of the transformer, in order to identify the winding faults in the lower part of the transformer, two sensor probes need to be arranged inside the winding lower-end insulation. The specific sensor installation positions are as Figure 8 shown. Since the influence of environmental factors is not considered in this magnetic field distribution test, a non-interference test platform is selected. After installing the sensors and arranging the test platform, the measurement can be carried out. Ten measurements are carried out separately for different situations. When the volatility of each group of data is small, the data is considered to meet the requirements. The average value of each group of data is selected as the corresponding measured data. By comparing and analyzing the measured data with the magnetic field distribution data to be verified, the magnetic field distribution test and verification of the transformer under the two types of winding faults of winding deformation and inter-turn short circuit can be realized.

[0058] It should be noted that one of the keys to using the magneto-optic crystal for magnetic field measurement in this application is to accurately obtain the magnitude of the Verdet constant of the magneto-optic crystal. However, the Verdet constant of the magneto-optic crystal will change with the change of the ambient temperature. When the temperature changes, if it is considered that the Verdet constant remains unchanged, it will affect the accuracy of magnetic field measurement. Therefore, this application uses a dual-probe structure to compensate for the temperature change. The two probes are respectively composed of magneto-optic crystals with different Verdet constants. When the two probes are in the same spatial position (that is, the ambient temperature and the magnetic field are the same), the difference in the Verdet constants of the two magneto-optic crystals at this temperature leads to different output optical intensity signals of the two probes. By analyzing the optical intensity signals output by the two probes, the relationship between the Verdet constants of the two magneto-optic crystals in the current environment can be obtained, so as to realize the magnetic field measurement at different ambient temperatures.

[0059] The specific measurement process is as follows:

[0060] The relationship between the ratio of the Verdet constants of the two magneto-optic crystals and the temperature obtained through calibration can be expressed as f(T), that is:

[0061]

[0062] In the formula, the Verdet constant V of the magneto-optic crystal1 , V 2 and the environmental temperature T are unknowns, while the relational expression f(T) is obtained by calibration and is a known quantity.

[0063] After the signal processing system processes the output of the photodetector, the Faraday rotation angles θ 1 and θ 2 produced by two magneto-optical crystals have the same relationship with temperature as in Equation (1), that is:

[0064]

[0065] In the formula, N 1 and N 2 are obtained by the photodetector processing the output light intensities of two probes and are known quantities. Combining Equation (1) and Equation (2), the current environmental temperature T can be accurately obtained, that is:

[0066]

[0067] After obtaining the environmental temperature, the Verdet constant V 1 and V 2 of the magneto-optical crystal can be solved. Then, combined with the length L of the magneto-optical crystal, the magnetic field measurement at this environmental temperature can be realized, that is:

[0068]

[0069] It can be understood that the above temperature acquisition process after using the dual-probe measurement is only an example in the prior art. Of course, other methods in the prior art can also be used in this application for measurement, and specific details are not limited. This application uses dual probes to measure the light intensity signals at different environmental temperatures, with higher measurement accuracy than the single-probe measurement. The error of the single-probe measurement method can reach more than 20%, while the dual-probe measurement can reduce the error to about 4%. On this basis, if distributed measurement is to be realized, a light source with a larger output light intensity and a fiber optic coupler with more branches can also be selected according to the number of measurement points. There are two branches for each measurement point, and the test method is the same as the dual-probe measurement method, which will not be elaborated here.

[0070] In the above embodiments, the test tooling includes a magnetic field measurement platform and an optical magnetic field sensor. Among them, the optical magnetic field sensor includes a light source, an optical fiber coupler, a photoelectric converter, and a signal processing system that are sequentially connected through an optical flange. The photoelectric converter contains at least one set of dual-probe structures. Each set of dual-probe structures includes a measurement probe and a compensation probe. Optical fiber penetrators are connected to both the left and right sides of the measurement probe and the compensation probe. The two optical fiber penetrators on the left are both connected to the optical coupler, and the two optical fiber penetrators on the right are respectively connected to the signal processing system through photodetectors. Both the measurement probe and the compensation probe include a probe bracket, a magneto-optical crystal located at the center of the probe bracket, polarizers located on both sides of the magneto-optical crystal, and collimators located on the sides of the two polarizers away from the magneto-optical crystal. The ends of the two collimators extend outside the probe bracket. The magneto-optical crystal, the two polarizers, and the two collimators are bonded together with optical glue. The included angle between the two polarizers is 45°. The overall structure of the optical magnetic field sensor of the present application can, to a certain extent, combine a relatively large measurement range and high resolution, and improve the measurement accuracy. The present application uses a dual-probe structure for measurement. The two probes can measure simultaneously and can achieve temperature compensation under the influence of environmental temperature, with higher measurement accuracy. The sensor structure design is easier to adjust and expand, that is, the light source can be replaced and an optical fiber coupler with more branches can be used to expand the number of sensing probes to achieve synchronous measurement of magnetic fields at more positions. In addition, both the bonded measurement probe and compensation probe of the present application meet the measurement requirements in different test environments, which can better ensure the accuracy of magnetic field measurement results in different situations. Further, the magnetic field measurement platform of the present application can change the test environment according to different test requirements, and thus can verify the magnetic field distribution under different requirements without considering environmental impact, considering environmental vibration impact, and considering environmental temperature impact. A set of dual-probe structures is fixed at each measurement point of the specimen to be tested on the magnetic field measurement platform. The two probes of each set of dual-probe structures are respectively composed of magneto-optical crystals with different Verdet constants. When an alternating magnetic field is generated in the specimen to be tested, the light intensity output by the light source is evenly divided into multiple optical fibers by the optical fiber coupler, and then received by each set of dual-probe structures and converted into voltage signals of the light intensity signals carrying magnetic field information in the two optical fibers. Then, according to the voltage signals of each path, the magnetic field distribution of the specimen to be tested in different test environments is output through the signal processing system. Furthermore, the installation position of the sensor and the judgment basis for different operating conditions are obtained in a more scientific and rigorous manner, realizing accurate measurement and analysis of the magnetic field distribution, and providing more reliable data support for research and applications in related fields.

[0071] In one embodiment, the output light intensity of the light source and the splitting number of the fiber optic coupler are proportional to the number of measurement points of the specimen to be tested. In this way, by changing the output light intensity of the light source and the splitting number of the fiber optic coupler, more fiber optic paths can be divided, and multiple probes can simultaneously measure multiple measurement points of the specimen to be tested. Then, the average value of the magnetic field intensities measured at multiple measurement points is used to characterize the magnetic field intensity of the specimen to be tested, thereby effectively improving the magnetic field detection accuracy of the present application.

[0072] In one embodiment, the working wavelength of the light source is 1310 nm, the output light intensity is adjustable from 0 to 50 mW, the output light intensity fluctuation within 24 hours is less than 0.2%, and the output connector is an FC / PC connector. In this way, it can not only stably output light intensities of different levels but also improve the accuracy of the measurement results.

[0073] In one embodiment, both connectors on both sides of the fiber optic through-pass are FC / PC connectors, and the light transmission efficiency is greater than 80%, so as to obtain measurement results with better accuracy.

[0074] In one embodiment, the maximum outer diameter of the glass tube of each collimator is 2.78 mm, the length is 14 mm, and the fiber optic connector is an FC / PC connector.

[0075] In one embodiment, the working distance between two collimators in the measurement probe or the compensation probe is 15 mm. In this way, it can not only avoid working interference between the two collimators but also couple the light intensity into the connected device with the highest efficiency.

[0076] In one embodiment, the diameter of each polarizer is 5 mm, the thickness is 2 mm, the working wavelength is 750 - 1400 nm, the light transmittance is greater than 83%, and the extinction ratio is greater than 104:1.

[0077] In one embodiment, the measurement probe is made of a TSAG crystal.

[0078] The compensation probe is made of a TGG crystal.

[0079] In one embodiment, the optical adhesive is a two-component epoxy resin optical adhesive, and the light transmittance at 1310 nm is greater than 90%. It can be understood that the two-component epoxy resin optical adhesive selected in the present application has a low viscosity and excellent fluidity before curing, which is convenient for bonding optical devices. After curing, it has excellent electrical insulation performance and a light transmittance greater than 90% at 1310 nm.

[0080] In one embodiment, the outer diameter of each probe holder is 8 mm and the length is 30 mm. In this way, it is not only convenient to measure different measurement points of the specimen to be tested but also convenient for installation.

[0081] Finally, it should also be noted that in this text, relational 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 any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the phrase "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the element.

[0082] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The various embodiments can be combined as needed, and the same or similar parts can be referred to each other.

[0083] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. A test fixture for testing and verifying magnetic field distribution, characterized in that: The test fixture comprises a magnetic field measurement platform with a variable test environment and an optical magnetic field sensor, wherein the optical magnetic field sensor comprises a light source, an optical fiber coupler, a photoelectric converter and a signal processing system connected in sequence through an optical flange; The photoelectric converter includes at least one set of dual-probe structures, each set of dual-probe structures includes a measuring probe and a compensating probe, and the left and right sides of the measuring probe and the compensating probe are connected to optical fiber penetrators, the two optical fiber penetrators on the left are connected to the optical fiber coupler, and the two optical fiber penetrators on the right are connected to the signal processing system through photoelectric detectors respectively; The measuring probe and the compensating probe both include a probe holder, a magneto-optical crystal located in the center of the probe holder, polarizing plates located on both sides of the magneto-optical crystal, and collimators located on the two polarizing plates respectively on the side away from the magneto-optical crystal, the ends of the two collimators both extend to the outside of the probe holder, the magneto-optical crystal, the two polarizing plates and the two collimators are bonded by optical glue, the angle between the two polarizing plates is 45°, and the bonded measuring probe and the compensating probe both meet the measurement requirements under different test environments; Wherein, each measuring point of the sample to be tested on the magnetic field measurement platform is fixed with a set of double-probe structures, and the two probes of each set of double-probe structures are respectively composed of magneto-optical crystals with different Verdet constants.

2. A test fixture for testing and verifying magnetic field distribution according to claim 1, characterized in that: The output light intensity of the light source and the number of branches of the optical fiber coupler are proportional to the number of measurement points of the sample to be tested.

3. The test fixture for testing and verifying magnetic field distribution according to claim 1, characterized in that: The working wavelength of the light source is 1310 nm, the output light intensity is adjustable from 0 to 50 mW, the output light intensity fluctuates less than 0.2% within 24 hours, and the output connector is an FC / PC connector.

4. The test fixture for testing and verifying magnetic field distribution according to claim 1, characterized in that: The connectors on both sides of the optical fiber through-hole are FC / PC connectors, and the optical transmission efficiency is greater than 80%.

5. The test fixture for testing and verifying magnetic field distribution according to claim 1, characterized in that: The maximum outer diameter of the glass tube of each collimator is 2.78 mm, the length is 14 mm, and the optical fiber connector is an FC / PC connector.

6. A test fixture for testing and verifying magnetic field distribution according to claim 1 or 5, characterized in that: The working distance between the two collimators in the measuring probe or the compensating probe is 15 mm.

7. The test fixture for testing and verifying magnetic field distribution according to claim 1, characterized in that: Each polarizer has a diameter of 5mm and a thickness of 2mm, an operating wavelength of 750-1400nm, a light transmittance greater than 83%, and an extinction ratio greater than 104:

1.

8. The test fixture for testing and verifying magnetic field distribution according to claim 1, characterized in that: The measuring probe is made of TSAG crystal; The compensation probe is made of TGG crystal.

9. The test fixture for testing and verifying magnetic field distribution according to claim 1, characterized in that: The optical adhesive is a two-component epoxy resin optical adhesive, and the optical transmittance at 1310 nm is greater than 90%.

10. The test fixture for testing and verifying magnetic field distribution according to claim 1, characterized in that: Each probe holder has an outer diameter of 8 mm and a length of 30 mm.

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