Magnetic property testing device and method for high-permeability material under low-frequency and weak-magnetic environment

Abstract

This invention relates to a testing device for the magnetic properties of high-permeability materials under low-frequency weak magnetic environments, comprising: a coil assembly, a magnetic property tester, a magnetic shielding cylinder, and a host computer; the coil assembly is wound around the sample under test and connected to the magnetic property tester, and the sample under test with the coil assembly placed inside the magnetic shielding cylinder; the magnetic shielding cylinder provides a weak magnetic environment for the sample under test; the magnetic property tester is used to provide excitation current to the coil assembly and detect the induced voltage of the sample under test, and transmit the measured data to the host computer; the host computer is used to acquire the data measured by the magnetic property tester and plot the magnetization curve. The technical solution of this invention solves the problem that current magnetic property testing devices for magnetic materials cannot obtain the permeability of high-permeability materials under low-frequency weak magnetic environments, thereby improving the accuracy and precision of theoretical and simulation calculations of magnetic shielding devices and reducing the error between design and actual values.

Description

Technical Field

[0001] This invention relates to the field of magnetic property measurement technology for high-permeability materials, specifically to a testing device and method for the magnetic properties of high-permeability materials under low-frequency weak magnetic environment. Background Technology

[0002] High-permeability materials are commonly used for shielding the Earth's magnetic field, using the magnetic circuit shunting effect to block external magnetic fields. The actual geomagnetic environment is a low-frequency alternating magnetic field, ranging from approximately 0.1 to 300 Hz. The shielding coefficient of an alternating magnetic field is related to the magnetic permeability and electrical conductivity of the shielding material. The magnetic permeability of materials such as permalloy varies with frequency; therefore, using accurate magnetic permeability under alternating magnetic fields to calculate the shielding coefficient is a prerequisite for ensuring calculation accuracy. However, currently, shielding material manufacturers worldwide lack test results of the magnetic properties of their materials under extremely low-frequency weak magnetic fields. Simulation and theoretical calculations typically use magnetic properties measured using DC testing methods to calculate the magnetic shielding coefficient.

[0003] Magnetic shielding devices are typically designed with a multi-layered structure, resulting in different magnetic field environments for each layer. The innermost magnetic shielding layer is situated in an extremely weak magnetic environment. Commonly used methods for testing the AC magnetic properties of materials are only applicable to high-frequency AC magnetic properties in open magnetic field environments. The sample is susceptible to interference from the ambient magnetic field, affecting the measurement results, and measurement data cannot be obtained under low-frequency, weak magnetic environments. Therefore, existing testing methods cannot test the magnetic properties of materials in weak magnetic environments. This lack of performance data leads to a significant discrepancy between the actual performance of the constructed magnetic shielding device and the simulation results. Summary of the Invention

[0004] The magnetic property testing device and method for high-permeability materials under low-frequency weak magnetic environment provided in this application at least solve the problems in related technologies, such as the inability to obtain the magnetic permeability of high-permeability materials under low-frequency weak magnetic environment, the low accuracy and precision of theoretical calculation and simulation calculation of magnetic shielding devices, and the large error between design value and actual value.

[0005] The first aspect of this application provides a device for testing the magnetic properties of high-permeability materials under low-frequency weak magnetic environment. The device includes: a coil group, a magnetic property tester, a magnetic shielding cylinder, and a host computer.

[0006] The coil assembly is wound around the sample under test and connected to the magnetic property tester via test leads. The sample under test with the coil assembly wound around it is placed inside a magnetic shielding cylinder.

[0007] The magnetic shielding cylinder is used to provide a weak magnetic environment for the sample placed inside the magnetic shielding cylinder and to shield it from external interference magnetic fields.

[0008] The magnetic property tester is used to provide excitation current to the coil group and detect the induced voltage of the sample under test, and transmit the measured data to the host computer.

[0009] The host computer is used to acquire the data measured by the magnetic property tester and plot the magnetization curve.

[0010] A second aspect of this application provides a method for testing the magnetic properties of high-permeability materials under low-frequency weak magnetic environment, the method comprising:

[0011] Step 1: Prepare the test sample and wind the coil assembly onto the test sample;

[0012] Step 2: Connect the coil assembly to the magnetic property tester via test leads;

[0013] Step 3: Place the sample under test with the coil winding on the sample platform of the shielding cylinder and cover it with the shielding cover to provide a weak magnetic environment for the sample under test;

[0014] Step 4: Start the magnetic property tester. The host computer acquires the data measured by the magnetic property tester and plots the magnetization curve.

[0015] The technical solutions provided by the embodiments of this application bring at least the following beneficial effects:

[0016] This invention provides a device and method for testing the magnetic properties of high-permeability materials under low-frequency weak magnetic environments. The device includes: a coil assembly, a magnetic property tester, a magnetic shielding cylinder, and a host computer. The coil assembly is wound around the sample under test and connected to the magnetic property tester via test leads. The sample under test, with the coil assembly wound around it, is placed inside the magnetic shielding cylinder. The magnetic shielding cylinder provides a weak magnetic environment for the sample under test and shields it from external interference magnetic fields. The magnetic property tester provides excitation current to the coil assembly and detects the induced voltage of the sample under test, transmitting the measured data to the host computer. The host computer acquires the data measured by the magnetic property tester and plots the magnetization curve. This invention solves the problem that current magnetic property testing devices cannot obtain the permeability of high-permeability materials under low-frequency weak magnetic environments, thereby improving the accuracy and precision of theoretical and simulation calculations of magnetic shielding devices and reducing the error between design and actual values.

[0017] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0018] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0019] Figure 1 This is a structural diagram of a device for testing the magnetic properties of high-permeability materials in a low-frequency weak magnetic environment according to an embodiment of this application;

[0020] Figure 2 This is a structural diagram of the magnetic shielding cylinder and the support in a magnetic property testing device for high permeability materials under low-frequency weak magnetic environment according to an embodiment of this application;

[0021] Figure 3 This is a flowchart of a method for testing the magnetic properties of high-permeability materials in a low-frequency weak magnetic environment according to an embodiment of this application;

[0022] Figure 4 This is a flowchart illustrating a method for testing the magnetic properties of high-permeability materials under low-frequency weak magnetic environment, according to an embodiment of this application.

[0023] Explanation of reference numerals in the attached figures:

[0024] Host computer-1; Magnetic property tester-2; Magnetic shielding cylinder-3; Test line-4; Test sample-5; Sample platform-6; Interlayer pad-7; Bracket-8; First opening-9; Second opening-10; Aluminum alloy shielding layer-301; Permalloy shielding layer-302; Aluminum alloy shielding cover-3011; Permalloy shielding cover-3021. Detailed Implementation

[0025] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0026] This application provides a device and method for testing the magnetic properties of high-permeability materials under low-frequency weak magnetic environments. The device includes: a coil assembly, a magnetic property tester 2, a magnetic shielding cylinder 3, and a host computer 1. The coil assembly is wound around a sample 5 under test and connected to the magnetic property tester 2 via test wires 4. The sample 5 with the coil assembly is placed inside the magnetic shielding cylinder 3. The magnetic shielding cylinder 3 provides a weak magnetic environment for the sample 5 placed inside and shields it from external interference magnetic fields. The magnetic property tester 2 provides excitation current to the coil assembly and detects the induced voltage of the sample 5 under test, transmitting the measured data to the host computer 1. The host computer 1 acquires the data measured by the magnetic property tester 2 and plots the magnetization curve. The technical solution of this invention solves the problem that current magnetic property testing devices for magnetic materials cannot obtain the permeability of high-permeability materials under low-frequency weak magnetic environments, thereby improving the accuracy and precision of theoretical and simulation calculations of magnetic shielding devices and reducing the error between design and actual values.

[0027] Example 1

[0028] Figure 1This is a structural diagram of the magnetic property testing device for high-permeability materials under low-frequency weak magnetic environment provided in the embodiments of this disclosure, as shown below. Figure 1 As shown, the system includes: a coil group, a magnetic property tester 2, a magnetic shielding cylinder 3, and a host computer 1;

[0029] The coil group is wound around the test sample 5 and connected to the magnetic property tester 2 through the test line 4. The test sample 5 with the coil group wound around it is placed inside the magnetic shielding cylinder 3.

[0030] The magnetic shielding cylinder 3 is used to provide a weak magnetic environment for the test sample 5 placed inside the magnetic shielding cylinder and to shield external interference magnetic fields.

[0031] The magnetic property tester 2 is used to provide excitation current to the coil group and detect the induced voltage of the sample under test 5, and transmit the measured data to the host computer 1;

[0032] The host computer 1 is used to acquire the data tested by the magnetic property tester 2 and plot the magnetization curve.

[0033] In this embodiment, the magnetic shielding cylinder 3 includes: a sample platform 6, an aluminum alloy shielding layer 301, a plurality of permalloy shielding layers 302 sequentially nested, an interlayer pad 7, and a bracket 8; the sample platform 6 is slidably disposed inside the magnetic shielding cylinder 3 for placing the sample 5 to be tested.

[0034] It is important to note that Figure 1 The diagram shown is only a schematic of a five-layer shielding magnetic shielding cylinder 3. Figure 1 The schematic diagram shown illustrates that the magnetic shielding cylinder 3 includes one aluminum alloy shielding layer 301 and four permalloy shielding layers 302. Figure 1 This is for illustrative purposes only and is not intended to limit the embodiments of this application.

[0035] The four permalloy shielding layers 302 are sequentially nested from the inside out, and the aluminum alloy shielding layer 301 is nested on the four permalloy shielding layers 302, that is, the aluminum alloy shielding layer 301 is set on the outermost layer of the shielding structure. Interlayer pads 7 are provided between each permalloy shielding layer 302 and between the outermost permalloy shielding layer 302 and the aluminum alloy shielding layer 301. The interlayer pads 7 are used to support the aluminum alloy shielding layers 301 and between the permalloy shielding layers 302 and the aluminum alloy shielding layer 301.

[0036] It should be noted that the interlayer spacer 7 is made of non-magnetic material.

[0037] A corresponding aluminum alloy shielding cover 3011 is provided on one side of the aluminum alloy shielding layer 301. The aluminum alloy shielding cover 3011 is installed on the aluminum alloy shielding layer 301 to shield the alternating magnetic field.

[0038] Each permalloy shielding layer 302 is also provided with a corresponding permalloy shielding cover 3021 on one side. Each permalloy shielding cover 3021 is installed on the corresponding permalloy shielding layer 302 to shield external interference magnetic fields and prevent the tested sample 5 from being magnetized and affected by external magnetic fields after demagnetization.

[0039] In summary, the shielding layer and the corresponding shielding cover work together to provide a weak magnetic environment for the sample under test 5 and shield it from external interference magnetic fields.

[0040] It is important to note that there are strict tolerance requirements between each shielding layer and its corresponding shielding cover to ensure proper installation and removal.

[0041] Figure 2 This is a structural diagram of the magnetic shielding cylinder and support in a magnetic property testing device for high-permeability materials under low-frequency weak magnetic environment provided in one embodiment of this disclosure, as shown below. Figure 2 As shown, the aluminum alloy shielding cover 3011 and each permalloy shielding cover 3021 are provided with a first opening 9. The first opening 9 is used for the test wire 4 to pass through. That is, after the test wire 4 passes through the first opening 9, the coil group wound on the sample 5 under test is connected to the magnetic property tester 2.

[0042] The aluminum alloy shielding cover 3011 is also provided with symmetrical second openings 10 on both sides of the lower edge, and the second openings 10 are used to arrange the demagnetizing coil.

[0043] Specifically, after the magnetic shielding cylinder 3 is assembled, a demagnetizing coil is arranged on the permalloy shielding layer 302 of the magnetic shielding cylinder 3. The demagnetizing coil is wound on the innermost permalloy shielding layer 302 and the outermost permalloy shielding layer 302. The demagnetizing coil is used to demagnetize before the first use or when the internal residual magnetism becomes significantly larger.

[0044] The bracket 8 is located at the bottom of the magnetic shielding cylinder 3 and is used to support and fix the magnetic shielding cylinder 3. In this embodiment, the bracket 8 is made of aluminum alloy. In other embodiments of the present invention, the material of the bracket 8 includes, but is not limited to, aluminum alloy.

[0045] In this embodiment, the sample platform 6 is slidably installed inside the magnetic shielding cylinder 3, which facilitates the extraction of the sample platform 6 from the magnetic shielding cylinder 3 and the pushing of the sample platform 6 containing the sample to be tested 5 into the magnetic shielding cylinder 3.

[0046] Specifically, the width of the sample platform 6 is slightly smaller than the inner diameter of the innermost permalloy shielding layer 302. The two sides of the sample platform 6 abut against the inner wall of the innermost permalloy shielding layer 302. By cooperating with the innermost permalloy shielding layer 302, the sample platform 6 can be installed within it. Furthermore, the sample platform 6 can move along the length of the permalloy shielding layer 302, that is, along the length of the magnetic shielding cylinder 3. In other embodiments of the invention, the sample platform 6 can also be slidably installed within the magnetic shielding cylinder 3 in other ways, as long as it is possible to pull the sample platform 6 out of the magnetic shielding cylinder 3 and simultaneously push the sample platform 6 containing the test sample 5 into the magnetic shielding cylinder 3.

[0047] Before the sample 5 is placed on the sample platform 6, a coil group needs to be wound around it. The coil group includes an excitation winding coil and an induction winding coil. After the coil group is wound around the sample, it is connected to the magnetic property tester 2 through the test line 4. The number and number of turns of the coil group depend on the measuring equipment used, the required magnetic field size, and the testing method.

[0048] In this embodiment of the present disclosure, the coil group includes: an excitation winding coil and an induction winding coil. The excitation winding coil and the induction winding coil are wound as tightly as possible around the entire circumference of the test sample 5 to reduce the influence of the air gap under the winding. At this time, the winding of the test sample 5 is completed.

[0049] It is important to note that care should be taken to ensure that the insulation of the wires is not damaged during the winding process, and to avoid short circuits between the winding and the test sample 5. An appropriate AC insulation resistance meter should be used for electrical checks to ensure that there is no direct connection between the wires in the coil group and the test sample 5.

[0050] Before use, the magnetic shielding cylinder 3 is demagnetized and the internal residual magnetism is tested by a magnetometer. The test sample 5 with the winding completed is placed on the test platform 6, and then the test platform 6 is pushed into the magnetic shielding cylinder 3. The residual magnetism intensity at the sample placement point is tested by a magnetometer. The test sample 5 should be placed at the position where the residual magnetism of the magnetic shielding cylinder 3 is weakest. The shielding layer cover corresponding to the shielding layer is then covered to provide a weak magnetic environment for the sample.

[0051] The test sample 5, after being wound, is placed inside the magnetic shielding cylinder 3. The test sample 5 is demagnetized before each test, and the demagnetization frequency is not greater than the test frequency. The test sample 5 inside the magnetic shielding cylinder 3 is in a weak magnetic environment. The demagnetized test sample 5 will not be additionally magnetized by external interference magnetic fields. At this time, by providing the sample with an alternating excitation magnetic field with a sufficiently low amplitude and frequency, the low-frequency alternating magnetic characteristics of the magnetic material under weak magnetic conditions can be measured.

[0052] In the embodiments disclosed herein, the magnetic characteristic tester 3 includes a signal generator, a power amplifier, and a power analyzer, etc. In other embodiments of the present invention, the magnetic characteristic tester 3 includes, but is not limited to, a signal generator, a power amplifier, and a power analyzer, etc.

[0053] The power analyzer is connected to the induction winding coil via test line 4 and is used to detect the induced voltage of the sample 5 under test.

[0054] The signal generator and power amplifier are connected to the excitation winding coil via test line 5, which is used to apply alternating excitation current to the excitation winding coil. During the test, the excitation current is adjusted to obtain the relationship between magnetic flux density and magnetic field strength under different magnetic field strengths. The magnetic characteristic tester 2 transmits the measured data to the host computer 1, and the host computer 1 plots the magnetization curve based on the data measured by the magnetic characteristic tester 2.

[0055] It should be noted that the test sample 5 is ring-shaped, mainly for but not limited to permalloy, ferrite and amorphous / nanocrystalline high magnetic permeability materials. The test sample is cut into a ring-shaped thin sheet, burrs are removed and heat treatment is performed.

[0056] The dimensional requirements for the tested sample 5 are shown in the following calculation formula:

[0057] 100mm 2 ≤A≤500mm 2

[0058]

[0059] In the formula: A is the cross-sectional area of ​​the sample 5 being tested; D is the outer diameter of the sample 5 being tested; d is the inner diameter of the sample 5 being tested; and h is the height of the sample 5 being tested.

[0060] The dimensions and number of turns of the tested sample 5 are determined based on the test principle, and the calculation formula is as follows:

[0061] The formula for calculating the excitation magnetic field strength H is as follows:

[0062]

[0063]

[0064] Where: N l I is the number of turns of the excitation winding coil, I is the excitation current, and l is the average magnetic path length of the sample.

[0065] The formula for calculating the induced magnetic flux density ΔB is as follows:

[0066]

[0067] In the formula, Ng f is the number of turns in the induction winding; f is the current frequency. The average value of the induced voltage after rectification.

[0068] As shown in the above calculations, to obtain a smaller excitation magnetic field and a larger change in the induced magnetic field, the number of turns in the excitation winding and the excitation current need to be sufficiently small, while the average magnetic circuit length, cross-sectional area, and the number of turns in the induction winding need to be sufficiently large. Therefore, the test sample 5 needs to be prepared with a large inner and outer diameter and a large difference between the inner and outer diameters. The number of turns in the coil on the test sample should be designed so that the number of turns in the excitation coil is small and the number of turns in the induction coil is large.

[0069] For example, with an outer diameter of 200mm, an inner diameter of 100mm, a thickness of 4mm, 2 turns in the excitation coil, 490 turns in the induction coil, and an excitation current of 1mA, the excitation magnetic field is 4.2 × 10⁻⁶. -4 The A / m is much smaller than the current conventional test excitation magnetic field of 0.08 A / m.

[0070] To achieve the best test results, the number of turns in the excitation coil was optimized to match the output impedance of the power amplifier.

[0071] The optimized formula for calculating the number of turns N1 of the excitation coil is as follows:

[0072] Z=jωL

[0073]

[0074] In the formula: Z is the power supply output impedance; ω is the excitation current angular frequency; L is the effective inductance of the excitation winding; μ0 is the air permeability; μ r The relative permeability of the sample can be obtained using parameters provided by the manufacturer.

[0075] It should be noted that when the magnetic property tester 2 is turned on, the test sample 5 is tested through the signal generator and power amplifier. The signal generator and power amplifier are set with excitation currents of different frequencies so that the test sample 5 is in an alternating magnetic field environment of different magnitudes. The test frequency starts from 0.01Hz and the maximum value is 1KHz. The induced voltage at the winding end of the induction coil is measured, and then the permeability of the material under a certain frequency and initial magnetic field can be obtained. During the test, the magnetizing current is set to gradually increase, and the relationship between magnetic field strength and magnetic flux density can be obtained. The magnetization curve is obtained through the host computer 1.

[0076] The calculation formula based on the magnetization curve and relative permeability is as follows:

[0077]

[0078] In the formula, B is the magnetic induction intensity; H is the excitation magnetic field intensity; μ0 is the air permeability; μ rThe relative permeability of the sample is given.

[0079] When the excitation current frequency is constant, the permeability of the material in a very weak magnetic environment and above magnetic field environment at that frequency can be obtained; when the excitation magnetic field is constant, changing the excitation magnetic field frequency can obtain the changes in magnetic properties at different magnetic field frequencies, with a frequency range of 0.01Hz-1KHz.

[0080] In summary, the magnetic property testing device for high-permeability materials under low-frequency weak magnetic environment proposed in this application includes: a coil group, a magnetic property tester 2, a magnetic shielding cylinder 3, and a host computer 1; the coil group is wound around the sample under test 5 and connected to the magnetic property tester 2 through test wires 4, and the sample under test 5 with the coil group wound around it is placed inside the magnetic shielding cylinder 3; the magnetic shielding cylinder 3 is used to provide a weak magnetic environment for the sample under test 5 placed inside the magnetic shielding cylinder and to shield external interference magnetic fields; the magnetic property tester 2 is used to provide excitation current to the coil group and detect the induced voltage of the sample under test 5, and transmit the measured data to the host computer 1; the host computer 1 is used to acquire the data measured by the magnetic property tester 2 and plot the magnetization curve. The technical solution of the present invention, on the one hand, is to test the low-frequency magnetic characteristics of the test sample 5 in a weak magnetic environment by placing the test sample 5 in a magnetic shielding cylinder 3 to avoid the influence of external interference magnetic fields on the test results. On the other hand, by using an improved signal generator and power amplifier to provide the test sample with an alternating excitation current starting at 0.01Hz, the low-frequency magnetic characteristics of high permeability materials in a weak magnetic environment can be tested conveniently and quickly.

[0081] Example 2

[0082] Figure 3 This is a flowchart of a method for testing the magnetic properties of high-permeability materials under low-frequency weak magnetic environment according to an embodiment of this application. The method includes:

[0083] Step 1: Prepare the test sample 5 and wind the coil assembly onto the test sample 5;

[0084] Step 2: Connect the coil assembly to the magnetic property tester 2 via test lead 4;

[0085] Step 3: Place the sample 5 with the coil winding on the sample platform 6 of the shielding cylinder 3 and cover it with the corresponding shielding cover to provide a weak magnetic environment for the sample 5.

[0086] Step 4: Start the magnetic property tester 2, and the host computer 1 acquires the data measured by the magnetic property tester 2 and plots the magnetization curve;

[0087] In this embodiment of the present disclosure, the test sample 5, after being wound, is placed on the test platform 6 in the shielding cylinder 3, and the residual magnetic intensity at the place where the sample 5 is placed is tested by a magnetometer, so that the test sample 5 is in the position where the residual magnetic field of the shielding cylinder 3 is weakest.

[0088] In step 4, the magnetic characteristic tester 3 is started, and the data measured by the magnetic characteristic tester 2 is obtained through the host computer 1 and the magnetization curve is plotted. This includes: turning on the magnetic characteristic tester 2, applying alternating excitation current to the excitation winding coil of the sample under test through a signal generator and a power amplifier to generate a corresponding excitation magnetic field, detecting the induced voltage of the induction winding coil through a power analyzer, gradually increasing the magnetization current to obtain the magnetic flux density under different magnetic field strengths, obtaining the relationship between different magnetic field strengths and magnetic flux density, and plotting the magnetization curve through the host computer 1.

[0089] It should be noted that the test sample 5 is demagnetized before each test. The demagnetization frequency is not greater than the test frequency. The test sample 5 located inside the magnetic shielding cylinder 3 is in a weak magnetic environment. After demagnetization, the test sample 5 will not be additionally magnetized by external interference magnetic fields. At this time, by providing the sample with an alternating excitation magnetic field with a sufficiently low amplitude and frequency, the low-frequency alternating magnetic characteristics of the magnetic material under weak magnetic conditions can be measured.

[0090] Figure 4 The following is a flowchart illustrating a method for testing the magnetic properties of high-permeability materials under low-frequency weak magnetic environment according to an embodiment of this application. Figure 4 As shown, the method specifically includes:

[0091] S1: Prepare ring-shaped test samples 5 of materials such as permalloy and amorphous / nanocrystalline materials;

[0092] The dimensional requirements for the tested sample 5 are shown in the following calculation formula:

[0093] 100mm 2 ≤A≤500mm 2

[0094]

[0095] In the formula: A is the cross-sectional area of ​​the sample 5 being tested; D is the outer diameter of the sample 5 being tested; d is the inner diameter of the sample 5 being tested; and h is the height of the sample 5 being tested.

[0096] S2: Wind the test sample 5 according to the required number of turns;

[0097] In this process, the excitation winding coil and the induction winding coil are wound as tightly as possible around the entire circumference of the sample 5 under test.

[0098] It should be noted that the dimensions and number of turns of the tested sample 5 are determined according to the test principle, and the calculation formula is as follows:

[0099] The formula for calculating the excitation magnetic field strength H is as follows:

[0100]

[0101]

[0102] Where: N l I is the number of turns of the excitation winding coil, I is the excitation current, and l is the average magnetic path length of the sample.

[0103] The formula for calculating the induced magnetic flux density ΔB is as follows:

[0104]

[0105] In the formula, N g f is the number of turns in the induction winding; f is the current frequency. The average value of the induced voltage after rectification;

[0106] To achieve the best test results, the number of turns in the excitation coil was optimized to match the output impedance of the power amplifier.

[0107] The optimized formula for calculating the number of turns N1 of the excitation coil is as follows:

[0108] Z=jωL

[0109]

[0110] In the formula: Z is the power supply output impedance; ω is the excitation current angular frequency; L is the effective inductance of the excitation winding; μ0 is the air permeability; μ r The relative permeability of the sample can be obtained using parameters provided by the manufacturer.

[0111] S3: Connect the excitation winding coil and the induction winding coil to the magnetic characteristic tester 3;

[0112] The magnetic characteristic tester 2 includes a signal generator, a power amplifier, and a power analyzer. The power analyzer is connected to the induction winding coil via test line 4 and is used to detect the induced voltage of the sample 5 under test. The signal generator and the power amplifier are connected to the excitation winding coil via test line 5 and are used to apply alternating excitation current to the excitation winding coil. During the test, the relationship between the magnetic flux density and the magnetic field strength under different magnetic field strengths is obtained by adjusting the excitation current.

[0113] S4: Place the sample to be tested 5 into the magnetic shielding cylinder 3;

[0114] Before use, the magnetic shielding cylinder 3 is demagnetized and its internal residual magnetism is tested by a magnetometer. The test sample 5, after being wound, is placed on the test platform 6, and then the test platform 6 is pushed into the magnetic shielding cylinder 3. The residual magnetism intensity at the sample placement point is tested by a magnetometer, and the test sample 5 should be placed at the position where the residual magnetism of the magnetic shielding cylinder 3 is weakest.

[0115] S5: The shielding cover on the shielding layer provides a weak magnetic environment for the sample 5 under test.

[0116] S6: Demagnetize the sample 5 being tested.

[0117] S7: Magnetization curves and amplitude permeability, etc., are measured using the voltammetric method and digital integration at frequencies from 0.01 Hz to 1 kHz.

[0118] It should be noted that when the magnetic property tester 2 is turned on, the test sample 5 is tested through the signal generator and power amplifier. The signal generator and power amplifier are set with excitation currents of different frequencies so that the test sample 5 is in an alternating magnetic field environment of different magnitudes. The test frequency starts from 0.01Hz and the maximum value is 1KHz. The induced voltage at the winding end of the induction coil is measured, and then the permeability of the material under a certain frequency and initial magnetic field can be obtained. During the test, the magnetizing current is set to gradually increase, and the relationship between magnetic field strength and magnetic flux density can be obtained. The magnetization curve is obtained through the host computer 1.

[0119] Based on the magnetization curve and the relative permeability formula:

[0120]

[0121] In the formula, B is the magnetic induction intensity; H is the excitation magnetic field intensity; μ0 is the air permeability; μ r The relative permeability of the sample is given.

[0122] When the excitation current frequency is constant, the permeability of the material in a very weak magnetic environment and above magnetic field environment at that frequency can be obtained; when the excitation magnetic field is constant, changing the excitation magnetic field frequency can obtain the changes in magnetic properties at different magnetic field frequencies, with a frequency range of 0.01Hz-1KHz.

[0123] In summary, this application proposes a method for testing the magnetic properties of high-permeability materials in a low-frequency, weak magnetic environment, comprising: preparing a test sample 5 and winding a coil assembly around it; connecting the coil assembly to a magnetic property tester 3 via test leads 4; placing the test sample 5 with the coil assembly on the sample platform 6 of the shielding cylinder 3 and covering it with a shielding cover to provide a weak magnetic environment for the test sample 5; starting the magnetic property tester 2, and the host computer 1 acquiring the data measured by the magnetic property tester 2 and plotting the magnetization curve. This technical solution can test the relative amplitude permeability, magnetization curve, and other magnetic properties of high-permeability materials in a weak magnetic environment, making up for the data deficiencies of the original method. Furthermore, it improves the accuracy of theoretical calculations and simulation calculations for various magnetic shielding devices, especially enabling more accurate acquisition of shielding effect data for the inner shielding layer of multi-layer magnetic shielding devices.

[0124] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0125] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing custom logic functions or processes, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of this application pertain.

[0126] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A device for testing the magnetic properties of high permeability material in a low frequency flux-weakening environment, characterized in that, The device includes: a coil assembly, a magnetic property tester, a magnetic shielding cylinder, and a host computer; The coil assembly is wound around the sample under test and connected to the magnetic property tester via test leads. The sample under test with the coil assembly wound around it is placed inside a magnetic shielding cylinder. The sample under test is ring-shaped and is cut into a ring-shaped thin sheet, burrs are removed, and heat treatment is performed. The sample under test is demagnetized before each test. The coil assembly includes an excitation winding coil and an induction winding coil, which are wound around the entire circumference of the sample under test. The induction winding coil is connected to a power analyzer via test leads, and the excitation winding coil is connected to a signal generator and a power amplifier via test leads. The magnetic shielding cylinder provides a weak magnetic environment for the sample under test placed inside and shields it from external interference magnetic fields. The magnetic shielding cylinder includes a sample platform, an aluminum alloy shielding layer, multiple permalloy shielding layers nested sequentially, interlayer pads, and supports. The system comprises: a sample platform housed inside the magnetic shielding cylinder for placing the sample to be tested; a permalloy shielding layer for shielding external interference magnetic fields; an aluminum alloy shielding layer outside the permalloy shielding layer for shielding AC magnetic fields; interlayer pads positioned between the permalloy shielding layers and between the permalloy shielding layer and the aluminum alloy shielding layer for supporting the permalloy shielding layers and between the aluminum alloy shielding layers; and a bracket positioned at the bottom of the aluminum alloy shielding layer for supporting and fixing the magnetic shielding cylinder. The sample platform is slidably installed inside the magnetic shielding cylinder, which makes it easy to pull the sample platform out of the magnetic shielding cylinder and place the test sample with coil assembly on the sample platform, and at the same time makes it easy to push the sample platform into the magnetic shielding cylinder. The magnetic characteristic tester is used to provide excitation current to the coil group and detect the induced voltage of the sample under test, and transmit the measured data to the host computer. The magnetic characteristic tester includes: a signal generator, a power amplifier, and a power analyzer. The power analyzer is connected to the induction winding coil through test leads and is used to detect the induced voltage of the sample under test. The signal generator and the power amplifier are connected to the excitation winding coil through test leads and are used to apply alternating excitation current to the excitation winding coil. During the test, the relationship between different magnetic field strengths and magnetic flux density is obtained by adjusting the excitation current. The host computer plots the magnetization curve based on the data measured by the magnetic characteristic tester. The host computer is used to acquire the data measured by the magnetic property tester and plot the magnetization curve. The dimensional requirements of the sample being tested are shown in the following calculation formula: wherein: A is the cross-sectional area of the sample being measured; D is the outer diameter of the sample being measured; I is the inner diameter of the sample being measured; H is the height of the sample 5 being measured; The dimensions of the tested sample and the number of winding turns are determined based on the testing principle, and the calculation formula is as follows: Excitation magnetic field strength The calculation formula is as follows: In the formula: This refers to the number of turns in the excitation winding coil. For excitation current, The average magnetic circuit length of the sample; Induced magnetic flux density The calculation formula is as follows: In the formula, This refers to the number of turns in the induction winding. The frequency is the current frequency. The average value of the induced voltage after rectification; The number of turns of the excitation coil on the test sample was optimized to match the output impedance of the power amplifier: the optimized number of turns of the excitation coil. The calculation formula is as follows: In the formula: The power supply output impedance; The excitation current angular frequency; The effective inductance of the excitation winding; air permeability; The relative permeability of the sample is given.

2. The apparatus according to claim 1, characterized in that, The aluminum alloy shielding layer and each permalloy shielding layer are provided with a corresponding shielding cover; The shielding cover is installed on the corresponding shielding layer, and the shielding layer and the corresponding shielding cover work together to provide a weak magnetic environment for the sample under test.

3. The apparatus according to claim 2, characterized in that, Each shielding cover is provided with a first opening for the test lead to pass through; The shielding cover corresponding to the aluminum alloy shielding is provided with a second opening for arranging the demagnetizing coil.

4. A method for testing the magnetic properties of high-permeability materials under low-frequency weak magnetic environment based on the testing device described in any one of claims 1-3, characterized in that, The method includes: Prepare the test sample and wind the coil assembly around it; Connect the coil assembly to the magnetic property tester via test leads; The sample under test, with the coil windings wound around it, is placed on the sample platform of the shielding cylinder and covered with the corresponding shielding cover to provide a weak magnetic environment for the sample under test. Start the magnetic property tester, and the host computer will acquire the data measured by the magnetic property tester and plot the magnetization curve.

5. The method according to claim 4, characterized in that, Also includes: The test sample with the winding completed is placed on the test platform inside the shielding cylinder, and the residual magnetic intensity at the place where the sample is placed is measured by a magnetometer, so that the test sample is in the position where the residual magnetic field of the shielding cylinder is weakest.

6. The method according to claim 4, characterized in that, The process of starting the magnetic characteristic tester and obtaining the data measured by the magnetic characteristic tester through the host computer and plotting the magnetization curve includes: turning on the magnetic characteristic tester, applying an alternating excitation current to the excitation winding coil of the sample under test through a signal generator and a power amplifier to generate a corresponding excitation magnetic field, detecting the induced voltage of the induction winding coil through a power analyzer, gradually increasing the magnetization current to obtain the magnetic flux density under different magnetic field strengths, obtaining the relationship between different magnetic field strengths and magnetic flux density, and plotting the magnetization curve through the host computer.

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