System for measuring axial alternating current hysteresis loop of soft magnetic material by open magnetic circuit

Abstract

The invention discloses a system for measuring an axial alternating-current hysteresis loop of a soft magnetic material by an open magnetic circuit, which utilizes an alternating-current Helmholtz coil to provide an axial alternating-current magnetic field, utilizes an induction coil positioned in the alternating-current Helmholtz coil to capture induction voltage, and utilizes an alternating-current magnetic field sensor in the alternating-current Helmholtz coil to obtain magnetic field intensity. And obtaining magnetic induction intensity based on the induced voltage, and obtaining an axial alternating-current hysteresis loop diagram of the soft magnetic material in an alternating-current excitation state through the magnetic field intensity and the magnetic induction intensity.

Description

Technical Field

[0001] The present invention belongs to the field of magnetic material measurement, and particularly relates to a system for measuring the axial AC hysteresis loop of soft magnetic materials with an open magnetic circuit. Background Art

[0002] Due to its extremely high magnetic permeability and extremely low coercivity, amorphous alloy materials have significant advantages in the field of soft magnetic materials. Amorphous alloy microfilaments (or narrow bands) have been widely used in fields such as invasive medical treatment, electronic compasses, electric bicycles, and fluxgate sensors due to their extremely small volume and excellent magnetic sensitivity characteristics. As the core component of magnetic detection devices, the magnetic performance characterization under actual working conditions is crucial. The hysteresis loop is a key method for measuring the soft magnetic characteristics of magnetic materials, and important parameters such as the saturation magnetization intensity, coercivity, and remanence of the material can be obtained through the loop. However, the currently widely used vibrating sample magnetometer (VSM) and B-H instrument can only measure the static magnetic properties of materials and cannot accurately reflect the magnetic performance of materials under actual working conditions.

[0003] The patent application with the publication number CN117269863A discloses an AC hysteresis loop measurement system and an AC hysteresis loop measurement method. The system includes: a magnetic core to be measured; a coil surrounding the magnetic core to be measured; a control module connected to the coil for outputting AC voltage signals of multiple frequencies on the coil, and the AC voltage signals cause the magnetic core to be measured to reach saturation; a measurement module connected to the coil for obtaining the measurement data fed back by the coil, calculating the magnetic field strength and magnetic flux density according to the measurement data, and drawing the hysteresis loop corresponding to each frequency according to the magnetic field strength and magnetic flux density. The present invention can directly test the hysteresis loop in the saturated state, has a short test time, and can automatically complete the tests of multiple frequencies. However, the AC hysteresis loop measurement method disclosed in this patent is limited to the test of a closed magnetic circuit.

[0004] The invention patent application with the publication number CN119148030A discloses a method for measuring the circumferential alternating current loop of magnetic microfilaments based on LabVIEW. This method realizes loop measurement based on LabVIEW program control. The steps include: connecting the magnetic microfilament in series with a resistor and then connecting them together to a signal generator, while connecting another channel of the signal generator to an oscilloscope. The other two channels of the oscilloscope simultaneously measure the voltage signals at both ends of the magnetic microfilament and the resistor, and connect them to a computer to achieve control. The LabVIEW program reads the voltage signals measured by the oscilloscope and performs digital filtering processing, numerical integration processing, image display processing, data recording and storage. Through the above two steps, the circumferential alternating current hysteresis loop of the magnetic microfilament can be measured. This patent application avoids the use of induction coils, and through physical derivation, an indirect measurement method is obtained and demonstrated to obtain the circumferential alternating current hysteresis loop of the material. The measurement method is simple enough, only requiring two common devices, namely a signal generator and an oscilloscope. The method disclosed in this patent application is applicable to orthogonal excitation type fluxgate sensors, but not applicable to parallel excitation type fluxgate sensors. Summary of the Invention

[0005] The present invention provides a system for measuring the axial alternating current hysteresis loop of soft magnetic materials in an open magnetic circuit. Through this system, the axial alternating current hysteresis loop diagram of soft magnetic materials under alternating current excitation can be accurately drawn.

[0006] The present invention provides a system for measuring the axial alternating current hysteresis loop of soft magnetic materials in an open magnetic circuit, including:

[0007] A signal generator for generating an alternating current excitation source;

[0008] A test module, where the test module includes:

[0009] An alternating current Helmholtz coil, which is connected to the signal generator and is used to access the excitation current and generate an axial alternating current magnetic field;

[0010] An alternating current magnetic field sensor, which is fixed in the uniform area of the alternating current Helmholtz coil and generates an alternating current excitation magnetic field intensity waveform under the action of the axial alternating current magnetic field;

[0011] An induction coil, which is made by a hollow solenoid. The induction coil is located in the uniform area of the alternating current Helmholtz coil and is parallel to the direction of the generated alternating current excitation field, and generates an induced voltage signal under the action of the alternating current magnetic field;

[0012] An oscilloscope, which is connected to the alternating current magnetic field sensor and the induction coil, and is used to display the alternating current excitation magnetic field intensity signal and the induced voltage signal respectively, so that the magnetic field intensity signal and the induced voltage signal share the same time series;

[0013] The host computer is connected to the oscilloscope and the signal generator, and is used to set the frequency and amplitude of the signal emitted by the signal generator. It is also used to display the waveform based on the signals obtained from each channel of the oscilloscope, and further obtain the magnetic induction intensity waveform by calculating the induced voltage. The axial AC hysteresis loop of the soft magnetic material is obtained by making a Lissajous figure based on the AC excitation magnetic field intensity signal and the magnetic induction intensity signal.

[0014] Preferably, the induction coil is obtained by connecting two coils with the same number of turns and cross-sectional area in series and in reverse.

[0015] Preferably, a power amplifier is further included. The power amplifier is connected to the signal generator, the test module and the host computer respectively, and is used to amplify the power of the signal based on the received instruction signal from the host computer, and connect the amplified signal to the AC Helmholtz coil.

[0016] Preferably, the AC magnetic field sensor is replaced by a sampling resistor and a voltmeter. The two ends of the sampling resistor are respectively connected to the power amplifier and the AC Helmholtz coil. The voltage of the sampling resistor is measured by the voltmeter, and then the excitation current I flowing through the sampling resistor is obtained. The magnetic field intensity H is obtained based on the H / I conversion coefficient of the AC Helmholtz coil. <U+ <U+

[0017] Preferably, the test module further includes a test connecting rod, a first fixing clamp, a second fixing clamp and a PCB test board;

[0018] The test connecting rod is connected to the first fixing clamp, so that the first fixing clamp is located in the uniform area of the AC Helmholtz coil;

[0019] The first fixing clamp is located at the top of the test connecting rod. The AC magnetic field sensor is inserted into the first fixing clamp, and the AC magnetic field sensor is fixed in the uniform area of the AC Helmholtz coil through the first fixing clamp;

[0020] The second fixing clamp is fixedly connected to the top of the first fixing clamp and is used to fix the PCB test board;

[0021] A hollow solenoid is provided on the PCB test board as the induction coil. The PCB test board is provided with pads for connecting the induction signal out with a BNC signal line and displaying it on the oscilloscope.

[0022] Preferably, the intrinsic voltage value of the test induction coil is measured, and the obtained induced voltage is subtracted by the intrinsic voltage value through the host computer to obtain the final induced voltage value.

[0023] Preferably, the magnetic induction intensity signal B is:

[0024]

[0025]

[0026] Among them, V in is the induced voltage, N represents the number of turns of the induction coil, S is the cross-sectional area of the soft magnetic material, and t is the time.

[0027] Preferably, the software adopted by the host computer includes LabVIEW, Pathon or MATLAB.

[0028] Preferably, the soft magnetic material is an amorphous alloy microfilament or an amorphous alloy narrow band.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] The present invention uses an alternating current Helmholtz coil to provide an axial alternating current magnetic field, uses an induction coil located in the uniform area of the alternating current Helmholtz coil to capture the induced voltage, and obtains the magnetic field intensity through an alternating current magnetic field sensor in the uniform area. The magnetic induction intensity is obtained based on the induced voltage, and the axial alternating current hysteresis loop diagram of the soft magnetic material under the alternating current excitation state is obtained through the magnetic field intensity and the magnetic induction intensity. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is the equipment connection diagram of the system for measuring the axial alternating current hysteresis loop of the soft magnetic material by the magnetic circuit in the specific embodiment of the present invention;

[0032] Figure 2 is the structural diagram of the test module provided in the specific embodiment of the present invention;

[0033] Figure 3 is the axial alternating current hysteresis loop of the amorphous material measured by the system for measuring the axial alternating current hysteresis loop of the soft magnetic material by the open magnetic circuit provided in the specific embodiment of the present invention.

[0034] Among them, 1 - Helmholtz coil, 2 - test connecting rod, 3 - first fixing clamp, 4 - alternating current magnetic field sensor, 5 - second fixing clamp, 6 - PCB test board, 7 - induction coil. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] The system for measuring the axial alternating current hysteresis loop of the soft magnetic material by the open magnetic circuit provided in the specific embodiment of the present invention will be described in detail in combination with the accompanying drawings provided by the present invention.

[0036] Since soft magnetic materials are generally used in an environment of alternating magnetic fields in reality, and the soft magnetic materials include amorphous alloy microfilaments or amorphous alloy narrow tapes, therefore, how to measure the axial alternating magnetic hysteresis loop of soft magnetic materials in an alternating magnetic field environment has become a technical problem that urgently needs to be solved. In a specific embodiment of the present invention, a solenoid with a test sample inside is placed in the uniform magnetic field area of an alternating current Helmholtz coil, and an accurate alternating current excitation current is generated through the control of a host computer, so that the coil generates a controllable axial alternating magnetic field; at the same time, an induction coil is used to collect the magnetic induction voltage signal, and the magnetic field intensity is monitored in real time through an alternating magnetic field sensor, and the obtained magnetic induction voltage signal is converted into magnetic induction intensity data; finally, based on the synchronously measured magnetic field intensity and magnetic induction intensity signals, the axial alternating magnetic hysteresis loop of the material can be accurately drawn after data processing.

[0037] The system for measuring the axial alternating magnetic hysteresis loop of soft magnetic materials with an open magnetic circuit provided by a specific embodiment of the present invention, as Figure 1 and Figure 2 shown, includes a signal generator, a test module, an oscilloscope and a host computer. The test module includes an alternating current Helmholtz coil 1, an alternating magnetic field sensor 4, and an induction coil 7 that wraps the soft magnetic material to be tested.

[0038] The signal generator provided by a specific embodiment of the present invention receives a combined signal of excitation voltage and frequency from the host computer and generates a corresponding alternating current excitation source.

[0039] In the test module provided by a specific embodiment of the present invention, the alternating magnetic field sensor 4 and the induction coil 7 that wraps the soft magnetic material to be tested are located in the uniform area of the alternating current Helmholtz coil 1. The alternating current Helmholtz coil 1 receives the alternating current excitation source to generate an axial alternating magnetic field. The alternating magnetic field sensor 4 located in the core area of the axial alternating magnetic field generates a magnetic field intensity signal, and the induction coil 7 generates an induced voltage.

[0040] In a specific embodiment, the induction coil 7 provided in this embodiment is obtained by connecting two coils with the same number of turns and cross-sectional areas in series in reverse. Since the induction coil 7 will generate an intrinsic inductance under the action of an alternating magnetic field, resulting in an excessive induced voltage, which will affect the measurement of the magnetic induction intensity. In this embodiment, two coils with the same number of turns and cross-sectional areas are connected in series in reverse, so that the two coils generate magnetic fluxes with the same magnitude and opposite directions, so that the final error voltage drops to zero, avoiding the influence of the solenoid inductance on the induced voltage and eliminating the inductance error in the test process.

[0041] This embodiment can also calculate and deduct by the host computer through testing the induced voltage value of the induction coil to eliminate the inductance error in the test process.

[0042] In a specific embodiment, the specific embodiment of the present invention also uses a sampling resistor and a voltmeter to replace the AC magnetic field sensor. In one embodiment, the sampling resistor is located on the PCB test board to reduce the usage cost. The two ends of the sampling resistor provided in this embodiment are respectively connected to a power amplifier and an AC Helmholtz coil. The voltage of the sampling resistor is measured by a voltmeter, and then the excitation current I flowing through the sampling resistor is obtained. Based on the H / I conversion coefficient of the AC Helmholtz coil, the magnetic field strength H is obtained.

[0043] The test module provided by the specific embodiment of the present invention further includes a test connecting rod 2, a first fixing clamp 3, a second fixing clamp 5, and a PCB test board 6; the test connecting rod 2 is connected to the first fixing clamp 3, so that the first fixing clamp 3 is located inside the AC Helmholtz coil 1;

[0044] The first fixing clamp 3 provided by the specific embodiment of the present invention is located at the top of the test connecting rod 2. The AC magnetic field sensor 4 is inserted into the first fixing clamp 3, and the AC magnetic field sensor 4 is fixed inside the AC Helmholtz coil 1 through the first fixing clamp 3;

[0045] The second fixing clamp 5 provided by the specific embodiment of the present invention is fixedly connected to the top of the first fixing clamp 3 and is used to fix the PCB test board 6;

[0046] A hollow solenoid is provided as an induction coil on the PCB test board provided by the specific embodiment of the present invention. The PCB test board is provided with pads for connecting the induction signal out with a BNC signal line and displaying it on an oscilloscope.

[0047] The oscilloscope provided by the specific embodiment of the present invention includes a first channel CH1 and a second channel CH2. The first channel CH1 is connected to the AC magnetic field sensor and is used to receive the magnetic field strength signal. The second channel CH2 of the oscilloscope is connected to the induction coil and is used to receive the induction voltage signal. Through the oscilloscope, the magnetic field strength signal and the induction voltage signal share the same time series.

[0048] The upper computer provided by the specific embodiment of the present invention is connected to the oscilloscope and the signal generator, and is used to send an excitation instruction to the signal generator. It is also used to convert the induction voltage into a magnetic induction intensity signal, and make a Lissajous figure based on the received AC excitation magnetic field strength signal and the magnetic induction intensity signal. The horizontal and vertical coordinates of the output Lissajous figure are the magnetic field strength and the magnetic induction intensity respectively, and the axial AC hysteresis loop of the soft magnetic material is obtained.

[0049] In a specific embodiment, the software adopted by the upper computer provided in this embodiment includes LabVIEW, Pathon or MATLAB.

[0050] The host computer provided by the specific embodiment of the present invention converts the induced voltage into a magnetic induction intensity signal, and the magnetic induction intensity signal B is as follows:

[0051]

[0052]

[0053] Among them, V in is the induced voltage, N represents the number of turns of the induction coil, S is the cross-sectional area of the soft magnetic material, S = pi(D / 2) 2 , D is the diameter of the soft magnetic material, and t is the time.

[0054] In a specific embodiment, the open magnetic circuit system for measuring the axial AC hysteresis loop of soft magnetic materials provided by the specific embodiment of the present invention further includes a power amplifier. The power amplifier is respectively connected to the signal generator, the test module, and the host computer, and is used to amplify the AC excitation source based on the received instruction signal from the host computer and send the amplified AC excitation source to the AC Helmholtz coil.

[0055] In a specific embodiment, the open magnetic circuit system for measuring the axial AC hysteresis loop of soft magnetic materials provided by the specific embodiment of the present invention further includes a shielding cylinder. The test module is located inside the shielding cylinder, and the shielding cylinder is used to eliminate the ambient magnetic field.

[0056] The specific embodiment of the present invention also provides a method for testing the axial AC hysteresis loop of soft magnetic materials using the above open magnetic circuit system for measuring the axial AC hysteresis loop of soft magnetic materials. In this embodiment, LabVIEW is selected as the host computer control software, the selected soft magnetic material is an amorphous wire with a diameter of 100μm, an AC magnetic field probe is used as the access source of the oscilloscope CH 2 signal, and the induction coil uses a double-coil series reverse connection method to eliminate the test error. The specific steps include:

[0057] The length of the amorphous wire provided in this embodiment is longer than the row width of the induction coil by 10mm. The amorphous wire is inserted into the induction coil, and both ends of the amorphous wire extend outside the induction coil. During the process of inserting the amorphous wire into the solenoid pair, the relative position of the amorphous wire and the solenoid may change due to equipment movement. If the lengths of the amorphous wire and the solenoid are the same, equipment movement may cause the amorphous wire not to be completely inside the solenoid, resulting in a shorter magnetic circuit length. If the amorphous wire is longer than the solenoid, even if the relative position of the amorphous wire and the solenoid changes, the magnetic circuit length of the amorphous wire inside the solenoid is still equal to the length of the solenoid.

[0058] In this embodiment, the combination of the required excitation current and frequency is edited on the host computer, and the combined signal is sent to the signal generator through the host computer.

[0059] In this embodiment, the AC test probe is inserted into the first fixed fixture and fixed with screws.

[0060] In this embodiment, the PCB board with an induction coil is inserted into the second fixed fixture and fixed with screws. A hollow solenoid is provided on the PCB test board as the induction coil. The PCB test board is provided with pads for connecting the induction signal out with a BNC signal line and displaying it on an oscilloscope.

[0061] In this embodiment, the output end of the signal generator is connected to the power amplifier, and the output signal of the power amplifier is connected to the AC Helmholtz coil. At the same time, one end of the power amplifier is connected to the host computer, which is used to receive the magnification command signal from the host computer and send the amplified AC excitation source to the AC Helmholtz coil.

[0062] In this embodiment, the output end of the induction coil is connected to the CH1 channel of the oscilloscope, and in this embodiment, the output end of the induction coil is connected to the CH2 channel of the oscilloscope.

[0063] In this embodiment, the Helmholtz coil is placed in the shielding barrel.

[0064] In this embodiment, the output frequency and voltage of the signal generator and the signal extraction of the oscilloscope are all realized by using the network communication of LabVIEW for program control.

[0065] In this embodiment, the signal generator is turned on to start excitation. At this time, the induction signal V in (t) output by the solenoid and the excitation magnetic field amplitude signal H(t) are respectively displayed on CH1 and CH2 of the oscilloscope, and the two groups of waveforms share the same time series.

[0066] In this embodiment, the LabVIEW software of the host computer integrates the signal of CHI and passes through the input coil turns N and the cross-sectional area of the amorphous wire S = pi(D / 2) 2 (D is the diameter of the amorphous wire) to obtain the waveform B(t) of the axial magnetic induction intensity of the amorphous wire changing with time.

[0067] In this embodiment, the excitation magnetic field waveform H(t) and the waveform B(t) of the axial magnetic induction intensity of the amorphous wire changing with time are respectively used as the X and Y axes to obtain the axial AC loop of the amorphous wire.

[0068] As Figure 3 shown, the axial AC hysteresis loops of the amorphous wire under different amplitude excitation magnetic fields at a fixed frequency of 15 kHz are obtained by the above method.

Claims

1. A system for measuring the axial AC hysteresis loop of soft magnetic materials with an open magnetic circuit, characterized in that, Comprising: A signal generator for generating an AC excitation source; A test module, the test module comprising: An AC Helmholtz coil connected to the signal generator for accessing an excitation current and generating an axial AC magnetic field; An AC magnetic field sensor fixed in the uniform region of the AC Helmholtz coil for generating an AC excitation magnetic field intensity waveform under the action of the axial AC magnetic field; An induction coil made by a hollow solenoid, the induction coil being located in the uniform region of the AC Helmholtz and parallel to the direction of the generated AC excitation field for generating an induced voltage signal under the action of the AC magnetic field; An oscilloscope connected to the AC magnetic field sensor and the induction coil for respectively displaying the AC excitation magnetic field intensity signal and the induced voltage signal, such that the magnetic field intensity signal and the induced voltage signal share the same time series; A host computer connected to the oscilloscope and the signal generator for setting the frequency and amplitude of the signal sent by the signal generator, and also for obtaining the signal display waveforms of each channel of the oscilloscope based on the acquired data, and further obtaining the magnetic induction intensity waveform by calculating the induced voltage, and obtaining the axial AC hysteresis loop of the soft magnetic material based on the AC excitation magnetic field intensity signal and the magnetic induction intensity signal by making a Lissajous figure; 2. The system for measuring the axial AC hysteresis loop of soft magnetic materials with an open magnetic circuit according to claim 1, wherein The induction coil is obtained by connecting two coils with the same number of turns and cross-sectional area in series in reverse; 3. The system for measuring the axial AC hysteresis loop of soft magnetic materials with an open magnetic circuit according to claim 1, characterized in that, Also included is a power amplifier connected to the signal generator, the test module and the host computer respectively for power amplifying the signal based on the received instruction signal from the host computer and connecting the amplified signal to the AC Helmholtz coil; 4. The system for measuring the axial AC hysteresis loop of soft magnetic materials with an open magnetic circuit according to claim 3, wherein Replace the AC magnetic field sensor with a sampling resistor and a voltmeter. The two ends of the sampling resistor are respectively connected to the power amplifier and the AC Helmholtz coil. The voltage of the sampling resistor is measured by the voltmeter to obtain the excitation current I flowing through the sampling resistor, and the magnetic field intensity H is obtained based on the H / I conversion coefficient of the AC Helmholtz coil; 5. The system for measuring the axial AC hysteresis loop of soft magnetic materials with an open magnetic circuit according to claim 1, wherein, The test module further includes a test connecting rod, a first fixing clamp, a second fixing clamp and a PCB test board; The test connecting rod is connected to the first fixing clamp such that the first fixing clamp is located in the uniform region of the AC Helmholtz coil; The first fixing clamp is located at the top of the test connecting rod. The AC magnetic field sensor is inserted into the first fixing clamp, and the AC magnetic field sensor is fixed in the uniform region of the AC Helmholtz coil through the first fixing clamp; The second fixing clamp is fixedly connected to the top of the first fixing clamp for fixing the PCB test board; A hollow solenoid is provided on the PCB test board as the induction coil. The PCB test board is provided with pads for connecting the induction signal out with a BNC signal line and displaying it on the oscilloscope; 6. The system for measuring the axial AC hysteresis loop of soft magnetic materials with an open magnetic circuit according to claim 1, characterized in that, Test the intrinsic voltage value of the induction coil, and subtract the obtained intrinsic voltage value from the induced voltage obtained by the host computer to obtain the final induced voltage value; 7. The system for measuring the axial AC hysteresis loop of soft magnetic materials with an open magnetic circuit according to claim 1, wherein The magnetic induction intensity signal B is: Among them, V in is the induced voltage, N represents the number of turns of the induction coil, S is the cross-sectional area of the soft magnetic material, and t is the time.

8. The system for measuring the axial AC hysteresis loop of soft magnetic materials with an open magnetic circuit according to claim 1, characterized in that, The software adopted by the host computer includes LabVIEW, Pathon or MATLAB; 9. The system for measuring the axial AC hysteresis loop of soft magnetic materials with an open magnetic circuit according to claim 1, wherein, The soft magnetic material is an amorphous alloy microfilament or an amorphous alloy narrow strip.

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