A soft magnetic AC magnetic properties measuring device and method

Abstract

The present invention relates to a soft magnetic AC magnetic property measuring device and method, comprising a host computer, a control unit, an excitation mechanism and a flat high-temperature atmosphere furnace, wherein the control unit is wirelessly connected to the host computer, the control output end of the control unit is connected to the control input end of the excitation mechanism, a magnetic parameter sample is arranged in the excitation mechanism, the excitation mechanism and the magnetic parameter sample are arranged in a shell, and the flat high-temperature atmosphere furnace is connected to the shell to prevent the magnetic parameter sample from being oxidized under high temperature conditions. The present invention obtains a more real and accurate magnetic field condition by obtaining the magnetic flux lost in the open circuit part through RCP coil compensation, and the measuring device has the characteristics of convenient operation and accurate results, thereby realizing automation.

Description

Technical Field

[0001] The invention relates to the technical field of AC magnetic property measurement, and in particular to a soft magnetic AC magnetic property measurement device and method. Background Art

[0002] Hysteresis loop is an important performance index of soft magnetic materials, which directly affects the magnetization characteristics of soft magnetic materials in a magnetic field. Soft magnetic materials refer to magnetic materials with small coercive force and easy magnetization and demagnetization. They are mainly used in transformers, sensors, filters, motors and other products, and widely serve high-tech fields such as aerospace, information communication, and power electronics.

[0003] At present, three methods are commonly used internationally to measure the AC magnetic properties of soft magnetic materials, namely the square circle method, the single-piece permeameter method and the ring sample method. The corresponding international measurement standards are IEC60404-2, IEC60404-3 and IEC60404-6, and the corresponding national standards are GB / T 3655, GB / T 13789 and GB / T 3658. The above standard methods have certain requirements for the samples to be measured, and require sampling and sample preparation processes. It is impossible to perform non-destructive measurements on semi-finished products and finished products. There are also certain problems in the detection methods. In the actual application environment and ideal measurement conditions, some users also measure the conventional properties of silicon steel inaccurately. Therefore, a soft magnetic AC magnetic property measurement device and method is needed. Summary of the invention

[0004] The purpose of the present invention is to provide a soft magnetic AC magnetic properties measuring device and method that avoids the stringent requirements on the sample to be tested, the need for sampling, sample preparation and winding, and the problem of being unable to achieve accurate measurement due to the gap between the U-shaped magnetic yoke and the sample to be tested.

[0005] To achieve the above object, the present invention is implemented according to the following technical solutions:

[0006] The present invention includes a host computer, a control unit, an excitation mechanism and a flat high-temperature atmosphere furnace. The control unit is wirelessly connected to the host computer, the control output end of the control unit is connected to the control input end of the excitation mechanism, a magnetic parameter sample is arranged in the excitation mechanism, the excitation mechanism and the magnetic parameter sample are arranged in a shell, and the flat high-temperature atmosphere furnace is connected to the shell to prevent the magnetic parameter sample from being oxidized under high temperature conditions.

[0007] Furthermore, the control unit includes a single-chip microcomputer, a touch screen, an arbitrary waveform generator, a power amplifier module and a multi-channel data acquisition module. The arbitrary waveform generator generates analog signals of various complex waveforms in real time; the power amplifier module has a small impedance and can amplify the signal at a larger peak amplitude. It adopts an output capacitor isolation method and uses an external high-power tube to expand the current output so that the output current reaches 5A. The multi-channel data acquisition module uses a differential amplifier as the first-stage amplifier, uses a three-stage amplification combination, and uses a channel switch for gear shifting. The output ends of the touch screen, arbitrary waveform generator, and channel data acquisition module are respectively connected to the input end of the single-chip microcomputer, and the output end of the single-chip microcomputer is wirelessly connected to the host computer.

[0008] Furthermore, the excitation mechanism includes a U-shaped yoke, an excitation coil, a measuring coil, a small measuring coil and an RCP coil group. The excitation coil and the measuring coil, i.e., the primary winding and the secondary winding, use high-temperature special wires and are wound in parallel on the U-shaped yoke. A semicircular small measuring coil with a winding is provided on the inner side of the U-shaped yoke. The winding direction is consistent with the U-shaped yoke and is wound in parallel on the skeleton leg. The RCP coil includes a winding wound on a rectangular skeleton core and is arranged inside the small measuring coil skeleton. The winding direction is a direction that forms an angle of 90° with the U-shaped yoke. The U-shaped yoke, the small measuring coil and the RCP coil are tightly attached to the surface of the sample to be tested, and the maximum gap does not exceed 0.01 mm.

[0009] Furthermore, the flat high temperature atmosphere furnace is provided with a flat high temperature atmosphere furnace temperature control module, the furnace body of the flat high temperature atmosphere furnace is made of a stainless steel shell, the interior is filled with heat preservation cotton, the heating furnace wire is a high temperature iron-chromium-aluminum alloy furnace wire, and the flat high temperature atmosphere furnace is also provided with an inert gas inlet and outlet.

[0010] A method for measuring soft magnetic AC magnetic properties, by obtaining the magnetic flux lost in the open circuit part through RCP coil compensation, comprises the following steps:

[0011] A. Collect the information of the sample to be tested, including sample number, brand, temperature, humidity, magnetic circuit length, primary turns, secondary turns, select the frequency as 50Hz, and determine the target magnetic field strength H t , making the end face of the U-shaped magnetic yoke leg, the end face of the leg of the measuring small coil and the bottom end face of the RCP coil close to the surface of the sample to be tested, so as to form a closed magnetic circuit;

[0012] B. Use RCP coil to measure the lost magnetic flux, calculate the lost magnetic induction intensity B, and get the formula of the real magnetic induction intensity B:

[0013] Magnetization curve B = f(H),

[0014] The RMS value or peak value of the excitation current and induced voltage can be determined by the integration circuit, and the magnetization curve can be determined by the hysteresis loop;

[0015] C. Collect the sampling resistor voltage and the integrating capacitor voltage of the alternating cycle, and calculate the magnitude of the instantaneous excitation current I1;

[0016] D. Use waveform analysis and feedback, and use waveform factor to indicate the degree of waveform distortion in magnetic parameter measurement. Change the waveform of the output voltage of the excitation power supply. Use digital waveform feedback to perform digital harmonic analysis on the induced voltage. Change the waveform of the output voltage of the excitation power supply. Use the iteration method to make the magnetic flux waveform sinusoidal. Use the following formula for integration:

[0017] dB / dt=-V / N2S-V' / N2'S

[0018] Where, B is the magnetic induction intensity, V is the generated voltage, N2 is the number of turns of the secondary winding, S is the cross-sectional area of ​​the magnetic parameter sample, V' is the voltage generated by the homemade RCP coil, and N2' is the number of turns of the secondary winding of the homemade RCP coil;

[0019] E. Complete the measurement of the magnetic induction intensity B value under the instantaneous state, use the host computer to output the calculation results, and calculate the magnetic polarization intensity J under the instantaneous state as follows:

[0020] J m =B m -μ0H m

[0021] In the formula, J m is the instantaneous magnetic polarization intensity, μ0 is the vacuum magnetic permeability value, 4π×10 -7 , H m is the instantaneous magnetic field strength.

[0022] Furthermore, an inert gas is used for protection during measurement.

[0023] Furthermore, in step D, the waveform factor used in the magnetic parameter measurement when waveform analysis and feedback are used to represent the degree of waveform distortion is the ratio of the effective value to the rectified average value, and the ideal sinusoidal waveform factor is 1.1107.

[0024] The beneficial effects of the present invention are:

[0025] The present invention is a soft magnetic AC magnetic property measurement device and method. Compared with the prior art, the present invention has the following technical effects:

[0026] 1. The requirements for the tested samples are simple, only the surface of the soft magnetic sample needs to be flat and in plate form. Especially for the measurement of special equipment when the material used cannot be removed, there is no need for sampling, sample preparation, winding and other processes, thus avoiding cumbersome and complicated operations;

[0027] 2. Avoid the problem of inaccurate magnetic flux measurement caused by the gap between the U-shaped magnetic yoke and the tested sample. Only by measuring the calibration of the magnetic field by the small coil and the magnetic flux calibration of the homemade RCP coil, the actual magnetic field strength and actual magnetic flux in the sample can be obtained, and the real working conditions can be achieved. Convenient and high-accuracy measurement of the sample is achieved;

[0028] 3. The operation is simple and automatic. The temperature is controlled by a flat high-temperature atmosphere furnace. By clicking and selecting the measurement items such as total loss, amplitude permeability, average voltage and maximum current in the software, the images of hysteresis loop, waveform, magnetization curve, permeability curve and loss curve can be automatically obtained. The operation is convenient and the results are accurate, thus realizing automation. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention is a schematic structural diagram of a soft magnetic AC magnetic property measuring device and method.

[0030] Figure 2 The present invention is a schematic structural diagram of an excitation mechanism of a soft magnetic AC magnetic property measuring device and method.

[0031] In the figure, 1-control unit, 2-excitation mechanism, 3-flat high temperature atmosphere furnace, 11-touch screen, 12-host computer, 13-waveform generator, 14-power amplifier module, 15-multi-channel data acquisition module, 21-U-shaped magnetic yoke, 22-excitation coil, 23-measuring coil, 24-small measuring coil, 25-RCP coil; 31-flat high temperature atmosphere furnace body, 32-flat high temperature atmosphere furnace temperature control module; 4-magnetic parameter sample DETAILED DESCRIPTION

[0032] The present invention is further described below with specific examples. The illustrative examples and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0033] like Figure 1 As shown, Figure 1 As shown, a soft magnetic AC magnetic property measurement device and method include: a control unit 1, a control system behind a touch screen 11 connected to a host computer 12 through a network, an arbitrary waveform generator 13 for excitation, data acquisition through a power amplifier module 14 and a multi-channel data acquisition module 15, and waveform feedback at the same time, so as to control the waveform sine. Under the same frequency and peak magnetic induction intensity conditions, the shape of the hysteresis loop is directly related to the magnetization process. This is to emphasize comparability, requiring the magnetic flux waveform to be sine (that is, the secondary induced voltage waveform coefficient is within ±1% of 1.1107), so that the hysteresis loop is unique and the measurement accuracy is improved.

[0034] Excitation mechanism 2, preferably, U-shaped yoke 21 is wound by high-performance oriented silicon steel sheet tape, excitation coil 22 and measuring coil 23 use high-temperature special wire, double wire is wound on U-shaped yoke 21, the direction is consistent, to ensure the magnetic field is consistent, the small measuring coil 24 also uses high-temperature special wire, double wire is wound in the same direction as U-shaped yoke, when measuring the magnetic field strength, the total magnetic field minus the magnetic field measured by the small coil is used, that is, the actual measured magnetic field. The homemade RCP coil 25 is wound at 90° to the U-shaped yoke 21. When the measuring current passes through these windings, according to Faraday's law, the induced electromotive force in the closed circuit is proportional to the rate of change of the magnetic flux passing through the circuit, so that the magnetic flux lost between the U-shaped yokes 21 is obtained by calculation. During this process, the leg end faces of the U-shaped magnetic yokes 21, 24, the small measuring coil and the homemade RCP coil 25 are in close contact with the surface of the magnetic parameter sample 4 to form a closed magnetic circuit. The winding and coil structure method adopted in the present invention is simple and low-cost, and it is easy to achieve the saturation magnetization of the magnetic parameter sample 4, and it is also for the purpose of measuring the actual hysteresis loop to characterize the excitation state of the material, rather than the equivalent hysteresis loop diagram.

[0035] The flat high-temperature atmosphere furnace 3 is composed of a flat high-temperature atmosphere furnace body 31 and a flat high-temperature atmosphere furnace temperature control module 32. The flat high-temperature atmosphere furnace body 31 is made of a stainless steel shell, filled with insulation cotton, and the heating wire is made of a high-temperature iron-chromium-aluminum alloy. It also includes a left air inlet and a right air outlet for inert gas to ensure gas circulation and prevent oxidation of the sample under high temperature conditions.

[0036] The principle of this measuring device is that all magnetic material parameters (power loss, magnetic permeability, hysteresis, etc.) depend on the magnetic induction intensity B and the magnetic field intensity H. In this measuring system, according to Ampere's law, the magnetic field intensity depends on the excitation current I1 of the primary winding N1.

[0037] H=I1N1 / L1-I1N2 / L2

[0038] Where H is the magnetic field intensity, I1 is the excitation current, N1 is the number of turns of the primary winding of the U-shaped yoke, L1 is the magnetic path length of the U-shaped yoke, N2 is the number of turns of the winding of the measuring small coil, and L2 is the magnetic path length of the measuring small coil.

[0039] The magnetic field strength is measured as the tangential field component near the sample being tested. According to Maxwell's equations, the legs of the U-shaped yoke 21 are very close to the magnetized surface, and the measured magnetic field and the magnetic parameter sample 4 can be considered to be the same. Since the coil output signal is relatively small (in the μV range), thin, and the output signal depends on the cross-sectional area of ​​the coil, the signal may be disturbed by the external magnetic field, and the output signal depends on dH / dt. Therefore, the power amplifier module 14 is particularly important. According to Faraday's law, the magnetic induction intensity is usually measured by the voltage V generated in the secondary winding N2.

[0040] dB / dt=-V / N2S,

[0041] Where B is the magnetic induction intensity, V is the generated voltage, N2 is the number of turns of the secondary winding, and S is the cross-sectional area of ​​the magnetic parameter sample.

[0042] Therefore, an integrating circuit is used to determine the amount of magnetic induction intensity B. In order to measure the value of magnetic induction intensity B, a small hole is usually drilled in the sample to wind a small coil. This method is cumbersome and will damage the magnetic parameter sample 4. Therefore, the measuring device adopts a simple structure and does not damage the magnetic parameter sample 4 for measurement. At the same time, in the space surrounded by the U-shaped magnetic yoke 21 and the magnetic parameter sample 4, there will be a magnetic flux value that is not along the direction inside the magnetic parameter sample 4, but a lost magnetic flux is generated. Therefore, the device uses a homemade RCP coil 25 to measure the lost magnetic flux, and calculates the lost magnetic induction intensity B, thereby obtaining the true magnetic induction intensity B. The magnetization curve B = f (H), the root mean square value or peak value (through the integrating circuit) of the excitation current and the induced voltage can be determined, and then the magnetization curve is determined by connecting the top of the hysteresis loop.

[0043] Among them, waveform analysis and feedback are used in this device. The waveform factor is used to indicate the degree of waveform distortion in magnetic parameter measurement. The waveform factor is the ratio of the effective value to the rectified average value. The ideal sine wave waveform factor is 1.1107. The measurement data is obtained through multiple digital waveform feedbacks. Digital waveform feedback performs digital harmonic analysis on the induced voltage, and then changes the output voltage waveform of the excitation power supply. The iterative method is used to make the magnetic flux waveform sinusoidal, replacing the traditional analog feedback loop. It has the characteristics of small waveform distortion, not easy to oscillate, and wide frequency range.

[0044] On the other hand, the present invention also provides the following technical solution: a soft magnetic AC magnetic property measurement device and method, comprising the following steps:

[0045] Step 1: Input basic information in the software, including sample number, brand, temperature (at room temperature), humidity, magnetic circuit length, primary turns, secondary turns, etc. Select the frequency as 50Hz and determine the target magnetic field strength H. t , and the items that need to be measured.

[0046] Step 2: Connect the measuring device so that the end face of the U-shaped yoke leg, the end face of the measuring small coil leg and the bottom end face of the homemade RCP coil are close to the surface of the magnetic parameter sample to form a closed magnetic circuit; the software performs single-point measurement or multi-point measurement, the arbitrary waveform generator starts running, and the connected power amplifier amplifies.

[0047] Step 3: Turn on the AC power supply, and the multi-channel data acquisition module 15 collects the sampling resistor voltage and the integral capacitor voltage of the alternating cycle, and calculates the magnitude of the instantaneous excitation current I1. The digital waveform feedback performs digital harmonic analysis on the induced voltage, and then changes the excitation power supply output voltage waveform, uses the iteration method to make the magnetic flux waveform sinusoidal, and uses the following formula for integration:

[0048] dB / dt=-V / N2S-V' / N2'S

[0049] In the formula, B is the magnetic induction intensity, V is the generated voltage, N2 is the number of turns of the secondary winding, S is the cross-sectional area of ​​the magnetic parameter sample, V' is the voltage generated by the homemade RCP coil, and N2' is the number of turns of the secondary winding of the homemade RCP coil. The measurement of the magnetic induction intensity B value under the instantaneous state is completed, and according to the formula:

[0050] J m =B m -μ0H m

[0051] In the formula, J m is the instantaneous magnetic polarization intensity, μ0 is the vacuum magnetic permeability value, 4π×10 -7 , H m is the instantaneous magnetic field strength.

[0052] Complete the measurement of the magnetic polarization intensity J in the instantaneous state (for soft magnetic materials, the magnetic field intensity is not greater than 10KA / m, so the second component μ0H can be ignored, so that the magnetic induction intensity B and the magnetic polarization intensity J have the same value).

[0053] Step 4: The host computer performs the BH calculation function, and the operation interface performs image display and data recording of hysteresis loop, waveform, magnetization curve, permeability curve, and loss curve.

[0054] On the other hand, the present invention also provides the following technical solutions: a method for using a simple saturation hysteresis loop measuring device, under high temperature conditions, it is necessary to set a flat high temperature atmosphere furnace temperature control module 32, set a target temperature, click heating, measure the temperature through the internal temperature collector, and set it as the current measurement temperature. During this process, the inert gas cylinder valve needs to be opened for gas protection.

[0055] Based on the above technical solution, the present invention can also be improved as follows.

[0056] The touch screen size of the control unit can be increased, and the switches, touch screen, and primary and secondary wire positions of the panel can be adjusted.

[0057] The size of the U-shaped yoke of the excitation mechanism can be increased to 50mm, 30mm, etc. The two end faces are rectangular, and the length of the vertical line connecting the ports can be the long side to ensure that the equivalent magnetic flux during measurement is equal to the magnetic flux actually characterizing the sample.

[0058] The magnetic parameter specimen is a plate-type soft magnetic material and is not limited to fixed steel for measurement.

[0059] Therefore, a U-shaped yoke measurement method is developed based on a single-chip permeameter, which is widely used in magnetic property detection of magnetic materials and magnetic Buckhaus noise measurement. The present invention develops an AC magnetic property measurement method for soft magnetic materials based on a U-shaped yoke.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A soft magnetic AC magnetic properties measuring device, characterized in that: It includes a host computer, a control unit, an excitation mechanism and a flat high-temperature atmosphere furnace. The control unit is wirelessly connected to the host computer. The control output end of the control unit is connected to the control input end of the excitation mechanism. A magnetic parameter sample is arranged in the excitation mechanism. The excitation mechanism and the magnetic parameter sample are arranged in a shell. The flat high-temperature atmosphere furnace is connected to the shell to prevent the oxidation of the magnetic parameter sample under high temperature conditions. The control unit includes a single-chip microcomputer, a touch screen, an arbitrary waveform generator, a power amplifier module and a multi-channel data acquisition module. The arbitrary waveform generator is used to generate analog signals of various complex waveforms in real time; the power amplifier module has a small impedance and can amplify the signal at a large peak amplitude. It adopts an output capacitor isolation method and uses an external high-power tube to expand the current output so that the output current reaches 5A. The multi-channel data acquisition module uses a differential amplifier as the first-stage amplifier , using a three-stage amplification combination, using a channel switch for gear switching, the output ends of the touch screen, arbitrary waveform generator, and channel data acquisition module are respectively connected to the input end of the single-chip microcomputer, and the output end of the single-chip microcomputer is wirelessly connected to the host computer, the excitation mechanism includes a U-shaped yoke, an excitation coil, a measuring coil, a small measuring coil and an RCP coil group, the excitation coil and the measuring coil, that is, the primary winding and the secondary winding, use high-temperature special wires, which are wound in parallel on the U-shaped yoke; a semicircular small measuring coil with a winding is provided on the inner side of the U-shaped yoke, and the winding direction is consistent with the U-shaped yoke, and the double wire is wound on the skeleton leg, the RCP coil includes a winding wound on a rectangular parallelepiped skeleton core, which is arranged inside the small measuring coil skeleton, and the winding direction is a direction with a 90° angle with the U-shaped yoke, the U-shaped yoke, the small measuring coil and the RCP coil are tightly attached to the surface of the sample to be tested, and the maximum gap does not exceed 0.01mm.

2. A soft magnetic AC magnetic property measuring device according to claim 1, characterized in that: The flat high temperature atmosphere furnace is provided with a flat high temperature atmosphere furnace temperature control module. The furnace body of the flat high temperature atmosphere furnace is made of stainless steel shell material, and the interior is filled with insulation cotton. The heating furnace wire is a high temperature iron-chromium-aluminum alloy material furnace wire. The flat high temperature atmosphere furnace is also provided with an inert gas inlet and outlet.

3. A method for measuring soft magnetic AC magnetic properties, used to implement a soft magnetic AC magnetic properties measuring device as claimed in any one of claims 1 to 2, characterized in that: By using the RCP coil compensation method, the magnetic flux lost in the open circuit is obtained, including the following steps: A. Collect the information of the sample to be tested, including sample number, brand, temperature, humidity, magnetic circuit length, primary turns, secondary turns, select the frequency as 50Hz, and determine the target magnetic field strength H t , making the end face of the U-shaped magnetic yoke leg, the end face of the leg of the measuring small coil and the bottom end face of the RCP coil close to the surface of the sample to be tested, so as to form a closed magnetic circuit; B. Use RCP coil to measure the lost magnetic flux, calculate the lost magnetic induction intensity B, and get the formula of the real magnetic induction intensity B: Magnetization curve B = f(H), The root mean square value or peak value of the excitation current and the induced voltage is determined by an integrating circuit, and the magnetization curve is determined by a hysteresis loop; C. Collect the sampling resistor voltage and the integral capacitor voltage of the alternating cycle, and calculate the magnitude of the instantaneous excitation current I1; D. Use waveform analysis and feedback, and use waveform factor to indicate the degree of waveform distortion in magnetic parameter measurement. Change the waveform of the output voltage of the excitation power supply. Use digital waveform feedback to perform digital harmonic analysis on the induced voltage. Change the waveform of the output voltage of the excitation power supply. Use the iteration method to make the magnetic flux waveform sinusoidal. Use the following formula for integration: Where, B is the magnetic induction intensity, V is the generated voltage, N2 is the number of turns of the secondary winding, S is the cross-sectional area of ​​the magnetic parameter sample, V' is the voltage generated by the homemade RCP coil, and N2' is the number of turns of the secondary winding of the homemade RCP coil; E. Complete the measurement of the magnetic induction intensity B value under the instantaneous state, use the host computer to output the calculation results, and calculate the magnetic polarization intensity J under the instantaneous state as follows: J m =B m -μ0H m In the formula, J m is the instantaneous magnetic polarization intensity, μ0 is the vacuum permeability value, 4π×10 -7 , H m is the instantaneous magnetic field strength.

4. A method for measuring soft magnetic AC magnetic properties according to claim 3, characterized in that: Inert gas was used for protection during measurement.

5. A method for measuring soft magnetic AC magnetic properties according to claim 3, characterized in that: In step D, the waveform factor is used to represent the degree of waveform distortion in the measurement of magnetic parameters when waveform analysis and feedback are used. The waveform factor is the ratio of the effective value to the rectified average value. The ideal sine wave waveform factor is 1.1107.

Images